arXiv subjects

I. Ya. Aref'eva

Publications and source records attributed to I. Ya. Aref'eva.

At least 19 recordsLinked to original sources

arXiv2024

Entanglement entropy in de Sitter: no pure states for conformal matter

In this paper, we consider the entanglement entropy of conformal matter for finite and semi-infinite entangling regions, as well as the formation of entanglement islands in four-dimensional de Sitter spacetime partially reduced to two dimensions. We analyze complementarity and pure state condition of entanglement entropy of pure states as a consistency test of the CFT formulas in this geometrical setup, which has been previously used in the literature to study the information paradox in higher-dimensional de Sitter in the context of the island proposal. We consider two different types of Cauchy surfaces in the extended static patch and flat coordinates, correspondingly. For former, we found that entanglement entropy of a pure state is always bounded from below by a constant and never becomes zero, as required by quantum mechanics. In turn, the difference between the entropies for some region and its complement, which should be zero for a pure state, in direct calculations essentially depends on how the boundaries of these regions evolve with time. Regarding the flat coordinates, it is impossible to regularize spacelike infinity in a way that would be compatible with complementarity and pure state condition, as opposed, for instance, to two-sided Schwarzschild black hole. Finally, we discuss the information paradox in de Sitter and show that the island formula does not resolve it, at least in this setup. Namely, we give examples of a region with a time-limited growth of entanglement entropy, for which there is no island solution, and the region, for which entanglement entropy does not grow, but the island solution exists.

hep-th↗

arXiv2023

Infrared Regularization and Finite Size Dynamics of Entanglement Entropy in Schwarzschild Black Hole

In this paper, infrared regularization of semi-infinite entangling regions and island formation for regions of finite size in the eternal Schwarzschild black hole are considered. We analyze whether the complementarity property and pure state condition of entanglement entropy can be preserved in the given approximation. We propose a special regularization that satisfies these two properties. With regard to entangling regions of finite size, we derive two fundamental types of them, which we call "mirror-symmetric" (MS) and "asymmetric" (AS). For MS regions, we discover a discontinuous evolution of the entanglement entropy of Hawking radiation due to finite lifetime of the island. The entanglement entropy of matter for semi-infinite regions in two-sided Schwarzschild black hole does not follow the Page curve. The lifetime of AS regions is bounded from above due to the phenomenon that we call "Cauchy surface breaking". Shortly before this breaking, the island configuration becomes non-symmetric. For both types of finite regions, there is a critical size, below which the island never dominates. For regions smaller than some other critical size, the island does not emerge. Finally, we show that the island prescription does not help to solve the information paradox for certain finite regions.

hep-th↗

arXiv2023

Bose Gas Modeling of the Schwarzschild Black Hole Thermodynamics

Black holes violate the third law of thermodynamics, and this gives rise to difficulties with the microscopic description of the entropy of black holes. Recently, it has been shown that the microscopic description of the Schwarzschild black hole thermodynamics in $D = 4$ spacetime dimensions is provided by the analytical continuation of the entropy of Bose gas with non-relativistic one particle energy to d =-4 negative spatial dimension. In this paper, we show that the D=5 and D=6 Schwarzschild black holes thermodynamics can be modeled by the d-dimensional Bose gas, d=1,2,3..., with the one particle energy $\varepsilon(k)=k^α$ under conditions $α=-d/3$ and $α=-d/4$, respectively. In these cases the free energy of the Bose gas has divergences and we introduce a cut-off and perform the minimal renormalizations. We also perform renormalizations using analytical regularization and prove that the minimal cut-off renormalization gives the same answer as the analytical regularization by the Riemann zeta-function.

hep-th↗

arXiv2018

Holographic Non-equilibrium Heating

We study the holographic entanglement entropy evolution after a global sharp quench of thermal state. After the quench, the system comes to equilibrium and the temperature increases from $T_i$ to $T_f$. Holographic dual of this process is provided by an injection of a thin shell of matter in the black hole background. The quantitative characteristics of the evolution depend substantially on the size of the initial black hole. We show that characteristic regimes during non-equilibrium heating do not depend on the initial temperature and are the same as in thermalization. Namely these regimes are pre-local-equilibration quadratic growth, linear growth and saturation regimes of the time evolution of the holographic entanglement entropy. We study the initial temperature dependence of quantitative characteristics of these regimes and find that the critical exponents do not depend on the temperature, meanwhile the prefactors are the functions on the temperature.

hep-th↗

arXiv2017

Waking and Scrambling in Holographic Heating up

We consider a holographic model of the heating up process. As a dual background we take a geometry describing thin shell accretion on a black brane. We find explicitly the time evolution of the mutual information during the non-equlibrium heating process from the initial temperature $T_i$ to the final temperature $T_f$ for the system of two intervals in the 1+1 dimensional case. We calculate widths and separation of twointervals for which the time dependence of the mutual information has the bell-like form, i.e. it starts from zero value at the wake up time, then reaches a maximal value and vanishes at the scrambling time. This form of the mutual information evolution was previously found in photosynthesis. The zone of the bell-like configurations exists for small distances $x<\log 2/2πT_i$ only for the particular interval sizes. For $x$ large enough, i.e. $x>>\log 2/2πT_i$, it exists only for large enough interval sizes and this zone becomes more narrow when $T_i$ increases and becomes larger with increasing of $T_f$.

hep-th↗

arXiv2016

Holography for Heavy Ions Collisions at LHC and NICA

This is a contribution for the Proceedings of 5th International Conference on New Frontiers in Physics (ICNFP 2016), held at Crete, 6-14 July 2016. Our goal is to obtain phenomenologically reliable insights for the physics of the quark-gluon plasma (QGP) from the holography. I briefly review how in the holographic setup one can describe the QGP formation in heavy ion collisions and how to get quantitatively the main characteristics of the QGP formation -- the total multiplicity and the thermalization time. To fit the experimental form of dependence of total multiplicity on energy, obtained at LHC, we have to deal with a special anisotropic holographic model, related with the Lifshitz-type background. Our conjecture is that this Lifshitz-type background with non-zero chemical potential can be used to describe future data expected from NICA. In particular, we present the results of calculations of the holographic confinement/deconfinement phase transition in the $(μ,T)$ (chemical potential, temperature) plane in this anisotropic background and show the dependence of the transition line on the orientation of the quark pair. This dependence leads to a non-sharp character of physical confinement/deconfinement phase in the $(μ,T)$-plane. We use the bottom-up soft wall approach incorporating quark confinement deforming factor and vector field providing the non-zero chemical potential. In this model we also estimate the holographic photon production.

hep-th↗

arXiv2016

Holographic Dual to Conical Defects III: Improved Image Method

The geodesics prescription in holographic approach in Lorentzian signature is valid only for geodesics which connect spacelike-separated points at the boundary, since there are no timelike geodesics which reach the boundary. There is also no straightforward analytic Euclidean continuation for a general background, such as e. g. moving particle in AdS. We propose an improved geodesic image method for two-point Lorentzian correlators which is valid for arbitrary time intervals in case of the bulk spacetime deformed by point particles. We illustrate that our prescription is consistent with the case when the analytic continuation exists and with the quasigeodesics prescription used in previous work. We also discuss some other applications of the improved image method, such as holographic entanglement entropy and multiple particles in AdS3.

hep-th↗

arXiv2016

Holographic Dual to Conical Defects: I. Moving Massive Particle

We study correlation functions of scalar operators on the boundary of the $AdS_3$ space deformed by moving massive particles in the context of the AdS/CFT duality. To calculate two-point correlation functions we use the geodesic approximation and the renormalized image method. We compare results of the renormalized image method with direct calculations using tracing of winding geodesics around the cone singularities, and show on examples that they are equivalent. We demonstrate that in the geodesic approximation the correlators exhibit a zone structure. This structure substantially depends on the mass and velocity of the particle.

hep-th↗

arXiv2015

Holographic Dual to Conical Defects: II. Colliding Ultrarelativistic Particles

We study instant conformal symmetry breaking as a holographic effect of ultrarelativistic particles moving in the AdS3 spacetime. We give the qualitative picture of this effect probing it by two-point correlation functions and the entanglement entropy of the corresponding boundary theory. We show that within geodesic approximation the ultra-relativistic massless defect due to gravitational lensing of the geodesics, produces a zone structure for correlators with broken conformal invariance. Meanwhile, the holographic entanglement entropy also exhibits a transition to the non-conformal behaviour. Two colliding massless defects produce more diverse zone structure for correlators and the entanglement entropy.

hep-th↗

arXiv2015

Shock waves in Lifshitz-like spacetimes

We construct shock waves for Lifshitz-like geometries in four- and five-dimensional effective theories as well as in D3-D7 and D4-D6 brane systems. The solutions to the domain wall profile equations are found. Further, the study makes a connection with the implications for the quark-gluon plasma formation in heavy-ion collisions. According to the holographic approach, the multiplicity of particles produced in heavy-ion collisions can be estimated by the area of the trapped surface formed in shock wave collisions. We calculate the areas of trapped surfaces in the geometry of two colliding Lifshitz domain walls. Our estimates show that for five-dimensional cases with certain values of the critical exponent the dependence of multiplicity on the energy of colliding ions is rather close to the experimental data ${\cal M} \sim s^{\,0.15}$ observed at RHIC and LHC.

hep-th↗

arXiv2014

Holographic Thermalization in Quark Confining Background

We study holographic thermalization of a strongly coupled theory inspired by two colliding shock waves in a vacuum confining background. Holographic thermalization means a black hole formation, in fact a trapped surface formation. As a vacuum confining background we considered a well know bottom-up AdS/QCD model that provides the Cornell potential as well as reproduces QCD beta-function. We perturb vacuum background by colliding domain shock waves, that are assumed to be holographically dual to heavy ions collisions. Our main physical assumption is that we can make a restriction on the time of a trapped surface production that makes a natural limitation on the size of the domain where the trapped surface is produced. This limits the intermediate domain where the main part of the entropy is produced. In this domain one can use an intermediate vacuum background as an approximation to the full confining background. In this intermediate background a dependence of the produced entropy on colliding energy is very similar to the experimental dependence of particles multiplicities on colliding ions energy obtained from RHIC and LHC. This permits us to conclude that the entropy produced in collisions of domain shock waves during a short time models rather well the experimental data.

hep-th↗

arXiv2014

Fermionic Meixner probability distributions, Lie algebras and quadratic Hamiltonians

We introduce the quadratic Fermi algebra, which is a Lie algebra, and show that the vacuum distributions of the associated Hamiltonians define the fermionic Meixner probability distributions. In order to emphasize the difference with the Bose case, we apply a modification of the method used in the above calculation to obtain a simple and straightforward classification of the 1--dimensional Meixner laws in terms of homogeneous quadratic expressions in the Bose creation and annihilation operators. There is a huge literature of the Meixner laws but this, purely quantum probabilistic, derivation seems to be new. Finally we briefly discuss the possible multi-dimensional extensions of the above results.

math-ph↗

arXiv2014

Holography and non-local operators in the BTZ black hole with non-zero angular momentum

We study quark-antiquark potential using the AdS/CFT correspondence in the BTZ black hole with non-zero angular momentum. Using explicit form of string configurations relevant to a calculation of the potential we find that the potential exhibits different dependencies on angular momentum values in the Euclidean and the Lorentzian signatures of the BTZ.

hep-th↗

arXiv2014

Non-minimally Coupled Cosmological Models with the Higgs-like Potentials and Negative Cosmological Constant

We study dynamics of non-minimally coupled scalar field cosmological models with Higgs-like potentials and a negative cosmological constant. In these models the inflationary stage of the Universe evolution changes into a quasi-cyclic stage of the Universe evolution with oscillation behaviour of the Hubble parameter from positive to negative values. Depending on the initial conditions the Hubble parameter can perform either one or several cycles before to become negative forever.

gr-qc↗

arXiv2014

Holographic estimation of multiplicity and membranes collision in modified spaces ${AdS}_5$

The quark-gluon plasma formed as a result of heavy-ion collisions is currently investigated actively both theoretically and experimentally. According to the holographic approach, forming a quark-gluon plasma in the four-dimensional world is associated with creating black holes in a five-dimensional anti-de Sitter space. The multiplicity of particles produced in heavy-ion collisions is then determined by the entropy of the five-dimensional black hole, which is estimated by the area of the trapped surface. To fit the experimental data for multiplicity Kiritsis and Taliotis have proposed to consider black holes formation in modified ${AdS}_5$ spaces with different $b$-factors. In this paper we consider the formation of black holes under collision of membranes in modified ${AdS}_5$ spaces with $b$-factors. Following the previous proposals we consider the power-law and exponential $b$-factors, as well as mixed types of $b$-factors. We study dynamics of the change of the trapped surface area depending on the energy for each investigated space. We find that the power-law and mixed factors fit better to the experimental date.

hep-th↗

arXiv2013

Note on the Unruh Effect

It was suggested by Unruh that a uniformly accelerated detector in vacuum would perceive a noise with a thermal distribution. We obtain a representation of solutions of the wave equation in two dimensions suitable for the Rindler regions. The representation includes the dependence on a parameter. The Unruh field corresponds to a singular limit of the representation.

hep-th↗

arXiv2012

FRW Cosmology with Non-positively Defined Higgs Potentials

We discuss the classical aspects of dynamics of scalar models with non-positive Higgs potentials in the FRW cosmology. These models appear as effective local models in non-local models related with string field theories. After a suitable field redefinition these models have the form of local Higgs models with a negative extra cosmological term and the total Higgs potential is non-positively defined and has rather small coupling constant. The non-positivity of the potential leads to the fact that on some stage of evolution the expansion mode gives place to the mode of contraction, due to that the stage of reheating is absent. In these models the hard regime of inflation gives place to inflation near the hill top and the area of the slow roll inflation is very small. Meanwhile one can obtain enough e-foldings before the contraction to make the model under consideration admissible to describe inflation.

hep-th↗

arXiv2012

Holographic phase diagram of quark-gluon plasma formed in heavy-ions collisions

The phase diagram of quark gluon plasma (QGP) formed at a very early stage just after the heavy ion collision is obtained by using a holographic dual model for the heavy ion collision. In this dual model colliding ions are described by the charged shock gravitational waves. Points on the phase diagram correspond to the QGP or hadronic matter with given temperatures and chemical potentials. The phase of QGP in dual terms is related to the case when the collision of shock waves leads to formation of trapped surface. Hadronic matter and other confined states correspond to the absence of trapped surface after collision. Multiplicity of the ion collision process is estimated in the dual language as area of the trapped surface. We show that a non-zero chemical potential reduces the multiplicity. To plot the phase diagram we use two different dual models of colliding ions, the point and the wall shock waves, and find qualitative agreement of the results.

hep-th↗