Monday, July 31, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Germany, theoretical physics, and string theory

DEUTSCH

One year after my report about our bike trip to Gross Arber, I will declare another German week on this blog and contemplate about the relations between Germany on one side and theoretical physics and string theory on the other side as seen from a Czech physicist's viewpoint. The reason is that the number of German visitors is going to double or triple. Many features of the Czech academic system as well as the general mood in the physics community resemble their German counterparts which could make my opinions slightly relevant even if I don't know the current facts about German science at a visceral level.



One hundred years or so, Germany became the world's epicenter of theoretical physics much like it was the leader in philosophy and music one or two centuries earlier. Why do I think so? Let us look at the key achievements one by one. Relativity was developed by Albert Einstein who was a German Jew. Because of certain infamous historical events, he has experienced some problems in Germany; Einstein also faced anti-Semitism in Prague around 1910 when he appreciated the equivalence principle for the first time.

He eventually became a part of the generous gift of Germany to the American science. Max Planck kickstarted quantum theory in 1900. He was also the editor of Annalen der Physik who was responsible for the immediate acceptance of Einstein's paper on special relativity. You should add many leading mathematicians of the early 20th century who were Germans or who spoke German.



The most important physics revolution of the 20th century was arguably the quantum mechanical revolution. Besides Sir Paul Adrien Maurice Dirac of England, Niels Bohr of Denmark, and a few others, this revolution was the work of precious German (or Austrian) physicists and mathematicians. Werner Heisenberg, Johann von Neumann, Erwin Schrödinger, Wolfgang Pauli, and many of their colleagues were the key players in the most thrilling developments in physics of the last century. There's no doubt that this German leading role in theoretical physics has mostly evaporated after the war. Insights such as Quantum Electrodynamics, Quantum Chromodynamics, the Standard Model, and String Theory (except for a couple of important discoveries at the very beginning) were dominated by the American physicists.

Friday, July 28, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

From strings to LHC

The Tata Institute of Fundamental Research, Mumbai, India is organising a meeting

FROM STRINGS TO LHC
at the International Centre, Goa

from 2nd Jan 2007 to 10th Jan 2007.

In this meeting, we are interested in bringing together string theorists and high-energy phenomenologists and hope to give this alliance a concrete shape. This alliance is particularly valuable in light of the experimental information that LHC will provide us very soon and which we hope will tell us about physics beyond the Standard Model.

Thursday, July 27, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Climate science in the House and Democrats

Guido has pointed out a recent TechCentralStation's article

about some "obtuse" Democratic representatives, as Guido puts it. The article includes excerpts from the recent hearing with the climate scientists - such as Gerry North who led the NAS panel - and statisticians - such as Edward Wegman, the author of the recent report showing that most climate scientists are crackpots in statistics.

After I read the comments by Ms. Jan Schakowsky, Ms. Tammy Baldwin, Mr. Bart Stupak, Mr. Jay Inslee and others, you may guess that my reaction would be slightly more violent than Guido's reaction or Prof. Hans von Storch's reaction - but I will ask you to try to imagine what I would say if I had to say something about it. But Hans von Storch is actually not that far from what I would say Ms. Schakowsky.

Note that I am politically correct, so my list of obtuse representatives included two women and two men - even though, I admit, the women were dumber, especially the first one.

Incidentally, Jay Inslee also thinks that theories of gravity should no longer be debated, apparently because he is ignorant of string theory as Duane Freese pointed out. ;-)

Wednesday, July 26, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Stueckelberg Z prime at the LHC




In the last two days, some intelligent media have paid attention to the paper by

about the possible detection of the Z' particles that obtain masses via the Stueckelberg mechanism i.e. from an additional U(1) without any new Higgs mechanism. These particles appear as very narrow resonances and are naturally predicted by many string vacua.

See physorg.com, news.google.com.

Tuesday, July 25, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Gabriel Agbasi demands Nobel prize

Well, some people are self-confident enough. We wish Gabriel Agbasi a lot of good luck. He will hopefully need it. ;-) His letter to the Nobel foundation is attached under his photograph. But let us start with a link.

Update: If you're fascinated by this Gentleman and author of "Ueber Alles", you should definitely read his own explanation of some events that brought him to the police station, jail, etc. because he studied in the library. If his presentation of the story is correct, The Reference Frame is leaning to his side in this particular controversy. But indeed, our support is partly based on the fact that Agbasi is a kind of right-winger.



Date: Tue, 25 Jul 2006 16:32:35 +0100
From: PHYSICS NOW
To: [All physicists at Harvard and probably the rest of the world]
Subject: (COURTESY EMAIL) Submission to the Nobel Prize Committee of the Scientific Discovery of the 4th Dimension

Gabriel Agbasi
PO BOX 3192
Bellingham, WA 98227-3192
360-603-9519

The Nobel Foundation
Sturegatan 14
Box 5232
SE-102 45 Stockholm
Sweden
Tel +46 8 663 09 20
Fax +46 8 660 38 47

July 6, 2006

RE: Submission of formal presentation to the Nobel Prize Committee of the Scientific Discovery of the 4th Dimension

To Whom It May Concern

Dear Sir/Madam,

I am a Physicist (BS 1995), a student at WESTERN WASHINGTON UNIVERSITY and I have made an important scientific discovery - The 4th Dimension. I will not get into scientific details, but a lot of our science will improve with the acceptance and use of this new discovery.

Resumming non-renormalizable theories?

John G. has asked me what I think about the following paper by B.F.L. Ward:

This paper claims to have found a technique to resum the loop diagrams of general relativity and potentially all other renormalizable as well as non-renormalizable theories and to calculate UV finite results.

Of course that with all my respect to the author, I think that all such attempts are most likely wrong. There exists one general and essential question that all the authors of such papers - much like all researchers in loop quantum gravity and Lee Smolin in particular - seem to misunderstand. The real problem is not to obtain finite results; the real problem is to obtain results that do not depend on infinitely many unknown parameters.

Sunday, July 23, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Essentials of life

The world around us is a remarkable structure, despite all of its annoying substructures such as hypocricy, bureaucracy, environmental advocacy; communism, Nazism, feminism, terrorism, alarmism, NGOism; insanity, loop quantum gravity, pity; regulation, explosion, Californication; IRS, INS, HIV, AIDS, NOW, PC, NSDAP; silliness, laziness, and the Loch Ness monster.

What are the most general features of the natural laws and the environment that are required for the existence of worlds that qualitatively resemble ours? The entries below may look too constraining to some readers and too vague to others but a working draft may turn out to be useful anyway. In each case, I will try to explain why the feature is important and whether we understand its origin.

One time

The world is interesting because many things happen in it. The important processes that will be discussed below take place in this Cosmos. The future may support more organized structures than the past. Something that looks like a time coordinate is necessary. We can also see that this kind of a world requires one time coordinate and not more. If you have (at least) two large time coordinates t1,t2, then you can continuously change the direction of worldlines in the t1-t2 plane. This means that there can't exist any sharp differences between the past and the future.

In perturbative string theory, we naturally predict the spacetime to have one time coordinate from the requirement that the physical Hilbert space is positively definite - a requirement discussed in the following paragraph. The Virasoro algebra is as large as we need to decouple negative-norm states arising from one set of time-like oscillators (and another set of longitudinal i.e. spacelike oscillators dies at the same moment). Similar arguments hold in all approaches to physics that admit the light-cone gauge.

Postulates of quantum mechanics

Although quantum mechanics was born less than 100 years ago, I think it is fair to say that the basic principles of quantum mechanics are probably necessary for life, too. By basic principles, I mean the existence of a complex Hilbert space that encodes possible states of the Universe, the existence of Hermitean linear operators on this space that represent real observables that can physically distinguish different states and/or are responsible for their evolution, and the procedure to calculate probabilities of different outcomes of a sequence of events as squared absolute values of certain complex amplitudes. The last postulate requires the Hilbert space to be equipped with a positively definite norm because negative probabilities make no sense even at the logical level. The evolution operators should be unitary in order for the total probability to be preserved.

Quantum mechanics is needed in order to create sharply separated discrete states - such as the bases of DNA discussed below - in a continuous world: I am talking about discrete energy eigenstates. It is also necessary for allowing some rather unlikely processes such as quantum tunnelling. In a classical world, different possibilities would be connected by a continuum, the existence of discrete and binary codes such as the DNA code or binary computers would be extremely problematic, and small effects would always modify the uncorrected process by small amounts rather than allowing qualitatively different processes with small probabilities. Burning of stars, the transistor effect, and many other things would be at risk. Of course, in a canonical classical world that is easy to write down, the atoms would be unstable which would have truly catastrophic consequences, but even if you tried to design a more stable set of classical laws, for example by replacing point-like electrons by solid balls, I guess that life would not start in such a world.

According to the state-of-the-art picture of physical reality, the postulates of quantum mechanics as described above are exact. It seems hard to modify them or deform them and they don't need to be modified even if we want to describe processes that are seemingly as incompatible with quantum mechanics as black hole evaporation. As far as we can say, the postulates of quantum mechanics need to be imposed at the very beginning. String theory wouldn't have most of its cool properties such as dualities without quantum mechanics, but at present, quantum mechanics itself can't be derived from a deeper principle. Many leading string theorists believe that the quantum postulates will be "unified" with other features of the real world such as the geometry of various spaces (configuration spaces, phase spaces, moduli spaces, spacetime) in the future which could make quantum mechanics look much more inevitable than today.

Enough spacetime for complicated structures

One of the general features of our Universe is that it is somewhat large. There are many animals and people living on our planet that orbits one star among tens of billions in a galaxy that is just one galaxy among tens of billions. You need about billions of bits to store the information from this blog and about 10^{100} of quantum bits to store the less important information about the rest of the Universe.

Evolution needed a lot of space and time to go through and there probably exist fundamental reasons why the complex processes could not have been too much faster. At the beginning, I wrote that time was essential and you could have asked why I didn't mention space. Yes, it was because I think that from a non-physics perspective, space that approximately follows the rules of the Euclidean geometry is less essential. Nevertheless, now we see that we need a lot of room where the information may be stored. If you have a lot of "room", it does not have to be organized according to the rules of Euclidean geometry. But the Euclidean geometry is certainly a natural choice. If you want to be more specific, life like ours requires 3+1 dimensions. But theoretical physicists would certainly not count a theory as "physically inconsistent" just because the dimension of its spacetime differs from 3+1.

At the end of the whole article, I will also argue that a symmetry between space and time is needed for some aspects of life.

How can we explain that the world is large? Where do the large numbers such as 10^{90} encoding the number of particles in the Cosmos come from? The best explanation we have is inflationary cosmology. Even if you start with a Planckian universe where all quantities are of order one, inflation can lead to a dramatic, exponential increase of the total volume and the total mass of the Universe: the energy density of the vacuum is essentially constant during the inflation while the volume expands exponentially. Many quantities of this kind can naturally be calculated as exponentials of numbers that are expected to be of order 10 or 100. Although we cannot yet calculate the exact number of e-foldings from the first principles, it is clear that the mystery why the Universe is so huge significantly diminishes once we appreciate the power of inflation. Inflation simultaneously explains many other mysteries that are potentially necessary for decent life such as the flatness and isotropy of the Cosmos.

Needless to say, a large spacetime in the era of thriving life also depends on a small value of the cosmological constant. We don't have a satisfactory explanation why it's so small. In other cases, I would be ready to accept the anthropic explanation of some principles of our world because these principles are qualitative ones - for example, the existence of one time coordinate or the validity of the quantum postulates. It is much harder for me to accept an anthropic explanation for quantitative features of reality.

Hierarchies and large dimensionless numbers

Inflation has allowed us to calculate some mysteriously large numbers as exponentials of more reasonable numbers which reduced the degree of mystery hiding in many numbers of that kind. However, there are other large universal constants that have not yet been explained by this exponential mechanism or a similar mechanism. One of them is the ratio of the Planck mass and the proton mass - the kind of number that governs the size of neutron stars (and perhaps other stars, too).

If evolution needs a lot of space and time, the stars that are naturally created and that must pump energy into this whole process must be large enough. Their size is dictated by various hierarchies. The ratio between the Planck scale and the QCD scale is a key player that helps to determine the size of some stars. The huge size of this particular ratio is understood, too. It's because the QCD scale is defined as the scale where the QCD coupling is of order one. It's plausible that the QCD coupling at the Planck scale is a reasonable number such as 1/25, and because this coupling only depends on the logarithm of the energy scale, we must go to very low energy scales to change 1/25 to 1. This is why the QCD scale is so much lower than the Planck scale. This is why the protons are so much lighter than the Planck mass i.e. why their gravitational interaction is so much weaker than other interactions between them. This is one of the conditions for evolution to have enough spacetime to go. Again, you see another example of an exponential explanation of a large constant.

In the previous paragraph, I was comparing the strong force with the force of gravity. The qualitative explanation of their difference exists. However, if we compare the electroweak interactions with gravity, we don't quite know where the huge ratio between their strengths comes from - not even qualitatively. This is called the hierarchy problem. Supersymmetry helps to make this problem less serious and the smallness of the weak scale more natural and more stable against corrections - but no one has found a sketch of a convincing calculation that would describe the ratio of the weak scale and the Planck scale as the exponential of a more reasonable number. If you were able to show that the weak scale and the QCD scale must be close to each other, it could also become a solution.

There exist other large dimensionless numbers in the real world that are important for life. The proton-electron mass ratio, about 1836.15, must be large in order for the nuclei to behave classically, while electrons determine the effective interactions between them. The fine structure constant is about 1/137.036. Its smallness is necessary not only for the impressive quantitative success of perturbative QED, but it is also needed for non-relativistic physics to be a good approximation for the physics of atoms because the speed of electrons in atoms divided by the speed of light is controlled by the fine structure constant.

Nowadays, all parameters of the natural laws we use to describe the world are reduced to 30 or so parameters of the Standard Model (with neutrino masses) expressed in the Planck units, and to the cosmological constant. The tiny cosmological constant is not really understood. Some patterns in the Standard Model parameters are qualitatively understood. For example, the neutrino masses are roughly where they are because of the see-saw mechanism, assuming that a relevant scale like a GUT scale exists. Other constants have potential quantitative explanations – such as one relation between the three gauge couplings that can be deduced from grand unification. The hierarchy between the Planck scale and the Higgs vev (weak scale) is not understood too well, much like the large ratios between the different Yukawa couplings. However, the top quark Yukawa coupling may have a semi-quantitative explanation, much like some relations between the bottom quark and tau lepton couplings. Some mysteries seem less serious than others, some large parameters seem to be more necessary for anthropic considerations than others, and so on - a typical example of chaos that is still waiting for a better explanation.

Causality and locality, at least approximate ones

When I mentioned that a time coordinate was needed, I implicitly required that this time coordinate gives us an ordering that can separate the past from the future by the present. The logic of our world is based on the past that can influence the future, but not the other way around. Using a more careful quantum language, the knowledge of the data from the past is used to predict the probabilities of different outcomes in the future, but I am convinced that you should never use these procedures backwards unless you become capable to account for the fact that the entropy in the past should be lower than today which is dictated by another principle, a low-entropy beginning of the Universe. This asymmetric relation between the past and the future is what we call "causality".

We also mentioned that the Universe should be large. For structures and ideas to be developed independently and to have a value that can approximately be separated from the rest of the world, the phenomena should occur locally, without too high an influence of the rest of the Universe. The most natural way to achieve this goal is to impose a strict locality: a signal can only get from A to C if it occurs somewhere in between, in B, before it reaches C. At the end of the article, I will also discuss that the principle of relativity may be needed for life in general. String theory predicts that the rules of special relativity are always respected locally in spacetime. Special relativity strengthens the constraints of causality - you are not only unable to influence your future but you can't influence spacelike-separated events in spacetime either. In fact, locality and causality become more or less synonyma in the relativistic context.

Although one could perhaps imagine more general schemes where life would be possible and locality and causality would be just an approximation, string theory and observations seem to agree about a rather strong way to satisfy these constraints: local physics is Lorentz-invariant and satisfies the laws of special relativity.

The existence of classical limits

While some important processes in the world have a quantum-mechanical essence, it is fair to say that an overwhelming portion of the key processes in the Cosmos can be interpreted using the language of classical physics, at least if you don't care about the detailed microscopic origin of these phenomena. The functions of a classical computer, human brain, or DNA reproduction probably belong to the classical realm: the decoherence time in all these cases is much shorter than the typical timescales at which these processes occur which is why the classical intuition is justified.

The existence of justifiable classical limits is therefore guaranteed by a sufficiently large environment and sufficiently strong interactions with the environment. Once again, these things are large because the number of atoms in the brain and similar numbers are large. In this sense, the previous points about the existence of large numbers also explain why there must inevitably exist processes that admit a classical description. The very same large parameters also explain why thermodynamics is a good approximation, and so forth. There is a lot of relationships between these principles although they could seem independent a priori.

Nearly permanent sources of usable energy

Everyone knows that the energy needed for the terrestrial life comes from the Sun's thermonuclear energy after all. It's a system of processes that clearly work and no sane person can argue otherwise. A question is whether very different alternatives are plausible.

I am not so sure. The energy from the Sun is modulated by various oscillating patterns at several timescales. It's a good driving force for many interesting events. You can hide from the Sun if you need to. The biosphere is getting about 1 part per million of energy from geothermal sources. Indeed, you could design planets where this fraction would become higher. Some people have argued that the life on such planets would not require any stars. I am not quite certain. Both answers seem plausible to me.

The large stars arise if the hierarchies explained above exist and if other parameters such as the cosmological constant belong to a certain window. Because this topic is often discussed in the anthropic context, I won't repeat these considerations here.

Large enough environment to get rid of entropy

Life leads to an evolution and creation of more organized structures. In some sense, more organized structures carry smaller entropy than the organized ones. A decrease of the total entropy would violate the second law of thermodynamics. In reality, of course, the decrease of the entropy of an animal is overcompensated by the increase of the entropy of its environment. There must exist a sufficiently large environment that acts as a dumping ground for the entropy generated by life. Indeed, the Earth and perhaps the Universe are large enough for us to throw our entropy away. The environmentalist simpletons could call this emission of entropy away from the biosphere a pollution, just like they do so in the case of carbon dioxide. They call it pollution; we call it life.

There are other processes involving entropy that may be needed for life. Non-gravitational physical systems typically maximize the entropy if they become completely uniform (like a purple gas). Gravity can change the rules of the game and clumped objects can actually carry a higher entropy and become natural final states of many processes. Black holes in particular carry the maximum entropy you can squeeze into a given volume. This feature of gravity was necessary for structure formation during the childhood of our Cosmos, and I recommend you Brian Greene's "The Fabric of the Cosmos" for additional words about this interesting semi-philosophical topic.

Metastable carriers of information

Animals, plants, as well as computers need to sharply define the message they represent. They do so in the form of DNA codes or computer files. Some of these structures must occur naturally – so let us start with the DNA molecules. The information is encoded in the A/C/G/T(U) bases. If the sharp and discrete information were impossible, everything would be vague and fuzzy. Everything could continuously collapse to one particular configuration - a ground state. However, physical systems in the real world admit discrete states - for example discrete bound states that are energy eigenstates.

Mechanisms to xerox bits of information

A DNA molecule carries a message - a piece of life that wants to spread. A necessary ingredient for life to spread is a procedure that can copy bits of information. Because of the quantum xerox no-go theorem, these bits must always be classical bits and the mechanisms must fit into the framework of classical physics. As you know, the DNA molecule is a double helix or a sequence of pairs of complementary bases. When it splits into the two strands, new bases absorbed from the environment replace the old members of the pairs and two copies of the original DNA appear. The mechanisms that copy bits in classical computers differ substantially but in both cases, copying of classical information is a must. The life before DNA - with RNA or protein folding only - was probably not able to lead to intelligent, complex life because of some rather general constraints but some experts in biology will correct me if I am wrong.

At any rate, the existence of these processes in biology and computation can be demonstrated in a simple non-relativistic quantum mechanical description of these systems. The presence of the relevant ingredients is a rather generic consequence of constraints from other sections of this article.

The reproduction of the information is guaranteed to be imperfect in the real world – and this imperfection and mutations are in fact necessary for the whole process of evolution to work. The technically difficult part of the physical processes is the task for Nature to make the processes reliable enough. Making them a bit unreliable is almost never a difficult problem.

Processes that depend on the information and evaluate it

Classical computers can behave according to a program encoded in the memory. In the same way, cells are able to produce proteins if they interpret the DNA. The protein production can be viewed as a translation from the binary discrete world of the DNA codes to a more continuous world of mechanics and macroscopic biology. Computers often come with analogous devices that can translate a binary code to a physical object embedded in the continuous world.

Framework for natural selection

These physical objects - proteins or pictures printed on your printer - then behave according to more general, continuous laws of physics. Different programs, DNA codes - or scientific theories, for that matter - fight for the room under the Sun. Their interaction with the real world and with each other acts as a method to evaluate the value of the original algorithms, memes, genes, or DNA codes - and the fittest statistically survive more often than the less fit ones. This mechanism leads to progress and the evolution of more viable life forms. In the context of scientific theories, "more viable" should really mean "more true" and it does if the scientific methods to evaluate ideas are "artifically" inserted instead of the fights between the animals and other life forms. Everyone should know how evolution works because of a combination of the key mechanisms above. Completely analogous mechanisms are at work when better ideas are being developed in science or better products, technologies or policies to regulate the society are being looked for by the humans.

Once again, the microscopic realization of the basic steps differs substantially if we study different systems that are able to improve themselves. However, some counterpart of these assumptions is needed in all cases.

Less general and more technical requirements:

The principle of relativity

Theories that are normally considered in the context of modern theoretical high-energy physics are relativistic theories: they respect the laws of special relativity. In perturbative string theory, short distance physics automatically respects the Lorentz invariance because nonlinear sigma-models, when expanded at very short distances, always resemble the Polyakov action in which the symmetry between all spacetime coordinates (scalar fields on the worldsheet) is manifest. Open strings can break the Lorentz symmetry spontaneously by introducing a non-commutativity. But at some fundamental level, the Lorentz symmetry still holds. And these conclusions are probably true non-perturbatively, too. I certainly think that string theory predicts that special relativity will be verified successfully with ever greater accuracy - except for phenomena that result from well-understood properties of the environment. String theory predicts that similar violations of well-motivated principles, violations that are predicted by not-so-consistent alternatives, will remain absent well beyond the level at which they have been verified as of today.

Is the principle of relativity necessary for life? I would tend to answer Yes, it is. Our planet is moving within the Solar system and the Solar system is moving within the Milky Way. Our Galaxy is in motion with respect to the cosmic microwave background, too. These nonzero velocities are more or less inevitable consequences of the violent history of our world that was necessary for the creation of life, too. We expect the "viability" of life structures that are selected by the natural selection to be independent of this motion at many different distance scales. Moreover, the life forms should still respect the rotational symmetry. I did not include the rotational symmetry among the essentials of life because we could hypothetically imagine a living world with a preferred direction even though it is helpful if animals can use the very same methods to move and look in all directions, but if the accurate enough rotational symmetry that remains relevant for the life forms is a condition, the previous argument shows that the principle of relativity should be another condition.

In the actual theories we use and believe, the rotational symmetry and the principle relativity are of course naturally unified in the Lorentz group. Because we are aware of no experimental evidence of a Lorentz violation, because such a violation does not seem necessary for life, and because it seems incompatible with the deepest description of the real world we have, namely string theory, I am among those who think that the Lorentz symmetry of local physics is probably an exact law of Nature. In our world, the principle of relativity is the relativistic one, with a finite speed of light; no, this sentence is not a tautology. It is certainly necessary for the life and cosmology as we know it but I don't know whether you could construct life in a non-relativistic world. At any rate, if you believe that special relativity and quantum mechanics from the beginning are conditions, it also means that the world should obey the rules of quantum field theory at long distances because quantum field theory follows from quantum mechanics and special relativity.

In combination with the requirement of gravity below, we can also deduce that string theory is needed for life even though we can’t yet offer a proof that every honest person with IQ above 100 would have to accept immediately.

The existence of fermions (and atoms)

The most obvious observation that makes fermions, particles that obey the Pauli exclusion principle, essential for life is the diversity of atoms. Chemistry as we know it is based on a table of elements with very different properties. Some of the qualitative properties are a quasiperiodic function of the atomic number. As you know, this is only possible because at most one electron can occupy a state with all quantum numbers fixed. The existence of fermions is probably important for other aspects of life, too. In the context of string theory, fermions are one of the reasons not to take bosonic string theory seriously. In other words, fermions force us to consider superstring theory that has other virtues such as the absence of bulk tachyons, a necessary condition for the perturbative stability of the vacuum. In the presence of fermions, supersymmetry is a natural extension of the well-established symmetries of spacetime. Some people feel certain that supersymmetry strictly below the Planck scale - and probably close to the electroweak scale - is an inevitable prediction of string theory for the real world. Others disagree.

The existence of a universally attractive force (gravity)

As mentioned previously, gravity has the ability to clump matter without violating the second law of thermodynamics that normally drives systems (such as gases) towards uniformity. It is related to the fact that gravity is universally attractive because it is sourced by a positively definite quantity, namely the mass. Forces with both signs such as electromagnetism tend to create neutral systems such as atoms. The leading force vanishes between neutral systems. This "neutral" outcome is even more obvious for confining forces such as the strong force because charged (colored) systems are completely unphysical and cannot appear in separation. It seems that a force similar to gravity must survive after the "neutralization" time scale if we still want planets that orbit around their stars at a fair distance. Needless to say, gravity in the very narrow sense - a spin 2 force that respects the diffeomorphism gauge symmetry at low energies - is an undeniable prediction of string theory.

The existence of a U(1) gauge field at low energies (electromagnetism)

It is a disputable technical feature of the real world. Nevertheless, life similar to the life we know requires at least one unbroken U(1) at low energies. Ions with both signs of their electric charge seem to be essential building blocks for many compounds and the key players in processes in chemistry and biochemistry. Electromagnetism controls virtually everything we know about life and technology and it is of course very hard to imagine a world without electromagnetism. Although I have no complete proof, my prejudice is that the world whose only force is the SU(3) Yang-Mills interaction of QCD could not produce intelligent life. One problem of such a world would be that animals could not see – photons and arbitrarily soft photons in particular are important to transfer information without paying huge amounts of energy.

The existence of hierarchies, the Born-Oppenheimer approximation, and many "nuclei" (strong force)

At the beginning, I mentioned the importance of large dimensionless numbers that allow the world to be large and complex. One of the minor examples was the proton-electron mass ratio that allows the motion of nuclei to be interpreted classically, as the Born-Oppenheimer approximation suggests. But do we need the nuclei at all? We have mentioned that different atoms were needed which required the Pauli exclusion principle. This principle controlled the electrons. But frankly speaking, electrons are not enough. You want the atoms to be neutral. There must exist something like the nuclei that can have many values of the charge. If we want to avoid the introduction of new special parameters for each nucleus, the structure of the nuclei should be governed by more fundamental microscopic laws of physics. The laws we know from our world are described by QCD and I am not able to imagine a working appealing theory that would allow many nuclei and atoms but avoided QCD-like physics. Again, I have no proof of a no-go theorem.

Summary

As you can see, many features of particle physics did not appear in the lists above. It is fair to say that I am not aware of any truly solid arguments that the existence of some life requires entities such as weak interactions, additional families of (heavy) quarks and leptons, CP-violation (except for baryogenesis or leptogenesis), a small CP-angle, and so forth. The apparent fact that some features are needed and some features are not is enough to convince yourself that the anthropic principle can't be the universal answer to all the questions that can't be answered at present. In other words, you have all the rights to say that the superficial successes of the principle in some cases are just coincidences.

The anthropic principle, much like this text, is a method to confirm that our world makes sense after all. But it is not a good framework for producing new predictions.

Saturday, July 22, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Rob Myers and Royal Society

The Royal Society of Canada has 10 people in physical sciences and Rob Myers is now one of them. Congratulations.

Friday, July 21, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Memorial conference in honor of Andrew Chamblin

There will be a memorial conference in honour of Andrew Chamblin in Cambridge on Saturday 14th October. It will consist of several talks by colleagues of his as well as discussion and reminiscences of Andrew and his life and work. The website with full details of the conference and online registration is:

All colleagues and friends of Andrew's as well as others in the field interested in his work and related topics are very welcome to attend and should register their planned attendance online via the website.

Via Jo.

Feminist totalitarianism: part 387

JoAnne Hewett is transforming herself into a typical representative of the feminist totalitarian ideology. In her article, she also offers four items to "remedy the systemic bias".

  1. Enhance leadership diversity in academic and scientific institutions.
  2. Recognize the importance of role models and increase the diversity of faculties
  3. Take the responsibility to speak out against discrimination.
  4. Boost the self-confidence of girls.

That can be translated into a more honest language:

  1. Further cripple the intellectual diversity of the Academia and make the life for those who are irritated by dumb feminist speeches and articles such as JoAnne's article really unbearable. Fire as many male officials as possible, especially male officials who don't accept feminism.
  2. Eliminate the remaining independence of thinking in the Academia and educate a new generation of scholars who will be just parroting other scholars, especially older female scholars - the “role models”.
  3. Proliferate lies about discrimination that has been working against men at least for 30 years, and criminalize all those who realize that the hypotheses about remaining substantial discrimination against women are malicious lies. Only one kind of comments may be allowed.
  4. Further cripple the self-confidence of boys and more generally the self-confidence of all those who would normally matter in scholarship, and make radical feminists who prefer their political agenda over science even more vocal and more obnoxious.

I think that all of these items are outrageous and the ideology behind them is irrational and hyenic. In a recent incident, the president of Harvard University was forced to resign primarily by the defenders of the feminist ideology above and closely related ideologies. So far, Harvard has lost about $390 million in donations although the moral and intellectual consequences are far more serious.

People like JoAnne Hewett have been effectively controlling the Academia at least for 30 years and their power goes far enough so that they can indirectly fire a famous university president for saying inconvenient comments behind the closed door. But they still have the stomach to paint themselves as victims.

Clearly, firing presidents and wasting of hundreds of millions of dollars on programs to discriminate against boys is not enough for them. What can be done to really satisfy them? Maybe those who think that the ideology about the equal aptitudes of men and women is crap should be sent to gas chambers? Perhaps those who don't want to codify 50% quota for women should join them, too?

It's a rather solid result of neurobiology and other fields - disciplines that Hewett and others would immediately ban if they could - that both the anatomy as well as physiology of female and male brains differ substantially and these differences are magnified if extreme abilities of certain sorts are required. These differences can be observed by a rich variety of methods and they can also be theoretically justified in the framework of evolution.

Women in average are very good and perhaps better with emotions, language, and two-dimensional organization of items. Men are better in three-dimensional visualization and math and engineering skills, among other things. Moreover, men have a measurably higher variance of a diverse list of quantities. The average IQ, the average number of children, and so on are all quantities that are more fluctuating in men than in women. The higher variance implies that it is easier to find more extreme men than more extreme women, regardless of the exact quantity that defines the extremality.

These facts combine in such a way that it can be predicted that for example, the number of male winners of the Fields medal exceeds the number of female winners roughly by two orders of magnitude.

JoAnne Hewett enumerates 21 female physicists who are automatically heroes because they are still discriminated against, she argues. If I wrote so many untrue assertions, I could not sleep. JoAnne Hewett has clearly no problems with her conscience.

Imagine that we would be talking about the rightwingers in physics rather than women in physics. I could not enumerate 21 rightwingers even though their proportion would "normally" be expected to be 50%, just like for women and there have existed societies in which the percentage exceeded 50 percent (unlike the case of women). Most optimistically, I could mention 2 or 3 people who are rightwingers according to some rumors or very private communication but I would not have the courage to write their names here because these guys care about their careers which makes it necessary for them to hide their political opinions.

Is there a woman who has to hide that she is a woman in order to do physics?

The political diversity is where the real discrimination lies, and people who continue to argue that women are systematically discriminated against in the Academia are not telling you the truth. On the contrary. I could also inform you about several stories how the positive discrimination works in a plethora of various committees in which I have served. It has become a substantial bias and I already know names of boys - including a gold medalist from the International Physics Olympiad - for whom the positive discrimination became an ordinary discrimination.

It's completely clear that men are already discriminated against in physical sciences. We could perhaps justify such an approach because of some social reasons unrelated to science itself. If I were justifying such policies, the first justification would be to assure that both the girls as well as the boys in physics are surrounded by some girls because it may be a psychologically healthier environment. However, no one can justify lies about the actual situation. Lies can never be expected to lead to good results.

The Jews were also painted as a group discriminating against others - or spoiling the life of others - in Germany of the 1930s, much like the capitalists were those who were painted as universally discriminating against the workers in the Eastern Europe after the Second World War. We know where these ideologies have led, and I don't see any truly qualitative differences between the three examples. In all cases, we face ideologies that reject reality as we observe it and that want to replace it by a conspiratory theory whose political goal is to substantially alter the natural structure of the society.

Thursday, July 20, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Evaluating extreme approaches to the theory of everything

One of the general strategies of some thinkers in theoretical physics is based on attempts to heavily extend the relevance of an existing concept or method. The hope is that all other difficult concepts become unnecessary or they will follow from a single, generalized and stretched idea. So one takes an existing procedure or a concept - a conceivably deep idea - and hopes that a more beautiful and a more powerful version of it will define and describe the whole Universe or all of string theory (or at least a much larger body of knowledge).

I will treat the "whole Universe" and "all of string theory" as synonyma because I am not aware of any controllable framework that would allow me to separate them sharply. Nevertheless, it is obvious that some of the ideas below will depend on our available knowledge of string theory more vitally than others.

One thing is clear: the principles below have almost nothing to do with the actual current research in string theory or the main ideas that drive the current research. Instead, the principles are possible speculations of string theorists as well as non-string theorists for the future. A certain Manhattan blogger has misunderstood this very basic point. It will be very difficult for him to correct his article because the critical error already appears in the title of his article. Well, the title of his blog is based on a profound ignorance, too, so it is difficult for him to write something reasonable on his whole blog.

Wednesday, July 19, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Congress on global warming

A committee of the U.S. Congress - or its Whitfield subcommittee - debates the paleoclimate reconstructions online. You can see this

Edward Wegman - who voted for Al Gore in 2000 - has deconstructed the "hockey stick graph". He and others have shown why the hockey stick shape is a result of a decentering error and disappears as soon as the error is fixed. He also says that the rest of the paleoclimate community is not independent of Michael Mann who has had 43 co-authors.

Michael Mann does not find the U.S. Congress too important, and he has sent a lawyer instead.

Meanwhile, the Democrats have mostly given up Michael Mann, agreeing that his kind of science is crap, and try to argue that there exists other evidence of anthropogenic global warming although it is not 100% clear to your humble correspondent what this other evidence is supposed to be. Crowley tries to confirm the Democrats' viewpoint with boreholes etc.

Some of the Gentlemen are rather impressive guys - Wegman, North, Carl, Crowley, von Storch, and McIntyre is the full list. Hans von Storch, the former chairman of the German Society of Donald Duck, got pretty lively, and you can already see his testimony.

An extensive discussion about this program can be followed at ClimateAudit.

Prof Schwinger repairs Hewlett-Packard laptops

This text is not important but it is somewhat entertaining.

The Brazilian server Fórum PCs has an interesting article that describes an omnipresent laptop keyboard timebomb of Hewlett-Packard notebooks (English translation). The punch line of the article is a "magic URL" to a very efficient guide written by Prof. Schwinger of Harvard University that tells you what is the reason of the problem and how to fix it.

Adrenaline sports

Have you ever attended a rope center, such as one in Dolní Polžice (gallery)? It's been slightly nontrivial but we have finished it. Polžice is the village where the enlightened and famous Czech 17th century aristocrat, Kryštof Harant z Polžic a Bezdružic, was born. The literal ;-) English translation of his name is

  • Christopher the Bastard from After Spoons and Without Satellites

A rope center consumes more energy than a bungee-jump that we tried a couple of years ago.

Tuesday, July 18, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Solar forcing

One of the most obvious phenomena that are important for determining the climate on the Earth is the solar activity. The Sun is important because we receive 99.998% of energy from this rather well-known star (the rest are mostly geothermal heat sources). Recall from the text

how those averaged 342 Watts per squared meter (one quarter of 1370 W/m^2, the solar constant) coming from the Sun are absorbed and/or reflected.

If the solar constant changes, the equilibrium temperature of the Earth changes, too. You can use the Stefan-Boltzmann law to have a rough idea about the effect. Because the heat (power) emitted by the Earth goes like

  • IR emission = const T^4

where T is the temperature in Kelvins, you can see that each change of the temperature by 0.2% (around 0.6 Kelvins because we live in nearly 300 Kelvins) requires a 0.8% change of the solar constant because of the fourth power; this relation is the black body value of temperature sensitivity. 0.8 percent from 342 W/m^2 is about 3 W/m^2, way too much. In fact, we should count these 0.8 percent from the actual IR emission only, which is about 2/3 of those 342 W/m^2, more precisely 235 W/m^2. Still, you might need a change of 2 W/m^2 or so to explain the warming by 0.6 Kelvins during the 20th century.

Bush uncensored

Noam Chomsky has recently visited the Hezbollah headquarters and offered his wholehearted support. Fortunately, Israel had a better idea what to do with these headquarters - bomb them.

Yesterday, George Bush's private comments to Tony Blair were recorded. Suddenly, you can hear Bush without the hypocricy imposed by political planning and by the pressure of various politically "correct" people.

Bush suggested that Kofi Annan is a naive guy who thinks that ceasefire is everything you need in the conflict between Israel and Hezbollah. Instead, Bush said that the U.N. should force Syria to prevent Hezbollah from doing this shit [sic].

Neither Israel nor the state of Lebanon are responsible for the current conflict.

It turned out that Condi Rice is planning a mission to the Middle East. Also, many other politicians except for Bush are talking about nothing for too long, Bush thinks and your humble correspondent certainly agrees.

Monday, July 17, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Harvard loses $265 million

The losses of Harvard University related to the forced resignation of Lawrence Summers climbed to 265 million USD or, according to the Wall Street Journal, to 390 million USD. The former donors - Ellison, Rockefeller, Zuckerman, Smith - are all Summers' supporters.

Now it's up to the feminists and their allies to pay quarter a billion of dollars, the cost of their experiments so far. If there are 200 of them, each of them can pay 2 million dollars to partially clear their conscience. Meanwhile, Harvard evacuates students from Lebanon to Syria because of the war between Hezbollah and Israel.

Life expectancy increases with age

Daniel Jafferis has pointed out an extraordinary discovery of the social scientists:

that was described in the Harvard Gazette. In other words, the social scientists have found a strong circumstantial evidence for the statement that

  • if you're Y years old, then you're unlikely to die at the age of X years if X is smaller than Y
For example, if you're 75 years old, it is likely that your life expectancy won't be 60 years. Isn't it amazing? Who could have thought? It's almost as ingenious as loop quantum gravity, especially if you realize how much money both of these things swallow.

Saturday, July 15, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

New official confirmation of McKitrick & McIntyre

Even though many people like to say that 1998 was the warmest year in the millenium, the underlying statistical treatment by Mann et al. - also known as the hockey stick graph - has been discredited by more recent investigations.

The recent report of the NAS panel could not confirm the millenial assertion of Mann, Bradley, and Hughes, citing high levels of uncertainty. Moreover, the House Energy and Commerce Committee made three researchers, Edward Wegman (a rather well-known statistician), David Scott, and Yasmin Said, to look at the hockey stick graph again. In a report that was just released, the criticism by McKitrick and McIntyre was confirmed. Mann's method is selectively mining for hockey sticks.

Sources:

The U.S. House committee has found that the sharing of research material, data, and results were haphazardly and grudgingly done. The players relied on peer-review too much even though it was not independent. The statisticians have studied the social network - the collaboration graph - of the extended hockey team in detail and showed that virtually all of the "independent" peer-reviewers are Michael Mann's direct co-authors, while some "cliques" are completely disconnected.

Friday, July 14, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Peter Svrček: quintessence with small vacuum energy

Peter Svrček proposes to explain the cosmological constant as

He is thinking about a compactification of M-theory on G2-holonomy manifolds and/or various type II string theories with a large number of axions. The potential for these axions is generated from D-brane instantons, and if the action of the instanton is around 210-290, Peter argues that you obtain more or less the observed value of the cosmological constant.

Yes, the number is the exponent from Polchinski's new favorite form of the cosmological constant written as a multiple of "M_{Planck}^4".

As far as I understand, Peter still does not explain why the remaining contributions to the vacuum energy cancel, but if they cancel, he could eliminate one of the "new cosmological constant problems" that appeared when a nonzero value was measured.

Thursday, July 13, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

LHC: Lords of the ring

The Seed magazine is one of the world's epicenters of the soft scientific jelly - science and culture, science is culture, all of us are interested in the same things, there is just a small continuous difference between a guy from the street and Juan Maldacena, blah blah blah as N.A.-H. would say :-) - but it may be fun anyway to link to their movie about the LHC collider:

The movie is in Apple's MOV format. If you don't want to install their QuickTime player just because of this video, it may be better for you to install

Basayev: death was not enough

Mark Trodden at Cosmic Variance celebrates that the BBC conjectured that the terrorists and their buddies at Guantanamo Bay will enjoy increased luxury in their lives. As you can imagine, your humble correspondent celebrates very different things, and in some sense the very opposite things than Mark Trodden does.

Ladies and Gentlemen, most of you have probably heard that Shamil Basayev is dead. The Russian president correctly says that death is not enough for such a monster. Well, Basayev is responsible for hundreds of deaths - 300+ people in the school at Beslan, the Moscow theater siege etc. - which are thousands of times more valuable than his life.

There are other reasons to be happy that this Islamic terrorist has joined his buddy al-Zarqawi. Basayev thought that Osama bin Laden had to be a great person because his face always emits light on all photographs. Moreover, Basayev was obsessed with the very same human garbage as some of our liberal friends - namely with the communist terrorist Che Guevara. ;-)

We may be cautious about Russia in many subtle cases and we can also sympathize with many nations whose independence was suppressed by the Russian bear, but in this particular case, all good people should admit that the Chechen Islamic terrorism affecting Russia is completely analogous to the Islamic fundamentalist terrorism directed against America and other Western countries. Basayev's death is not a sufficient punishment but it is still a good news.

I wonder whether the explosion was a result of a good work of the Russian intelligence forces or whether it was a genuine accident. It is likely that we won't ever learn the answer, and if we learn it, it will not necessarily be the correct answer because of the intense propaganda war in the background.

Wednesday, July 12, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Dualities and equivalences

Most of the misunderstandings of physics and myths have a characteristic left-wing flavor. The following flawed concepts can often be identified as the primary obstacles that prevent many people from comprehending certain important ideas in theoretical physics:

  • social arguments used to find the answers to scientific questions
  • egalitarianism of theories, ideas, or even numbers

The first error appears whenever someone tries to guess a correct answer to a physical question according to various social features of the proponents of the different answers - which is a typical approach of postmodern social scientists. In the 1930s, some German physicists would discard a physical theory because its discoverer was Jewish. Most of us are no longer doing the same mistake but many of us are doing similar mistakes. Some people think that only famous or highly-paid people can be right. Other people think, on the contrary, that it is only the outsiders who should be correct and those who have been believed to be right so far must have been cheating. A third, "neutral" group of people believes that all people talking about physics should be right equally frequently. Then there are people who believe that only tough physicists may be right, and other people who believe that only polished or sissy liberals can be right. Needless to say, all these and similar ideas are scientifically absurd. Correct scientific ideas can indeed emerge in all environments. They are more likely to occur in some environments but one can never use the environment as a universal criterion because the probabilities that the right ideas occur in all environments are nonzero. All these arguments are unscientific.

The second error is based on egalitarianism of ideas, theories, formulae, or numbers. This error can also be described as the celebration of ignorance. Imagine that a schoolkid is asked what is Ohm's law. The kid answers "U=RI" or "U=R/I" or "U=I/R" or "U=1/IR", and perhaps also "U=R+I". The teacher won't be too satisfied and the kid won't have the opportunity to become terribly proud about her ignorance.

However, there are cases in which there is no teacher with the desired authority around. Our colleague from Santa Barbara argued that because we have not seen an evaporating black hole yet, all real positive numbers are equally good candidates for the entropy/area ratio. One quarter is just one possibility among infinitely many - just like ln(3)/sqrt(2)pi. Well, it is just one possibility among infinitely many from the viewpoint of a person who does not know how the semiclassical calculations are performed. More than 30 years ago, these calculations have shown that the correct constant is certainly one quarter, and independent microscopic calculations in string theory always confirmed this number. There is no doubt that "S=A/4" for macroscopic black holes. You can guess that once the colleague from Santa Barbara writes that she is a wiser, brighter, more tolerant, more cultural, broader, or a better human being because she considers all numbers to be as good as "1/4", my blood starts to boil. I just can't stand this behavior. If someone is ignorant about something and she admits it, it's OK. But if someone starts to paint her ignorance as a virtue or even the essence of humanity, it becomes a small disaster.

Similar egalitarian myths lead many other people to believe that the probabilities that string theory and loop quantum gravity are correct must be comparable. Fifty percent of people should be working on each, and so forth. Some people just can't understand reality. The fact that the probability that string theory is correct exceeds the analogous probability for loop quantum gravity by dozens of orders of magnitude is something "unfair" for them, and they just don't want to accept such a fact because it does not agree with their egalitarian sentiments. It's just like the "unfair" fact that Bill Gates is richer than others.

It is thus refreshing to see anti-egalitarian myths in action. At last, one can see some diversity here. ;-) The myth I will be talking about below is the misunderstanding of the meaning of "dualities" and "equivalences" in physics. The particular discussion that led me to write this text was about the gravity dual of the phenomena at RHIC - i.e. the gravity dual of QCD. Because this particular gravity dual is not exactly uniquely and exactly known, let me talk about a similar theory where the gravity dual is known perfectly: the N=4 gauge theory in 4 spacetime dimensions that is dual to type IIB string theory on the product of a five-dimensional anti de Sitter space and a five-dimensional sphere of the same radius. If the program to search for the gravity dual of QCD succeeds perfectly, the situations will be perfectly analogous. Consequently, we can talk about N=4 gauge theory without a loss of generality.

An anonymous reader suggested - and interpreted a comment by Prof. Mark Srednicki - that the dual gravity calculations in AdS/CFT are just mathematical tricks, but the "real" physics is still physics of gauge theory. He or she proposed an "analogous" example with a pendulum and an electrical circuit. The fact that they follow the same equations does not mean that we can say that an electrical circuit is a pendulum. Fair enough.

But the situation in AdS/CFT or any other duality in string theory is very different. In the case of the pendulum, we can find many other physical features that distinguish it from the electrical circuit. A pendulum should have a certain design, people with common sense would say. A more sophisticated way to distinguish a pendulum from an electrical circuit is based on the fact that the pendulum oscillates because of gravity, and the oscillations thus emit gravity waves made of gravitons whose spin is two, which you can measure in principle, while the circuits emit electromagnetic waves, streams of spin one photons. At any rate, there are other details that distinguish the two cases, and the two systems only share the rough differential equations. We have tools to say: this is a pendulum, not an electrical circuit.

But in the AdS/CFT correspondence, there are no other details that could tell you whether your world follows physics of gravity or physics of the conformal theory. Any phenomenon on one side has an equivalent description on the other side. It makes no sense to ask which of the two descriptions is correct if they are fully mathematically equivalent. It is equally meaningless as asking whether the German or French translation of the European constitution is correct. (In the latter case, both of them are wrong, of course.) It is equally meaningless as asking whether the Schrodinger picture or the Heisenberg picture is correct. These frameworks use slightly different concepts or intermediate equations, but they lead to exactly identical predictions of those physical observables that can actually be measured.

If such an equivalence is obvious, we would not spend hours with it; we would say that the "two" things are simply one thing. Equivalences in modern theoretical physics are only interesting because they're not so obvious. We like to use the word "duality" because the two descriptions of the same physics originally look like two different theories. Obvious examples include strong-weak S-dualities, large-small T-dualities of compactifications, large-weak-strong-small U-dualities mixing many parameters, and especially the gauge-gravity and AdS/CFT holographic dualities relating a gravitational theory with a non-gravitational theory defined on the boundary of the gravitational spacetime.

In each case, it is simply meaningless to ask which of the two descriptions is correct and which of them is just a trick. If they're exactly equivalent - giving exactly the same predictions for physically measurable quantities such as cross sections - they are equally correct. Because they're equivalent, it means that if one of them is a relevant set of laws for XY phenomena, the second of them is relevant, too. If one of them is irrelevant, the other is also irrelevant. If one of them is valuable, the other must also be valuable. And so on, and so on.

One of the descriptions might be more useful in one context or another, but usefulness and the truth are different things. For a theoretical physicist, they are very different things.

In the particular case of the gravity dual of QCD, it is indeed important to note that the gravity dual is not just a "trick" but the "real" theory of the phenomena in different variables. If you are optimistic and imagine that our colleagues will find an exact gravity dual of the Standard Model, such a geometry will literally be a part of the geometry that is relevant for the real world in string theory. Because the Standard Model is not valid at arbitrarily high energies, the geometry dual to the Standard Model will have to be cut and modified to obtain the geometry describing everything - it will have to be glued to a smooth Calabi-Yau manifold, to mention the most typical example, that will be responsible for the physics at the Planck scale.

At any rate, if the program is fully quantitatively successful, one will obtain a background that carefully follows the rules of string theory. By string theory, I mean the same theory that other string theorists study, with the same strings, branes, black holes, low-energy fields, their interactions, transitions, moduli spaces, and everything else. The same string theory that is most likely the correct description of everything in the real world including the ordinary gravity in four nearly flat spacetime dimensions.

In the case of the gauge-gravity duality or any other exact duality in string theory, claiming that one side is true and the other is either wrong or just a "trick" is simply a misunderstanding of the meaning of the concept of dualities. Dual theories are exactly equivalent, no one has any right to discriminate against one of the dual descriptions, and when we talk about string theory, we always mean the same string theory that always contains quantum gravity, and always contains other forces and objects. The gravitational duals of gauge theories are backgrounds of string theory. String theory in this context or any other context is no trick but reality, and once we accept that the rules of string theory are relevant for some questions in physics - such as the dual description of gauge theories - the rest of string theory logically follows from the same rules. Within the established theoretical insights of string theory, there is no way how to build walls of political correctness within string theory that would separate things that can be done and that are valuable from those that aren't. Only people who misunderstand the internal structure of string theory - for example a certain controversial blogger at Manhattan - propose to build such walls.

And that's the memo.

Tuesday, July 11, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

RHIC: string-bashing beats child pornography

Imagine that it is 2006, you are a very big guy and a boring blogger who has nothing interesting or insightful to say. The only virtue of your blog is that it is one of the thousands of uninformative worthless and colorness negativistic far left-wing activist anti-Bush anti-capitalist anti-American anti-religious pseudoscience blogs - and you want to increase the traffic on your particular blog by 500 visits a day. Moreover, you have virtually no moral constraints and all principles you might have are uncertain principles. What do you do?

Monday, July 10, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Jacques Distler's patience

The discussion at Musings about

has been very long, and whoever is interested in this hypothetical alternative to string theory may want to read it.

Jacques Distler has originally asked a simple, well-defined question, but he can't get any answers although he has probably deduced the right answers from the non-answers anyway if he did not know them already before the discussion. ;-)

Hep-th papers on Monday

There are seven papers on hep-th on Monday.

Jarah Evslin and Hisham Sati focus on some subtle differences between K-theory and homology in defining charges of D-branes. Recall that homology used to be viewed as the right classification of the possible lattices of charges of D-branes, in agreement with the simple picture in which a D-brane wraps a submanifold. However, work based on tachyonic considerations of Ashoke Sen has led Edward Witten to argue that K-theory, a structure analogous to homology but based on gauge bundles, is a better more accurate description of the charges because it treats some torsion classes more carefully. The present authors study homology cycles of nice smooth manifolds that cannot be represented by a nonsingular submanifold. I suppose they mean a connected submanifold. For cycles that can be represented by submanifolds, the Freed-Witten anomaly must cancel for the cycle to be usable as a living room for a D-brane. K-theory, a huge hobby of Jarah Evslin, contains most cycles that homology does, but as the authors argue, some of them must be non-representable by submanifolds. Examples are provided.

Tamiaki Yoneya reviews the Penrose (BMN) limit of the AdS/CFT correspondence. It's really one talk so don't expect that he gets to things as complex as integrability or magnons.

Kazunobu Maruyoshi studies gauged N=2 supergravities with various U(1) and U(N) vector multiplets that he breaks spontaneously to N=1 supergravity. Although the resulting theory probably can't have chiral couplings and can't be semi-realistic (which makes it different from the usual mechanisms of supersymmetry breaking in phenomenology), and although the implementation into the big picture of string theory is not given, I must say that it is a very impressive master thesis.

Sunday, July 09, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Culture wars: hard vs. soft sciences

For a few decades, we could have observed symptoms of the culture wars between the scientifically minded scholars and people in general who think that their task is to search for the truth using the hard, scientific methods on one side - and humanity oriented academics and social scientists who think that the task for the Academia is to search for the "truth" by the easy, social methods, by consensus, and the main criterion of success and truth is whether they look nice according to other soft people.

Recently, the soft side has been vigorously attacking the hard side and the hard side does not seem to be defending itself anymore. The extremely soft segments forced Lawrence Summers, an eminent economist and an extraordinary university leader, to resign. There are many episodes behind the Summers controversy. However, the main lasting consequence of this story for the big picture is clear: the resignation was a significant victory of the soft side in the culture wars.

Friday, July 07, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

CO2 vs temperature: ice core correlation & lag

Abstract

The temperatures and carbon dioxide concentrations have been correlated - see e.g. Petit et al., Nature 1999 - but we know for sure that the temperature was the cause and the concentration was its consequence, not the other way around. This fact has also been explained in The Great Global Warming Swindle. It follows that the C0₂ greenhouse effect has not been important in the history and we shouldn't expect that it will become important in the future.

Special comment for Australian readers on Sep 28, 2007: just yesterday, there was a new paper in Science - Lowell et al., Science 2007 - that showed that CO₂ lagged by about 1,000 years when the last ice age started to end 18,000 years ago
The direction of the causal relationship can be shown in many ways: for example, it is not just CO₂ but other gases such as methane that follow temperature. The hypothesis of CO₂ as the primary reason wouldn't explain why these other gases are correlated, too. Also, we understand how oceans react to temperature changes by releasing gases. Finally, the gas concentrations lag behind the temperature by 800 years, see e.g. this 2003 paper in Science by Caillon et al.

Main text

The movie of the former future U.S. president - "An Inconvenient Truth" - has impressed many viewers: it is an optimized promotion of the alarmist understanding of the global climate. Moreover, it shows a more attractive Al Gore than the old Al Gore whom we know from the 2000 campaign.

A few years ago, Gore visited Harvard and with Jochen Brocks, my fellow Fellow, we went to see him. Jochen is a leftist, of course, but he claimed that Gore looked repulsive, unhuman, and evil. I am a rightist but paradoxically, I never had terribly serious complaints about Gore's looks.

Universities UK hate pure science and love politicized science

One can't certainly be swimming and relaxing the whole days.

The British socialist daily "The Guardian" has published what they think are the top 100 world-changing British scientific discoveries in the last 50 years.

Although there are many entries in this list that are good science (and technology and medicine), I think that the bulk of their list is another outrageous example of politicization of science, another example of misunderstanding of the truly important values and ideas, and another example of increasing influence and pressure of ignorant people who are not willing to think much on science.

Three sections out of nine are dedicated to health sciences. That may look too much to some but medicine is important, after all. However, there are much more serious problems with their list. Let me mention a couple of entries that I view as purely political ones and, from a scientific viewpoint, more or less worthless.

Most of the section 6 is a political dumping ground

  • someone "found" that poverty is behind learning difficulties ;-)
What sort of top 100 discovery is this one? It's complete BS. Everyone who has common sense has always known that wealth can speed up learning. For centuries, the rich families were the most educated ones. Everyone who has observed the real world knows that there are also other reasons behind the problems in learning, especially innate aptitudes but also things like family circumstances - in sharp contradiction with the "discovery" of Richard Morris Titmuss who claims that family circumstances can't play any role.

Thursday, July 06, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Czech hurricane



Figure 1: the eye of a Czech hurricane as seen on 6/29/2006

Kevin Vranes has nearly predicted that the global warming judgement day was coming to the Czech Republic. After a very cold May and a hot June, the Czech Republic had several days of rain last week. Right now, it is sunny again and I got a mild sunburn yesterday. No one in the Czech Republic has noticed the hurricane. The rains caused some floods at the upper portion of some rivers - a 60-year flood at one particular place - but there were no floods at the lower parts of the rivers, certainly not anything that could be compared for example to the floods in summer 2002.

Nonsupersymmetric black holes: entropy

For more than twenty years since the Bekenstein-Hawking calculations of black hole thermodynamics, people were unsuccessfully trying to find a microscopic description of the entropy. Strominger and Vafa succeeded in early 1996 and explained the entropy of a special BPS black hole composed of D1-, D5-branes, and momentum. That was a breakthrough. The result agreed including the numerical constant. It had to agree and their main task was to find an example where the agreement can be proved, and check it.

Meanwhile, people have calculated the entropy of many black holes with 3 or 4 types of charges that are supersymmetric (and therefore extremal). An agreement was always found. People have also checked near-extremal black holes, and the microscopic stringy result agreed with the macroscopic prediction in all cases. Near-extremal black holes are black holes that differ from the extremal supersymmetric ones by epsilon and their parameters are expanded up to the leading order in epsilon.

Black holes with up to seven parameters describing various types of charges and angular momentum have been successfully checked. If the black holes are extremal or near-extremal, there are rigorous arguments based on supersymmetry that the entropy had to match if the theory is consistent, and indeed, they do match.

The corrections to the entropy of various black holes have been calculated to all orders; the recent Ooguri-Strominger-Vafa formula plays an important role in this direction of thinking. The successfully checked examples include black holes with unusual topologies such as black rings. The dependence on the charges knows about the exceptional groups and we encounter interesting mathematical structures such as the hyperdeterminant. A lot of other links with interesting mathematical structures and modular functions occured in the heterotic case.

Wednesday, July 05, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Columbia University crackpot joins Mark McCutcheon

On this blog, we have extensively discussed ethically problematic acts of a crackpot named Mark McCutcheon who has written a 1-star book "The Final Theory" that denies, among many other things, the existence of gravity acting both on the celestial as well as terrestrial bodies.

Because all the amazon.com reviews appeared at some moment in the past, we know that Mark McCutcheon has erased - or forced amazon.com to erase - at least 222 reviews, mostly one-star reviews. They were just inconvenient for the author and his somewhat immoral profits. The remaining 100 or so reviews incorrectly indicate that McCutcheon's worthless 1-star book deserves 5 stars.

I was just told that a lecturer in discipline from Columbia University - and the owner of the world's most active physics crackpots' discussion forum - who has written a 2-star book that everyone knows has joined Mark McCutcheon and made amazon.co.uk erase all reviews of his book - for example my 2-star review - except the 5-star reviews written by idiots most of whom have not read the book - and neither of whom has any idea about the content of the book. This kind of fraud leads to the average rating of this 2-star book to be displayed as 5 stars. Also, several 5-star reviews that were not deleted have been edited by a third party.

The author has personally confirmed that he has contacted amazon.co.uk with his desire to remove the "inappropriate" reviews - and he is quite obviously proud about it.

I think that the lecturer in discipline - and amazon.co.uk - should be ashamed for this immoral, despicable behavior. The lesson for all of us is clear: those who don't and can't accept the standard rules of making progress in science always follow the same procedures. Crackpots not only share some common errors in their thinking and they also love to criticize the existing science by their nonsensical pseudoarguments but they can never stand criticism - or peer-review - themselves.

Monday, July 03, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Bad guys form Slovak government

Exactly as we predicted, the coalition agreement in Slovakia was just signed by the following three guys:

  • Robert Fico, a former communist and a leader of the left-wing populist party "Smer"
  • Ján Slota, on behalf of the far-right Slovak National Party
  • Vladimír Mečiar, the boss of HZDS (The Movement for Democratic Slovakia) and the former authoritarian prime minister

At www.sme.sk, visitors were asked what they think about the new government and 63% answered that they are thinking about emmigration. ;-) The figure probably should not be taken too serious but the sentiment should.

Saturday, July 01, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Summers era ended

Larry Ellison has just cancelled his $115 million gift to Harvard.

According to The Crimson, the official justification is exactly what The Reference Frame wrote some time ago:

  • “Larry Ellison had an agreement with Larry Summers. Larry Summers’ departure from Harvard has changed that agreement,” said Bob Wynne, a spokesman for Oracle.

It is not surprising that The Reference Frame finds this explanation rather meaningful: additional $115 million has been added to the total cost of the numerous shameful decisions of the feminists and their allies at Harvard. Political correctness is an expensive beast, indeed.