Talk:Four-momentum

message: In the first paragraph is says "The contravariant four-momentum of a particle with relativistic energy E and three-momentum p = (px, py, pz) = γmv... This seems like it is saying p=γmv. Unless I've misunderstood, that is not correct? Jpipersson (talk) 17:36, 15 June 2023 (UTC)
thread_title: A clarification

message: You can find some info here:
.
Also note that are two conventions:
# Take c = 1. In that case x = t,  E = m = P  etc.
# Keep on classical units of time and space and take x = c*t so c keeps its MKS\CGS value (MKS refrenced on the International System of Units page). I formulated my addition according to that convension. 
Both are valid and should be appeared in the article.
MathKnight 21:54, 16 Mar 2004 (UTC)
thread_title: Untitled

message: In special relativity, four-momentum is a four-vector that replaces classical momentum; the four-momentum of a particle is defined as the particle's mass times the particle's four-velocity.
The highlighted sections mean nothing to the layman. And if you're not a layman and know all about four-momentum, then why did you come here?
User:70.25.138.179|70.25.138.179]]
: I did some major rejiggering of the article -- expanded the intro and divided the rest up into sections.  Hopefully I've addressed your concerns about incomprehensibility!  Please comment again if it's still too obscure. HEL 02:56, 5 November 2006 (UTC)
replies: text: You need to read the first sentence of the second ¶ more carefully: "The highlighted sections mean nothing to the layman ". JohndanR (talk) 18:00, 14 October 2020 (UTC)
thread_title:  Excuse me? 

message: Why is this tag there? Shouldn't the person who put that tag up have discussed their reasoning? Anyway, I disagree. The four-momenum concept is very distinct from momentum, and it needs its own page. Fresheneesz 11:35, 21 May 2006 (UTC)
thread_title:  Merge to momentum 

message: Should we comment somewhere that there are two different sign conventions for the metric?  This article uses the East Coast / general relativity convention; most particle physics texts these days use the West Coast metric, so that p2 = +m2 (c=1). HEL 18:32, 9 February 2007 (UTC)
thread_title:  Sign convention for the metric 

message: Anyone want to address the part about "WRONG WRONG WRONG."  Not exactly encyclopedia material.  —Preceding unsigned comment added by 169.233.41.11 (talk) 02:29, 12 October 2007 (UTC)
thread_title:  What the...? 

message: This article defines 4-momentum as covariant but several other articles (e.g. four-vector and four-force) define it as contravariant. This may confuse some of our readers, so what's the best way to avoid such confusion?
As a separate issue, it would be nice to adopt the convention that 4-vectors are in bold capitals and 3-vectors in bold lowercase. To achieve this we'd need to use a different letter for canonical momentum. Any thoughts?--Dr Greg (talk) 16:49, 3 October 2008 (UTC)
replies: text: Assertion that four-momentum is covariant was introduced in this edit by JRSpriggs (talk, contributions) without giving any reason to do so. --93.136.187.125 (talk) 08:28, 5 December 2009 (UTC)
thread_title:  Covariance and typography 

message: I've modified all the equations to use the convention x^0 = ct. The version back on 10:37 22 September 2008 correctly used the alternative convention x^0 = t, but subsequent edits managed to confuse both conventions. The convention I'm using is the same as the four-velocity article and therefore probably less confusing for readers. Someone who's an expert in 4-potentials should check I've modified the relevant equation correctly, as that is outside my area of expertise. --Dr Greg (talk) 12:00, 18 April 2009 (UTC)
thread_title:  Coordinate convention 

message: Hello, I quote the text "This allows the potential energy from the charged particle in an electrostatic potential and the Lorentz force on the charged particle moving in a magnetic field to be incorporated in a compact way into the Schrödinger equation." Isn't it the Dirac equation instead of schrodinger?  — Preceding unsigned comment added by Klinfran (talk • contribs) 00:12, 3 July 2011 (UTC)
thread_title:  équation 

message: I would like to see some background information about this topic for people who don't (or remember) enough math to follow the current text.
Kevink707 (talk)  —Preceding undated comment added 14:54, 26 September 2011 (UTC)
replies: text: Agreed. A classical encyclopedia entry was never an exercise in explicatory essay-writing to satisfy one's Prof that one understands the term lecture on a topic. JohndanR (talk) 18:06, 14 October 2020 (UTC)
thread_title:  Introduction for the novice 

message: The formulation in Clifford Algebra removes unnecessary complexity (Covariance, contravariance, etc.). CaffeineWitcher (talk) 21:24, 7 December 2022 (UTC)
thread_title:  Shouldn't there be another formulation, in Clifford Algebra. 

message: In the Derivation section, just before the second equation, the article reviews the basis changes (from contravariant to covariant) according to the aforementioned metric convention: that the metric signature is (- + + +), or in the article's words, "x0 = −x0, x1 = x1, x2 = x2, x3 = x3 in the present metric convention"; however, it then states the covariant 4-momentum has negated spacelike components, both in the equation p_\mu=\left (\frac{E}{c},-\bold{p}\right ) and, in agreement, in the clarification following. I believe this statement would actually correspond to the (+ - - -) signature. Considering the product of the contravariant 4-momentum with the covariant 4-momentum shown, p^\mu p_\mu=\frac{E^2}{c^2}-|\bold{p}|^2, which contradicts the first equation in the Minkowski norm section, which explicitly uses the (- + + +) metric signature.
It doesn't seem this affects anything else in the article, but can someone else verify this? ManOfPretzel (talk) 22:16, 8 April 2023 (UTC)
thread_title:  Covariant 4-momentum metric signature issue