Questions tagged [non-equilibrium]

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13
votes
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194 views

Does the fluctuations-dissipation theorem hold in active matter for macroscopic physical quantities?

I am trying to understand how the fluctuation–dissipation theorem applies to active matter. I simulated a system with motors which may consume energy from the environment to move and exert force on ...
11
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0answers
476 views

Capturing (perturbatively) non-equilibrium field theory effects using “elementary” methods

I am considering a system of two interacting scalar fields: $\psi$, and $\phi$. The Lagrangian is given by: \begin{equation} \mathcal{L}[\psi]=\frac{1}{2}\partial_\mu\psi\partial^\mu\psi+\frac{1}{2}\...
8
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0answers
144 views

Do bipartite spin glasses have simple relaxation dynamics?

From what I gather, a Boltzmann machine (BM) is essentially a spin glass with no applied field evolving under Glauber dynamics (if this is at all mistaken, I don't think it will be off enough to ...
5
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0answers
217 views

Violations of Onsager reciprocity?

As far as I understand it, the modern statement of Onsager reciprocity is that the linear-response transport coefficient matrix, when transposed, is equal to that of the time-reversed system (reversed ...
5
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0answers
307 views

Thermodynamic equilibrium or thermal equilibrium and equipartition theorem

In all derivations of the equipartition theorem I can find a thermodynamic equilibrium distribution is used to show it's validity. But more vague sources (physics.stackexchange answer by Luboš Motl, ...
5
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1answer
182 views

How to perform stroboscopic measurements for Floquet topological insulators?

Floquet topological insulators (arXiv:1008.1792, arXiv:1211.5623) have attracted much research interests in condensed matter physics. The goal is to realize topological insulators from trivial ...
5
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1answer
214 views

Proof of periodicity of Floquet Green's function

It is claimed in many papers that the two-time Green's function in time periodic Hamiltonian case is periodic in the average time, i.e. \begin{equation} G(t+T,t'+T)=G(t,t') \end{equation} when $H(t+...
4
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0answers
690 views

Validity of topological thermodynamics?

I've been reading some material by R. Kiehn, developing a topological approach to non-equilibrium thermodynamics through Cartan forms, where the fundamental claim is that irreversible processes are ...
3
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0answers
26 views

Is there a classical correspondence of the entanglement entropy in isolated quantum systems?

For an isolated quantum system, one can study the time evolution of entanglement entropy after a quantum quench (always a pure state), which has a rich behaviour in various different models. However, ...
3
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0answers
69 views

Fluctuation-Dissipation Theorem in the Keldysh Formalism

In Kamenev's book Field Theory of Non-Equilibrium Systems (he also has lecture notes online here, which contains the relevant statement on pg. 17), he states that the following equation $$G^K(\epsilon)...
3
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80 views

How are boundary consitions implemented correctly in time dependent hydrodynamics?

I posted this question more than one year ago and got an answer recently. This answer looks good to me, but indicates that something is wrong in my original approach to the problem. Can someone tell ...
3
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0answers
168 views

Can the occupation of Floquet bands be calculated from the Keldysh Green's function?

A periodically driven band structure can be semiclassically described by Floquet theory, resulting in photon-dressed Floquet bands (non-equilibrium steady states). Usually, for non-equilibrium systems,...
2
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0answers
68 views

Detailed Balance Violation and Fokker-Planck Equation

Suppose I have a system with N sites, and each site can be modified (M) or anti-modified (A). Transitions between these two states are in part random, and in part auto-regulated by recruitment of At ...
2
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0answers
259 views

Exact solution for non-linear Fokker-Planck equation

I'm searching for exact (analytical) results for FP equation in 2 variables (such as $x$ and $p$ in 1D) with a steady state. Kramer's like (with force due to confining potential, such as harmonic ...
2
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0answers
31 views

Is there a multiscale analysis for field theories?

Consider a (zero dimensional) Gaussian field theory described by the dynamical action $$S = \int_t \tilde{\phi}(t) \left[\partial_t \phi(t) + M(t) \phi(t)\right] - \gamma \tilde{\phi}(t)^2\, .$$ $\...
2
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1answer
103 views

Do electrons really diffuse when a temperature gradient is applied?

In many websites and books, it is generally said that the charge carriers, be it electrons or holes, diffuse through the considered material when a temperature gradient is applied. However I have ...
2
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0answers
84 views

How to numerically calculate Fisher zeros?

The main quantity in the study of dynamical quantum phase transition (DQPT) is Loschmidt echo amplitude defined as $G(t)=\langle \Psi_{0}|\Psi_{0}(t)\rangle=\langle \Psi_{0}|e^{-iHt}|\Psi_{0}\rangle$...
2
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0answers
39 views

What sense is there in entropy arguments when the system can't be known to be ergodic?

What sense does "entropy" make in non-equilibrium dynamics? What is its definition? How is the "entropy of the early universe" calculated, for example? And how can the "entropy of the universe" be ...
2
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0answers
156 views

What is the relation between eigenstate thermalisation and infinite heating in Floquet systems?

Closed quantum systems with periodically changing parameters (Floquet systems) typically heat up to an infinite temperature at large times. I have read multiple times (the last time was here) that ...
2
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0answers
76 views

Relationship between Keldysh formalism and time-dependent perturbation theory

When treating systems in weak external time-dependent electromagnetic field we can use usual time-dependent perturbation theory or the Keldysh formalism which is tailored for such non-equilibrium ...
2
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0answers
140 views

Entropy production in non-equilibrium systems: physical interpretation?

I have been learning about entropy production in non-equilibrium systems as developed by Prigogine and others, especially in the context of chemical reactions. I now understand that from the first law ...
2
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0answers
131 views

Does the Lindblad equation satisfy a fluctuation dissipation relation?

The fluctuation dissipation relation is usually stated in terms of an identity that relates the retarded, advanced and either the Keldysh or time-ordered correlators. This is easily enforced in ...
2
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39 views

Non-equilibrium electronic distribution in the time-relaxation approximation - Which is the boundary condition?

In Chapter 13 of Ashcroft-Mermin - "Solid State Physics", the following non equilibrium electronic phase-space distribution for the semiclassical electrons in a periodic crystal is derived: $$g(\...
2
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0answers
291 views

Textbooks for non-equilibrium quantum field theory

What are good textbooks for non-equilibrium quantum field theory? Please answer by naming quality books and a short description and review about each one that you have personally read or benefited ...
2
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0answers
1k views

Diffusion in a chemical potential gradient

I am having troubles to understand to connection between equilibrium and non equilibrium thermodynamics. I am studying a mixture of molecules $A,B,C$ and solvent $S$. The free energy $F$ is given by ...
1
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0answers
25 views

Where can I find careful discussions of equilibrium?

I want to know what physical equilibrium is precisely. I'd like to understand dynamical equilibrium vs. static equilibrium, and I'd like to understand approaches to understand non-equilibrium ...
1
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0answers
32 views

Derivation of Feynman rules from generating functional for non-eq QFT

I consider Yukawa non-equilibrium theory with interaction $g\bar{\psi}\phi\psi$ with massive fermionic field $\psi$ with mass $m$ and massive scalar field $\phi$ with mass $M$. I would like to ...
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0answers
38 views

Non-eq QFT: functional formalism

I am looking for references (papers, books etc.) where I can find pedagogical introduction to non-eq QFT without hamiltonian approach. I mean that an author start from writing down the generating ...
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0answers
49 views

Question about the Markovian property of the velocity of a Brownian particle following Langevin equation

I'am now studying Langevin model and Fokker-Planck equation with the lecture notes by Borghini Topics in Nonequilibrium Physics (NB: PDF). On page 92, he talks about the Markovian property of the ...
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0answers
52 views

Statistical physics at very large particle number

According to this manuscript http://www.math.lmu.de/~michel/credits/Federica_Pezzotti_phd.pdf it is proposed (e.g. at page 18) that particle correlations between particles can be neglected in the ...
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0answers
47 views

Closed form of Iterated integrals arising in Fredholm's integral equation solution in the context of Nonequilibrium Quantum field Theory?

While solving a Non-equilibrium quantum field theory problem I came across this class of $2n_{}^{\text{th}}$ order iterated integral : $$F(T_{}^{},T_{0}^{},\epsilon)=\int_{T_{0}^{}}^{T_{}^{}}dt_{1}^{}...
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0answers
38 views

Generalized reaction rate for elementary process

Most textbooks give the reaction rate $$r = k [\mathrm{R}_1]^{a_1}[\mathrm{R}_2]^{a_2} \tag{1}$$ for the elementary process $a_1 \mathrm{R}_1 + a_2 \mathrm{R}_2 \rightarrow \mathrm{P}$. However, ...
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0answers
82 views

Derivation of the Keldysh-Non-Linear-Sigma model

I have to give a presentation on the Keldysh Non Linear Sigma model in a proseminar at my university. I am new to the topic and I have had some problems with understanding the literature. My main ...
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0answers
27 views

Why is a quantum quench considered as a quantum analog of a thermodynamic transformation?

In the paper of A. Silva, he mentioned that it is possible to characterize a quantum quench, from the perspective of nonequilibrium physics, using work statistics because the quantum quench is ...
1
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0answers
158 views

The role of time-reversal in detailed balance

For a stationary stochastic process (representing the internal time-evolution of a certain physical system which on average is stationary) we speak of detailed balance when, roughly speaking, the ...
1
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0answers
106 views

Reference request for semiclassical approximations for Schwinger-Keldysh path integrals

Can some one provide some resources for understanding semi-classical approximations for Schwinger-Keldysh path integrals. Is there any discussion about instanton (and multi-instanton) (for even single ...
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0answers
36 views

Is there an equivalency between fluctuation and effective degrees of freedom?

Is it possible to use the fluctuation-dissipation theorem to introduce a new "fictitious" degree of freedom (d.o.f) for an existing coordinate/d.o.f which fluctuates a lot? Consider a non ...
1
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0answers
40 views

Is there a generic procedure to find Free energy functional (a.k.a. Large deviation functional) in Non-equilibrium statistical mechanics?

In equilibrium statistical mechanics, one often writes free energy functional for a system. But is there a generic procedure to find free energy functional for systems in non-equilibrium statistical ...
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0answers
168 views

Expectation values in Doi-Peliti formalism

I'm trying to understand how the Doi-Peliti (DP) action is constructed, and specifically how they compute expectation values. To this end, I've been using the book by Taüber as a reference (Critical ...
1
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0answers
33 views

Many-particle systems where current and applied force are in opposite direction

Are there instances known (both observed or theoretic) of large-$N$ systems where applying an external force causes a current of the "corresponding charge" (present in the system) in the direction ...
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0answers
72 views

How is zonal flow defined and computed?

The transition to turbulence in pipe flow was recently observed to be in the same universality class as directed percolation. This was done by reinterpreting the turbulence and laminar flow in terms ...
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0answers
47 views

Construct recurrence relation for the temporal evolution of a Master equation

Say that we have a system evolving over discrete timesteps. The quantity we are interested is X and is given by a distribution $P_X$. This distribution is evolving temporally, and we have a ...
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0answers
104 views

Open Quantum Systems: Limitations of Self-Energy Method

In low field quantum transport, steady state regime, a popular method to compute Non-Equilibrium Green's functions to study transport, as introduced by Datta (see for reference pdf), accounts for open ...
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0answers
42 views

Canonical treatment of thermalization of two gases at different temperatures

I'd like to understand the thermalization process when two gases of different species and different temperatures are allowed to mix in an insulated container, interacting only through an elastic ...
1
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0answers
66 views

Making Pudding; A complicated non-equilibrium statistical process?

There are a lot of non-equilibrium processes examples given in physics literature. But some processes that are present in everyday life are not treated. As an example, the formation of pudding can be ...
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0answers
56 views

What conditions are needed for Onsager reciprocal relations?

I often find a thorough discussion of the conditions that must hold for a theorem lacking, especially in the sense of what they actually mean physically. Could anyone write up what kind of systems ...
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0answers
61 views

Is the system in equilibrium?

If the time derivative of the Liapunov functional related to free energy of my system is zero, can I say my system is in chemical equilibrium?
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0answers
112 views

Modeling the creation of transverse waves

Suppose I hang one end of a jump rope against a wall and start waving the other end. I'm interested in knowing the behavior of the jump rope as it starts generating waves. In other words, how can I ...
1
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0answers
656 views

Fluctuations in energy for macro and micro canonical ensembles

I was thinking about fluctuations in energy for a system in thermal equilibrium. I think that the Boltzmann distribution itself has an standard deviation approximately equal to the mean, as it is ...
1
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0answers
148 views

Is there a systematic way to determine the relevant variables needed to describe a nonequilibrium system?

In strong nonequilirium, the statistical operator describing the system depends on an infinite number of variables (BBGKY-hierarchy), contains information about all the previous states starting from ...