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## U(1) and SU(2) quantum dissipative systems: The Caldeira-Leggett vs. the Amegaokar-Eckern-Schön approaches

Journal of Experimental and Theoretical Physics. 2016. Vol. 122. P. 576-586.

There are two paradigmatic frameworks for treating quantum systems coupled to a dissipative environment: the Caldeira–Leggett and Ambegaokar–Eckern–Schön approaches. Here, we recall the differences between them and explain the consequences of applying each to a zero-dimensional spin (having an SU(2) symmetry) in a dissipative environment (a dissipative quantum dot near or beyond the Stoner instability point).

Keywords: spin dynamics

Kolokolov I., Michael Chertkov, Physical Review B: Condensed Matter and Materials Physics 1995 Vol. 51 No. 6 P. 3974-3977

The transverse autocorrelation function at an arbitrary temperature is calculated rigorously for a system with an arbitrary number of quantum spins, each of which is coupled to all the other spins with equal exchange. It is shown that the cluster approximation, formed by a model for a real magnet, explains short- and intermediate-time (up to ...

Added: March 28, 2017

V.V. Belykh, Kuntsevich A., M.M. Glazov et al., Physical Review X 2018 Vol. 8 P. 031021-1-031021-8

Manifestations of quantum interference effects in macroscopic objects are rare. Weak localization is one
of the few examples of such effects showing up in the electron transport through solid state. Here, we show
that weak localization becomes prominent also in optical spectroscopy via detection of the electron spin
dynamics. In particular, we find that weak localization controls the ...

Added: September 10, 2018

Glazov M., Oxford: Oxford University Press, 2018

In recent years, the physics community has experienced a revival of interest in spin effects in solid state systems. On one hand, the solid state systems, particularly, semiconductors and semiconductor nanosystems, allow us to perform benchtop studies of quantum and relativistic phenomena. On the other hand, this interest is supported by the prospects of realizing ...

Added: January 13, 2021

S. K. Gotovko, L. E. Svistov, A. M. Kuzmenko et al., Physical Review B: Condensed Matter and Materials Physics 2019 Vol. 100 No. 17 P. 174412-1-174412-12

We present a combined experimental and theoretical investigation of the low-frequency ESR dynamics in the ordered phases of magnetic mineral linarite. This material consists of weakly coupled spin-1/2 chains of copper ions with frustrated ferro- and antiferromagnetic interactions. In zero magnetic field, linarite orders into a spiral structure and exhibits a peculiar magnetic phase diagram ...

Added: November 19, 2019

Kolokolov I., Michael Chertkov, Physical Review B: Condensed Matter and Materials Physics 1994 Vol. 49 No. 5 P. 3592-3595

Infinite-temperature long-time dynamics of Heisenberg model H^=-1/2tsumi,jJijS^i⋅S^j is investigated. It is shown that the quantum-spin pair correlator is equal to the correlator of a classically evaluated vector field averaged over the initial conditions with respect to the Gaussian measure. In the continuous-limit case, the scaling estimations allow one to find the one-point correlator that turns out to ...

Added: March 28, 2017

Kolokolov I., Journal of Experimental and Theoretical Physics 1986 Vol. 64 No. 6 P. 1373-1375

Added: March 31, 2017

P. Schad, A. Shnirman, Makhlin Y., Physical Review B: Condensed Matter and Materials Physics 2016 Vol. 93 P. 174420

The Majorana representation for spin operators enables efficient application of field-theoretical methods for the analysis of spin dynamics. Moreover, a wide class of spin correlation functions can be reduced to Majorana correlations of the same order, simplifying their calculation. For the spin-boson model, direct application of this method in the lowest order allows for a ...

Added: October 13, 2016

Kolokolov I., International Journal of Modern Physics B 1996 Vol. 10 No. 18-19 P. 2189-2215

A number of problems in statistical physics can be reformulated in terms of a two-state system evolving in a random field. The corresponding evolution operator can be written in the form of time-ordered operator exponential. Functional formalism allows us to rewrite the latter as a product of usual matrix exponentials using a nonlinear change of ...

Added: March 28, 2017

Kolokolov I., Eugenii V. Podivilov, Journal of Experimental and Theoretical Physics 1989 Vol. 68 No. 1 P. 119-125

Added: March 30, 2017

Shchepetilnikov A., Alina Khisameeva, Yu. A. Nefyodov et al., Physical Review B: Condensed Matter and Materials Physics 2021 Vol. 103 No. 19 Article 195313

The spin relaxation of a strongly correlated electron system hosted in a narrow AlAs quantum well is studied experimentally in the regime of the quantum Hall ferromagnet, i.e., near odd fillings of the integer quantum Hall effect. The relaxation rate is evaluated by analyzing the linewidth of the electrically detected electron-spin resonance. The measured spin ...

Added: January 9, 2022

Alexander Shnirman, Arijit Saha, Burmistrov I. et al., Physical Review Letters 2015 Vol. 114 P. 176806

The presence of geometric phases is known to affect the dynamics of the systems involved. Here, we consider a quantum degree of freedom, moving in a dissipative environment, whose dynamics is described by a Langevin equation with quantum noise. We show that geometric phases enter the stochastic noise terms. Specifically, we consider small ferromagnetic particles ...

Added: October 15, 2016

Kolokolov I., Michael Chertkov, Journal of Experimental and Theoretical Physics 1994 Vol. 79 No. 5 P. 824-832

Using the functional integration method we compute exactly the time-dependent correlation
functions of local spins in a finite quantum Heisenberg magnet with a position-independent
exchange between spins. Explicit expressions for such correlation functions for an arbitrary
number (N) of spins in the cluster and for all temperatures are presented. The spin correlation
function for a cluster placed in an ...

Added: March 28, 2017

Kolokolov I., Annals of Physics 1990 Vol. 202 No. 1 P. 165-185

The representation of the generating functional for quantum Heisenberg ferromagnets as an integral over two uncostrained c-number valued fields, charged and neutral, obeying the initial conditions (instead of commonly used periodic boundary conditions) is obtained. With the help of this representation the long-time dynamics of the longitudinal spin component at low temperatures is studied. The infrared-singular ...

Added: March 29, 2017

Terekhovich V., Эпистемология и философия науки 2019 Т. 56 № 1 С. 169-184

The framework of simple opposition realism - anti-realism is not enough to analyze the views on the reality of unobservable objects of quantum theory. First, it is necessary to distinguish between realism in relation to the theory and realism in relation to the theory’s objects. Secondly, realism in relation to classical objects can be combined, ...

Added: February 12, 2020

M.Yu. Kagan, JETP Letters 2016 Vol. 103 No. 11 P. 728-738

In this short review, we first discuss the results, which are mainly devoted to the generalizations of the famous Kohn–Luttinger mechanism of superconductivity in purely repulsive fermion systems at low electron densities. In the context of repulsive-U Hubbard model and Shubin–Vonsovsky model we consider briefly the superconducting phase diagrams and the symmetries of the order parameter ...

Added: November 18, 2016

I.Kolokolov, Lebedev V., Michael Chertkov et al., Journal of Lightwave Technology 2004 Vol. 22 No. 4 P. 1155-1168

This paper presents a method that allows evaluating the performance of an optical fiber system where bit errors result from a complex interplay of spontaneous noise generated in optical amplifiers and birefringent disorder of the transmission fiber. We demonstrate that in the presence of temporal fluctuations of birefringence characteristics, the bit-error rate (BER) itself is ...

Added: February 23, 2017

Alfimov M., Alexey Litvinov, Journal of High Energy Physics 2022 No. 01 Article 43

We study regularization scheme dependence of beta-function for sigma models with two-dimensional target space. Working within four-loop approximation, we conjecture the scheme in which the beta-function retains only two tensor structures up to certain terms containing zeta_3. Using this scheme, we provide explicit solutions to RG flow equation corresponding to Yang-Baxter- and lambda-deformed SU(2)/U(1) sigma ...

Added: February 1, 2022

Дарья Дмитриевна Ружицкая, Алексей Андреевич САМОЙЛЕНКО, Алексей Дмитриевич Иванов et al., Optoelectronics, Instrumentation and Data Processing 2017 Vol. 54 No. 1 P. 1-8

This paper presents an algorithm for processing the transmission spectra of whisperinggallery optical microcavities for use as a nanoparticle detector. The algorithm is based on the broadening of the microcavity resonance curve during precipitation of nanoparticles on the microcavity surface. Experimental results on the detection of particles are compared with Langmuir adsorption theory. The contribution ...

Added: May 25, 2018

Nagaev K., Андрей Андреевич Маношин, Physical Review B: Condensed Matter and Materials Physics 2020 Vol. 102 Article 155411

We calculate the electrical and thermal conductivity of a two-dimensional electron gas with strong spin-orbit
coupling in which the scattering is dominated by electron-electron collisions. Despite the apparent absence of
Galilean invariance in the system, the two-particle scattering does not affect the electrical conductivity above
the band-crossing point where both helicity bands are filled. Below the band-crossing point ...

Added: October 14, 2021

Yu.E. Lozovik, Станислав Леонидович Огарков, A.A. Sokolik, Physical Review B: Condensed Matter and Materials Physics 2012 Vol. 86 No. 04-5429 P. 1-6

Condensation of pairs formed by spatially separated electrons and holes in a system of two isolated graphene layers is studied beyond the mean-field approximation. Suppression of the screening of the pairing interaction at large distances, caused by the appearance of the gap, is considered self-consistently. A mutual positive feedback between the appearance of the gap ...

Added: March 14, 2013

Maslov V., Теоретическая и математическая физика 2019 Т. 201 № 1 С. 65-83

We study the process of a nucleon separating from an atomic nucleus from the mathematical standpoint
using experimental values of the binding energy for the nucleus of the given substance. A nucleon becomes
a boson at the instant of separating from a fermionic nucleus. We study the further transformations of
boson and fermion states of separation in a ...

Added: November 1, 2019

M.: Faculty of Physics, MSU, 2017

The Low Temperature Physics Conference is an international event held every three years, under the auspices of the IUPAP through its Commission C5 on Low Temperature Physics. The aim of these conferences is to exchange information and views among the members of the international scientific community in the general field of Low Temperature Physics. It ...

Added: October 1, 2017

Min Namkung, Kwon Younghun, Scientific Reports 2018 Vol. 8 No. 1 P. 16915-1-16915-18

Sequential state discrimination is a strategy for quantum state discrimination of a sender’s quantum
states when N receivers are separately located. In this report, we propose optical designs that can
perform sequential state discrimination of two coherent states. For this purpose, we consider not
only binary phase-shifting-key (BPSK) signals but also general coherent states, with arbitrary prior
probabilities. Since ...

Added: November 16, 2020

Загорский Д. Л., И.М. Долуденко, В. М. Каневский et al., Известия РАН. Серия физическая 2021 Т. 85 № 8 С. 1088-1094

FeCo and FeNi alloyed nanowires (NW) were obtained by the matrix synthesis method: the effect of the
growth voltage and the effect of using a reference electrode were studied. It is shown that the composition of
FeNi nanowires strongly depends on the growth potential (with its increase, the bcc structure is changing into
fcc), and it is also ...

Added: November 12, 2021