http://arxiv.org/ High Energy Physics - Theory (hep-th) updates on the arXiv.org e-print archive en-us 2010-02-08T20:30:00-05:00 www-admin@arxiv.org High Energy Physics - Theory 1901-01-01T00:00+00:00 1 daily http://arxiv.org/icons/sfx.gif http://arxiv.org/ http://arxiv.org/abs/1002.1659 <p>In this paper we address the issue of the Gribov copies in SU(N), N&gt;2, Euclidean Yang-Mills theories quantized in the maximal Abelian gauge. A few properties of the Gribov region in this gauge are established. Similarly to the case of SU(2), the Gribov region turns out to be convex, bounded along the off-diagonals directions in field space, and unbounded along the diagonal ones. The implementation of the restriction to the Gribov region in the functional integral is discussed through the introduction of the horizon function, whose construction will be outlined in detail. The influence of this restriction on the behavior of the gluon and ghost propagators of the theory is also investigated together with a set of dimension two condensates. </p> M. A. L. Capri, A. J. Gomez, M. S. Guimaraes, V. E. R. Lemes, S. P. Sorella http://arxiv.org/abs/1002.1358 <p>Using Noether's procedure we directly construct a complete cubic selfinteraction for the case of spin s=4 in a flat background and discuss the cubic selfinteraction for general spin s with s derivatives in the same background. The leading term of the latter interaction together with the leading gauge transformation of first field order are presented. </p> Ruben Manvelyan, Karapet Mkrtchyan, Werner Ruehl http://arxiv.org/abs/1002.1349 <p>We use the Kerr/CFT correspondence to calculate the entropy for all known extremal stationary and axisymmetric black holes. This is done with the help of two ansatzs that are general enough to cover all such known solutions. Considering only the contribution from the Einstein-Hilbert action to the central charge(s), we find that the entropy obtained by using Cardy's formula exactly matches with the Bekenstein-Hawking entropy. </p> Jianwei Mei http://arxiv.org/abs/1002.1362 <p>We propose a new type of interaction of closed superstrings with the electromagnetic field, other than the usual Kaluza-Klein type or a gauge field with internal gauge group origin. This model with a constant magnetic field is also shown to have an exact solution. We consider a regularization criterion. Some models will be excluded according to this criterion. The spectrum-generating algebra is also constructed in our interacting model. </p> Akira Kokado, Gaku Konisi, Takesi Saito http://arxiv.org/abs/1002.1373 <p>We develop the off-shell nilpotent finite field dependent BRST transformations and show that for different choices of the finite field dependent parameter these connect the generating functionals corresponding to different effective theories. We also construct both on-shell and off-shell finite field dependent anti-BRST tranformations for Yang Mills theories and show that these transformations play the similar role in connecting different generating functionals of different effective theories. Analogous to the finite field dependent BRST transformations, the non-trivial Jacobians of the path integral measure which arise due to the finite field dependent anti-BRST transformations are responsible for the new results. We consider several explicit examples in each case to demonstrate the results. </p> Sudhaker Upadhyay, Sumit Kumar Rai, Bhabani Prasad Mandal (BHU) http://arxiv.org/abs/1002.1391 <p>The vacuum expectation value of the fermionic current is evaluated for a massive spinor field in spacetimes with an arbitrary number of toroidally compactified spatial dimensions in presence of a constant gauge field. By using the Abel-Plana type summation formula and the zeta function technique we present the fermionic current in two different forms. Non-trivial topology of the background spacetime leads to the Aharonov-Bohm effect on the fermionic current induced by the gauge field. The current is a periodic function of the magnetic flux with the period equal to the flux quantum. In the absence of the gauge field it vanishes for special cases of untwisted and twisted fields. Applications of the general formulae to Kaluz-Klein type models and to cylindrical and toroidal carbon nanotubes are given. In the absence of magnetic flux the total fermionic current in carbon nanotubes vanishes, due to the cancellation of contributions from two different sublattices of the graphene hexagonal lattice. </p> S. Bellucci, A. A. Saharian, V. M. Bardeghyan http://arxiv.org/abs/1002.1651 <p>It is argued that selection criteria usually referred to as "anthropic conditions" for the existence of intelligent (typical) observers widely adopted in cosmology amount only to preconditions for primitive life. The existence of life does not imply in the existence of intelligent life. On the contrary, the transition from single-celled to complex, multi-cellular organisms is far from trivial, requiring stringent additional conditions on planetary platforms. An attempt is made to disentangle the necessary steps leading from a selection of universes out of a hypothetical multiverse to the existence of life and of complex life. It is suggested that what is currently called the "anthropic principle" should instead be named the "prebiotic principle." </p> Marcelo Gleiser http://arxiv.org/abs/1002.1649 <p>The infrared behaviour of the n-point functions of a Yang-Mills theory with a charged scalar field in the fundamental representation of SU(N) is studied in the formalism of Dyson-Schwinger equations. Assuming a stable skeleton expansion solutions in form of power laws for the Green functions are obtained. For a massless scalar field the uniform limit is sufficient to describe the infrared scaling behaviour of vertices. Not taking into account a possible Higgs-phase it turns out that kinematic singularities play an important role for the scaling solutions of massive scalars. On a qualitative level scalar Yang-Mills theory yields similar scaling solutions as recently obtained for QCD. </p> Leonard Fister http://arxiv.org/abs/1002.1634 <p>We show that correlators of the hermitian one-Matrix model with a general potential can be mapped to the counting of certain triples of permutations and hence to counting of holomorphic maps from world-sheet to sphere target with three branch points on the target. This allows the use of old matrix model results to derive new explicit formulae for a class of Hurwitz numbers. Holomorphic maps with three branch points are related, by Belyi's theorem, to curves and maps defined over algebraic numbers $\bmQ$. This shows that the string theory dual of the one-matrix model at generic couplings has worldsheets defined over the algebraic numbers and a target space $ \mP^1 (\bmQ)$. The absolute Galois group $ Gal (\bmQ / \mQ) $ acts on the Feynman diagrams of the 1-matrix model, which are related to Grothendieck's Dessins d'Enfants. Correlators of multi-matrix models are mapped to the counting of triples of permutations subject to equivalences defined by subgroups of the permutation groups. This is related to colorings of the edges of the Grothendieck Dessins. The colored-edge Dessins are useful as a tool for describing some known invariants of the $ Gal (\bmQ / \mQ) $ action on Grothendieck Dessins and for defining new invariants. </p> Robert de Mello Koch, Sanjaye Ramgoolam http://arxiv.org/abs/1002.1596 <p>In this paper we consider the problem of a moving heavy quark through hot non-relativistic, non-commutative Yang-Mills plasma. We discuss about the configuration of the static quark and obtain the quasi-normal modes. Also we find the diffusion constant for the moving heavy quark. The main goal of this study is calculating the jet-quenching parameter for the non-relativistic, non-commutative theory and comparing it with drag forces which recently obtained from the another independent work [1]. </p> J. Sadeghi, B. Pourhassan http://arxiv.org/abs/1002.1553 <p>With the new physical interpretation of quasinormal modes proposed by Maggiore, the quantum area spectra of black holes have been investigated recently. It is shown that, the area spectrum for a non-rotating black hole with no charge is equidistant. While, for a rotating black hole, it is non-equidistant and depends on the angle momentum $J$. So, it is worth to investigate the area spectrum for a charged black hole. Following the Kunstatter's method, we obtain the area spectrum and entropy spectrum of the charged Garfinkle-Horowitz-Strominger black hole, originated from the effective action that emerges in the low-energy of string theory. Both the area spectrum and entropy spectrum are found to be equally spaced and do not depend on the charge $q$, which is different from that of the rotating black hole. Combing with possible observational data from gravity waves, we hope our results can give us answers to the open questions such as the black hole entropy. </p> Shao-Wen Wei, Yu-Xiao Liu, Ke Yang, Yuan Zhong http://arxiv.org/abs/1002.1550 <p>We investigate the thermodynamics of black hole in the deformed Horava-Lifshitz gravity with coupling constant $\lambda=1$. We show that the black hole behaves like the Reissner-Norstrom (RN) black hole with regarding $\sqrt{\frac{1}{2\omega}}$ as a new thermodynamic parameter, where $\omega$ is a parameter in the Horava-Lifshitz gravity. Further, we also obtain the Ruppeiner geometry of the Kehagias-Sfetsos black hole. The results are very different from the RN black hole, which mainly due to the different gravity theory. </p> Shao-Wen Wei, Yu-Xiao Liu, Yong-Qiang Wang, Heng Guo http://arxiv.org/abs/1002.1462 <p>We argue that the Quadratic Spinor Lagrangian approach allows us to approach the problem of forming a geometrical condensate of spinorial tetrads in a natural manner. This, along with considerations involving the discrete symmetries of lattice triangulations, lead us to discover that the quasiparticles of such a condensate are tetrahedra with braids attached to its faces and that these braid attachments correspond to the preons in Bilson-Thompson's model of elementary particles. These "spatoms" can then be put together in a tiling to form more complex structures which encode both geometry and matter in a natural manner. We conclude with some speculations on the relation between this picture and the computational universe hypothesis. </p> Deepak Vaid http://arxiv.org/abs/1002.1435 <p>We establish a connection between the agegraphic models of dark energy and Chaplygin gas energy density in non-flat universe. We reconstruct the potential of the agegraphic scalar field as well as the dynamics of the scalar field according to the evolution of the agegraphic dark energy. We also extend our study to the interacting agegraphic generalized Chaplygin gas dark energy model. </p> Ahmad Sheykhi http://arxiv.org/abs/1002.1429 <p>We investigate the linear cosmological perturbations in Ho\v{r}ava-Lifshitz gravity with a scalar field. Starting from the most general expressions of the metric perturbations as well as that of a canonical scalar field, we decompose the scalar, vector and tensor parts of the perturbed action. By reducing the Hamiltonian, we find that there are two independent degrees of freedom for the tensor perturbations while none for the vector perturbations. For the scalar perturbations, the remaining number of degrees of freedom, which are all gauge invariant, depends on whether the projectable condition is applied or not. For both cases, we lose the time reparametrization symmetry of any kind. </p> Jinn-Ouk Gong, Seoktae Koh, Misao Sasaki http://arxiv.org/abs/1002.1416 <p>This is a pedagogical review on primordial non-Gaussianities from inflation models. We introduce formalisms and techniques that are used to compute such quantities. We review different mechanisms which can generate observable large non-Gaussianities during inflation, and distinctive signatures they leave on the non-Gaussian profiles. They are potentially powerful probes to the dynamics of inflation. We also provide a non-technical and qualitative summary of the main results and underlying physics. </p> Xingang Chen http://arxiv.org/abs/0911.2118 <p>The paper concerns standard supersymmetry algebras in diverse dimensions, involving bosonic translational generators and fermionic supersymmetry generators. A cohomology related to these supersymmetry algebras, termed supersymmetry algebra cohomology, and corresponding "primitive elements" are defined by means of a BRST-type coboundary operator. A method to systematically compute this cohomology is outlined and illustrated by simple examples. </p> Friedemann Brandt http://arxiv.org/abs/0910.4315 <p>This is a short summary of main results of our paper <a href="/abs/0811.2435">arXiv:0811.2435</a> where the concept of motivic Donaldson-Thomas invariant was introduced. It also contains a discussion of some open questions from the loc.cit., in particular, the geometry related to the split attractor flow. </p> Maxim Kontsevich, Yan Soibelman http://arxiv.org/abs/0910.2661 <p>We consider a noncritical holographic model constructed from an intersecting brane configuration D4/$\overline{\rm{D4}}$-D4 with an external magnetic field. We investigate the influences of this magnetic field on strongly coupled dynamics by the gauge/gravity correspondence. </p> Sheng-liang Cui, Yi-hong Gao, Yunseok Seo, Sang-jin Sin, Wei-shui Xu http://arxiv.org/abs/0909.0508 <p>The enumeration of BPS bound states in string theory needs refinement. Studying partition functions of particles made from D-branes wrapped on algebraic Calabi-Yau 3-folds, and classifying states using split attractor flow trees, we extend the method for computing a refined BPS index, <a href="/abs/0810.4301">arXiv:0810.4301</a>. For certain D-particles, a finite number of microstates, namely polar states, exclusively realized as bound states, determine an entire partition function (elliptic genus). This underlines their crucial importance: one might call them the `chromosomes' of a D-particle or a black hole. As polar states also can be affected by our refinement, previous predictions on elliptic genera are modified. This can be metaphorically interpreted as `crossing-over in the meiosis of a D-particle'. Our results improve on <a href="/abs/hep-th/0702012">hep-th/0702012</a>, provide non-trivial evidence for a strong split attractor flow tree conjecture, and thus suggest that we indeed exhaust the BPS spectrum. In the D-brane description of a bound state, the necessity for refinement results from the fact that tachyonic strings split up constituent states into `generic' and `special' states. These are enumerated separately by topological invariants, which turn out to be partitions of Donaldson-Thomas invariants. As modular predictions provide a check on many of our results, we have compelling evidence that our computations are correct. </p> Walter Van Herck, Thomas Wyder http://arxiv.org/abs/0906.3580 <p>Based on our idea of an alternative supersymmetrization of the Nambu--Jona-Lasinio model for dynamical symmetry breaking, we analyze the resulted new model with a holomorphic dimension-five operator in the superpotential. The approach provides a new direction for modeling dynamical symmetry breaking in a supersymmetric setting. In particular, we adopt the idea to formulate a model that gives rise to the Minimal Supersymmetric Standard Model as the low energy effective theory with both Higgs superfields as composites. A renormalization group analysis is performed to establish the phenomenological viability of the scenario, with admissible background scale that could go down to the TeV scale. We give the Higgs mass range predicted. </p> D.-W. Jung, O.C.W. Kong (Nat&#x27;l Central U, Taiwan), J.S. Lee (NCTS, Taiwan) http://arxiv.org/abs/0906.1385 <p>We investigate the effect of the intrinsic spin of a fundamental spinor field on the surrounding spacetime geometry. We show that despite the lack of a rotating stress-energy source (and despite claims to the contrary) the intrinsic spin of a spin-half fermion gives rise to a frame-dragging effect analogous to that of orbital angular momentum, even in Einstein-Hilbert gravity where torsion is constrained to be zero. This resolves a paradox regarding the counter-force needed to restore Newton's third law in the well known spin-orbit interaction. In addition, the frame-dragging effect gives rise to a {\it long-range} gravitationally mediated spin-spin dipole interaction coupling the {\it internal} spins of two sources. We argue that despite the weakness of the interaction, the spin-spin interaction will dominate over the ordinary inverse square Newtonian interaction in any process of sufficiently high-energy for quantum field theoretical effects to be non-negligible. </p> Andrew Randono http://arxiv.org/abs/0906.1376 <p>We propose to take advantage of using the Wiener path integrals as the formal solution for the joint probability densities of coupled Langevin equations describing particles suspended in a fluid under the effect of viscous and random forces. Our obtained formal solution, giving the expression for the Lyapunov exponent, i) will provide the description of all the features and the behaviour of such a system, e.g. the aggregation phenomenon recently studied in the literature using appropriate approximations, ii) can be used to determine the occurrence and the nature of the aggregation - non-aggregation phase transition which we have shown for the one-dimensional case and iii) allows the use of a variety of approximative methods appropriate for the physical conditions of the problem such as instanton solutions in the WKB approximation in the aggregation phase for the one-dimensional case as presented in this paper. The use of instanton approximation gives the same result for the Lyapunov exponent in the aggregation phase, previously obtained by other authors using a different approximative method. The case of non-aggregation is also considered in a certain approximation using the general path integral expression for the one-dimensional case. </p> M. Chaichian, A. Tureanu, A. Zahabi http://arxiv.org/abs/0905.2700 <p>It is known that non-holomorphic corrections are necessary in order to get duality invariant free energy and entropy function. However the present methods of incorporating non-holomorphic corrections are in conflict with special geometry properties of moduli space. The moduli fields do not transform in duality covariant way and their duality transformation also involves the graviphoton field strength. In the present note we construct duality covariant moduli fields for STU-model perturbatively in powers of the graviphoton field strength and demonstrated their existence upto second order. </p> Shamik Banerjee, Rajesh Kumar Gupta http://arxiv.org/abs/0811.2939 <p>By employing a recently constructed hyperon-nucleon potential the equation of state of \beta-equilibrated and charge neutral nucleonic matter is calculated. The hyperon-nucleon potential is a low-momentum potential which is obtained within a renormalization group framework. Based on the Hartree-Fock approximation at zero temperature the densities at which hyperons appear in neutron stars are estimated. For several different bare hyperon-nucleon potentials and a wide range of nuclear matter parameters it is found that hyperons in neutron stars are always present. These findings have profound consequences for the mass and radius of neutron stars. </p> Haris Djapo, Bernd-Jochen Schaefer, Jochen Wambach http://arxiv.org/abs/0809.0381 <p>We propose a manifestly SO(8) invariant BF type Lagrangian for describing the dynamics of M2-brane-anti-M2-brane system in flat spacetime. When one of the scalars which satisfies a free-scalar equation takes a large expectation value, the M2-brane-anti-M2-brane action reduces to the tachyon DBI action of D2-brane-anti-D2-brane system in flat spacetime. </p> Mohammad R. Garousi http://arxiv.org/abs/0911.2708 <p>We apply the techniques of special Kaehler geometry to investigate AdS_4 vacua of general N=2 gauged supergravities underlying flux compactifications of type II theories. We formulate the scalar potential and its extremization conditions in terms of a triplet of prepotentials P_x and their special Kaehler covariant derivatives only, in a form that recalls the potential and the attractor equations of N=2 black holes. We propose a system of first order equations for the P_x which generalize the supersymmetry conditions and yield non-supersymmetric vacua. Special geometry allows us to recast these equations in algebraic form, and we find an infinite class of new N=0 and N=1 AdS_4 solutions, displaying a rich pattern of non-trivial charges associated with NSNS and RR fluxes. Finally, by explicit evaluation of the entropy function on the solutions, we derive a U-duality invariant expression for the cosmological constant and the central charges of the dual CFT's. </p> Davide Cassani, Sergio Ferrara, Alessio Marrani, Jose F. Morales, Henning Samtleben http://arxiv.org/abs/0911.2831 <p>We present the metric for the $(n+1)$-dimensional charged rotating dilaton black branes with cylindrical or toroidal horizons in the background of anti-de Sitter spacetime. We find the suitable counterterm which removes the divergences of the action in the presence of the dilaton potential in all higher dimensions. We plot the Penrose diagrams of the spacetime and reveal that the spacetime geometry crucially modifies in the presence of the dilaton field. The conserved and thermodynamic quantities of the black branes are also computed. </p> A. Sheykhi, S.H. Hendi http://arxiv.org/abs/1002.1136 <p>In a recent paper [<a href="/abs/1001.0785">arXiv:1001.0785</a>], Verlinde has shown that the Newton gravity appears as an entropy force. In this paper we show how gravity appears as entropy force in Einstein's equation of gravitational field in a general spherically symmetric spacetime. We mainly focus on the trapping horizon of the spacetime. We find that when matter fields are absent, the change of entropy associated with the trapping horizon indeed can be identified with an entropy force. When matter fields are present, we see that heat flux of matter fields also leads to the change of entropy. Applying arguments made by Verlinde and Smolin, respectively, to the trapping horizon, we find that the entropy force is given by the surface gravity of the horizon. The cases in the untrapped region of the spacetime are also discussed. </p> Rong-Gen Cai, Li-Ming Cao, Nobuyoshi Ohta http://arxiv.org/abs/1002.1075 <p>We perform a full perturbative stability analysis of the 6D cascading gravity model in the presence of 3-brane tension. We demonstrate that for sufficiently large tension on the (flat) 3-brane, there are no ghosts at the perturbative level, consistent with results that had previously only been obtained in a specific 5D decoupling limit. These results establish the cascading gravity framework as a consistent infrared modification of gravity. </p> Claudia de Rham, Justin Khoury, Andrew J. Tolley http://arxiv.org/abs/1002.0742 <p>We examine the completeness of bi-orthogonal sets of eigenfunctions for non-Hermitian Hamiltonians possessing a spectral singularity. The correct resolutions of identity are constructed for delta like and smooth potentials. Their form and the contribution of a spectral singularity depend on the class of functions employed for physical states. With this specification there is no obstruction to completeness originating from a spectral singularity. </p> A.A. Andrianov, F. Cannata, A.V. Sokolov http://arxiv.org/abs/1002.0104 <p>Holographic functional methods are introduced as probes of discrete time-stepped maps that lead to chaotic behavior. The methods provide continuous time interpolation between the time steps, thereby revealing the maps to be splintered Hamiltonian systems underlain by novel potentials. A sequence of successively deepening switchback potentials for a particle driven by Hamiltonian dynamics explains, in very physical terms, the frequency doubling and trajectory folding that occur on the particular route to chaos revealed by the logistic map, x --&gt; 4x(1-x). </p> Thomas L. Curtright, Cosmas K. Zachos http://arxiv.org/abs/1001.5349 <p>We show that in modified $f(R)$ type gravity models with non-minimal coupling between matter and geometry, both the matter Lagrangian, and the energy-momentum tensor, are completely and uniquely determined by the form of the coupling. This result is obtained by using the variational formulation for the derivation of the equations of motion in the modified gravity models with geometry-matter coupling, and the Newtonian limit for a fluid obeying a barotropic equation of state. The corresponding energy-momentum tensor of the matter in modified gravity models with non-minimal coupling is more general than the usual general-relativistic energy-momentum tensor for perfect fluids, and it contains a supplementary, equation of state dependent term, which could be related to the elastic stresses in the body, or to other forms of internal energy. Therefore, the extra-force induced by the coupling between matter and geometry never vanishes as a consequence of the thermodynamic properties of the system, or for a specific choice of the matter Lagrangian, and it is non-zero in the case of a fluid of dust particles. </p> T. Harko http://arxiv.org/abs/1001.5238 <p>It is generally thought that there exists a logarithmic term in the entropy/area relation for the deformed Horava-Lifshitz gravity. With the entropy/area relation, we obtain the modified Friedmann equations from the first law of thermodynamics and the entropic force, respectively. Although the modified Friedmann equations derived from the two methods are different, they will reduce to the standard Friedmann equation in the case of small energy density $\rho$. </p> Shao-Wen Wei, Yu-Xiao Liu, Yong-Qiang Wang http://arxiv.org/abs/1001.3608 <p>In this work, we study Lagrangian formulations for self-dual gauge theories, also known as chiral $n$-form gauge theories, for $n = 2p$ in $D = 4p+2$ dimensional spacetime. Motivated by a recent formulation of M5-branes derived from the BLG model, we generalize the earlier Lagrangian formulation based on a decomposition of spacetime into $(D-1)$ dimensions plus a special dimension, to construct Lagrangian formulations based on a generic decomposition of spacetime into $D'$ and $D" = D - D'$ dimensions. Although the Lorentz symmetry is not manifest, we prove that the action is invariant under modified Lorentz transformations. </p> Wei-Ming Chen, Pei-Ming Ho http://arxiv.org/abs/1001.1088 <p>After reviewing recently suggested operational "principles of the quantumness", I address the problem on whether Quantum Theory (QT) and Special Relativity (SR) are unrelated theories, or instead, if the one implies the other. I show how SR can be indeed derived from causality of QT, within the computational paradigm "the universe is a huge quantum computer", reformulating QFT as a Quantum-Computational Field Theory (QCFT). In QCFT SR emerges from the fabric of the computational network, which also naturally embeds gauge invariance. In this scheme even the quantization rule and the Planck constant can in principle be derived as emergent from the underlying causal tapestry of space-time. In this way QT remains the only theory operating the huge computer of the universe. Is QCFT only a speculative tautology (theory as simulation of reality), or does it have a scientific value? The answer will come from Occam's razor, depending on the mathematical simplicity of QCFT. Here I will just start scratching the surface of QCFT, analyzing simple field theories, including Dirac's. The number of problems and unmotivated recipes that plague QFT strongly motivates us to undertake the QCFT project, since QCFT makes all such problems manifest, and forces a re-foundation of QFT. </p> Giacomo Mauro D&#x27;Ariano http://arxiv.org/abs/0912.4333 <p>We study the nonforward Compton scattering in particular the deeply virtual Compton scattering from AdS/CFT. We first calculate the contributions from the s-channel and u-channel supergravity diagrams as well as the four point interaction diagram which correspond to the Compton scatterings on a dilaton target in CFT. Furthermore, we study the Compton scattering on a dilatino target. Assuming that protons can be identified as supergravity modes of dilatino, we compare the calculated DVCS cross section to the low-energy experimental data from the H1 and ZEUS collaborations and find good agreement. We also discuss the t-channel graviton exchange contribution and show that it should be dominant in the high-energy limit. </p> Jian-Hua Gao, Bo-Wen Xiao http://arxiv.org/abs/0709.3593 <p>The hypersurface in a 3-dimensional vector space with an isolated quasi-homogeneous elliptic singularity of type E_r,r=6,7,8, has a natural Poisson structure. We show that the family of del Pezzo surfaces of the corresponding type E_r provides a semiuniversal Poisson deformation of that Poisson structure. </p> <p>We also construct a deformation-quantization of the coordinate ring of such a del Pezzo surface. To this end, we first deform the polynomial algebra C[x,y,z] to a noncommutative algebra with generators x,y,z and the following 3 relations (where [u,v]_t = uv- t.vu): </p> <p>[x,y]_t=F_1(z), </p> <p>[y,z]_t=F_2(x), </p> <p>[z,x]_t=F_3(y). </p> <p>This gives a family of Calabi-Yau algebras A(F) parametrized by a complex number t and a triple F=(F_1,F_2,F_3), of polynomials in one variable of specifically chosen degrees. </p> <p>Our quantization of the coordinate ring of a del Pezzo surface is provided by noncommutative algebras of the form A(F)/(g) where (g) stands for the ideal of A(F) generated by a central element g, which generates the center of the algebra A(F) if F is generic enough. </p> Pavel Etingof, Victor Ginzburg http://arxiv.org/abs/1002.1278 <p>Careful exploration of the idea that equation for radial wave function must be compatible with the full Schrodinger equation shows appearance of the delta-function while reduction of full Schrodinger equation in spherical coordinates. Elimination of this extra term produces a boundary condition for the radial wave function, which is the same both for regular and singular potentials. </p> Anzor A.Khelashvili, Teimuraz P. Nadareishvili http://arxiv.org/abs/1002.1097 <p>The one-dimensional Hubbard model is an exceptional integrable spin chain which is apparently based on a deformation of the Yangian for the superalgebra gl(2|2). Here we investigate the quantum-deformation of the Hubbard model in the classical limit. This leads to a novel classical r-matrix of trigonometric kind. We derive the corresponding one-parameter family of Lie bialgebras as a deformation of the affine gl(2|2) Kac-Moody superalgebra. In particular, we discuss the affine extension as well as discrete symmetries, and we scan for simpler limiting cases, such as the rational r-matrix for the undeformed Hubbard model. </p> Niklas Beisert http://arxiv.org/abs/1002.0834 <p>[Abridged] In a Universe with a detectable nontrivial spatial topology the last scattering surface contains pairs of matching circles with the same distribution of temperature fluctuations -- the so-called circles-in-the-sky. Searches for nearly antipodal circles-in-the-sky in maps of cosmic microwave background radiation have so far been unsuccessful. This negative outcome along with recent theoretical results concerning the detectability of nearly flat compact topologies is sufficient to exclude a detectable nontrivial topology for most observers in very nearly flat positively and negatively curved Universes ($0&lt;|\Omega_{tot}-1| \lesssim 10^{-5}$). Here we investigate the consequences of these searches for observable nontrivial topologies if the Universe turns out to be exactly flat ($\Omega_{tot}=1$) as is often assumed. We demonstrate that in this case the conclusions deduced from such searches can be radically different. We show that for all multiply-connected orientable flat manifolds it is possible to directly study the action of the holonomies in order to obtain an upper bound on the angle that characterizes the deviation from antipodicity of pairs of matching circles associated with the shortest closed geodesic. We also show that in a flat Universe there are observers for whom the circles-in-the-sky searches already undertaken are insufficient to exclude the possibility of a detectable nontrivial spatial topology. It is remarkable how such small variations in the spatial curvature of the Universe, which are effectively indistinguishable geometrically, can have such a drastic effect on the detectability of cosmic topology. </p> B. Mota, M.J. Reboucas, R. Tavakol http://arxiv.org/abs/1001.1509 <p>We study the hidden sector effects to the mass renormalization of a simplest gauge-mediated supersymmetry breaking scenario. We point out that possible hidden sector contributions render the soft scalar masses smaller, resulting in drastically different sparticle mass spectrum at low energy. In particular, in the ${\bf 5}+\bar{\bf 5}$ minimal gauge mediated supersymmetry breaking with high messenger scale (that is favored by the gravitino cold dark matter scenario), we show that stau can be the next lightest superparticle for moderate values of hidden sector self coupling. This provides a very simple theoretical model of long-lived charged next lightest superparticles, that imply distinctive signals in ongoing and upcoming collider experiments. </p> Masato Arai, Shinsuke Kawai, Nobuchika Okada http://arxiv.org/abs/0912.4968 <p>This paper deals with $\tilde{\chi}^{(6)}$, the six-particle contribution to the magnetic susceptibility of the square lattice Ising model. We have generated, modulo a prime, series coefficients for $\tilde{\chi}^{(6)}$. The length of the series is sufficient to produce the corresponding Fuchsian linear differential equation (modulo a prime). We obtain the Fuchsian linear differential equation that annihilates the "depleted" series $\Phi^{(6)}=\tilde{\chi}^{(6)} - {2 \over 3} \tilde{\chi}^{(4)} + {2 \over 45} \tilde{\chi}^{(2)}$. The factorization of the corresponding differential operator is performed using a method of factorization modulo a prime introduced in a previous paper. The "depleted" differential operator is shown to have a structure similar to the corresponding operator for $\tilde{\chi}^{(5)}$. It splits into factors of smaller orders, with the left-most factor of order six being equivalent to the symmetric fifth power of the linear differential operator corresponding to the elliptic integral $E$. The right-most factor has a direct sum structure, and using series calculated modulo several primes, all the factors in the direct sum have been reconstructed in exact arithmetics. </p> S. Boukraa, S. Hassani, I. Jensen, J.-M. Maillard, N. Zenine http://arxiv.org/abs/0912.4111 <p>Transition radiation from relativistic electrons is investigated in an ultrasonic superlattice excited in a finite thickness plate. In the quasi-classical approximation formulae are derived for the vector potential of the electromagnetic field and for the spectral-angular distribution of the radiation intensity. The acoustic waves generate new resonance peaks in the spectral and angular distribution of the radiation intensity. The heights of the peaks can be tuned by choosing the parameters of the acoustic wave. </p> A. R. Mkrtchyan, V. V. Parazian, A. A. Saharian http://arxiv.org/abs/0911.5466 <p>We give an example of infinite order rational transformation that leaves a linear differential equation covariant. This example can be seen as a non-trivial but still simple illustration of an exact representation of the renormalization group. </p> A. Bostan, S. Boukraa, S. Hassani, J.-M. Maillard, J-A. Weil, N. Zenine, N. Abarenkova