Littérature scientifique sur le sujet « AdS/CFT, flavor symmetry, meson »

We study mesons in an [Formula: see text] super Yang-Mills theory with fundamental matter from its dual string theory on AdS5 × S5 with a D7-brane probe. For quarks with a finite mass mq, the meson spectrum is discrete and exhibits a mass gap of order [Formula: see text]. The spectrum of mesons with large spin J is obtained from semiclassical rotating open strings attached to the D7-brane. It displays Regge behaviour for [Formula: see text] whereas for [Formula: see text] it corresponds to that of two non-relativistic quarks bound by a Coulomb potential. We calculate 〈 Tr F2〉 around an isolated quark, to gain insight into the Regge behaviour of the spinning mesons.

Strongly interacting theories of electroweak (EW) symmetry breaking provide an elegant solution to the hierarchy problem. In these models the EW symmetry can either be broken without a Higgs or by means of a composite Higgs boson. These scenarios have been recently investigated in the framework of five-dimensional warped models that, according to the AdS/CFT correspondence, have a four-dimensional holographic interpretation in terms of strongly coupled field theories. We describe the minimal Higgsless and composite Higgs model and show how they can successfully pass all the electroweak precision tests and solve the flavor problems. We explore the implications of these models at the LHC (Large Hadron Collider).

Abstract We present a systematic study of holographic correlators in a vast array of SCFTs with non-maximal superconformal symmetry. These theories include 4d $$ \mathcal{N} $$ N = 2 SCFTs from D3-branes near F-theory singularities, 5d Seiberg exceptional theories and 6d E-string theory, as well as 3d and 4d phenomenological models with probe flavor branes. We consider current multiplets and their generalizations with higher weights, dual to massless and massive super gluons in the bulk. At leading order in the inverse central charge expansion, connected four-point functions of these operators correspond to tree-level gluon scattering amplitudes in AdS. We show that all such tree-level four-point amplitudes in all these theories are fully fixed by symmetries and consistency conditions and explicitly construct them. Our results encode a wealth of SCFT data and exhibit various interesting emergent structures. These include Parisi-Sourlas-like dimensional reductions, hidden conformal symmetry and an AdS version of the color-kinematic duality.

Abstract We investigate dispersion relation of Nambu-Goldstone modes in a dissipative system realized by the AdS/CFT correspondence. We employ the D3/D7 model which represents $$ \mathcal{N} $$ N = 4 supersymmetric Yang-Mills theory coupled to $$ \mathcal{N} $$ N = 2 flavor fields. If we consider massless quarks in the presence of an external magnetic field, the system exhibits the phase transition associated with the spontaneous symmetry breaking of the chiral symmetry. We find that the Nambu-Goldstone modes show a diffusive behavior in the dispersion relation, which agrees with that found with the effective field theory approach. We also study a non-equilibrium steady state which has a constant current flow in the presence of an external electric field. In a non-equilibrium steady state, we find that the Nambu-Goldstone modes show a linear dispersion in the real part of the frequency in addition to the diffusive behavior. Moreover, we analyze the linear dispersion of the Nambu-Goldstone modes in the hydrodynamic approximation. As a result, we find that the linear dispersion can be written as the analytic functions of quantities in the dual field theory. Our results imply that such a linear dispersion is a characteristic behavior of Nambu-Goldstone modes in a non-equilibrium steady state.

Abstract We study strongly coupled ABJM theory on the 3-sphere with massive quenched flavor using the AdS/CFT correspondence. The holographic dual consists of type IIA supergravity with probe D6-branes. The flavor mass is a relevant deformation driving an RG flow whose IR endpoint is pure ABJM theory. At non-zero mass, we find that the theory on the 3-sphere exhibits a quantum phase transition at a critical value of the sphere radius. The transition corresponds to a topology change in the D6-brane embeddings whose dual interpretation is the meson-melting transition. We perform the holographic computation of the free energy on 3-sphere and we use it to construct various candidate F-functions. These were recently proposed in the context of Einstein-scalar gravity to interpolate monotonically between the values of the sphere free energies of the UV and IR CFTs. We find that while the F-functions of the flavored ABJM theory have the correct UV and IR limits, they are not monotonic. We surmise that the non-monotonicity is related to the presence of the phase transition.

In this thesis two different topics in SYM theories are investigated. In the first part we use the AdS/CFT correspondence to study the problem of flavor symmetry for theories that are marginal deformations of the maximal SYM theory. In particular, we compute exactly the masses of the mesons of these theories. The results show that the mass spectrum is discrete, with a mass gap and a Zeeman-like splitting of the mass levels occurs. In the second part of the thesis, we develop a direct computational technique for scattering amplitudes in SYM theories. A combined use of background field method, superspace technologies and new pc programs makes a Feynman diagrammatic approach available. We apply this technique to compute the full two-loop MHV effective action of the maximal SYM theory. From there we move towards the extraction of the four point MHV scattering amplitude.