String/M-theory Dual of Large-N Thermal QCD-Like Theories at Intermediate Gauge/’t Hooft Coupling and Holographic Phenomenology

Abstract

Considering the setup of [1] involving UV-complete top-down type IIB holographic dual of large-N thermal QCD with a fluxed resolved warped deformed conifold, in [2] delocalized type IIA S(trominger)-Y(au)-Z(aslow)mirror of the type IIB background of [1] was constructed via three T dualities along a special Lagrangian T3 fibered over a large base and then uplifted, locally, to the 11-dimensional M-theory. Considering the aforementioned setup [2] in the “MQGP” limit, this thesis makes the following contributions. In [3] we obtained the masses of the 0++, 0−+, 0−−, 1++, 2++ (‘glueball’) states which correspond to fluctuations in the dilaton or complexified two-forms or appropriate metric components in the aforementioned backgrounds in the ‘MQGP’ limit of [2]. We used WKB quantization conditions and Neumann/Dirichlet boundary conditions at an IR cut-off (‘r0’)/horizon radius (‘rh’) on the solutions to the equations of motion. We found that the former technique produced results closer to the lattice results [4], [5]. We also discussed the rh = 0-limits of all calculations which correspond to the thermal background. This thesis fills the gap in the literature by computing the meson spectroscopy at finite gauge coupling and a finite number of colors, from a top-down holographic string model. In [6], we obtained analytical expressions for the vector and scalar meson spectra by using the delocalized type IIA SYZ mirror of the holographic type IIB dual of large-N thermal QCD of [1] as obtained in [2]. We verified via explicit computations that the spectra for v both vector and scalar mesons obtained by the gravity dual with a black hole for all ranges of temperature are nearly isospectral with the spectra obtained by a thermal gravity dual valid only for low temperatures. Subsequently, in [7] we obtained the interaction Lagrangian corresponding to exotic scalar glueball (GE) − / - meson by using the pull-back of the perturbed type IIA metric corresponding to the perturbation of [1]’s M-theory uplift of [2]’s. The coupling constants in the interaction Lagrangian, linear in the exotic scalar glueball and up to quartic in the mesons, were obtained as (radial integrals of) [2]’sM-theory uplift’s metric components and six radial functions appearing in theM-theory metric perturbations. Assuming MG > 2M , we then computed ! 2 ,GE ! 2 , 2 , + 2 decay widths as well as the direct and indirect (mediated via mesons) GE ! 4 decays. In [8] we obtained O

l6 p

corrections to the MQGP background of [2] to study a top-down holographic dual of the thermal QCD-like theories at intermediate ’t Hooft coupling and in [9] we obtained the values of the coupling constants of the O(p4) PT Lagrangian in the chiral limit involving the NGBs and meson (and its flavor partners) from the M-theory/type IIA dual of large-N thermal QCD [2], inclusive of the O(R4) corrections. We observed that there is a competition between non-conformal IR enhancement and Planckian and large-N suppression and going to orders beyond the O(l6 p) is necessitated if the former wins out. For the latter part [9], we observed that ensuring compatibility with phenomenological/lattice results (the values ) as given in [10], required a relationship relating the O(R4) corrections and large-N suppression.