Wikipedia talk:WikiProject Physics/Archive February 2019

More bimetric gravity fun times


A little while back, I removed a couple citations from bimetric gravity on the grounds that they were "references to papers that have barely been cited (and mostly by their own authors at that)". They were today restored on the grounds of "neutrality", which just doesn't seem to hold water to me. Indeed, the rationale for restoring them seems, if anything, to argue that they are redundant. Further opinions welcome. XOR&#39;easter (talk) 17:13, 31 January 2019 (UTC)
 * Hello XOR'easter. Your post seems to be referring to some edits by, so I have notified them. EdJohnston (talk) 19:01, 31 January 2019 (UTC)
 * Thank you. XOR&#39;easter (talk) 19:16, 31 January 2019 (UTC)
 * I note that they have restored the citations with the edit summary Researchers working in the field of 1) negative mass 2) bimetric theories of gravity and 3) who publish in peer-reviewed journals (a valid source according to Wikipedia's policy) can be counted on the fingers of one hand. Authors can be exhaustively cited in that article for a neutral point of view, and one cannot judge of the validity of a particular peer-reviewed paper against another. This seems honestly counterproductive to me: the first sentence verges on arguing that the topic is not notable, and the second conflates judging the "validity" of a paper (which I am not doing) with judging its relative significance. I don't have strong opinions about this edit, but I can't see it as contributing more content than clutter, either. To put it another way, "exhaustive" citation is not necessarily the way to neutrality. Wikipedia should reflect the attention which the scientific community has already granted an idea, not manufacture significance by directing extra attention to an overlooked idea, or by disproportionately emphasizing the less-influential versions of an idea. XOR&#39;easter (talk) 19:27, 31 January 2019 (UTC)
 * Hi, I am not suggesting referencing exhaustively all possible papers on this subject (which would indeed disproportionately emphasize one particular author), but only main authors who have contributed notably to the field. "Notability" is not ONLY about the number of citations of one particular paper, it is also about the whole number of papers published on that subject. Hossenfelder published two peer-reviewed papers (one of which is a conference paper) while Petit published 20+ peer-reviewed papers on bimetric gravity. The two approaches share the same foundations (same set of coupled field equations giving the same gravitational interaction laws). Guess who is the specialist of bimetric gravity with negative mas? Hossenfelder is notable here because she was the first to make a Lagrangian derivation of the coupled field equations. Petit is more notable than Hossenfelder on the subject at a large scale, as he developed a whole cosmological model from it. yet in the wikipedia page Hossenfelder is put on par with Petit, citing her two papers (100% of her contributions). On the contrary, only one paper selected to briefly illustrate Petit's contribution in the field, chosen in his whole bibliography (representing 5%) is not exactly "emphasizing disproportionately" on that author. In fact, it is quite the contrary. I agree that in the past few weeks, an editor disproportionately emphasized Petit's theory, hijacking the whole bimetric gravity page. This has been rightly reverted. Nevertheless, one cannot totally erase 40 years of scientific work, especially if that work is only briefly mentioned with one reference only. — Tokamac (talk) 22:07, 31 January 2019 (UTC)
 * Thank you for your reply. I don't believe that the total number of papers published by an individual is a meaningful criterion (it is a quantity that is easily inflated, by schemes with which we are all familiar, and so we should not lean upon it). Nor does the fraction of an author's bibliography devoted to a topic strike me as a very good guideline. Moreover, Petit's having developed a whole cosmological model from it does not contribute to notability, in the Wikipedian sense of the word, unless that model has been influential, and as our article on Petit admits, "this non-standard cosmological model has not triggered much interest in the scientific community throughout the years". Merely having written a lot doesn't matter; what matters is impact and influence. Overall, what I would really like is one or more secondary sources (e.g., review articles by a third party) so that our page on bimetric gravity relies less on primary sources. Unfortunately, on niche topics, those can be hard to come by. Cheers, XOR&#39;easter (talk) 00:15, 1 February 2019 (UTC)
 * Recent positive comments about the Janus model by astrophysicist Matt O'Dowd on PBS Space Time (1.5 million subscribers) endorsed by PBS should be added as referenced secondary source. — Tokamac (talk) 11:55, 8 February 2019 (UTC)

What pages should link to Hayward metric?
I've just created the page Hayward metric. However, I'm not sure if there are any obvious pages to link to the article, any suggestions? Absolutelypuremilk (talk) 17:23, 11 February 2019 (UTC)
 * I have not verified the notability of the subject, but the article has a problem. It uses too many arXiv papers as sources. --MaoGo (talk) 18:25, 11 February 2019 (UTC)
 * Those papers have all been published - I've just added the full citations. Absolutelypuremilk (talk) 18:34, 11 February 2019 (UTC)
 * Probably nonsingular black hole models could link to this page. If it isn't notable, that could be a merge candidate. -- 18:52, 11 February 2019 (UTC)

Vandalism check
I'm not at work, so I can't verify if this is vandalism or not since I don't have access to the reference. Could someone check? Headbomb {t · c · p · b} 20:29, 11 February 2019 (UTC)
 * ✅, reverted, it was not what the source said. I do not like that paper as reference, I'm going to try too look for a better source anyway. --MaoGo (talk) 20:55, 11 February 2019 (UTC)
 * Comparing with the Electron heat capacity article the answer may have the $$\pi^2$$, the internal energy of a free electron model and the entropy should be the same, aside from a factor of $$T$$. --MaoGo (talk) 21:39, 11 February 2019 (UTC)

Cosmological constant problem
Could someone with some relavent expertise please review Cosmological constant problem? Thanks Tayste (edits) 01:46, 12 February 2019 (UTC)
 * I doubt the removed text actually belongs, especially at that length. It appears to be a legitimate proposal, but not one that has swept the field away, so spending that many words on it might be giving it undue weight. Without investigating the page history too deeply, I suspect it was significantly shaped by self-promotion. I was also mildly surprised to find some proposals missing, e.g., that of Bill Unruh and collaborators . XOR&#39;easter (talk) 01:35, 13 February 2019 (UTC)

Template:Erratum and Template:Retracted
See
 * Erratum
 * Retracted

I've just created Erratum to offer simliar functionality to Retracted. Enjoy. Headbomb {t · c · p · b} 01:09, 16 February 2019 (UTC)
 * Oh this is great!. --MaoGo (talk) 11:03, 16 February 2019 (UTC)

I need some advice
Hello,

I don't quite know whether or not this is the right page to ask my question. I have put some work into the Diesel engine article, and I have added a section that explains power and torque: Diesel engine. It ended up being more complicated than anticipated, and I wonder if it is believed that the "average reader" can understand what I have written? I doubt that it is factually incorrect, but it may be unusual. Are there ways of further improving that section to make it more understandable, or should I leave it as it is? I'd appreciate any advice. --Johannes Maximilian (talk) 13:11, 15 February 2019 (UTC)


 * This is out of my area, but I have some questions: Why is there a $$\pi^{-1}$$ in the formula? Does $$dm^3$$ mean cubic deci-meters (i.e. liters)? Why are you using the displacement volume rather than the area of the cylinder since one must multiply pressure by area to get a force? Where is the "length of the lever" (distance between the crank-pin and the center of the crank-shaft) in the formula, after all you are calculating torque? Where is the angle between that lever and the rod which connects the crank-pin to the cylinder? What about the angle at which that rod meets the cylinder? JRSpriggs (talk) 14:08, 16 February 2019 (UTC)


 * It's not my favourite topic too, but
 * - the "d" of "m³" cancels with the "k" of "N" in pressure
 * - the displacement is a figure every nerd knows about his favourite engines (4 litres and above? It's like "hemis".)
 * - nobody adores cylinder areas and piston's linear displacement
 * - two strokes engines rotate by 2$\pi$, 4 strokes by 4π for completing one cycle of activity
 * - all missing facts are hidden in the "effective" piston pressure, which, acting over the cycle, balances the torque
 * - the "crankshaft speed" is an angular one in units of Hz ;), converting to rad introduces some π
 * I do not dare to intervene there with my competence in using the English language. Cheers, Purgy (talk) 15:28, 16 February 2019 (UTC)


 * Hello User:JRSpriggs, thank you for your reply.
 * dm3 means cubic decimetres, and is a common unit of displacement, and we can assume that it equals the litre.
 * You can also put liters for volume or bar (or Pascal) for pressure there, but that would make the way it works less obvious, as neither of these units comes with an exponent.
 * To make it more clear, the formula would also work like so: N·m−2·m3·π−1·4−1. The idea is that the exponents -2 and 3 result in 1, making N·m1 = N·m (torque).
 * You are correct, multiplying pressure (N·m−2) by area (m2) would result in force (N·m−2·m2=N·m0=N. But that is not what we want.
 * The "length of the lever" is "included" in the volume (N·m−2·m3 → N·m). This means that no connecting rod angle is required.
 * The π−1 (and the 4−1) are there because I am too lazy to use a fraction, but, in general, $$\frac {N \cdot m^{-2} \cdot m^{3}}{\pi \cdot 4}$$ would work as well. We need the π because the crank's motion resembles a circle: 2π for a two-stroke engine, and 4π for a four-stroke engine.


 * Hello Purgy, thank you for your reply, too.
 * You are correct, "crankshaft speed" is an angular speed and can be expressed in Hz. Hz however can be expressed in SI base units, which would be s&minus;1 (or the derived min&minus;1).


 * Best regards, --Johannes Maximilian (talk) 15:40, 16 February 2019 (UTC)

insource:/physics\.gen-ph/
Since particularly loopy stuff often gets reclassified to physics.gen-ph on the arxiv, every now and then, it's good to have a look at what cites that sub-repository. This can be done search for insource:/physics\.gen-ph/. Headbomb {t · c · p · b} 09:18, 23 February 2019 (UTC)

WP 1.0 Bot Beta
Hello! Your WikiProject has been selected to participate in the WP 1.0 Bot rewrite beta. This means that, starting in the next few days or weeks, your assessment tables will be updated using code in the new bot, codenamed Lucky. You can read more about this change on the Wikipedia 1.0 Editorial team page. Thanks! audiodude (talk) 06:47, 27 February 2019 (UTC)

Capillary length and Jurin's law
I could use some help here: Talk:Capillary length. I'm about to WP:3RR. Maybe somebody with more diplomatic experience could help us solve this out. --MaoGo (talk) 10:09, 19 February 2019 (UTC)
 * The differences are not big but the user wants his version to prevail .--MaoGo (talk) 13:01, 19 February 2019 (UTC)

User just doesn't want to follow guidelines of style. --MaoGo (talk) 12:38, 28 February 2019 (UTC)