What is Nonequilibrium: Definition and 15 Discussions

Non-equilibrium thermodynamics is a branch of thermodynamics that deals with physical systems that are not in thermodynamic equilibrium but can be described in terms of variables (non-equilibrium state variables) that represent an extrapolation of the variables used to specify the system in thermodynamic equilibrium. Non-equilibrium thermodynamics is concerned with transport processes and with the rates of chemical reactions. It relies on what may be thought of as more or less nearness to thermodynamic equilibrium.
Almost all systems found in nature are not in thermodynamic equilibrium, for they are changing or can be triggered to change over time, and are continuously and discontinuously subject to flux of matter and energy to and from other systems and to chemical reactions. Some systems and processes are, however, in a useful sense, near enough to thermodynamic equilibrium to allow description with useful accuracy by currently known non-equilibrium thermodynamics. Nevertheless, many natural systems and processes will always remain far beyond the scope of non-equilibrium thermodynamic methods due to the existence of non variational dynamics, where the concept of free energy is lost.The thermodynamic study of non-equilibrium systems requires more general concepts than are dealt with by equilibrium thermodynamics. One fundamental difference between equilibrium thermodynamics and non-equilibrium thermodynamics lies in the behaviour of inhomogeneous systems, which require for their study knowledge of rates of reaction which are not considered in equilibrium thermodynamics of homogeneous systems. This is discussed below. Another fundamental and very important difference is the difficulty or impossibility, in general, in defining entropy at an instant of time in macroscopic terms for systems not in thermodynamic equilibrium; it can be done, to useful approximation, only in carefully chosen special cases, namely those that are throughout in local thermodynamic equilibrium.

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    I Standard measure of distance from equilibrium for all systems

    Is there a standard way to measure how far a system is displaced from equilibrium that can be applied to all physical systems? So, for example, a ball that is kicked, a spring that is stretched, a liquid that’s heated, and a charged battery are all systems that are displaced from equilibrium. I...
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    A Calculating nonequilibrium Green's Functions

    Hey :) Firstly I want to thank everyone who takes their time to read through this post and who tries to help me. So the issue is the following: I wrote a python code that creates a Lindbladian, and I wanted to try to calculate the Greens function using the Lehmann representation. For the...
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    A Understanding & Solving Electron/Phonon Interaction Problems

    I am wondering if there is a book with solved example problems I can follow so that I can carry out the following calculation: I have a set of unperturbed electron Green functions $g^{r0},g^{a0},g^{<0},g^{>0}$ and phonon Green functions $d^{r0},d^{a0},d^{<0},d^{>0}$ which are for a central...
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    I Derivation of the Onsager symmetry

    Derivation of the Onsager symmetry in many textbooks and papers is as follows: First, assume that the correlation function of two state variables,##a_i## and ##a_j## satifsies for sufficiently small time interval ##t## that $$\langle a_i(t) a_j(0) \rangle = \langle a_i(-t) a_j(0) \rangle =...
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    Finding a Booklist to Learn Nonequilibrium Thermodynamics/Statistical Mechanics

    Hi, guys I have posted this question on StackExchange, but no one seems to care answer. Because I don't think this is a simple textbook question, I start my thread here: I know this is a big question. But as a graduate student, my research is somehow related to nonequilibrium...
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    Other Nonequilibrium Thermodynamics Request

    I've started using LaTeX to take notes on Donald Fitts' Nonequilibrium Thermodynamics. After I finish, I intend to use other resources to add more to it. Fitts' book focuses on classical fluid nonequilibrium thermodynamics (i.e. doesn't use statistical mechanics but instead uses continuum...
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    Distance between equilibrium and nonequilibrium states

    Recently, the properties of nonequilibrium many-body quantum systems have aroused great curiosity of physicists. Numerous papers have been published about this area. But how do we measure how far the system is from equilibrium states? There are several proposals have been published, for...
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    Getting to the Boltzmann Equation from a Nonequilibrium Distribution Function

    Homework Statement Hi. I have a course where I am supposed to show how to get to the Boltzmann equation from a nonequilibrium distrubution function. At the moment I'm kinda lost to how this is done, so hopefully a hint or two would be of some help :)Homework Equations The nonequilibrium...
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    How Does Weight Influence Net Force on a Submarine?

    A 1450 kg submarine rises straight up toward the surface. Seawater exerts both an upward buoyant force of 16,140 N on the submarine and a downward resistive force of 1030 N.My question: Is the weight of the submarine included in the net force? If the weight is taken into account, is it included...
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    Nonequilibrium applications of Newton's laws of motion

    A fisherman is fishing from a bridge and is using a "32.0-N test line." In other words, the line will sustain a maximum force of 32.0 N without breaking. What is the weight of the heaviest fish that can be pulled up vertically, when the line is reeled in with an acceleration whose magnitude is...
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    How can you calculate nonequilibrium torque and its effects on an extended body?

    Can somebody give an example of nonequilibrium torque and how to go about doing calculations for it? So, for example, for an EQUILIBRIUM problem if you have an aircraft moving with constant velocity there's a drag force in one horizontal direction and a tension opposing it 2 m below the center...
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    Help about the Nonequilibrium Green's Function

    help about the Nonequilibrium Green's Function in H. Haug and A.-P. Jauho Book Quantum kinetics in transport and Optics of Semiconductors Eq.(4.31) C^r(t,t')=A^<(t,t')B^r(t,t')+A^r(t,t')B^<(t,t')+A^r(t,t')B^r(t,t') I can not derive this equation, my result has a extra term \theta(t-t') i.e...
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    Nonequilibrium Applications of Newton's 2nd Law Problem

    I along with a buddy of mine in the same course have been trying to figure out the following question. We spent at least an hour and a half to two hours and nothing makes sense. Any help would be greatly appreciated. Here's the question as it's written: One way to measure the acceleration...
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    Nonequilibrium Applications of Newton's Laws of Motion

    A 292 kg motor cycle is accelerating up along a ramp that is inclined 30.0 degrees above the horizontal. The propulsion force pushing the motorcycle up the ramp is 3150 N, and air resistance produces a force of 250 N that opposes the motion. Find the magnitude of the motorcycle's acceleration.