Let me summarize each of the 24 hepth papers that appeared last night.
Freed, Moore, and Segal argue that the electric and magnetic fluxes on a spacetime manifold can't be measured simultaneously because of a version of the uncertainty principle. That should not be unexpected. Only the electric potential or the magnetic potential may be chosen as a fundamental degree of freedom which makes their fluxes welldefined for a given configuration: the fluxes of the dual field are then undetermined.
Moreover, the authors argue that the uncertainty principle only applies to torsion classes. One of the implications is that the Ktheory class of the RamondRamond fields can't be physically measured. There also exists a less mathematically formal version of that paper even though I am a bit confused which of the two is addressed to the physicists. The insights have special consequences for selfdual form fields; they're connected with Pontrjagin dual groups.
Ben Craps offers the written version of his CERN lectures about bigbanglike singularities in string theory. He reviews the role of the winding modes, the Milne orbifold, attempts to use the AdS/CFT correspondence, and the matrix big bang.
Dasgupta, Grisaru, Gwyn, Katz, Knauf, and Tatar rederive the metric describing certain wrapped fivebranes (based on functions among which "cot" is the most complex one). Also, they write down certain new nonKähler geometries, and offer you a table that relates the nonKähler deformations of certain backgrounds to other effects related by dualities, something that Anke Knauf has shown us some time ago.
Washington Taylor has written a mostly nontechnical review of string field theory for a book. While it does not annoy the reader with too many formulae, it contains many references, including the references on newest developments, and may be viewed as a stateoftheart summary of the subject.
Donagi, Reinbacher, and Yau take one of the simplest CalabiYau manifolds, namely the quintic hypersurface, define heterotic string theory on them, but consider very general configurations of the gauge field (the bundle). Using similar diagrams that were important for the recent heterotic standard model papers, they derive things as complicated as the Yukawa couplings of these backgrounds.
Bambah, Mahajan, and Mukku propose the nonAbelian version of an unusual kind of unification that one of the authors proposed in the Abelian case. What unification do we mean? It is a unification of Maxwell's theory with fluid dynamics, speculated to be relevant for the quarkgluon plasma. Well, I personally see no unification in that paper. What I see is some theory that contains the YangMills field (previously Maxwell) together with an additional scalar field and a vector field, and they are coupled in some strange way. The Republican Party and the Democratic Party exist in the same country and interact, but that still does not make them unified. As you can see, it seems that the entertainment value of this paper exceeds most others (but not all of them, as you will see below).
Damiano Anselmi offers a proof (?) that general relativity is a renormalizable theory, if defined as "acausal gravity". The first sentences of the body of the paper indicate that the acausality is far from being the worst thing in this proposal: the first sentence argues that "the necessity to quantize gravity is a debatable issue". Because it seems likely that these initial sentences play an important role and because I personally consider a nonquantized gravity within the quantum world to be an obvious inconsistency, I can't recommend you to read the full paper.
Svrček and Witten study the axion decay constant "F" in various scenarios in string theory, including Mtheory on G2 manifolds, intersecting braneworlds, heterotic Mtheory, and others. Recall that the axions are useful to explain the strong CPproblem i.e. the smallness of the QCD thetaangle that couples to the instanton number. Also, the axions could be relevant to describe various potentially exciting recent experiments. However, astrophysical bounds tell you that the axions that couple to visible matter should not be too heavy. They should be lighter than the GUT scale or so. The authors find that this is naturally achieved only if the visible matter lives on shrunk cycles.
Buividovich and Kuvshinov investigate gauge theories  such as QCD  using the method of the random walk. Define the open Wilson line from a given point in spacetime to the point "(t,0,0,0)". You will get a point in the gauge group manifold, and you may ask what is the probability distribution to obtain a certain particular element of the group. The heat kernel equation on the group manifold becomes relevant.
W.F. Kao starts by saying that recently there is a growing interest in the KantowskiSachs (KS) universe  a term that I've never heard of  based on some purely higherderivative gravity (?). While the phrase "pure higherderivative gravity" may sound insulting, it does not seem to play much role in the paper. On the other hand, the KS universe seems to be nothing else than the FRW universe with an extra dependence on the coordinate "theta", making it anisotropic. The growing interest in this geometry is proved by three papers from 1999, 2003, 2004. This KS Universe is supposed to be relevant for inflation. Because I don't know where to put this paper in my understanding of the world, I can't tell you more.
Laamara, Drissi, and Saidi want to relate topological string theory on the conifold with the fractional quantum hall effect (FQHE). Well, there are already quite many things that are claimed to be equivalent to topological string theory on the conifold. The links between FQHE and fluids of Dbranes (with their characteristic noncommutativity) were investigated by Susskind, Hellerman, Polychronakos, and others years ago, but the conifold seems to be a novelty introduced by the present authors.
Justin David and Ashoke Sen prove the formula for the generating function for the degeneracies of dyons of the CHL string  the kind of formulae that Davide Gaiotto knows very well. They map the system to the D1D5 system and use, among other tools, various properties of the modular functions.
Delduc and Ivanov explain the origin of some dualities in supersymmetric quantum mechanics. They're dualities between theories with the same number of fermions and different numbers of bosons. The equivalence is shown by gauging additional superfields.
Gherghetta and Giedt realize the RandallSundrum models in terms of type IIB string theory on "AdS5 times T11" where "T11" is the base of the conifold, equipped with probe D7branes. The tip is governed by the KlebanovStrassler theory; the following region by the KlebanovWitten regime; and the rest is connected to a compact CalabiYau manifold. The additional D7branes provide you with bulk gauge fields  something very popular among the RS phenomenologists. They also claim to have some purely stringy natural predictions for physics of these models but I have not found what they are.
R.P. Malik studies QED using the BRST formalism written in terms of superfields. Not only that I have never heard of the "horizontality condition", but the BRST formalism itself seems like an overkill to me if it is applied to QED, especially in this BRST superfield formalism.
Lee and Yee construct new 7manifolds "X" that can be multiplied by "AdS4" to give you new solutions of Mtheory. These sevendimensional manifolds  in fact, "triSasakian" manifolds  are obtained from twelverealdimensional hyperKähler manifolds. Four dimensions are lost by a method I have not understood, and the last fifth dimension disappears by quotienting by a U(1). They also say something about the dual CFT3 theory, for example things that follow from their calculated volume of the sevenmanifold.
Neznamov only offers a PDF file with a few pages that only seem to contain some trivial  but not necessarily correct  manipulation with the Dirac gamma matrices. His following PDF paper is a bit longer but even more entertaining. He argues that the Standard Model fermions may be massive even without Yukawa couplings by generalizing  more precisely, by screwing  the covariant derivative. Neznamov's covariant derivative has the standard timecomponent, but the spatial component has an extra term "inverse nabla times squared mass". Lorentz invariance, unitarity, gauge invariance, mathematics, and common sense must be sacrificed for more noble goals.
Hortacsu and Taskin provide more than the PDF file. They argue that in some model, a composite spin 1 particle must interact although the spin 1/2 partons don't interact. I am not sure what they exactly claim and why but it sounds like an attempt to violate the WeinbergWitten theorem  although the latter is not even cited.
Janos Polonyi wants to study the emergence of the classical limit in QED. Well, yes, I don't quite follow what is the open question that is being answered. At any rate, to answer "this" question, the author defines some kind of generalized density matrix, to make the quantum theory look more classical. Because I don't believe that anything from the quantum character of quantum field theory has to be sacrificed to understand the classical limit properly, I doubt that one can learn something new and true from that paper.
Edward Shuryak discusses AdS/QCD. He claims that he was the first discoverer of the statement that confinement in the field theory should be described as an explicitly added potential in the AdS bulk that depends on the holographic dimension and increases as you go away from the UV. This picture, recently promoted by Karch et al., is certainly a natural and qualitatively correct dual parameterization of the same effect except that I don't know how this follows from string theory, which makes it hard to imagine that a new precise understanding of physics of confinement.
Berenstein and Cotta look at "emergent geometry" within the AdS/CFT context. It is an orbifold of a previous paper by David Berenstein. David's conceptually intriguing goal is to construct the bulk geometry from certain partons  particles that live on the moduli space of D3branes in flat space  that can be identified within the gauge theory. These partons effectively repel each other which makes them arrange themselves into the right geometry, assuming that you believe the statistical mechanical kind of reasoning. It is a sort of cute heuristic description of the origin of the compact part of the geometry. It would be even more interesting if one could derive something about the moduli space of possible geometries from this starting point.
Mintz, Farina, Maia Neto, and Rodrigues look at particle production (controlled by the Bogoliubov coefficients) of bosons in a 1+1dimensional theory with a boundary where the boundary conditions interpolate between the Neumann ones and the Dirichlet ones.
Tuesday, May 23, 2006 ... //
Hepth papers on Tuesday
Vystavil
Luboš Motl
v
1:51 PM



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