Given a $K3$ surface, a supersymmetric non-linear K3 sigma model is the internal superconformal field theory (SCFT) in a six dimensional compactification of type IIA superstring on $\mathbb{R}^{1,5} \times K3$. These models have attracted attention due to the discovery of Mathieu moonshine phenomena for the elliptic genera of K3 surfaces, and have played a pivotal role in extending Mukai's theorem on classification of symplectic automorphisms of $K3$ surfaces. We report on recent progress (arXiv:2402.08719 [hep-th]) in characterizing topological defects in $K3$ models, generalizing the notion of symmetries to categories of topological operators supported on arbitrary codimension submanifolds with possibly non-invertible fusion rules. Taking advantage of the interpretation of Mukai lattice as the D-brane charge lattice, we present a number of general results for the category of topological defect lines preserving the superconformal algebra and spectral flow, obtained by studying their fusion with boundary states. While for certain K3 models infinitely many simple defects, and even a continuum, can occur, at generic points in the moduli space the category is actually trivial, i.e. it is generated by the identity defect. Furthermore, if a K3 model is at the attractor point for some BPS configuration of D-branes, then all topological defects have integral quantum dimension. We also introduce a conjecture that a continuum of topological defects arises if and only if the K3 model is a (possibly generalized) orbifold of a torus model. These general results are confirmed by the analysis of significant examples. We also point out the connection to recent studies of topological defects in the Conway moonshine module theory (arXiv:2412.21141 [hep-th],arXiv:2504.18619 [hep-th]).
We investigate dynamics of probe particles moving in the near-horizon limit of (2N+1)-dimensional extremal Myers-Perry black hole (in the cases of N=3,4,5) with arbitrary rotation parameters. Very recently it has been shown arXiv:1703.00713v1 [hep-th] that in the most general case with nonequal nonvanishing rotational parameters the system admits separation of variables in N-dimensional ellipsoidal coordinates. We wrote down the explicit expressions of Liouville integrals of motion, given in arXiv:1703.00713v1 [hep-th] in ellipsoidal coordinates, in initial "Cartesian" coordinates in seven, nine and eleven dimensions, and found that these expressions hold in any dimension. Then, taking the limit where all of the rotational parameters are equal, we reveal that each of these N-1 integrals of motion results in the Hamiltonian of the spherical mechanics of a (2N+1)-dimensional MP black hole with equal nonvanishing rotational parameters.
Une « actualité » française et internationale autour d’Epstein (colloques, publications, inédits) invite à revenir sur l’œuvre protéiforme du cinéaste qui est tout autant poète, essayiste, philosophe. C’est l’ouverture du fonds Epstein de la Cinémathèque française qui change désormais l’appréhension de cette œuvre et ouvre à de nouvelles approches. On en propose ici quelques-unes en complément des deux études de ce numéro en éclairant les rapports d’Epstein et du Dr Ramain, musicologue et esthéticien dont la correspondance, inédite, vient d’être versée au fonds de la Cinémathèque française ; en révélant, à partir des images mêmes du film les Bâtisseurs, un Epstein antifasciste ; en documentant les difficultés que rencontra le cinéaste théoricien après la Deuxième Guerre mondiale à publier et à se faire entendre, ignoré d’une nouvelle génération critique qui rejette « l’avant-garde » comme sa conception de la « machine » du cinéma.
By studying global AdS using different foliations, global and Rindler-AdS, we show that there are two different asymptotic Fefferman–Graham expansions possible and thus two different definitions of "boundaries". We demonstrate that imposing boundary conditions on the two boundaries is not mutually compatible even when these boundaries are pushed to infinity. Thus, these two procedures define two genuinely distinct theories that we call global-CFT and Rindler-CFT. We show that the Rindler-CFT is not the same as the theory one gets by "Rindlerizing the global-CFT" described in hep-th/9804085. We conjecture that the Rindler theory is incapable of capturing the dynamics inside the horizon and discuss its implications for the BTZ-CFT duality proposed in hep-th/0106112.
Inspired by Jacobson's thermodynamic approach[gr-qc/9504004], Cai et al [hep-th/0501055,hep-th/0609128] have shown the emergence of Friedmann equations from the first law of thermodynamics. We extend Akbar--Cai derivation [hep-th/0609128] of Friedmann equations to accommodate a general entropy-area law. Studying the resulted Friedmann equations using a specific entropy-area law, which is motivated by the generalized uncertainty principle (GUP), reveals the existence of a maximum energy density closed to Planck density. Allowing for a general continuous pressure $p(ρ,a)$ leads to bounded curvature invariants and a general nonsingular evolution. In this case, the maximum energy density is reached in a finite time and there is no cosmological evolution beyond this point which leaves the big bang singularity inaccessible from a spacetime prospective. The existence of maximum energy density and a general nonsingular evolution is independent of the equation of state and the spacial curvature $k$. As an example we study the evolution of the equation of state $p=ωρ$ through its phase-space diagram to show the existence of a maximum energy which is reachable in a finite time.
We review the study of influence of the so-called soft BRST symmetry breaking within the Batalin-Vilkovisky (BV) formalism introduced in our papers [JHEP 1110 (2011) 043, arXiv:1108.4820 [hep-th], MPLA 27 (2012) 1250067, arXiv:1201.4720 [hep-th]] on gauge dependence of the effective action and vacuum expectation values of gauge invariant operators. We derive the Ward identities for generating functionals of Green’s functions for a given theory with soft BRST symmetry breaking term being added to the quantum action and investigate theirs gauge dependence. It is strongly argued that gauge theories with a soft breaking of BRST symmetry are inconsistent within the BV formalism because of the gauge-dependence of S-matrix. The application to the Gribov-Zwanziger action (enlarging SU(N) Yang-Mills gauge theory by means of not gauge-invariant horizon function) for the ¯ ¯
A recent article by Mathur attempts a "precise formulation" for the paradox of black hole information loss [S. D. Mathur, arXiv:1108.0302v2 (hep-th)]. We point out that a key component of the above work, which refers to entangled pairs inside and outside of the horizon and their associated entropy gain or information loss during black hole evaporation, is a presumptuous false outcome not backed by the very foundation of physics. The very foundation of Mathur's above work is thus incorrect. We further show that within the framework of Hawking radiation as tunneling the so-called small corrections are sufficient to resolve the information loss problem.
Flávio S. Coelho, Carlos Herdeiro, Marco O. P. Sampaio
Recently, in arXiv:1105.2298 [hep-th], we have estimated the energy radiated in the head-on collision of two equal D-dimensional Aichelburg-Sexl shock waves, for even D, by solving perturbatively, to first order, the Einstein equations in the future of the collision. Here, we report on the solution for the odd D case. After finding the wave forms, we extract the estimated radiated energy for D=5,7,9 and 11 and unveil a remarkably simple pattern, given the complexity of the framework: (for all D) the estimated fraction of radiated energy matches the analytic expression 1/2-1/D, within the numerical error (less than 0.1%). Both this fit and the apparent horizon bound converge to 1/2 as D goes to infinity.
We present a new, two-parameter family of string solutions corresponding to the holographic duals of specic 1/8-BPS Wilson loops on S 2 inN = 4 supersymmetric Yang-Mills theory. The solutions are obtained using the dressing method on the known longitude solution in the context of the auxiliary -model on S 3 put forth in arXiv:0905.0665[hep-th]. We verify that the regularized area of the world-sheets are consistent with expectations.
We point out that in some situations it is possible to use matrix model techniques a la Dijkgraaf-Vafa to perturbatively compute D-brane instanton effects. This provides an explanation in terms of stringy instantons of the results in hep-th/0311181. We check this proposal in some simple scenarios. We point out some interesting consequences of this observation, such as the fact that it gives a perturbative way of computing stringy multi-instanton effects. It also provides a further interpretation of D-brane instantons as residual instantons of higgsed supergroups.
In this note we describe how N=1 SQCD-like theories with a large number of flavors can be given a dual description in terms of a string background containing a large number of additional D5-branes. The dual geometries account for the backreaction of the additional branes: they depend on the ratio between the number of flavors and colors of the gauge theory. This note is based on hep-th/0602027. We present here also a new set of solutions, which are not included in the original paper.