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## Publications

Publications (49)

A bstract
This work addresses the response of a holographic conformal field theory to a homogeneous gravitational periodic driving. The dual geometry is the AdS-soliton, which models a strongly coupled quantum system in a gapped phase, on a compact domain. The response is a time-periodic geometry up to a driving amplitude threshold which decreases...

This work addresses the response of a holographic conformal field theory to a homogeneous gravitational periodic driving. The dual geometry is the AdS-soliton, which models a strongly coupled quantum system in a gapped phase, on a compact domain. The response is a time-periodic geometry up to a driving amplitude threshold which decreases with the d...

A bstract
We study periodically driven scalar fields and the resulting geometries with global AdS asymptotics. These solutions describe the strongly coupled dynamics of dual finite-size quantum systems under a periodic driving which we interpret as Floquet condensates. They span a continuous two-parameter space that extends the linearized solutions...

We numerically investigate spherically symmetric collapses in the Gross–Pitaevskii equation with attractive nonlinearity in a harmonic potential. Even below threshold for direct collapse, the wave function bounces off from the origin and may eventually become singular after a number of oscillations in the trapping potential. This is reminiscent of...

We construct a family of very simple stationary solutions to gravity coupled to a massless scalar field in global AdS. They involve a constantly rising source for the scalar field at the boundary and thereby we name them pumping solutions. We construct them numerically in $D=4$. They are regular and, generically, have negative mass. We perform a st...

We numerically investigate spherically symmetric collapses in the Gross-Pitaevskii equation with attractive nonlinearity in a harmonic potential. Even below threshold for direct collapse, the wave function bounces off from the origin and may eventually become singular after a number of oscillations in the trapping potential. This is reminiscent of...

We study linear and nonlinear stability of asymptotically AdS$_4$ solutions in Einstein-Maxwell-scalar theory. After summarizing the set of static solutions we first examine thermodynamical stability in the grand canonical ensemble and the phase transitions that occur among them. In the second part of the paper we focus on nonlinear stability in th...

In order to holographically model quenches with a gapped final hamiltonian, we consider a gravity-scalar theory in anti-de Sitter space with an infrared hard wall. We allow a time dependent profile for the scalar field at the wall. This induces an energy exchange between bulk and wall and generates an oscillating scalar pulse. We argue that such ba...

We study holographic models related to global quantum quenches in finite size systems. The holographic set up describes naturally a CFT, which we consider on a circle and a sphere. The enhanced symmetry of the conformal group on the circle motivates us to compare the evolution in both cases. Depending on the initial conditions, the dual geometry ex...

We study the dynamics of a spherically symmetric thin shell of perfect fluid
embedded in d-dimensional Anti-de Sitter space-time. In global coordinates,
besides collapsing solutions, oscillating solutions are found where the shell
bounces back and forth between two radii. The parameter space where these
oscillating solutions exist is scanned in arb...

We study holographic models related to global quantum quenches in finite size
systems. The holographic set up describes naturally a CFT, which we consider on
a circle and a sphere. The enhanced symmetry of the conformal group on the
circle motivates us to compare the evolution in both cases. Depending on the
initial conditions, the dual geometry ex...

We study holographically the out of equilibrium dynamics of a finite size
closed quantum system in 2+1 dimensions, modelled by the collapse of a shell of
a massless scalar field in AdS4. In global coordinates there exists a variety
of evolutions towards final black hole formation which we relate with different
patterns of relaxation in the dual fie...

We study the holographic dual of flavors in a Chern-Simons matter theory at
non-zero temperature, realized as D6-branes in the type IIA black hole dual in
the ABJM background geometry. We consider both massive and massless flavors.
The former are treated in the quenched approximation, whereas the massless ones
are considered as dynamical objects an...

Gravity solutions holographically dual to strongly coupled Quark-Gluon Plasmas with non-zero quark density are reviewed. They are motivated by the urgency of finding novel tools to explore the phase diagram of QCD-like theories at finite chemical potential. After presenting the solutions and their regime of validity, some of their physical properti...

We study the holographic dual model of quenched flavors immersed in a
quark-gluon plasma with massless dynamical quarks in the Veneziano limit. This
is modeled by embedding a probe D7 brane in a background where the backreaction
of massless D7 branes has been taken into account. The background, and hence
the effects, are perturbative in the Venezia...

We review the construction of gravitational solutions holographically dual to
N=1 quiver gauge theories with dynamical flavor multiplets. We focus on the
D3-D7 construction and consider the finite temperature, finite quark chemical
potential case where there is a charged black hole in the dual solution.
Discussed physical outputs of the model inclu...

We present the string dual to SU(Nc) N=4 SYM, coupled to Nf massless
fundamental flavors, at finite temperature and baryon density. The solution is
determined by two dimensionless parameters, both depending on the 't Hooft
coupling $\lambda_h$ at the scale set by the temperature T:
$\epsilon_h\sim\lambda_h Nf/Nc$, weighting the backreaction of the...

We study the AC optical and hall conductivities of Dp/Dq-branes intersections
in the probe approximation and use sum-rules to study various associated
transport coefficients. We determine that the presence of massive fundamental
matter, as compared to massless fundamental matter described holographically by
a theory with no dimensional defects, red...

We provide a framework for calculating holographic Green's functions from general bilinear actions and fields obeying coupled differential equations in the bulk. The matrix-valued spectral function is shown to be independent of the radial bulk coordinate. Applying this framework we improve the analysis of fluctuations in the D3/D7 system at finite...

We present the string dual to finite temperature SU(Nc) N=4 SYM coupled to massless fundamental matter introduced by Nf D7 branes, with Abelian flavor symmetry. The analytic solution includes the backreaction of the flavors up to second order in the parameter that weighs the internal flavor loops, epsilon_h=(lambda_h Nf)/(8 pi^2 Nc), lambda_h being...

We study the holographic D3/D7 setup dual to N=4 supersymmetric Yang-Mills with quenched fundamental matter. We extend the previous analyses of conductivity and photoproduction to the case where there is a finite electric field. Due to the electric field a special region in the D7-brane geometry, labelled the singular shell, appears generically, an...

We analyze the charge diffusion and conductivity in a Dp/Dq holographic setup that is dual to a supersymmetric Yang-Mills theory in p+1 dimensions with Nf << Nc flavor degrees of freedom at finite temperature and nonvanishing U(1) baryon number chemical potential. We provide a new derivation of the results that generalize the membrane paradigm to t...

We study the conductivity, susceptibility and diffusion of a strongly coupled quark gluon plasma from the holographic perspective. We calculate general expressions for these quantities in the presence of finite baryon density and show that in this context, for the D3/D7 intersection the Einstein relation holds, providing another non-trivial check o...

Using the AdS/CFT correspondence, we compute the spectral functions of thermal super Yang Mills at large N_c coupled to a small number of flavours of fundamental matter, N_f<<N_c, in the presence of a nonzero baryon density. The holographic dual of such a theory involves the addition of probe D7-branes with a background worldvolume gauge field swit...

We compute the shear viscosity of the non-commutative N=4 super Yang-Mills quantum field theory at strong coupling using the dual supergravity background. Special interest derives from the fact that the background presents an intrinsic anisotropy in space through the distinction of commutative and non-commutative directions. Despite this anisotropy...

We complete the computation of viscous transport coefficients in the near horizon geometries that arise from a stack of black Dp-branes for p=2,...,6 in the decoupling limit. The main new result is the obtention of the bulk viscosity which, for all p, is found to be related to the speed of sound by the simple relation \zeta/\eta = -2(v_s^2-1/p). Fo...

Following the nonperturbative prescription for the jet quenching parameter recently proposed by Liu, Rajagopal and Wiedemann, we compute the first correction in the inverse `t Hooft coupling corresponding to string alpha' corrections in the dual background. We also consider the introduction of a chemical potential for the U(1)^3 gauged R-symmetry....

We compute the shear viscosity in the supersymmetric Yang-Mills theory dual to the STU background. This is a thermal gauge theory with a chemical potential. The quotient of the shear viscosity over the entropy density exhibits no deviation from the well known result 1/4\pi. Comment: 9 pages, some references updated, abstract and some typos correcte...

A class of solutions to Supergravity in 10 or 11 dimensions is presented which extends the non-standard or semi-local intersections of Dp-branes to the case of non-extremal p-branes. The type of non-extremal solutions involved in the intersection is free and we provide two examples involving black-branes and/or D-\bar{D} systems. After a rotation a...

We study supersymmetric intersections of M2 and M5 branes
with different pp-waves of M-theory. We consider first M-brane probes
in the background of pp-waves and determine under which conditions the
embedding is supersymmetric. We particularize our formalism to the
case of pp-waves with 32, 24 and 20 supersymmetries. We also construct
supergravity...

Using differential renormalization, we calculate the complete two-point function of the background gauge superfield in pure N=1 Supersymmetric Yang-Mills theory to two loops. Ultraviolet and (off-shell) infrared divergences are renormalized in position and momentum space respectively. This allows us to reobtain the beta function from the dependence...

We embed the Seiberg–Witten solution for the low energy dynamics of super Yang–Mills theory with an even number of massive hypermultiplets into the Whitham hierarchy. Expressions for the first and second derivatives of the prepotential in terms of the Riemann theta function are provided which extend previous results obtained by Gorsky, Marshakov, M...

We study the electric flux tubes that undertake color confinement in N=2 supersymmetric Yang-Mills theories softly broken down to N=1 by perturbing with the first two Casimir operators. The relevant Abelian Higgs model is not the standard one due to the presence of an off-diagonal coupling among different magnetic U(1) factors. We perform a prelimi...

We compute instanton corrections to the low energy effective prepotential of supersymmetric theories in a variety of cases, including all classical gauge groups and even number of fundamental matter hypermultiplets. To this end, we take profit of a set of first- and second-order equations for the logarithmic derivatives of the prepotential with res...

We study the Seiberg-Witten-Whitham equations in the strong coupling regime of the script N sign = 2 super Yang-Mills theory in the vicinity of the maximal singularities. In the case of SU(2) the Seiberg-Witten-Whitham equations fix completely the strong coupling expansion. For higher rank SU(N) they provide a set of non-trivial constraints on the...

We study = 2 super Yang-Mills theory with gauge group SU(N) from the point of view of the Whitham hierarchy. We develop a new recursive method to compute the whole instanton expansion of the prepotential using the theta function associated with the root lattice of the group. Explicit results for the one- and two-instanton corrections in SU(N) are p...

We review recent work on the study of N=2 super Yang-Mills theory with gauge group SU(N) from the point of view of the Whitham hierarchy, mainly focusing on three main results: (i) We develop a new recursive method to compute the whole instanton expansion of the low-energy effective prepotential; (ii) We interpret the slow times of the hierarchy as...

In this paper we continue with the program to explore the topography of the space of {ital W}-type algebras. In the present case, the starting point is the work of Khesin, Lyubashenko, and Roger on the algebra of {ital q}-deformed pseudodifferential symbols and their associated integrable hierarchies. The analysis goes on by studying the associated...

It is well known that the centerless W1+∞ algebra provides a hamiltonian structure for the KP hierarchy. In this letter we address the question whether the centerful version plays a similar rôle in any related integrable system. We find that, surprisingly enough, the centrally extended W1+∞ algebra yields yet another Poisson structure for the same...

Recently much attention has been paid to the restriction of KP to the submanifold of operators which can be represented as a ratio of two purely differetial operators L = ABf-1. Whereas most of the aspects concerning this reduced hierarchy, like the Lax flows and the Hamiltonians, are by now well understood, there still lacks a clear and conclusive...

The KP hierarchy is hamiltonian relative to a one-parameter family of Poisson structures obtained from a generalized Adler map in the space of formal pseudodifferential symbols with noninteger powers. The resulting W-algebra is a one-parameter deformation of WKP admitting a central extension for generic values of the parameter, reducing naturally t...

Classical W-algebras in higher dimensions have been recently constructed. In this letter we show that there is a finitely generated subalgebra which is isomorphic to the algebra of local diffeomorphisms in D dimensions. Moreover, there is a tower of infinitely many fields transforming under this subalgebra as symmetric tensorial one-densities. We a...

We chart out the landscape of W∞-type algebras using WKP(q) — a recently discovered one-parameter deformation of WKP. We relate all hitherto known W∞-type algebras to WKP(q) and its reductions, contractions, and/or truncations at special values of the parameter.

The KP hierarchy is hamiltonian relative to a one-parameter family of Poisson structures obtained from a generalized Adler map in the space of formal pseudodifferential symbols with noninteger powers. The resulting $\W$-algebra is a one-parameter deformation of $\W_{\rm KP}$ admitting a central extension for generic values of the parameter, reducin...

A two-boson realization of the second hamiltonian structure for the KP hierarchy has recently appeared in the literature. Furthermore, it has been claimed that this is also a realization of the hierarchy itself. This is surprising because it would mean that the dynamics of the KP hierarchy---which in its usual formulation requires an infinite numbe...

We study reductions of the even order SKP hierarchy. We prove that these systems are integrable and bihamiltonian. We derive an infinite set of independent polynomial conservation laws, prove their nontriviality, and derive Lenard relations between them. A further reduction of the simplest such hierarchy is identified with the supersymmetric KdV hi...

We construct the second hamiltonian structure of the KP hierarchy as a natural extension of the Gel'fand-Dickey brackets of the generalized KdV hierarchies. The first structure — which has been recently identified as W1+∞—is coordinated with the second structure and arises as a trivial (generalized) cocycle. The second structure gives rise to a non...

We prove that the supersymmetric SKdV hierarchy is bihamiltonian. One of the hamiltonian structures (the "second") is a classical version of the supervirasoro algebra whereas the other structure is nonlocal. We exhibit these two structures as hamiltonian reductions of the recently constructed supersymmetric Gel'fand-Dickey brackets, derive Lenard r...