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34 votes
3 answers
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Renormalization Group for non-equilibrium

For equilibrium/ground state systems, a (Wilson) renormalization group transformation produces a series of systems (flow of Hamiltonians/couplings $H_{\Lambda}$ where $\Lambda$ is the cut-off) such ...
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23 votes
6 answers
4k views

Is thermodynamics only applicable to systems in equilibrium?

So I was going through callen's thermodynamics book and their he says that thermodynamics is only applicable to systems which are in equilibrium and that naturally raised a few questions in my mind ...
Metric's user avatar
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20 votes
2 answers
6k views

What is "Dynamical phase transition"?

What is "Dynamical phase transition"? It is a fancy notion now. But what exactly does it mean? What is the difference between it and the conventional phase transition?
John's user avatar
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19 votes
5 answers
10k views

What are some of the best books on complex systems and emergence?

I'm rather interested in getting my feet wet at the interface of complex systems and emergence. Can anybody give me references to some good books on these topics? I'm looking for very introductory ...
18 votes
2 answers
2k views

Applications of the Feynman-Vernon Influence Functional

I am looking for a reference where the Feynman-Vernon influence functional was defined and used in the context of relativistic quantum field theory. This functional is one method to describe non-...
user avatar
16 votes
5 answers
2k views

How does radiation become black-body radiation?

Textbooks treat black body radiation as radiation in thermal equilibrium with its environment (more specifically - with a black body): Planck's formula is essentially derived from the partition ...
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16 votes
1 answer
2k views

Relation between Langevin and Fokker-Planck for exponentially correlated noise

What is the corresponding Fokker-Planck equation for, $\frac{df(t)}{dt}=-kf(t)+\zeta(t)$ where, $\zeta(t)$ is random noise? In particular, how will the Fokker-Planck equation look if $\zeta(t)$ is ...
nitin's user avatar
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16 votes
1 answer
3k views

Maximum Principle vs. Minimum Principle in Non-equilibrium Thermodynamics

Prigogine's Min. principle states that in steady-state non-equilibrium systems the entropy generation rate is at a minimum, i.e., a system will seek a steady-state that has min entropy generation. ...
Sankaran's user avatar
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14 votes
4 answers
430 views

How quickly should a fluid come to hydrostatic equilibrium?

Let's say I'm holding a one-liter water bottle, full of water, which I then drop. Before dropping the water bottle, the equilibrium is for there to be a pressure gradient in the water canceling the ...
Mark Eichenlaub's user avatar
12 votes
2 answers
376 views

What is the intuition behind the statement that non-equilibrium systems with static disorder are self-averaging?

In this paper(1) by C. De Dominics, he makes the argument that in a dynamical statistical mechanics system, one doesn't need to apply the replica trick and can directly disorder average the generating ...
Adam B's user avatar
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12 votes
4 answers
1k views

Is "equilibrium state" equivalent to "well-defined state variables"?

Follow up to Intuitively, why is a reversible process one in which the system is always at equilibrium? and How slow is a reversible adiabatic expansion of an ideal gas? Suppose you have a piston ...
Mark Eichenlaub's user avatar
12 votes
2 answers
469 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 active motors which may consume energy from the environment to move and exert ...
0x90's user avatar
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12 votes
0 answers
512 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}\...
zudumathics's user avatar
11 votes
4 answers
3k views

Diffusion coefficient for asymmetric (biased) random walk

I want to obtain a Fokker-Planck like equation by taking the continuous limit of a discrete asymmetric random walk. Let the probability of taking a step to the right be $p$, and the probability of ...
SarthakC's user avatar
  • 225
10 votes
3 answers
3k views

Book recommendation for nonequilibrium thermo/stat mech

I'm doing an undergrad research project that lies at the intersection of biology and nonequilibrium thermodynamics, but I'm starting to realize almost none of my equilibrium thermo/stat mech knowledge ...
9 votes
6 answers
2k views

How is Newton's first law compatible with transport equations?

So, I'm studying non-equilibrium thermodynamics and the first thing I've learned is that the discipline has a first scope of generalizing the idea of transport equations. Transport equations are ...
Swike's user avatar
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9 votes
5 answers
1k views

Sufficient and necessary conditions on random walk to obtain standard diffusion equation

In the simplest random walk model that is generally considered, the probability of the finding the particle at time $t$ in $x$, $P(x,t)$ is given by, $$ P(x,t) = \frac{1}{2}\big[ P(x-a, t-\tau) + P(x+...
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8 votes
4 answers
2k views

Non equilibrium statistical mechanics [closed]

A question kept bothering me about the Non-Equilibrium Statistical mechanics, can somebody give a simple description of how one approaches this subject? Is there a exact formalism, as we have for ...
Jaswin's user avatar
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8 votes
5 answers
2k views

How is temperature defined in non-equilibrium?

I see that temperature is defined always in equilibrium. But systems which are not in equilibrium with their environment. How is temperature defined in these cases? Humans for example, have a body ...
veronika's user avatar
  • 2,706
8 votes
2 answers
786 views

Assumptions of thermodynamic & chemical equilibrium in fluid-dynamics

I am reading about the Euler equations of fluid dynamics from Leveque's Numerical Methods for Conservation Laws. After introducing the mass, momentum and energy equations, some thermodynamic concepts ...
smilingbuddha's user avatar
8 votes
1 answer
4k views

Local and global detailed balance

I'm taking a course on nonequilibrium statistical mechanics and I encountered the terms local and global detailed balance. I'm a bit confused about what is their exact definition and what is the ...
Lagrangian's user avatar
8 votes
2 answers
843 views

Hydrodynamics, non-equilibrium thermodynamics and equations of states

Why is it that in non-equilibrium hydrodynamic modelling, e.g. when the solution is time dependent, people use equations of state that are derived from equilibrium considerations (i.e. the ideal gas ...
mathdummy's user avatar
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8 votes
1 answer
2k views

The Bhatnagar-Gross-Krook (BGK) approximation of the collision integral

Bhatnagar, Gross and Krook (BGK) proposed a relaxation term for the collision integral $ Q$ as follows $$J = \frac{1}{\tau} (f^{eq} - f)$$ where $f^{eq}$ is the distribution at equilibrium. $Q$ has ...
alekhine's user avatar
  • 211
8 votes
1 answer
332 views

Deviation from power law distribution of earthquakes

One of the most accepted frameworks for the relationship between the magnitude and frequency of an earthquake is that of the critical phenomena. In this framework, the magnitude of events must be ...
Emanuele Luzio's user avatar
8 votes
1 answer
394 views

How to dress free Green functions with constant broadening?

I want to find a way to dress free Keldysh Green functions with the simplest level broadening. But there seems to be some quite unexpected result. Let's consider free Keldysh Green functions in ...
xiaohuamao's user avatar
  • 3,661
8 votes
1 answer
355 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 ...
Everett You's user avatar
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8 votes
0 answers
165 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 ...
S Huntsman's user avatar
7 votes
1 answer
4k views

Calculating conductivity from Green's functions

I am trying to calculate the conductivity in the linear response regime of a disordered electron gas. (or eventually of a mean field Heavy fermion system with known one particle green's functions). I ...
Garvan's user avatar
  • 71
7 votes
1 answer
1k views

Definition of entropy in nonequilibrium states

Thermodynamical definition of entropy $$S(p)=-\int p\ln p~dx$$ is defined only on equilibrium system. But why can't we use it for non-equilibrium system? Is there a well-accepted definition for it?
zhangwfjh's user avatar
  • 301
7 votes
4 answers
2k views

Is Fourier's law of conduction a consequence of the second principle?

In classical thermodynamics courses, entropy is often motivated by the need to justify that heat flows from high temperatures zones to lower temperatures zones: this is seen as a consequence of ...
Whelp's user avatar
  • 3,996
7 votes
3 answers
772 views

What does "an average over noise" mean in Zwanzig's book

This is a very specific question about Robert Zwanzig's book Nonequilibrium Statistical Mechanics. Specifically, what is he talking about in equation 1.25 on page 10 that he calls "an average over ...
lnmaurer's user avatar
  • 4,155
7 votes
5 answers
5k views

Does high entropy means low symmetry?

According to Bogolubov postulate (various texts name it differently) in Non-equilibrium thermodynamics, the number of needed parameters to describe our system is decreasing with time, and finally at ...
TMS's user avatar
  • 2,051
7 votes
2 answers
1k views

Statistical Mechanics treatment of the reaction process?

I'm searching for an at least semi-rigorous Statistical Mechanics description/treatment of a (spatially resolved) chemical reaction process of a macroscopic portion of at least two different species ...
Nikolaj-K's user avatar
  • 8,493
7 votes
3 answers
861 views

Is entropy maximum in equilibrium?

Usually, in the context of non-equilibrium thermodynamics, it is said that entropy achieves a maximum in equilibrium, so the Taylor series expansion of entropy around the equilibrium state as a ...
1__'s user avatar
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7 votes
1 answer
1k views

``What is life?'' by a physicist definition [closed]

The question is about defining ``What is life?'' in the field of Physics. Whether there is any (insightful) way of defining ``What is life?'' from physicists. There are pioneer works, including ...
wonderich's user avatar
  • 7,838
7 votes
0 answers
400 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 ...
Nanite's user avatar
  • 3,400
7 votes
0 answers
854 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 ...
Robert Mastragostino's user avatar
6 votes
1 answer
2k views

What is the use of Schwinger-Keldysh formalism?

In non-equilibrium statistical mechanics, there is this formidable formalism, called the Schwinger-Keldysh formalism. I have read about it, and I understand what it is. However, what I what to know ...
Raghu Mahajan's user avatar
6 votes
2 answers
1k views

Keldysh formalism and Kubo formula

I am working on out-of-equilibrium problems of strongly correlated materials, so I am interested in the Keldysh formalism. I just started reading about the subject, and I don't understand quite well ...
lakehal's user avatar
  • 636
6 votes
3 answers
6k views

How to understand temperatures of different degrees of freedom?

So I'm reading this book, where after the preface and before the models there is a section called General Notions and Essential Quantities, which introduce some things I don't understand. They regard ...
Nikolaj-K's user avatar
  • 8,493
6 votes
3 answers
820 views

Confusion regarding entropy, reference papers request

1.a In paragraph at Wikipedia/Entropy it is stated: This is because energy supplied at a high temperature (i.e. with low entropy) tends to be more useful than the same amount of energy ...
Mooncer's user avatar
  • 391
6 votes
1 answer
188 views

Why turbulence is non-equilibrium?

I've encountered this notion many times that turbulence is non-equilibrium (e.g., Falkovich & Sreenivasan, Physics Today, 59, 2006). However, I am confused about what does it mean by "non-...
TurbPhys's user avatar
6 votes
1 answer
336 views

Are ultracold atoms only created by intelligent life?

Nature has particle accelerators that are far beyond our capacity, but occasionally I hear atomic physicists claim that they are able to make something that has never been formed in any natural ...
Rococo's user avatar
  • 7,740
6 votes
2 answers
3k views

Modern textbook on statistical field theory with an emphasis on applications to non-equilibrium phenomena?

What is a good textbook on statistical field theory, with an emphasis on applications to non-equilibrium phenomena? I am a final-year undergraduate, have already taken introductory classes in ...
6 votes
2 answers
892 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)...
Henry Shackleton's user avatar
6 votes
1 answer
2k views

What is the difference between non-equilibrium and equilibrium phase transitions? [duplicate]

My question is about the distinction between certain kinds of phase transitions. I understand what the difference between first and second order ones are. What is the difference between non ...
jrex 's user avatar
  • 619
6 votes
1 answer
770 views

Dynamic Renormalization group in Momentum space

I am trying to reproduce the computations of Appendix B of Fractal Concepts on Surface Growth (Barabási & Stanley), about the computation of the critical exponents of KPZ equation using Dynamic ...
Victor Buendía's user avatar
6 votes
1 answer
1k views

Relating the variance of the current operator to measurements

(EDIT: Thanks to Nathaniel's comments, I have altered the question to reflect the bits that I am still confused about.) This is a general conceptual question, but for definiteness' sake, imagine a ...
Mark Mitchison's user avatar
6 votes
2 answers
837 views

Can the work done between two non-equilibrium states be calculated?

The work done during a process between two equilibrium states can be described by thermodynamics. Even when process itself is out of equilibrium, the thermodynamic laws can still be used, though ...
Jordan's user avatar
  • 1,593
6 votes
1 answer
195 views

Can you prove the interesting relation in equilibrium thermodynamics?

Problem and background I noted the following interesting relation in a paper discussing the liquid-vapor phase change, in which it was given directly without any derivation and reference: $$d\ln p^\...
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