arXiv subjects

Hesam Soltanpanahi

Publications and source records attributed to Hesam Soltanpanahi.

18 recordsLinked to original sources

arXiv2026

An Information-Theoretic Characterization of Optimal Value-Readout in Response-Register Quantum Oracles

Response-register quantum oracles admit two complementary operational interpretations: value readout and phase kickback. Although their computational equivalence is well understood, the quantitative relation between these two operational interpretations has lacked an exact characterization. We prove that, for finite Abelian response groups, the optimal single-query value-readout probability is exactly the normalized Rényi-1/2 effective Fourier support of the response state. This identity provides an exact information-theoretic characterization of optimal value-readout capability, gives the Rényi-1/2 effective Fourier support a direct operational interpretation in the oracle setting, and yields a tight phase--value complementarity theorem together with an explicit family of saturating response states.

quant-ph↗

arXiv2022

A perfect fluid hydrodynamic picture of domain wall velocities at strong coupling

We show that for a range of strongly coupled theories with a first order phase transition, the domain wall or bubble velocity can be expressed in a simple way in terms of a perfect fluid hydrodynamic formula, and thus in terms of the equation of state. We test the predictions for the domain wall velocities using the gauge/gravity duality.

hep-th↗

arXiv2020

Nonlinear Oscillatory Shear Tests in Viscoelastic Holography

We provide the first characterization of the nonlinear and time dependent rheologic response of viscoelastic bottom-up holographic models. More precisely, we perform oscillatory shear tests in holographic massive gravity theories with finite elastic response, focusing on the large amplitude oscillatory shear (LAOS) regime. The characterization of these systems is done using several techniques: (I) the Lissajous figures, (II) the Fourier analysis of the stress signal, (III) the Pipkin diagram and (IV) the dependence of the storage and loss moduli on the amplitude of the applied strain. We find substantial evidence for a strong strain stiffening mechanism, typical of hyper-elastic materials such as rubbers and complex polymers. This indicates that the holographic models considered are not a good description for rigid metals, where strain stiffening is not commonly observed. Additionally, a crossover between a viscoelastic liquid regime at small graviton mass (compared to the temperature scale), and a viscoelastic solid regime at large values is observed. Finally, we discuss the relevance of our results for soft matter and for the understanding of the widely used homogeneous holographic models with broken translations.

hep-th↗

arXiv2019

Dynamics near a first order phase transition

We study various dynamical aspects of systems possessing a first order phase transition in their phase diagram. We isolate three qualitatively distinct types of theories depending on the structure of instabilities and the nature of the low temperature phase. The non-equilibrium dynamics is modeled by a dual gravitational theory in 3+1 dimension which is coupled to massive scalar field with self interacting potential. By numerically solving the Einstein-matter equations of motion with various initial configurations, we investigate the structure of the final state arising through coalescence of phase domains. We find that static phase domains, even quite narrow are very long lived and we find a phenomenological equation for their lifetime. Within our framework we also analyze moving phase domains and their collision as well as the effects of spinodal instability and dynamical instability on an expanding boost invariant plasma.

hep-th↗

arXiv2019

Instability of BTZ black holes in parity-even massive gravity

We investigate the linearized equations of motion in three dimensional Born-Infeld gravity theory. Motivated by this model, we calculate the quasinormal modes of BTZ black hole solutions of parity-even gravity theories in three dimensions by using numerical methods. The results are classified in three families and they are so accurate such that it allows us to propose analytical form for the quasinormal frequencies. We find new quasinormal modes which have been missing in the literature of the analytical studies of three dimensional massive gravitons. These new modes do not have the known tower structure and they are purely imaginary for any value of the angular momenta. Considering the complete set of the quasinormal modes, we show that the BTZ black hole solutions are unstable for any value of the parameters of the theory. We confirm our numerical results by computing the new eigenmodes analytically at zero angular momentum.

hep-th↗

arXiv2018

Real-Time dynamics and phase separation in a holographic first order phase transition

We study the fully nonlinear time evolution of a holographic system possessing a first order phase transition. The initial state is chosen in the spinodal region of the phase diagram, and includes an inhomogeneous perturbation in one of the field theory directions. The final state of the time evolution shows a clear phase separation in the form of domain formation. The results indicate the existence of a very rich class of inhomogeneous black hole solutions.

hep-th↗

arXiv2016

Quasinormal modes and the phase structure of strongly coupled matter

We investigate the poles of the retarded Green's functions of strongly coupled field theories exhibiting a variety of phase structures from a crossover up to different first order phase transitions. These theories are modeled by a dual gravitational description. The poles of the holographic Green's functions appear at the frequencies of the quasinormal modes of the dual black hole background. We focus on quantifying linearized level dynamical response of the system in the critical region of phase diagram. Generically non-hydrodynamic degrees of freedom are important for the low energy physics in the vicinity of a phase transition. For a model with linear confinement in the meson spectrum we find degeneracy of hydrodynamic and non-hydrodynamic modes close to the minimal black hole temperature, and we establish a region of temperatures with unstable non-hydrodynamic modes in a branch of black hole solutions.

hep-th↗

arXiv2016

Non-equilibrium dynamics and phase transitions

We study the poles of the retarded Green's functions of strongly coupled field theories exhibiting a variety of phase structures from a crossover up to a first order phase transition. These theories are modeled by a dual gravitational description. The poles of the holographic Green's functions appear at the frequencies of the quasinormal modes of the dual black hole background. We establish that near the transition, in all cases considered, the applicability of a hydrodynamic description breaks down already at lower momenta than in the conformal case. We establish the appearance of the spinodal region in the case of the first order phase transition at temperatures for which the speed of sound squared is negative. An estimate of the preferential scale attained by the unstable modes is also given. We additionally observe a novel diffusive regime for sound modes for a range of wavelengths.

hep-th↗

arXiv2015

Linearized nonequilibrium dynamics in nonconformal plasma

We investigate the behaviour of the lowest nonhydrodynamic modes in a class of holographic models which exhibit an equation of state closely mimicking the one determined from lattice QCD. We calculate the lowest quasinormal mode frequencies for a range of scalar self-interaction potentials and find that the damping of the quasinormal modes at the phase transition/crossover falls off by a factor of around two from conformality after factoring out standard conformal temperature dependence. The damping encoded in the imaginary part of the frequencies turns out to be correlated with the speed of sound and is basically independent of the UV details of the model. We also find that the dynamics of the nonhydrodynamic degrees of freedom remains ultralocal, even to a higher degree, as we deviate from conformality. These results indicate that the role of nonhydrodynamic degrees of freedom in the vicinity of the crossover transition may be enhanced.

hep-th↗

arXiv2014

Universal Properties of the Langevin Diffusion Coefficients

We show that in generic isotropic holographic theories the longitudinal Langevin diffusion coefficient along the string motion is larger compared to that of the transverse direction. We argue that this is a universal relation and we derive the generic conditions in order to be satisfied. A way to violate the relation is to consider anisotropic gauge/gravity dualities. We give an explicit example of this violation where the noise along the transverse direction is larger than the noise occurring along the quark motion. Moreover, we derive the effective world-sheet temperature for any generic theory and then the conditions for negative excess noise. We argue that isotropic theories can not have negative excess noise and we additionally remark that these conditions are difficult to get satisfied, indicating positivity of the excess noise, even in a large class of anisotropic holographic theories.

hep-th↗

arXiv2014

Near Horizon of 5D Rotating Black Holes from 2D Perspective

We study the CFT dual to five dimensional extremal rotating black holes, by investigating the two dimensional perspective of their near horizon geometry. From two dimensional point of view, we show that both gauge fields, related to the two rotations, appear in the same manner in the asymptotic symmetry and in the associated central charge. We find that, our results are in perfect agreement with the generalization of Kerr/CFT approach to five dimensional extremal rotating black holes.

hep-th↗

arXiv2013

Heavy Quark Diffusion in Strongly Coupled Anisotropic Plasmas

We study the Langevin diffusion of a relativistic heavy quark in anisotropic strongly coupled theories in the local limit. Firstly, we use the axion space-dependent deformed anisotropic N=4 sYM, where the geometry anisotropy is always prolate, while the pressure anisotropy may be prolate or oblate. For motion along the anisotropic direction we find that the effective temperature for the quark can be larger than the heat bath temperature, in contrast to what happens in the isotropic theory. The longitudinal and transverse Langevin diffusion coefficients depend strongly on the anisotropy, the direction of motion and the transverse direction considered. We analyze the anisotropy effects to the coefficients and compare them to each other and to them of the isotropic theory. To examine the dependence of the coefficients on the type of the geometry, we consider another bottom-up anisotropic model. Changing the geometry from prolate to oblate, certain diffusion coefficients interchange their behaviors. In both anisotropic backgrounds we find cases that the transverse diffusion coefficient is larger than the longitudinal, but we find no negative excess noise.

hep-th↗

arXiv2013

The Imaginary Part of the Static Potential in Strongly Coupled Anisotropic Plasma

Using the gauge/gravity duality we study the imaginary part of the static potential associated to the thermal width in finite temperature strongly coupled anisotropic plasma. We firstly derive the potential for a generic anisotropic background. Then we apply our formulas to a theory where the anisotropy has been generated by a space dependent axion term. We find that using our method there exist a peculiar turning point in the imaginary part of the potential, similar to the one appearing in the real part. The presence of anisotropy leads to decrease of the imaginary potential, where larger decrease happens along the anisotropic direction when the temperature is kept fixed. When the entropy density is fixed, increase happens along the parallel direction while along the transverse plane we observe a decrease. To estimate the thermal width we use an approximate extrapolation beyond the turning point and we find a decrease in presence of the anisotropy, independently of the comparison scheme used.

hep-th↗

arXiv2013

Entanglement Entropy of Extremal BTZ

In this note, we use entanglement entropy as a tool to explore the universal properties of CFTs dual to extremal BTZ black holes. We demonstrate that the entanglement entropies computed in the CFTs at the boundary of the extremal BTZ and the boundary of the near-horizon limit of the extremal BTZ are in perfect agreement and have the form appropriate to a two-dimensional CFT with only the chiral part excited and the anti-chiral in the ground state. Furthermore, we analyze the universal limits of the entanglement entropy and recover the correct value of the thermal entropy for large entangling intervals and the first-law like relation for the small interval.

hep-th↗

arXiv2012

Energy loss in a strongly coupled anisotropic plasma

We study the energy loss of a rotating infinitely massive quark moving, at constant velocity, through an anisotropic strongly-coupled N=4 plasma from holography. It is shown that, similar to the isotropic plasma, the energy loss of the rotating quark is due to either the drag force or radiation with a continuous crossover from drag-dominated regime to the radiation dominated regime. We find that the anisotropy has a significant effect on the energy loss of the heavy quark, specially in the crossover regime. We argue that the energy loss due to radiation in anisotropic media is less than the isotropic case. Interestingly this is similar to analogous calculations for the energy loss in weakly coupled anisotropic plasma.

hep-th↗

arXiv2011

Non-planar Anomalous Dimensions in the sl(2) Sector

In this note we compute the non-planar one loop anomalous dimension of restricted Schur polynomials that belong to the sl(2) sector of N=4 super Yang-Mills theory and have a bare dimension of order N. Although the details are rather different, ultimately the problem of diagonalizing the dilatation operator in the sl(2) sector can be reduced to the su(2) sector problem. In this way we establish the expected dynamical emergence of the Gauss Law for giant gravitons and further show that the dilatation operator reduces to a set of decoupled harmonic oscillators.

hep-th↗

arXiv2010

On Born-Infeld Gravity in Three Dimensions

In this paper we explore different aspects of three dimensional Born-Infeld as well as Born-Infeld-Chern-Simons gravity. We show that the models have AdS and AdS-wave vacuum solutions. Moreover we observe that although Born-Infeld-Chern-Simons gravity admits a logarithmic solution, Born-Infeld gravity does not, though it has a limiting logarithmic solution as we approach the critical point.

hep-th↗

arXiv2010

Form field theory on Calabi-Yau threefold

We show how the natural Abelian duality of 2 and 3-form gravity theories on seven dimensional manifold CY3xS1, leads to an S-duality between 2 and 3-form theories on simply connected CY3. The massless sector of the 2-form field theory on CY3 corresponds to the A model string field theory. We discuss the complex structure independence of the 2-form theory for a general Kahler manifold and derive the holomorphic anomaly equations for simply connected CY3.

hep-th↗