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seen Jul 28 at 15:06

Jul
22
awarded  Popular Question
Jul
22
accepted What is the entropy of a mixed state in classical physics?
Jul
17
comment What is the entropy of a mixed state in classical physics?
It seems for me that it is actually $\langle -R \log \frac{\rho}{\exp(S/R)} \rangle$. How to get this? This is not obvious at all for me, otherwise I wouldn't be asking the question. Is this derivation available anywhere in the literature? Probably not physics textbooks, but the ones on information theory.
Jul
17
comment What is the entropy of a mixed state in classical physics?
Yes, indeed I have found the formula of the same structure when a mixed state was a generalised canonical ensemble in the book Beyond equilibrium thermodynamics. However, what I really would like to know is how it is derived. What is the rationale behind it?
Jul
15
comment What is the entropy of a mixed state in classical physics?
@rmhleo I can't admit that this would be the only interpretation, but I'd say that yes, one can take it, provided the states do not change in time.
Jul
14
asked Entropy change in Heisenberg picture
Jul
14
revised Is it possible to have a Gas heavier than a liquid?
added 87 characters in body
Jul
14
answered Is it possible to have a Gas heavier than a liquid?
Jul
13
comment What is the entropy of a mixed state in classical physics?
@SebastianRiese State being pure has nothing to do with zero or nonzero entropy. It has to do whether it gives a unique value for all the observables (pure state) or probability distributions for their values (mixed state). For example a pure state for a macroscopical description of a common fluid is given by the fields of density, velocity and temperature. Obviously such description implies the fluid has a nonzero entropy. A mixed state might be of interest in turbulence research when you don't know the fluid velocity at a point, but rather assume there is a probability distribution for it.
Jul
13
asked What is the entropy of a mixed state in classical physics?
Jun
14
awarded  Yearling
Mar
19
accepted What is the gas entropy as a functional of a one-particle distribution function?
Mar
18
answered What is the gas entropy as a functional of a one-particle distribution function?
Mar
16
asked What is the gas entropy as a functional of a one-particle distribution function?
Jan
16
awarded  Self-Learner
Dec
8
comment What Is the Physics principle behind dropping a stone into a cup of water?
I wasn't the one who downvoted, but I can understand that, since the second sentence is clumsy and requires a bit of thinking on what was meant.
Dec
3
comment How does a bowl of hot water move by itself?
I do observe this phenomenon from time to time with plates and hot food on it. For me usually the plate also rotates in addition to mere displacement. The displacement is of no more then 2-3cm I recon and the rotation of the edge is of the same magnitude. The whole movement takes around the second, then the plate stands still. When I pick up the plate there is a sizeable amount of steam condensate on the underside of the plate and on the surface of the table.
Sep
30
awarded  Explainer
Sep
27
awarded  Popular Question
Jul
16
awarded  Nice Answer