arXiv subjects

Martin Schvellinger

Publications and source records attributed to Martin Schvellinger.

At least 37 records · Page 2Linked to original sources

arXiv2012

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 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 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.

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arXiv2012

Thermalization with a chemical potential from AdS spaces

The time-scale of thermalization in holographic dual models with a chemical potential in diverse number of dimensions is systematically investigated using the gauge/gravity duality. We consider a model with a thin-shell of charged dust collapsing from the boundary toward the bulk interior of asymptotically anti-de Sitter (AdS) spaces. In the outer region there is a Reissner-Nordström-AdS black hole (RNAdS-BH), while in the inner region there is an anti-de Sitter space. We consider renormalized geodesic lengths and minimal area surfaces as probes of thermalization, which in the dual quantum field theory (QFT) correspond to two-point functions and expectation values of Wilson loops, respectively. We show how the behavior of these extensive probes changes for charged black holes in comparison with Schwarzschild-AdS black holes (AdS-BH), for different values of the black hole mass and charge. The full range of values of the chemical potential over temperature ratio in the dual QFT is investigated. In all cases, the structure of the thermalization curves shares similar features with those obtained from the AdS-BH. On the other hand, there is an important difference in comparison with the AdS-BH: the thermalization times obtained from the renormalized geodesic lengths and the minimal area surfaces are larger for the RNAdS-BH, and they increase as the black hole charge increases.

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arXiv2011

Deep Inelastic Scattering from Holographic Spin-One Hadrons

We study deep inelastic scattering structure functions from hadrons using different holographic dual models which describe the strongly coupled regime of gauge theories in the large $N$ limit. Particularly, we consider scalar and vector mesons obtained from holographic descriptions with fundamental degrees of freedom, corresponding to ${\cal {N}}=2$ supersymmetric and non-supersymmetric Yang-Mills theories. We explicitly obtain analytic expressions for the full set of eight structure functions, i.e., $F_1$, $F_2$, $g_1$, $g_2$, $b_1$, $b_2$, $b_3$, $b_4$, arising from the standard decomposition of the hadronic tensor of spin-one hadrons. We obtain the relations $2 F_1 = F_2$ and $2 b_1 = b_2$. In addition, we find $b_1 \sim {\cal {O}}(F_1)$ as suggested by Hoodbhoy, Jaffe and Manohar for vector mesons. Also, we find new relations among some of these structure functions.

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arXiv2011

Diagnostics of plasma photoemission at strong coupling

We compute the spectrum of photons emitted by the finite-temperature large-N SU(N) ${\cal {N}}=4$ 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 ${\cal{O}}(α'^3)$ 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 towards the infra-red, as expected from weak-coupling computations. The total number of emitted photons also increases as the 't Hooft coupling weakens.

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arXiv2011

Plasma conductivity at finite coupling

By taking into account the full order(α'^3) type IIB string theory corrections to the supergravity action, we compute the leading finite 't Hooft coupling order(λ^{-3/2}) corrections to the conductivity of strongly-coupled SU(N) {\cal {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.

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arXiv2010

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(α'^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.

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arXiv2010

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

By studying the effect of the order(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 order(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.

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arXiv2008

Kerr-AdS black holes and non-relativistic conformal QM theories in diverse dimensions

We study the discrete light cone quantization of Kerr-AdS_{d+3} black holes with a plane wave boundary. The resulting backgrounds are conjectured to be dual of non-relativist conformal quantum mechanical theories in d spatial dimensions at finite temperature and finite chemical potential. This includes the discrete light cone quantization of Kerr-AdS_4 and Kerr-AdS_6 black holes. These are conjectured to be dual of non-relativistic conformal quantum mechanical theories in one and three spatial dimensions, respectively, which are defined on plane wave backgrounds. We also consider the case of the BTZ black hole. We calculate thermodynamic properties of these systems by using the gravity dual models. We discuss the embedding of these backgrounds in string theory and M-theory. We give general formulas for the discrete light cone quantization of Kerr-AdS black holes in higher dimensions and their thermodynamic properties.

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arXiv2008

Kaon Decays from AdS/QCD

We briefly review one of the current applications of the AdS/CFT correspondence known as AdS/QCD and discuss about the calculation of four-point quark-flavour current correlation functions and their applications to the calculation of observables related to neutral kaon decays and neutral kaon mixing processes.

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arXiv2007

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 $ΔI = 1/2$ 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.

hep-ph↗

arXiv2007

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.

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arXiv2006

On the Delta I = 1/2 Rule in Holographic QCD

We study the $ΔI = 1/2$ rule for kaon decays and the $B_K$ parameter for $K^0 - {\bar K}^0$ mixing in a dual 5-dimensional holographic QCD model. We perform, in the chiral limit, computations of the relevant four-point current-current correlators, which depend upon self-interactions among the 5D bulk fields. Spontaneous chiral symmetry breaking ($χ$SB) is realized through boundary conditions on the bulk fields. Numerical results are analyzed in comparison with QCD, chiral perturbation theory ($χ$PT) and data, finding reasonable agreement with the experimental values of the $g_8$ and $g_{27}$ parameters describing the $ΔI =1/2,3/2$ decay channels.

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arXiv2004

Glueballs, symmetry breaking and axionic strings in non-supersymmetric deformations of the Klebanov-Strassler background

We obtain an analytic solution for an axionic non-supersymmetric deformation of the warped deformed conifold. This allows us to study D-strings in the infrared limit of non-supersymmetric deformations of the Klebanov-Strassler background. They are interpreted as axionic strings in the dual field theory. Following the arguments of [hep-th/0405282], the axion is a massless pseudo-scalar glueball which is present in the supergravity fluctuation spectrum and it is interpreted as the Goldstone boson of the spontaneously broken U(1) baryon number symmetry, being the gauge theory on the baryonic branch. Besides, we briefly discuss about the Pando Zayas-Tseytlin solution where the SU(2) \times SU(2) global symmetry is spontaneously broken. This background has been conjectured to be on the mesonic branch of the gauge theory.

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arXiv2003

Spinning and rotating strings for N=1 SYM theory and brane constructions

We obtain spinning and rotating closed string solutions in AdS_5 \times T^{1,1} background, and show how these solutions can be mapped onto rotating closed strings embedded in configurations of intersecting branes in type IIA string theory. Then, we discuss spinning closed string solutions in the UV limit of the Klebanov-Tseytlin background, and also properties of classical solutions in the related intersecting brane constructions in the UV limit. We comment on extensions of this analysis to the deformed conifold background, and in the corresponding intersecting brane construction, as well as its relation to the deep IR limit of the Klebanov-Strassler solution. We briefly discuss on the relation between type IIA brane constructions and their related M-theory descriptions, and how solitonic solutions are related in both descriptions.

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arXiv2002

RG flows from Spin(7), CY 4-fold and HK manifolds to AdS, Penrose limits and pp waves

We obtain explicit realizations of holographic renormalization group (RG) flows from M-theory, from E^{2,1} \times Spin(7) at UV to AdS_4 \times \tilde{S^7} (squashed S^7) at IR, from E^{2,1} \times CY4 at UV to AdS_4 \times Q^{1,1,1} at IR, and from E^{2,1} \times HK (hyperKahler) at UV to AdS_4 \times N^{0,1,0} at IR. The dual type IIA string theory configurations correspond to D2-D6 brane systems where D6 branes wrap supersymmetric four-cycles. We also study the Penrose limits and obtain the pp-wave backgrounds for the above configurations. Besides, we study some examples of non-supersymmetric and supersymmetric flows in five-dimensional gauge theories.

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arXiv2001

Supergravity duals of gauge theories from F(4) gauged supergravity in six dimensions

We construct supergravity solutions dual to twisted field theories that are the worldvolume theories of D4-branes wrapped on 2, 3-cycles, and NS-fivebranes on 3-cycles. We first obtain the solutions for the Romans' six-dimensional gauged supergravity theories and then up-lift them to ten dimensions. In particular, we find solutions for field configurations with either non-Abelian fields or B-fields being excited. One of these solutions, in the massless case, is up-lifted to the massless type IIA string theory. This is the first example of such a kind. The cases studied provide new examples of the AdS/CFT duality involving twisted field theories.

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arXiv2001

Supergravity duals of gauge field theories from SU(2) x U(1) gauged supergravity in five dimensions

We study the SO(4)-symmetric solution of the five-dimensional SU(2) x U(1) gauged N=4 supergravity theory obtained in [hep-th/0101202]. This solution contains purely magnetic non-Abelian and electric Abelian fields. It can be interpreted as a reduction of seven-dimensional gauged supergravity on a torus, which comes from type IIB supergravity on S^3. We also show how to obtain that solution from six-dimensional Romans' theory on a circle. We then up-lift the solution to massless type IIA supergravity. The dual gauge field theory is twisted and is defined on the worldvolume of a NS-fivebrane wrapped on S^3. Two other spatial directions of the NS-fivebrane are on a torus. In the IR limit it corresponds to a three-dimensional gauge field theory with two supercharges.

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arXiv2001

Brane Worlds, String Cosmology, and AdS/CFT

Using the thin-shell formalism we discuss the motion of domain walls in de Sitter and anti-de Sitter (AdS) time-dependent bulks. This motion results in a dynamics for the brane scale factor. We show that in the case of a clean brane the scale factor describes both singular and non-singular universes, with phases of contraction and expansion. These phases can be understood as quotients of AdS spacetime by a discrete symmetry group. We discuss this effect in some detail, and suggest how the AdS/CFT correspondence could be applied to obtain a non perturbative description of brane-world string cosmology.

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