Talk:Pseudo-Riemannian manifold

message: I added the context tag. I had followed the Lorentzian manifold link (redirected to here) on the General relativity page hoping the get a better understanding of the subject. However, this article is difficult to follow and could use improvement. Judging by the comments above I'm not the only one. Ryan Roos 22:40, 1 December 2006 (UTC)
replies: text: Do you have a specific question you wish to ask? If you haven't studied Riemannina geometry, you won't magically grok this article no matter how much "context" is added to it. FWIW, this article is nt well written, but it says nothing that is actually complicated, this is pretty introductory material.  linas 23:41, 1 December 2006 (UTC)
replies: text: I suspect most of the complaints regarding this page are coming from people who arrive here from a general relativity article looking for a definition of a Lorentzian manifold when they don't even know what a manifold is, much less a Riemannian one. Calabi-Yau manifold gets similar complaints. Perhaps its necessary to fork off Lorentzian manifold to its own page and start the discussion at a much lower level. -- Fropuff 00:27, 2 December 2006 (UTC)

text: linas and Fropuff thank you for your thoughtful replies. I found the discussion on the Talk:Calabi-Yau manifold of the technical tag that had been used there helped to resolve some of my problems with the article. The main basis of my concern was result my lack of knowledge of manifolds.  (On a side note linas I enjoyed following several of the links on your user page) Ryan Roos 02:04, 3 December 2006 (UTC)
thread_title: Comment on Context Tag

message: This article was automatically assessed because at least one WikiProject had rated the article as stub, and the rating on other projects was brought up to Stub class. BetacommandBot 10:01, 10 November 2007 (UTC)
thread_title:  WikiProject class rating

message: I'd like to separate out an article about Lorentzian manifolds. This could emphasise their use in physics and in general relativity. It would link to pseudo-Riemannian manifold. What do people think? SJ 17.00 5 December 2007.  —Preceding comment was added at 17:13, 5 December 2007 (UTC)
thread_title:  Lorentzian Manifold 

message: There are a number of special characters or symbols that do not display correctly, or at all, in four different browsers I have tried:
* Internet Explorer shows some as " " [box symbol for non-display characters] and some as a " " [a blank space]
* Firefox and Safari show all as blank spaces, so it is not clear something is missing
* Opera shows all as empty boxes, so it is clear something is not showing
I have tried looking at the source code, editing the page within wikipedia, and copying the characters/symbols to a word processor. I cannot figure our what the writer intended. This requires the author of the text to fix this problem if it is desired to communicate completely with the reader.
Colin.campbell.27 (talk) 21:08, 27 March 2011 (UTC)
thread_title: Special characters or symbols

message: This is odd. If I do a google search on '"locally non-decreasing" sylvester signature', http://www.google.com/#hl=en&sclient=psy-ab&q=%22locally+non-decreasing%22+sylvester+signature&oq=%22locally+non-decreasing%22+sylvester+signature&gs_l=hp.3...720.10192.0.10353.48.44.2.0.0.0.167.3998.30j14.44.0.les%3B..0.0...1c.1.W7Ns9Kjyc-0&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.&fp=a7217b4391070716&biw=1280&bih=905 , I get a hit from google books for a book by Sussman and Wisdom, which contains text from this article. When I saw this, I assumed the article was plagiarized from the book. But when I click through on the google books link, I get a link that claims to be to a *different* book, by Kleppner and Kolenkow. And even this is wrong. I have the book by K&K, and what's in google books in not that book -- it's a compilation of wikipedia articles. Very mysterious.--75.83.64.6 (talk) 00:00, 2 October 2012 (UTC)
thread_title:  copyvio? 

message: Seriously, I'm a biologist now, but when I write WP articles, I pretend that my readers are morons--seriously, it's hard to teach people if they can't understand what you're saying.  Furthermore, drawing on experience explaining evolution to undergrads (an experience roughly analogous to skateboarding into the same giant stack of rusty nails and CMUs three hundred times in a row), I can safely say that the simpler language you use to explain a complex topic (even if it takes 300x longer to explain it that way than you could with the proper jargon) the more people (even people conversant in said jargon) will understand the points which you are trying to make.  Seriously, explaining a topic in plain English does not reflect poorly on your knowledge of a given topic.  Quite the opposite, it shows that you have an intuitive understanding of it.--99.112.106.168 (talk) 18:27, 15 September 2013 (UTC)
replies: text: Seriously, I just noticed that I used the interjection "seriously" three times in a row.  I hope that underscores just how serious I am!--99.112.106.168 (talk) 18:28, 15 September 2013 (UTC)
thread_title:  I took 3/4 of an undergraduate physics major and the introduction made my head hurt! 

message: ...to a manifold for admitting a Lorentzian metric. There is a large body of literature on this. Will be nice to add a word or two about it. -  Subh83 (talk | contribs) 07:01, 10 November 2013 (UTC)
thread_title:  topological obstructions... 

message: While the talk page is cluttered with pettifogging, the article states that a flat space with the
:g = dx_1^2 + \cdots + dx_p^2 - dx_{p+1}^2 - \cdots - dx_{p+q}^2
metric is called… the Minkowski space. Can  believe that nobody of you knows the correct name of this concept for general  and ? Incnis Mrsi (talk) 19:12, 19 February 2014 (UTC)
replies: text: It does not seem to say that; perhaps you misread? My guess is that pseudo-Euclidean space is reserved for the indefinite cases, and is thus not general. Flat space? —Quondum 21:53, 19 February 2014 (UTC)
thread_title:  Meanwhile… 

message: Does anyone know what was the first use of pseudo-Riemannian manifold?
David edwards  — Preceding unsigned comment added by David edwards (talk • contribs) 15:47, 2 June 2018 (UTC)
thread_title: First use?

message: I reverted an edit () with the promise of elaborating here.
This is an article that deals with mathematical aspects of a metric tensor on a pseudo-Riemannian manifold, which need not be flat, even in the Lorentzian case, and example being general relativity.  As such, defining even the separation between two points entails defining a curve along which to integrate, and this usually is taken to be a geodesic, the definition of which in turn requires a lot of theory based on the metric tensor.  So in a sense, describing a Lorentzian metric tensor in terms of distances is inherently circular.  In the flat case (a Minkowski space), a lot of short-cuts are possible and the circularity can be avoided, but that intuition does not work to define distances directly in this context.  A second major point is that the ideas of a "time separation" and a "space distance" are ill-defined in this context, and even in the Minkowski space case need specification in terms of a selected frame of reference.  Without mentioning this (in the Minkowski case, where it applies), one risks confusing the reader with Galilean intuitions of absolute time and space.  Defining such frames in the Lorentzian case are not possible in general.  One is left with building the concept of distances along curves from the concepts already stated, and one cannot start from the concept of distance or time separation: one cannot really appeal the intuitions of special relativity except in the limit of shrinking a region to a point.
A more productive approach might be to resolve the WP:REDIR#ASTONISH problem by looking at where the redirect was used.  Note that the redirect itself seems to be appropriate; a Lorentzian metric (which I presume "Lorentz metric" might be used in place of) is more general than a Minkowski metric: allowing non-flat space in addition to an arbitrary number of spatial dimensions; there should be no violation of the no-astonishment principle with this redirect.  —Quondum 12:06, 19 August 2020 (UTC)
replies: text: This is not the correct explanation. The metric is defined on the tangent space (of the spacetime manifold), where it is linear as in linear algebra. No appeal to geodesics is needed to define the metric. Quite the opposite: *after* defining the metric (on the tangent space), you can ask what the shortest distance  between two points on a manifold. Be sure to read and grok manifold. The shortest distance is gotten via variational principles, solved by the Hamilton-Jacobi equations. These are partial differential equations, and when you integrate them, only then do you get the geodesics.  There aren't any circular definitions here. 67.198.37.16 (talk) 08:40, 18 November 2023 (UTC)
thread_title:  My revert of a good-faith edit aimed at addressing [[WP:REDIR#ASTONISH]] 

message: Currently (Aug 8, 2022), in the LM section of this article "... signature of the metric is (1, (-1)(n-1 occurrences) or (equivalently, (-1, 1(n-1 occurrences))" is a hot, stinking mess. My first suggestion is that the FULL signature (p,q, 0) be mentioned. (I assume that's what (p,q) means, as per convention). I also note that if p, q must be integers, that calling them numbers is just plain sloppy; no reason for that. Anyway, my suggested correction is "...signature of the metric is (1, (-1)(n-1)) ( or equivalently, (-1, 1(n-1)). (see Sign Convention)" but also include an explanation of n AND to explain how  -1 is allowable when p and q are to be NON-NEGATIVE. So, that's like four things. 1. Easiest: clean up the parenthesis - "or (blah blah)" is wrong, should be "(or blah, blah)" 2.Most obvious: remove "occurrences" from formula, it is NO WHERE defined. 3. Almost as obvious: Before using n, DEFINE (or explain) it. 4.Lastly:YOU MUST EXPLAIN why negative (integers?) are allowable as a "special case" when non-negative integers are required in the more general case.174.131.48.89 (talk) 17:24, 8 August 2022 (UTC)
replies: text: The dimension of space is always a (non-negative) integer, like "1D space and 2D space and 3D space" and its unfair to ask that an advanced article to stop and explain this first, before doing anything else. You will have an easier time of it all if you get a good book on special relativity and another on differential geometry and get through the basics, first. Also, Feynman "Lectures in Physics" are great. 67.198.37.16 (talk) 08:53, 18 November 2023 (UTC)
thread_title:  Lorentzian Metric ...again (1)