Narrow Results

By using the generalized version of gauge/gravity correspondence, we study the mass spectra of several typical QCD₄ glueballs in the framework of AdS₆ black hole metric of Einstein gravity theory. The obtained glueball mass spectra are numerically in agreement with those from the AdS₇×S⁴ black hole metric of the 11-dimensional supergravity.

Recently there has been progress on the computation of two- and three-point correlation functions with two "heavy" states via semiclassical methods. We extend this analysis to the case of AdS₅×T^{1, 1}, and examine the suggested procedure for the case of several simple string solutions. By making use of AdS/CFT duality, we derive the relevant correlation functions of operators belonging to the dual gauge theory.

We review the holographic duals of gauge theories with eight supercharges obtained by adding very few flavors to pure supersymmetric Yang–Mills with 16 supercharges. Assuming a brane-probe limit, the gravity duals are engineered in terms of probe branes (the so-called flavor brane) in the background of the color branes. Both types of branes intersect on a given subspace in which the matter is confined. The gauge theory dual is thus the corresponding flavoring of the gauge theory with 16 supercharges. Those theories have in general a nontrivial phase structure; which is also captured in a beautiful way by the gravity dual. Along the lines of the gauge/gravity duality, we review also some of the results on the meson spectrum in the different phases of the theories.

Using a holographic proposal for the entanglement entropy we study its behavior in various supergravity backgrounds. We are particularly interested in the possibility of using the entanglement entropy as way to detect transitions induced by the presence horizons. We consider several geometries with horizons: the black hole in AdS₃, nonextremal Dp-branes, dyonic black holes asymptotically to AdS₄ and also Schwarzschild black holes in global AdS_p coordinates. Generically, we find that the entanglement entropy does not exhibit a transition, that is, one of the two possible configurations always dominates.

We study magnetic flux tubes in the Higgs vacuum of the mass deformation of SU(N_c), SYM and its large N_c string dual, the Polchinski-Strassler geometry. Choosing equal masses for the three adjoint chiral multiplets, for all N_c we identify a "colour-flavour locked" symmetry, SO(3)_C+F which leaves the Higgs vacuum invariant. At weak coupling, we find explicit non-Abelian k-vortex solutions carrying a ℤ_Nc-valued magnetic flux, with topological winding 0 < k < N_c. These k-strings spontaneously break SO(3)_C+F to U(1)_C+F resulting in an S² moduli space of solutions. The world-sheet sigma model is a nonsupersymmetric ℂℙ¹ model with a theta angle θ₁₊₁ = k(N_c - k)θ₃₊₁ where θ₃₊₁ is the Yang-Mills vacuum angle. We find numerically that k-vortex tensions follow the Casimir scaling law T_k ∝ k(N_c - k) for large N_c. In the large N_c IIB string dual, the SO(3)_C+F symmetry is manifest in the geometry interpolating between AdS₅ × S⁵ and the interior metric due to a single D5-brane carrying D3-brane charge. We identify candidate k-vortices as expanded probe D3-branes formed from a collection of kD-strings. The resulting k-vortex tension exhibits precise Casimir scaling, and the effective world-sheet theta angle matches the semiclassical result. S-duality maps the Higgs to the confining phase so that confining string tensions at strong 't Hooft coupling also exhibit Casimir scaling in theory in the large N_c limit.

Meson spectra given as fluctuations of a D7-brane are studied under the background driven by the dilaton. This leads to a dual gauge theory with quark confinement due to the gauge condensate. We find that the effect of the gauge condensate on the meson spectrum is essential in order to make a realistic hadron spectrum in the non-supersymmetric case. In the supersymmetric case, however, only the spectra of the scalars are affected, but they are changed in an opposite way compared to the non-supersymmetric case.

The holographic principle has a concrete realization in the Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence. If this principle is a true fact about quantum gravity then it must also hold beyond AdS/CFT. In this paper, we address specifically holographic field theory duals of gravitational theories in asymptotically flat spacetimes. We present some evidence of our recent conjecture that three-dimensional (3d) conformal Chern–Simons gravity (CSG) with flat space boundary conditions is dual to an extremal CFT.

The operators with large scaling dimensions can be labeled by Young diagrams. Among other bases, the operators using restricted Schur polynomials have been known to have a large N but nonplanar limit under which they map to states of a system of harmonic oscillators. We analyze the oscillator algebra acting on pairs of long rows or long columns in the Young diagrams of the operators. The oscillator algebra can be reached by a Inonu–Wigner contraction of the u(2) algebra inside of the u(p) algebra of p giant gravitons. We present evidences that integrability in this case can persist at higher loops due to the presence of the oscillator algebra which is expected to be robust under loop corrections in the nonplanar large N limit.

We study magnetic flux tubes in the Higgs vacuum of the mass deformation of SU(N_c), and its large N_c string dual, the Polchinski-Strassler geometry. Choosing equal masses for the three adjoint chiral multiplets, for all N_c we identify a "colour-flavour locked" symmetry, SO(3)_C+F which leaves the Higgs vacuum invariant. At weak coupling, we find explicit non-Abelian k-vortex solutions carrying a ℤ_Nc-valued magnetic flux, with topological winding 0 < k < N_c. These k-strings spontaneously break SO(3)_C+F to U(1)_C+F resulting in an S² moduli space of solutions. The world-sheet sigma model is a nonsupersymmetric ℂℙ¹ model with a theta angle θ₁₊₁ = k(N_c - k)θ₃₊₁ where θ₃₊₁ is the Yang-Mills vacuum angle. We find numerically that k-vortex tensions follow the Casimir scaling law T_k ∝ k(N_c - k) for large N_c. In the large N_c IIB string dual, the SO(3)_C+F symmetry is manifest in the geometry interpolating between AdS₅ × S⁵ and the interior metric due to a single D5-brane carrying D3-brane charge. We identify candidate k-vortices as expanded probe D3-branes formed from a collection of kD-strings. The resulting k-vortex tension exhibits precise Casimir scaling, and the effective world-sheet theta angle matches the semiclassical result. S-duality maps the Higgs to the confining phase so that confining string tensions at strong 't Hooft coupling also exhibit Casimir scaling in theory in the large N_c limit.