Talk:Causal structure

Merging with Causal Structure

The two concepts, while closely related, are quite different. The article on Causal Structure provides the mathematical definitions. The article on Causality Conditions provides a physical interpretation of certain conditions on the properties of those mathematical definitions. Joining the two articles will confuse this distinction. 139.80.48.109 (talk) 23:31, 19 June 2011 (UTC)

Tentatively agree. Let's see if the new hatnotes solve any perceived problem. False vacuum (talk) 02:19, 21 September 2011 (UTC)

Page too technical?

I disagree. The page discusses the mathematically precise formulation of causal structure within General Relativity. It must state the mathematics and must do so in an accurate way. 139.80.48.109 (talk) 23:31, 19 June 2011 (UTC)

The mathematic definitions (Causal structure) and the closely related physical interpretation (Causality conditions) should surley be merged! Particularly with regard to the critics ("unphysical") of the purely mathematic definitions which are contained in Causality conditions. Chris 16:01, 6 September 2011 (UTC)

Disagree. Firstly, the talk page of Causality conditions contains no complaints about purely mathematical definitions. If you have complaints please air them. Both articles need substantial work and the best place to start is from the criticisms of people who want to use the pages. That is, your help would be appreciated in identifying the problems with the pages. Secondly, the two topics discuss two very different things. Causal structure defines mathematical objects. These objects are used in areas quite different from Classical General Relativity, e.g. the causal set approach to quantum gravity and hyperbolic PDES. Thirdly, they are also objects of study in their own right, see the work of Flores, Harris, Sanchez or "Marolf and Ross" (for recent examples related boundary structures).

Combining the pages will perpetuate the confusion about the difference between causal structure and the causality conditions and prevent the development of connections between causal structure and topics other than the causality conditions in the future.

That being said I agree that the pages need substantial work; Both pages read as collections of facts not as articles. They are not accessible to laymen. They do not explain the motivation for the definitions and don't go into the implications of the definitions. I have fixed one factual error on this page but there may well be other such errors. Please contribute to the development of the articles either by writing something, or by giving your criticisms in the talk page.139.80.48.109 (talk) 00:40, 17 January 2012 (UTC)

Term for spacelike-related events?

Is there a term for spacelike-related events that can be added here? It would nice to be able to say something like:

"Any two distinct events A and B are related in one of five ways: A chronologically precedes B, B chronologically precedes A, A horismos B, B horismos A, or A (blank) B."

At present I would have to say something like "A and B are not causally related" or maybe "A and B are relatively simultaneous" or something, and those are kind of ungainly.TricksterWolf (talk) 16:25, 12 August 2014 (UTC)

I don't think there is an accepted term for spacelike related that also implies "not causally related" that isn't "not causally related". I'd stay away from "relatively simultaneous", the term isn't used in the standard textbooks (as far as I am aware) and may already have technical definitions in subfields of GR or related fields... e.g. maybe in for hyperbolic PDEs? PinkiePie7075 (talk) 02:26, 31 August 2014 (UTC)

Equivalence relation?

The time-orientability equivalence relation defined does not obey reflexivity. — Preceding unsigned comment added by 137.205.238.88 (talk) 22:00, 5 February 2015 (UTC)

Timelike vector sign

Shouldn't for the diagonal metric g={1,-1,-1,-1} the timelike vector have a positive sign, that is g(X,X)>0 for a vector X? — Preceding unsigned comment added by 178.59.243.86 (talk) 17:18, 14 September 2016 (UTC)

External links modified

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Correction

According to here. https://www.researchgate.net/publication/274967123_From_Horismos_to_Relativistic_Spacetimes The horismos relation is not transitive. 11cookeaw1 (talk) 07:30, 3 December 2021 (UTC)

Bad Terminology

Linear algebra has the custom of calling a null-vector a vector which is a neutral element for the algebraic operation of vector addition. Physics in special relativity has the custom of calling a null-vector a vector which has zero length in the Minkoswki metric. These two things are, of course, not the same. It is calling for problems and misunderstandings when one uses both of these terms in a single encyclopedia. It would, therefore, be better, if we called a null-vector (in the physical sense) a light-like vector, and a null-vector (in the mathematical sense) a null-vector. This would reflect physical semantics and prevent confusion. — Preceding unsigned comment added by 87.163.194.54 (talk) 20:32, 5 April 2022 (UTC)