# Talk:Scalar field

## new page

I've started a page on Scalar field theory, which no longer just redirects to scalar field. I've done quite a bit myself, but any help from other physicists would be useful and appreciated.--Jpod2 11:15, 19 September 2006 (UTC)

## Why real numbers?

This article directly requires that a scalar field be real-valued and be from a space with real-valued coordinates (RnR). However, that seems to neglect complex-valued fields and complex coordinates (RnC or CnC), which of course can be thought of simply as a different representation, but is nevertheless common. Hpa (talk) 19:45, 30 August 2008 (UTC)

## Impenetrable to the layman

I am not the person who posted the above--I'm not even sure where I should be posting this. I am a random layman who has been poking around Wikipedia's pages on the Higgs boson, gauge theory, quantum field theory, etc., in an effort to understand the LHC... and been completely baffled. I understand that physics can only be simplified so much, but I would appreciate it if any experts would go over those pages (and this one!) and elaborate the definitions, i.e. add longer explanations with smaller words to the compact explanations already there. —Preceding unsigned comment added by 75.153.170.206 (talk) 16:03, 10 September 2008 (UTC)

As an example, why should anyone be expected to understand how this sentence is relevant to the article?:

In mathematics, or more specifically, differential geometry, the set of functions defined on a manifold define the commutative ring of functions.

LokiClock (talk) 21:11, 8 April 2009 (UTC)

## Time for deletion?

Given that the page Scalar Field Theory now exists and is far more comprehensive, this page simply appears to be redundant. The topic is identical, and handled much better on the other page. Could this page be deleted to avoid confusion? Dusty14 (talk) 16:59, 15 May 2010 (UTC)

Given that the article has not yet been deleted (though I think it ought to be), I have at least clarified some of its statements. I think the entire section on scalars in gravity should be removed, if the article isn't otherwise. It is too technical, describes topics that are not really related to scalar fields in general, and should be kept only if it can be boiled down to one sentence. It would be better to put into a more topical page relating to gravity. I removed the comment on continuity, because in most cases I am aware of, some important solutions are distributions, not continuous at all. I also added comments to clarify what it means to be a scalar, since there is a symmetry requirement. In spite of my opinions on the gravity section, I couldn't resist adding a line to it on dilatons in string theory. —Preceding unsigned comment added by Dusty14 (talkcontribs) 17:42, 15 May 2010 (UTC)

## Discussion on new lead image

I reverted an edit to include a new lead image here. My edit was subsequently reverted by the same editor who added it (much contrary to WP:BRD and WP:CON). I have posted to WT:WPM to get further input on the suitability of this image. Sławomir Biały (talk) 20:06, 13 June 2010 (UTC)

The same image is used in the related Vector field and Tensor field articles. The image compares the fields. For consistency the image should therefore be included in all, or excluded in all - and if the latter then a good reason must be given for exclusion. JohnArmagh (talk) 20:32, 13 June 2010 (UTC)

## "Ordinary" scalars vs scalar densities, etc.

Wikipedia's articles about scalars seems to have a major flaw. Scalars come in a variety of types (and also tensors) depending on how they transform under a coordinate transformation. In general a scalar field of weight ${\displaystyle w}$ is a scalar field (i.e., no free index object), ${\displaystyle f}$, that transforms as ${\displaystyle {\bar {f}}({\bar {x}}^{j})=J^{w}f(x^{i})}$, where ${\displaystyle J}$ is the Jacobian determinant. Here ${\displaystyle w}$ is an integer. There are two "important" cases, ${\displaystyle w=0}$ and ${\displaystyle w=1}$, which can be termed "ordinary scalars" and "scalar densities", respectively. The distinction is important because the integral of an "ordinary scalar" is not an invariant but the integral of a "scalar density" is. (Lovelock and Rund's book is a good source for the background here.) Physically, temperature and pressure are "ordinary" scalar fields while wave functions and probability densities are scalar densities. Wikipedia seems not to have considered the case of scalars with ${\displaystyle w\neq {}0}$ and inconsistencies seem to abound. I started a page for scalar density but it needs a lot more work. The semantics of what is meant by "integrating over a region" become very important when discussing these new types of scalars. It's also very easy to get confused where factors of the Jacobian belong. I'll look forward to comments and slowly I'll help remedy this issue. Jason Quinn (talk) 23:38, 22 April 2011 (UTC)