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Irina Aref'eva

Publications and source records attributed to Irina Aref'eva.

At least 19 recordsLinked to original sources
arXiv2025

Notes on Real Quantum Mechanics in a Kahler Space

The necessity of complex numbers in quantum mechanics has long been debated. This paper develops a real Kahler space formulation of quantum mechanics [19], asserting equivalence to the standard complex Hilbert space framework. By mapping the complex Hilbert space ${\mathbb C}^n$ to a real Kahler space $K ^{2n}$, i.e. ${\mathbb R}^{2n}$ equipped with a metric, a symplectic structure and an automorphism, we establish a correspondence between Hermitian operators in ${\mathbb C}^n$ and real operators in $K^{2n}$. While the isomorphism appears straightforward some subtleties emerge: (i) the overcounting of composite system states under tensor products in ${\mathbb R}^{2n}$, and (ii) the double degeneracy of operator spectra in the real formulation. Through a systematic investigation of these challenges, we clarify the structural relationship between real and complex formulations, resolve ambiguities in composite system representations, and analyze spectral consequences. Our results reaffirm the equivalence of the two frameworks while highlighting nuanced distinctions with implications for foundational debates on locality, phase invariance, and the role of complex numbers in quantum theory.

quant-ph↗
arXiv2024

Black Brane/Bose Gase Duality and Third Law of Thermodynamics

In the thermodynamics of black holes in asymptotically flat space, the third law of thermodynamics is violated, and entropy cannot be consistently modeled through conventional statistical mechanics. Notably, the third law of thermodynamics is violated for the Schwarzschild black hole, and its entropy can only be described using an unconventional model, such as a Bose gas in negative dimensions. In contrast, for certain black brane solutions such as Poincare AdS black branes, Lifshitz black branes, and anisotropic Lifshitz-type black branes, the third law is preserved, with entropy vanishing as temperature approaches zero. In this paper, we extend the previously established duality between black hole and Bose gas thermodynamics to black branes. Specifically, the Poincare black brane in $D$ spacetime dimensions corresponds to a non-relativistic Bose gas in $2(D-2)$ spatial dimensions. Furthermore, the duality between Lifshitz branes and Bose gases relates a Lifshitz brane with exponent $α$ in $D$-dimensional spacetime to a Bose gas of quasi-particles with energy $k^α$ in $D-2$ spatial dimensions.

hep-th↗
arXiv2023

Violation of the Third Law of Thermodynamics by Black Holes, Riemann Zeta Function and Bose Gas in Negative Dimensions

Black holes violate the third law of thermodynamics in its standard formulation. Schwarzschild black hole entropy is inverse proportional to the square of the temperature $S=1/(16 πT^2) $ and tends to infinity rather than zero when the temperature goes to zero. We search for quantum statistical models with such exotic thermodynamic behaviour. It is shown that the Schwarzschild black hole in $D=4 $ spacetime dimensions corresponds to a Bose gas in a space with $d=-\, 4$ negative spatial dimensions. The Riemann zeta function is used to define the entropy of the Bose gas in negative dimension. The correspondence between black holes in higher dimensions and de Sitter spacetime with Bose gases is considered.

hep-th↗
arXiv2022

Complete evaporation of black holes and Page curves

The problem of complete evaporation of Schwarzschild black holes raised by Hawking is that one has an explosion of the temperature $T=1/8πM$ for vanishing black hole mass M. We consider the Reissner-Nordstrom black hole and note that if mass $M$ and charge Q M-C M^3, C>0 for small M then the complete evaporation of black holes without blow-up of temperature is possible. We describe curves on the surface of state equations such that the motion along them provides complete evaporation. The radiation entropy follows the Page curve and vanishes at the end of evaporation. Similar results for rotating Kerr, Schwarzschild-de-Sitter and Reissner-Nordstrom-(Anti)-de-Sitter black holes are discussed.

hep-th↗
arXiv2021

A Note on Islands in Schwarzschild Black Holes

We consider evaporation of the Schwarzschild black hole and note that island configurations do not provide a bounded entanglement entropy. The same remark is valid also for some other static black holes. A proposal for improving the situation is discussed

hep-th↗
arXiv2021

Holographic Anisotropic Model for Light Quarks with Confinement-Deconfinement Phase Transition

We present a five-dimensional anisotropic holographic model for light quarks supported by Einstein-dilaton-two-Maxwell action. This model generalizing isotropic holographic model with light quarks is characterized by a Van der Waals-like phase transition between small and large black holes. We compare the location of the phase transition for Wilson loops with the positions of the phase transition related to the background instability and describe the QCD phase diagram in the thermodynamic plane -- temperature $T$ and chemical potential $μ$. The Cornell potential behavior in this anisotropic model is also studied. The asymptotics of the Cornell potential at large distances strongly depend on the parameter of anisotropy and orientation. There is also a nontrivial dependence of the Cornell potential on the boundary conditions of the dilaton field and parameter of anisotropy. With the help of the boundary conditions for the dilaton field one fits the results of the lattice calculations for the string tension as a function of temperature in isotropic case and then generalize to the anisotropic one.

hep-th↗
arXiv2021

Quantum explosions of black holes and thermal coordinates

The Hawking temperature for Schwarzschild black hole $T_H=1/8πM$ is singular in the limit of vanishing mass $M\to 0$. However, the Schwarzschild metric itself is regular in this limit, it is reduced to the Minkowski metric and there are no reasons to believe that the temperature becomes infinite. This discrepancy may be due to the singularity of the Kruskal coordinates in this limit. To improve the situation, new coordinates for the Schwarzschild metric are introduced, called thermal coordinates, which depend on the black hole mass $ M $ and the parameter $b$. The thermal coordinates are regular in the limit $M\to 0$ when the Schwarzschild metric reduces to Minkowski metric, written in coordinates dual to the Rindler coordinates. Using the thermal coordinates the Schwarzschild black hole radiation is reconsidered and it is found that the Hawking formula for temperature is valid only for large black holes while for small black holes the temperature is $T=1/2π(4M+b)$. The thermal observer in Minkowski space sees radiation with temperature $T=1/2πb$, similar to the Unruh effect with non-constant acceleration. During evaporation, in the thermal coordinates the black hole mass is decreasing inverse proportional to time and the black hole lifetime is infinite. More general spherically symmetric metrics are considered and it is found that the property to have a temperature is not restricted to the cases of black holes or constant acceleration, but is valid for any spherically symmetric metric written in thermal coordinates. Implications for primordial black holes and for the information loss problem are mentioned.

hep-th↗
arXiv2019

Replica-nondiagonal solutions in the SYK model

We study the SYK model in the large $N$ limit beyond the replica-diagonal approximation. First we show that there are exact replica-nondiagonal solutions of the saddle point equations for $q=2$ for any finite replica number $M$. In the interacting $q=4$ case we are able to construct the numerical solutions, which are in one-to-one correspondence to the analytic solutions of the quadratic model. These solutions are singular in the $M \to 0$ limit in both quadratic and quartic interaction cases. The calculations of the on-shell action at finite integer $M$ show that the nondiagonal replica-symmetric saddles are subleading in both quadratic and quartic cases. We also study replica-nondiagonal solutions of the SYK in the strong coupling limit. For arbitrary $q$ we show that besides the usual solutions of the replica-diagonal saddle point equations in the conformal limit, there are also replica-nondiagonal solutions for any value of $M$ (including zero). The specific configurations that we study, have factorized time and replica dependencies. The corresponding saddle point equations are separable at strong coupling, and can be solved using the Parisi ansatz from spin glass theory. We construct the solutions which correspond to the replica-symmetric case and to one-step replica symmetry breaking. We compute the regularized free energy on these solutions in the limit of zero replicas. It is observed that there are nondiagonal solutions with the regularized free energy lower than that of the standard diagonal conformal solution.

hep-th↗
arXiv2019

Gas of baby universes in JT gravity and matrix models

It has been shown recently by Saad, Shenker and Stanford that the genus expansion of a certain matrix integral generates partition functions of Jackiw-Teitelboim (JT) quantum gravity on Riemann surfaces of arbitrary genus with any fixed number of boundaries. We use an extension of this integral for studying gas of baby universes or wormholes in JT gravity. To investigate the gas nonperturbatively we explore the generating functional of baby universes in the matrix model. The simple particular case when the matrix integral includes the exponential potential is discussed in some detail. We argue that there is a phase transition in the gas of baby universes

hep-th↗
arXiv2019

Revealing nonperturbative effects in the SYK model

We study the large $N$ saddle points of two SYK chains coupled by an interaction that is nonlocal in Euclidean time. We start from analytic treatment of the free case with $q=2$ and perform the numerical study of the interacting case $q=4$. We show that in both cases there is a nontrivial phase structure with infinite number of phases. Every phase correspond to a saddle point in the non-interacting two-replica SYK. The nontrivial saddle points have non-zero value of the replica-nondiagonal correlator in the sense of quasi-averaging, when the coupling between replicas is turned off. Thus, the nonlocal interaction between replicas provides a protocol for turning the nonperturbatively subleading effects in SYK into non-equilibrium configurations which dominate at large $N$. For comparison we also study two SYK chains with local interaction for $q=2$ and $q=4$. We show that the $q=2$ model also has a similar phase structure, whereas in the $q=4$ model, dual to the traversable wormhole, the phase structure is different.

hep-th↗
arXiv2019

Orientation Dependence of Confinement-Deconfinement Phase Transition in Anisotropic Media

We study the T-μ phase diagram of anisotropic media, created in heavy-ion collisions (HIC). Such a statement of the problem is due to several indications that this media is anisotropic just after HIC. To study T-μ phase diagram we use holographic methods. To take into account the anisotropy we use an anisotropic black brane solutions for a bottom-up QCD approach in 5-dim Einstein-dilaton-two-Maxwell model constructed in our previous work. We calculate the minimal surfaces of the corresponding probing open string world-sheet in anisotropic backgrounds with various temperatures and chemical potentials. The dynamical wall (DW) locations, providing the quark confinement, depend on the orientation of the quark pairs, that gives a crossover transition between confinement/deconfinement phases in the dual gauge theory.

hep-th↗
arXiv2019

Spontaneous symmetry breaking in fermionic random matrix model

A fermionic random matrix model, which is a 0-dimensional version of the SYK model with replicas, is considered. The replica-off-diagonal correlation functions vanish at finite N, but we show that they do not vanish in the large N limit due to spontaneous symmetry breaking. We use the Bogoliubov quasi-averages approach to studying phase transitions. The consideration may be relevant to the study of the problem of existence of the spin glass phase in fermionic models.

hep-th↗
arXiv2018

On 1/N diagrammatics in the SYK model beyond the conformal limit

In the present work we discuss aspects of the 1/N expansion in the SYK model, formulated in terms of the semiclassical expansion of the bilocal field path integral. We derive cutting rules, which are applicable for all planar vertices in the bilocal field diagrams. We show that these cutting rules lead to novel identities on higher-point correlators, which could be used to constrain their form beyond the solvable conformal limit. We also demonstrate how the cutting rules can simplify the computation of amplitudes on an example of the six-point function.

hep-th↗
arXiv2018

Holographic control of information and dynamical topology change for composite open quantum systems

We investigate how the compositeness of a quantum system influences the characteristic time of equilibration. We study the dynamics of open composite quantum systems strongly coupled to the environment after a quantum perturbation accompanied by non-equilibrium heating. We use a holographic description of the evolution of entanglement entropy. The non-smooth character of the evolution with holographic entanglement is a general feature of composite systems, which demonstrate a dynamical change of topology in the bulk space and a jump-like velocity change of entanglement entropy propagation. Moreover, the number of jumps depends on the system configuration and especially on the number of composite parts. The evolution of the mutual information of two composite systems inherits these jumps. We present a detailed study of the mutual information for two subsystems with one of them being bipartite. We have found 5 qualitatively different types of behavior of the mutual information dynamics and indicated the corresponding ranges of system parameters.

hep-th↗
arXiv2018

Holographic Anisotropic Background with Confinement-Deconfinement Phase Transition

We present new anisotropic black brane solutions in 5D Einstein-dilaton-two-Maxwell system. The anisotropic background is specified by an arbitrary dynamical exponent $ν$, a nontrivial warp factor, a non-zero dilaton field, a non-zero time component of the first Maxwell field and a non-zero longitudinal magnetic component of the second Maxwell field. The blackening function supports the Van der Waals-like phase transition between small and large black holes for a suitable first Maxwell field charge. The isotropic case corresponding to $ν= 1$ and zero magnetic field reproduces previously known solutions. We investigate the anisotropy influence on the thermodynamic properties of our background, in particular, on the small/large black holes phase transition diagram. We discuss applications of the model to the bottom-up holographic QCD. The RG flow interpolates between the UV section with two suppressed transversal coordinates and the IR section with the suppressed time and longitudinal coordinates due to anisotropic character of our solution. We study the temporal Wilson loops, extended in longitudinal and transversal directions, by calculating the minimal surfaces of the corresponding probing open string world-sheet in anisotropic backgrounds with various temperatures and chemical potentials. We find that dynamical wall locations depend on the orientation of the quark pairs, that gives a crossover transition line between confinement/deconfinement phases in the dual gauge theory. Instability of the background leads to the appearance of the critical points $(μ_{\vartheta,b}, T_{\vartheta,b})$ depending on the orientation $\vartheta$ of quark-antiquark pairs in respect to the heavy ions collision line.

hep-th↗
arXiv2018

Notes on the SYK model in real time

Nonperturbative formulation of the Sachdev-Ye-Kitaev (SYK) model is discussed. The partition function of the model can be represented as a functional integral over the Grassmann variables in Euclidean time which is well defined but it diverges after the transformation to the fermion bilocal fields. We point out that the generating functional of the SYK model in real time is well defined even after the transformation to the bilocal fields and it can be used for nonperturbative investigations of its properties. The SYK model in zero dimensions is studied, its large N expansion is evaluated and phase transitions are investigated.

hep-th↗
arXiv2016

Holographic Photosynthesis

There are successful applications of the holographic AdS/CFT correspondence to high energy and condensed matter physics. We apply the holographic approach to photosynthesis that is an important example of nontrivial quantum phenomena relevant for life which is being studied in the emerging field of quantum biology. Light harvesting complexes of photosynthetic organisms are many-body quantum systems, in which quantum coherence has recently been experimentally shown to survive for relatively long time scales even at the physiological temperature despite the decohering effects of their environments. We use the holographic approach to evaluate the time dependence of entanglement entropy and quantum mutual information in the Fenna-Matthews-Olson (FMO) protein-pigment complex in green sulfur bacteria during the transfer of an excitation from a chlorosome antenna to a reaction center. It is demonstrated that the time evolution of the mutual information simulating the Lindblad master equation in some cases can be obtained by means of a dual gravity describing black hole formation in the AdS-Vaidya spacetime. The wake up and scrambling times for various partitions of the FMO complex are discussed.

hep-th↗