What is Non-equilibrium: Definition and 20 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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  1. ORF

    A What is the heat capacity of water in meta-stable equilibrium?

    Dear experts, I noticed that super-heated water (liquid water with temperature above 100*C) undergoes boiling when pushed outside the meta-stable equilibrium. I was wondering, is the heat capacity of liquid water above 100*C the same as liquid water with temperature between 0*C and 100*C...
  2. T

    Physics Non-equilibrium statistical physics and complex systems

    Is Non-equilibrium statistical physics and complex systems a good area of study to go into? Is it a well respected field? Thank you
  3. vjrajsingh

    Non-equilibrium thermodynamics

    Biological systems act as dissipative structures and obey the universal laws of thermodynamics in spite of being open structures as they follow non-equilibrium thermodynamics. In accordance with the second law, entropy generation occurs. Is it possible to limit the entropy generation in a...
  4. L

    A Non-equilibrium Statistical Mechanics of Liquids

    Molecular Transport equations for Liquids are harder to compute than that for gases, because intermolecular interactions are far more important in liquids. A System of equations for particle Distribution function and the correlation functions (BBGKY-Hierarchy) is used in General. For gases, it...
  5. S

    Review of modern non-equilibrium thermodynamics theories

    Looking for thorough serious comparative review of modern generalisations of classical non-equilibrium thermodynamics of continua. I have heard about several such generalisations: 1) rational mechanics by Truesdell, Coleman, Noll. 2) extended thermodynamics by Müller (and Ruggeri). 3) the...
  6. S

    Schools Who are the Top Non-Equilibrium Research Groups in North America and Europe?

    I realize the question is quite broad but what research groups working on statistical physics, stochastic processes, and complex systems are generally considered the best? Would like to know about Europe and America alike.
  7. Curiose

    WaveGrid - Non-equilibrium Emergence Sandbox

    [Mentors' note: one short paragraph of speculation in violation of the Physics Forums rules has been removed from this post] Follow the link below to play with my experimental sandbox. The rest of this post includes some instructions for use and then observations and a little bit of theory...
  8. Wrichik Basu

    Other Books for Non-Equilibrium Statistical Mechanics

    Can anyone refer to some good book on Non-Equilibrium Statistical Mechanics? The book should contain the basics, and can go up to any advanced level. Any level of math is acceptable.
  9. S

    Assumption of local thermodynamic equilibrium in a fluid

    Moving fluids are generally in a state of non-equilibrium. However, in fluid dynamics, people generally assume a state of local thermodynamic equilibrium and argue that in such a condition, equilibrium thermodynamic concepts such as pressure, temperature, entropy, internal energy etc. can be...
  10. Auto-Didact

    A Correspondence between entanglement and chaos?

    Neill et al. 2016, Ergodic dynamics and thermalization in an isolated quantum system NB: For a more introductory version, phys.org ran a piece on this article last summer From my understanding entanglement is generally seen as purely a quantum phenomenon, while on the other hand chaos is...
  11. Eric Walker

    B Non-equilibrium variation in electron density in a metal

    Consider two atoms of platinum, A and B, in a sample of platinum. Atom A lives deep within the sample, and atom B lives at the tip of a sharp protuberance at the surface. My understanding is that electrons in the sample will accumulate within a surface defect such as the tip of a sharp needle...
  12. A

    Two temperatures state in non-equilibrium plasma

    Hello Two temperatures state in non-equilibrium plasma has different vibrational temperature and translational temperature. Vibrational temperature is more than translational temperature usually. Help me to find a book or article for describing thermodynamics of this state.
  13. D

    Boltzmann equation for the early Universe

    I'm currently reading about the Boltzmann equation, used for the early Universe. The equation I end up with, after some simplifications is the following: \begin{equation} a^{-3}\frac{d}{dt}\left(n_1a^3\right) = n_1^{(0)}n_2^{(0)}\langle\sigma v\rangle\left[\frac{n_3 n_4}{n_3^{(0)}n_4^{(0)}} -...
  14. D

    Fermi Level of Electrons and Holes in Equilibrium and Non-Equilibrium

    Hi all, Why do the fermi level for electrons and holes coincide in equilibrium condition and why they separate as quasi fermi levels in non equilibrium situation?
  15. R

    Book recommendations for Non-Equilibrium Statistical Physics

    Hello. I am currently working on my master's thesis in entropy production in non-equilibrium systems using stochastic methods. I am also working on boosting my understanding of statistical physics by studying many different textbooks on the subject, and on related subjects such as...
  16. D

    How Is Tension Calculated in a Helicopter Rescue Operation?

    1. "A 2800 kg helicopter with a cable and harness is rescuing an injured snowboarder. The harness and snowboarder weigh 1730 N." The question is asking for the "tension in the cable if the snowboarder and helicopter accelerate upward at 1.5 m/s2." 2. ∑Fy=may=T- Is the equation (above)...
  17. M

    Non-equilibrium applications of Newton's Laws of motion

    Homework Statement A 1380kg car is moving due east with an initial speed of 27 m/s . after 8.00s the car has slowed down to 17.0 m/s . Find the magnitude and direction of the net force that produces the deceleration Homework Equations Net force of x= MAx Net force of y= MAy The...
  18. I

    Non-Equilibrium Applications of Newtons Laws

    1. In the drawing, the weight of the block on the table is 388 N and that of the hanging block is 175 N. Ignore all frictional effects, and assuming the pulley and the cord to be massless. Find the acceleration of the two blocks as well as the tension in the cord 2. Fnet = mass of the...
  19. N

    Non-equilibrium states in Semiconductor

    Just to clarify - non equilibrium states in semiconductor means that the semiconductor is affected by external factors such as light?
  20. B

    Non-equilibrium conduction electrons

    Here's the issue I'm trying to wade through: 1. If you excite electrons from valence band to conduction band (with a laser say), you are out of thermodynamic equilibrium. In some recombination time, the system will go back to equilibrium. All well in good. 2. Now let us consider a very...