[en] We study various dynamical aspects of solitons in noncommutative gauge theories and find surprising results. Among them is the observation that the solitons can travel faster than the speed of light for arbitrarily long distances

[en] We study dynamical aspects of large N QCD₄ via supergravity on anti-de Sitter black hole geometry. We compute the mass spectrum, the topological susceptibility and the gluon condensate and make a comparison to lattice simulations. We present analogous results for QCD₃

[en] Recently it was suggested that a graviton in AdS₅xS⁵ with a large momentum along the sphere can blow up into a spherical D-brane in S⁵. In this paper we show that the same graviton can also blow up into a spherical D-brane in AdS₅ with exactly the same quantum numbers (angular momentum and energy). These branes are BPS, preserving 16 of the 32 supersymmetries. We show that there is a BPS solution for SYM on S³xR with exactly the same quantum numbers. The solution has non-vanishing Higgs expectation values and hence is dual to the large brane in AdS. (author)

[en] We investigate the low-energy effective description of non-geometric compactifications constructed by T-dualizing two or three of the directions of a T³ with non-vanishing H-flux. Our approach is to introduce a D3-brane in these geometries and to take an appropriate decoupling limit. In the case of two T-dualities, we find at low energies a non-commutative T² fibered non-trivially over an S¹. In the UV this theory is still decoupled from gravity, but is dual to a little string theory with flavor. For the case of three T-dualities, we do not find a sensible decoupling limit, casting doubt on this geometry as a low-energy effective notion in critical string theory. However, by studying a topological toy model in this background, we find a non-associative geometry similar to one found by Bouwknegt, Hannabuss, and Mathai

[en] In this note we consider N=4 SYM theories in 2+1 dimensions with gauge group U(N)×U(M) and k hypermultiplets charged under the U(N). When k>2(N−M), the theory flows to a superconformal fixed point in the IR. Theories with k<2(N−M), on the other hand, flows to strong coupling. We explore these theories from the perspective of gravity dual. We find that the gravity duals of theories with k<(N−M) contain enhancons even in situations where repulson singularities are absent. We argue that supergravity description is unreliable in the region near these enhancon points. Instead, we show how to construct reliable sugra duals to particular points on the Coulomb branch where the enhancon is screened. We explore how these singularities reappear as one moves around in Coulomb branch and comment on possible field theory interpretation of this phenomenon. In analyzing gauge/gravity duality for these models, we encountered one unexpected surprise, that the condition for the supergravity solution to be reliable and supersymmetric is somewhat weaker than the expectation from field theory. We also discuss similar issues for theories with k=0.

[en] We consider a relativistic effective field theory of vector boson whose vacuum exhibits spontaneous breaking of Lorentz invariance. We argue that a simple model of this type, considered recently by Kraus and Tomboulis, is obstructed from having a ultraviolet completion which is unitary, analytic, and local, according to the diagnostic recently suggested by Adams, Arkani-Hamed, Dubovsky, Nicolis, and Rattazzi.

[en] We find exact solutions for rotating and nonrotating neutral black holes in the Goedel universe of five-dimensional minimal supergravity theory. We also describe the embedding of this solution in M-theory. After dimensional reduction and T-duality, we obtain a supergravity solution corresponding to placing a black string in a pp-wave background

[en] We construct the supergravity solution for fully localized D2/D6 intersection. The near horizon limit of this solution is the supergravity dual of supersymmetric Yang-Mills theory in 2+1 dimensions with flavor. We use this solution to formulate mirror symmetry of 2+1 dimensional gauge theories in the language of AdS/CFT correspondence. We also construct the supergravity dual of a non-commutative gauge theory with fundamental matter. (author)

[en] We generalize the construction by Aharony, Hashimoto, Hirano, and Ouyang of N=4 quiver gauge theory with gauge group U(N+M)×U(N), k fundamentals charged under U(N) and bi-fundamentals, to the case with gauge group ∏_i_=_1"k"̂U(N_i) with k_i fundamentals charged under U(N_i). This construction is facilitated by considering the resolved ALE_k_̂×TN_k background in M-theory including non-trivial fluxes through the resolved 4-cycles in the geometry. We also describe the M-theory lift of the IIA Page charge quantization condition. Finally, we clarify the role of string corrections in various regimes of parameter space.

[en] We construct a solution of eleven dimensional supergravity corresponding to a stack of M2 branes localized at the center of a particular eight dimensional hyper-Kaehler manifold constructed by Gauntlett, Gibbons, Papadopoulos, and Townsend, generalizing the earlier construction of Cherkis and Hashimoto. In the decoupling limit, this solution is dual to a Chern-Simons/Yang-Mills/Matter theory in 2+1 dimensions with N = 3 supersymmetry, which flows in the infra red to a superconformal Chern-Simons/Matter system preserving N = 6, 8 supersymmetry, constructed recently by Aharony, Bergman, Jafferis, and Maldacena.