Talk:Gibbs paradox

message: Gibbs paradox is 
resolved through the introduction of Planck's constant, or  at least the quantization of phase space, resulting in the Sackur-Tetrode equation. PAR 11:46, 13 May 2005 (UTC)
replies: text: If the question is wether the article should be also in the category "qm", then I completely agree with you. Please go ahead :-) -- mkrohn 11:49, 13 May 2005 (UTC)
thread_title:  Category - Quantum mechanics 

message: The number of states \phi/h^3, of which one takes the logarithm to get the entropy, has dimension (mass × length / time)-1, since the dimension of the constrained phase space is lenght3N×momentum3N-1 and not lenght3N×momentum3N . Shouldn't this be made dimensionless somehow? --V79 22:17, 15 October 2005 (UTC)
replies: text: Good point. Talking about the "area" of the cylinder wall is bad form, it has zero volume, in contradiction to the idea that you can't specify a volume smaller than h^3N. I fixed it in a hand-waving kind of way, but maybe it needs to be more fully explained. PAR 00:24, 16 October 2005 (UTC)
thread_title:  Dimensions 

message: i removed the tag.  since there's a "context" tag on the article itself, it seems redundant.  if you want, go ahead and reinsert the tag, but please leave some specific suggestions about what you think the article needs.  thanks.  Lunch 04:43, 24 September 2006 (UTC)
thread_title: too technical tag

message: This article makes no sense.  Unfortunately, I have to say I think the contributions by Linshukun are entirely to b.  You can see Lin's very first edit here, a paragraph of raw text jammed at the top of what used to be a pretty concise article: http://en.wikipedia.org/w/index.php?title=Gibbs_paradox&diff=prev&oldid=109172335  As you can see, it consists of simply adding her opinion to the article.  This has continued in progressively more wikified forms for 2 years.  Finally the article is unrecognizable.  All the math is gone, as is the encyclopedic tone.  The article is not even logically consistent in its current state.
There is no statement of what Gibbs' paradox is.  Perhaps it is the discontinuity in "figure A"... which Lin's "figure C" simply omits.  
It is true that Lin appears to have written a paper on this topic.  However, this violates the spirit if not the letter of WP:OR. 76.208.71.19 (talk) 03:40, 23 September 2009 (UTC)
replies: text: The article itself looks genuine enough. But Linshukun's extensive additions to it appear to be a joke. At best, they are original research and should be removed for that reason. Maproom (talk) 23:10, 5 October 2009 (UTC)
replies: text: Just for clarity, could somebody list all the disputed parts - or tag them as ? I realize this may not be easy due to the amount of material in question. --catslash (talk) 00:11, 6 October 2009 (UTC)
replies: text:  For reasons I have stated above (RFC: Review of new material requested), I agree that Linshukun's contributions are completely wrong, but since they are published, I was reluctant to remove them. The contentious parts, in my view, are the inclusion of any material from the Linshukun references. I agree that the mathematics of the statistical mechanical "explanation" should be restored. The "Classical explanation" is fine. The "quantum explanation" of Von Neumann is not familiar to me, but if it is indeed an accurate description of an opinion of Von Neumann, it cannot be ignored. PAR (talk) 10:43, 6 October 2009 (UTC)
replies: text:  Please note some of Linshukun's articles seems to be published through http://www.mdpi.org/ which he evidently co-founded and for which he served as editor-in-chief.  http://www.mdpi.org/lin/modi601001.pdf  Note the "see also" link is maintained by him, and led to some major confusion for me as the reader.  Thanks.  (Trolou (talk) 18:07, 11 February 2010 (UTC)
thread_title:  RFC: Can a physicist check this article? 

message: I did a series of edits on this section, putting in new section and subsection titles and a fuller paragraph at the beginning explaining the plan of the section. Here is the current outline of this section.
4 Non-extensive entropy of two ideal gases and how to fix it
4.1 Setup
4.2 Gibb's paradox in a one-dimensional gas
4.3 Two standards ways to make the classical entropy extensive
4.4 Swendsen's particle-exchange approach
4.5 Visualizing the particle-exchange approach in three dimensions
Together with the fuller paragraph at the beginning, for me this makes the section much easier to follow because it tells you at the beginning where you're going. 
Here are two remaining difficulties with the structure:
(A)  The derivation in subsections 4.1 and 4.2 of the non-extensive entropy for a 1-dimensional gas largely repeats the calculations that are already done in section 2, Calculating the entropy of ideal gas, and making it extensive. 
In defense of the redundancy (which is not due to me!): it's nice to read the same thing said two different ways and there are a number of interesting remarks included that aren't found in section 2.
(B) Even if 4.1 and 4.2 are left alone, perhaps the section would be improved if 4.3 were removed and absorbed into the earlier part of the article. One of the "fixes" in section 4.3 was already treated earlier, and the other one is rather simple to state and it could perhaps be moved out of the way. 
89.217.15.87 (talk) 00:11, 17 March 2015 (UTC)
thread_title:  Clarified the structure of section now entitled "Non-extensive entropy of two ideal gases and how to fix it" 

message: ♦ Strangely, the net result of the Swendson approach appears to be the equation
::S =\ln \Omega_{E,\ell,N}  
\approx n_A\ln\left(\frac{n_A}{\ell_A}\sqrt{\frac{E_A}{\ell_A}}\right)+
n_B\ln\left(\frac{n_B}{\ell_B}\sqrt{\frac{E_B}{\ell_B}}\right)+
N\ln N + const.
followed by the remark This can be interpreted as the sum of the entropy of system-A and system-B, both extensive.  And there is a term, N\ln N, that is not extensive.
My question is this: since it has a term that is not extensive, then how does it remotely fix the problem of the non-extensive entropy? This is totally puzzling.
Even more puzzling is the next sentence (at the start of the following section): The correct (extensive) formulas for systems A and B were obtained because we included all the possible ways that the two systems could exchange particles.
So now suddenly the above-cited entropy formula is correct?
♦ The whole Swendsen approach is a mystery to me. Somehow, the most central part of the explanation is missing.
(a) What are the two systems? Are they supposed to be two volumes that are adjacent to each other, with a barrier between, like in the Gibbs paradox? If so, why do they have two different sizes, and appear to overlap?
(b) How is the exchange actually implemented at the formal level? 
I understand that if you select a subset containing n_A indices from {1,...,N}, then you are somehow saying that the first set of particles is in the first "box" (actually an interval) and the complimentary set is in the second "box". And that if you consider this for various values of n_A, then you are countenancing the possibility that particles move between boxes.
But how is this implemented formally? Shouldn't there be a sum or product somewhere where n_A varies? What concrete part of the formalism gives us the right to say that the number of particles actually does vary, and that we are accounting for them?
(c) An off-putting remark a bit later on is This counting is not justified on physical grounds, but on the need to integrate over phase space.
This seems to echo the fact that the setup was never really explained, and that the article simply would rather not "go there".
♦ Miscellaneous questions:
(a) What are the question marks in the integral expression for \Omega_{E,\ell,N}? I understand that they stand for all subsets of {1,...,N}, but unless you spell out these variables as actual symbols, it's hard to tell what you're doing with these variables. Such as summing or producting over them.
(b) What is \ell in this expression? An ordered pair?
♦ Upshot:
I'm not going to say that the Swendsen approach is nonsense, because it has some right elements. But it's not possible to understand the presentation in this article and there are a number of gaps. Given the level of mathematical effort that has been expended in these sections of the article, there ought to be at least an adequate explanation of the conceptual ansatz.
89.217.15.87 (talk) 00:11, 17 March 2015 (UTC)
replies: text: In the entropy of mixing, one considers the entropy before and after mixing: i.e. the change. In that setting, the N log N term is there, both before and also after, so it cancels: it does not contribute to the change. I don't know how to reconcile that with the large raft of text in this article. 67.198.37.16 (talk) 01:15, 20 May 2024 (UTC)
thread_title: Complaints about the  Swendsen approach

message: since impossible to get this situation in reality (in other words entropy will be exactly the same in any volume or number of identical particles)....This statement is a scientific disgrace: "There is a certain amount of entropy S associated with each container of gas, and this depends on the volume of each container."  — Preceding unsigned comment added by 134.7.190.150 (talk) 04:05, 29 March 2015 (UTC)
replies: text: I have no idea what this comment is talking about because entropy always increases with volume and/or number of particles if the temperature is constant. Ywaz (talk) 11:17, 25 January 2016 (UTC)
thread_title:  paradox is a nonsence 

message: Substituted at 16:15, 29 April 2016 (UTC)
thread_title: Assessment comment