arXiv subjects

D. S. Ageev

Publications and source records attributed to D. S. Ageev.

8 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.

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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.

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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.

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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 $T_f$.

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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.

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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.

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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.

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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.

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