Talk:Schrödinger–Newton equation

Some Ideas for Improvement
Just quickly sketching out a few ideas that could improve the article.

First, the equivalence principle connection using Lie point symmetries should be sketched a little further.

Second, the connection with quantum gravity should be made manifest (or again sketched).

Third, the details of Penrose's quantum collapse should be expanded.

Feel free to add anything :) —Pqnelson (talk) 15:21, 14 August 2012 (UTC)


 * Maybe for the first point a section "Mathematical properties" could be added. Although I looked through the paper by Robertshaw and Tod once, I don't really feel like I understood it well enough to write something about the Lie point symmetries. In particular I have no idea what you mean with the connection to the equivalence principle. Also didn't understand the sentence in the old version of the article.
 * I am working on the second point.
 * I think it has enough information about Penrose's idea now. I would elaborate on that in the article Penrose interpretation
 * Xaggi (talk) 09:55, 5 June 2014 (UTC)

This equation was discussed (and solved explicitly) with reference to Ruffini and Bonazola, Diosi and Penrose in the 1995 paper:

Newtonian Quantum Gravity by K.R.W. Jones Aust. J. Phys., 1995, 48, 1055-81

See...

http://www.publish.csiro.au/?act=view_file&file_id=PH951055.pdf

and references therein.

That paper pre-dates the alleged "introduction" by Penrose of this eqaution.

Completeness and accepted standards of scientific priority would suggest that this article really should include a reference to the cited article.

The author of that article certainly did reference Diosi, Penrose and Ruffini and Bonazola.

The article appeared in 1995, was refereed and predates the references cited here as the point of introduction.

Anybody can verify that simply by reading the cite article (Newtonian Quantum Gravity by K.R.W. Jones Aust. J. Phys., 1995, 48, 1055-81) — Preceding unsigned comment added by 129.94.68.16 (talk) 01:06, 10 May 2016 (UTC)


 * I have no problem with citing the paper somewhere in the article (where?). I don't think, however, that it is really of the same relevance as the other mentioned papers for an encyclopedia article: Firstly, it is not the first appearance of the equation, since Diosi was more than a decade earlier. It is not even really before Penrose, since Penrose already mentioned his ideas about state reduction in 1993 (as cited in the paper by Jones), although the later papers from 1996, 1998 were more detailed on that idea. Secondly, the relevance of Penrose's contributions comes mainly from the fact that his 1998 paper is still the first one assigning the name "Schrödinger-Newton equation" (or any other name) to this equation. Also the gravity related model for wave-function collapse is commonly referred to as "Diosi-Penrose" model. Another indicator for the relevance of the cited articles: Jones gets 26 citations according to Google Scholar, compared to 726 for Penrose and 173 for Diosi. Xaggi (talk) 06:15, 10 May 2016 (UTC)

ρ in the Poisson equation makes no sense
In my opinion there is no point in mentioning a "classical mass density" ρ in the Poisson equation.

As long as Ψ is considered a one-particle wave-function the very idea of the SN equation is that the probability density is the (active gravitational) mass density. The point particle as such has a mass m. There is no point in introducting some sort of "smearing" of this mass. From a physical point of view ρ has no interpretation.

On the other hand, if you consider Ψ to be the center-of-mass wave-function of a many-particle system, the mass density ρ is of course meaningful describing the particle distribution but in this case first of all the SN equation is only approximately right in certain limits. More important it does not take the form given here, where ρ and the absolute-value-squared of Ψ are considered at the same point, but rather one where the convolution of ρ and the absolute-value-squared of Ψ act as a source in the Poisson equation. · 78.12.159.251 (talk) 21:33, 16 February 2014 (UTC) · André (that was me, Xaggi (talk) 10:00, 5 June 2014 (UTC))


 * Considered done with my review Xaggi (talk) 10:00, 5 June 2014 (UTC)

Name of the equation
The equation is referred to also as Schrödinger-Newton equations, Newton-Schrödinger equations etc. but since Penrose, who first used named it in his 1998 paper, used the name "Schrödinger-Newton equation" I would suggest this as the main name. Xaggi (talk) 08:23, 4 June 2014 (UTC)

cantilever superpositions?
Sooo.... there are recent experiments where micro-mechanical cantilevers (like the kind used in automotive airbag triggers) are placed into cavities with the walls sufficiently conductive that one can trap photons in the cavity, and couple the cantilever to the photon. There's some kind of entanglement witness one can construct, to show that the photon really is entangled with the cantilever. I forget how it works ... one looks at some microwave sideband coming out of the cavity. Lets assume the experiment is correct ... is this violating the Penrose collapse condition, given that the cantilevers are (many?) trillions of atoms in mass? Or are the cantilevers still smaller than a Plank mass? The displacement of them is also quite large, I imagine ... covering this experimental configuration in this article would seem like a really important thing, as these are maybe the largest objects placed in a superposition... 14.0.224.248 (talk) 13:24, 5 September 2018 (UTC)