Warped Deformed Throats have Faster (Electroweak) Phase Transitions

We study the dynamics of the finite-temperature phase transition for warped Randall-Sundrum(RS)-like throat models related to the Klebanov-Tseytlin solution. We find that, for infrared branes stabilized near the tip of the throat, the bounce action has a mild N^2 dependence, where N(y) \sim [M_5 L(y)]^{3/2} is the effective number of degrees of freedom of the holographic dual QFT, and where L(y) is the local curvature radius, which decreases in the infrared. In addition, the bounce action is not enhanced by large numbers. These features allow the transition to successfully complete over a wider parameter range than for Goldberger-Wise stabilized RS models. Due to the increase of L(y) in the ultraviolet, the throat has a reliable gravitational description even when the number of infrared degrees of freedom is small. We also comment on aspects of the thermal phase transition in Higgsless models, where the gauge symmetry breaking is achieved via boundary conditions. Such models include orbifold-GUT models and the Higgsless electroweak symmetry breaking theories of Csaki et al., with Standard Model gauge fields living in the bulk.Comment: published version, 18 pages, minor typo corrected, reference adde

Pseudo-Goldstones from Supersymmetric Wilson Lines on 5D Orbifolds

We consider a U(1) gauge theory on the five dimensional orbifold $\mathcal{M}_4\times S^1/Z_2$, where $A_5$ has even $Z_2$ parity. This leads to a light pseudoscalar degree of freedom $W(x)$ in the effective 4D theory below the compactification scale arising from a gauge-invariant brane-to-brane Wilson line. As noted by Arkani-Hamed et al in the non-supersymmetric $S^1$ case the 5D bulk gauge-invariance of the underlying theory together with the non-local nature of the Wilson line field leads to the protection of the 4D theory of $W(x)$ from possible large global-symmetry violating quantum gravitational effects. We study the $S^1/Z_2$ theory in detail, in particular developing the supersymmetric generalization of this construction, involving a pseudoscalar Goldstone field (the `axion') and its scalar and fermion superpartners (`saxion' and `axino'). The global nature of $W(x)$ implies the absence of independent Kaluza-Klein excitations of its component fields. The non-derivative interactions of the (supersymmetric) Wilson line in the effective 4D theory arising from U(1) charged 5D fields $\Phi$ propagating between the boundary branes are studied. We show that, similar to the non-supersymmetric $S^1$ case, these interactions are suppressed by $\exp(-\pi R m_{\Phi})$ where $\pi R$ is the size of the extra dimension.Comment: LaTex, 16 page

Holographic current correlators at finite coupling and scattering off a supersymmetric plasma

By studying the effect of the O(α′3) string theory corrections to type IIB supergravity, including those corrections involving the Ramond-Ramond five-form field strength, we obtain the corrected equations of motion of an Abelian perturbation of the AdS_5-Schwarzschild black hole. We then use the gauge theory/string theory duality to examine the coupling-constant dependence of vector current correlators associated to a gauged U(1) sub-group of the global R-symmetry group of strongly-coupled N=4 supersymmetric Yang-Mills theory at finite temperature. The corrections induce a set of higher-derivative operators for the U(1) gauge field, but their effect is highly suppressed. We thus find that the O(α′3) corrections affect the vector correlators only indirectly, through the corrected metric. We apply our results to investigate scattering off a supersymmetric Yang-Mills plasma at low and high energy. In the latter regime, where Deep Inelastic Scattering is expected to occur, we find an enhancement of the plasma structure functions in comparison with the infinite 't Hooft coupling result.Instituto de Física La Plat

Plasma photoemission from string theory

Leading ’t Hooft coupling corrections to the photoemission rate of the planar limit of a strongly-coupled N = 4 SYM plasma are investigated using the gauge/string duality. We consider the full O(α ′3) type IIB string theory corrections to the supergravity action, including higher order terms with the Ramond-Ramond five-form field strength. We extend our previous results presented in [1]. Photoemission rates depend on the ’t Hooft coupling, and their curves suggest an interpolating behaviour from strong towards weak coupling regimes. Their slopes at zero light-like momentum give the electrical conductivity as a function of the ’t Hooft coupling, in full agreement with our previous results of [2]. Furthermore, we also study the effect of corrections beyond the large N limit.Instituto de Física La Plat

Plasma conductivity at finite coupling

By taking into account the full O(α′3) type IIB string theory corrections to the supergravity action, we compute the leading finite ’t Hooft coupling O(λ−3/2) corrections to the conductivity of strongly-coupled SU(N ) N = 4 supersymmetric Yang-Mills plasma in the large N limit. We find that the conductivity is enhanced by the corrections, in agreement with the trend expected from previous perturbative weak-coupling computations.Instituto de Física La Plat

Towards 't Hooft parameter corrections to charge transport in strongly-coupled plasma

We study R-charge transport in a wide class of strongly-coupled supersymmetric plasmas at finite temperature with 't Hooft coupling corrections. To achieve this, we use the gauge/string duality and include the full set of order(\alpha'^3) corrections to the supergravity backgrounds given at zeroth order by the direct product of the AdS-Schwarzschild black hole with a five-dimensional compact Einstein manifold. On general grounds, the reduction leads to a large number of higher derivative operators, which we reduce using the symmetries of the solution. We are left with a universal set of operators whose coefficients can in principle be fixed by carrying out an explicit compactification. We apply our results to the computation of the R-charge conductivity of the supersymmetric plasma at finite yet strong coupling.Instituto de Física La Plat

Diagnostics of plasma photoemission at strong coupling

We compute the spectrum of photons emitted by the finite-temperature large- N SU(N) N = 4 supersymmetric Yang-Mills plasma coupled to electromagnetism, at strong yet finite ’t Hooft coupling. We work in the holographic dual description, extended by the inclusion of the full set of O (α'3) type IIB string theory operators that correct the minimal supergravity action. We find that, as the t’ Hooft coupling decreases, the peak of the spectrum increases, and the momentum of maximal emission shifts toward the infrared, as expected from weak-coupling computations. The total number of emitted photons also increases as the ’t Hooft coupling weakens.Instituto de Física La Plat

Four-point functions and kaon decays in a minimal AdS/QCD model

We study the predictions of holographic QCD for various observable four-point quark flavour current-current correlators. The dual 5-dimensional bulk theory we consider is a $SU(3)_L \times SU(3)_R$ Yang Mills theory in a slice of $AdS_5$ spacetime with boundaries. Particular UV and IR boundary conditions encode the spontaneous breaking of the dual 4D global chiral symmetry down to the $SU(3)_V$ subgroup. We explain in detail how to calculate the 4D four-point quark flavour current-current correlators using the 5D holographic theory, including interactions. We use these results to investigate predictions of holographic QCD for the $\Delta I = 1/2$ rule for kaon decays and the $B_K$ parameter. The results agree well in comparison with experimental data, with an accuracy of 25% or better. The holographic theory automatically includes the contributions of the meson resonances to the four-point correlators. The correlators agree well in the low-momentum and high-momentum limit, in comparison with chiral perturbation theory and perturbative QCD results, respectively.Comment: Published version, title changed to conform with Journal format, references and clarifying remarks added, 40 pages, 5 figure

Plasma photoemission from string theory

Leading 't Hooft coupling corrections to the photoemission rate of the planar limit of a strongly-coupled {\cal {N}}=4 SYM plasma are investigated using the gauge/string duality. We consider the full order \alpha'^3 type IIB string theory corrections to the supergravity action, including higher order terms with the Ramond-Ramond five-form field strength. We extend our previous results presented in arXiv:1110.0526. Photoemission rates depend on the 't Hooft coupling, and their curves suggest an interpolating behaviour from strong towards weak coupling regimes. Their slopes at zero light-like momentum give the electrical conductivity as a function of the 't Hooft coupling, in full agreement with our previous results of arXiv:1108.6306. Furthermore, we also study the effect of corrections beyond the large N limit.Comment: 36 pages, 5 figures, paragraph added in the conclusions, references added, typos correcte