Talk:Quantum gravity/Archive for 2020

Delete Dilaton Section

The Dilaton section describes some interesting but rather specific research. I think it should be moved to a subsection on the Dilaton page. — Preceding unsigned comment added by Marpauly (talk • contribs) 15:00, 15 May 2020 (UTC)

A problem with this transfer is that if the editors of the dilaton section don't approve of your changes, they could just wipe out that section entirely and we lose the mention of a promising body of work connecting quantum gravity, Bose-Einstein condensates e.g. superfluids and the Higgs' boson. Superfluid models are used in MOND and Superfluid vacuum theory. I did not see you secure approval on the dilaton talk-page (?) I do agree the dilaton is distinct from the graviton and GRT, but that does not mean it should not be in the quantum gravity section. The graviton needs 3+1 dimensions i.e. 3 spatial dimensions in which to propagate. For 2+1 and especially 1+1 quantum gravity theories, you need a dilaton. These lower-dimensional models are easier to solve and theoretically instructive. Also, even if we leave this addition in the dilaton section where you put it, some redundancies have to be removed in order to stream-line the dilaton article. Who will do that? As I said before, I do not want to start a tug of war. I suppose for now, we just make note of this and do nothing more but if the editors of the dilaton section disapprove of your addition, we have to find an alternate solution such as e.g. transfer it to the R=T model section (an acceptable place though the 3+1 material could stick out like a sore thumb). Concerning my earlier comment about supersymmetry on your talk-page, I would say the Current status of Supersymmetry and the Criticisms against String Theory confirm my earlier point though perhaps more politely. As it stands now, the quantum gravity section can only offer optimism for the loop quantum gravity subsection (which actually overlaps with this dilaton work, though that was not made clear - a body of work in loop quantum gravity does consider F(R) theories). May I suggest that you leave a note of explanation on the dilaton talk-page at least? in case the editors take issue with your changes. Kakorn8 (talk) 21:25, 1 June 2020 (UTC)

FYI, the disappointment concerning e.g. String Theory and SuSY has been expressed in the media (e.g. [1] and [2] etc..). This is why I think it important to emphasize alternatives. I suggest the part "other approaches" includes "Dilatonic quantum gravity" with a link to the material put in the dilaton wiki section. Kakorn8 (talk) 22:26, 1 June 2020 (UTC)

I would be fine with adding "Dilatonic quantum gravity" to "Other approaches", feel free to add the corresponding link. Additionally, I am sure it would be very much appreciated if you cleaned up the Dilaton article a bit. Regarding your view of string theory, I agree that it is important to make it very clear that string theory is just one of many possible approaches to quantum gravity and that there are many other interesting and promising ideas. In that regard I would also propose to move everything String- and LQG-related to the String and LQG subsection, respectively, instead of leaving bits and pieces scattered around the quantum gravity article. If noone objects, I will implement that in the future. Marpauly (talk) 18:40, 7 June 2020 (UTC)

Towards Quantum Gravity

Another approach to quantum gravity can be considered. According to this approach, the main role in quantum gravity will be played by the uncertainty relation $\Delta r_{s}\Delta r\geq \ell _{P}^{2}$, where $r_{s}$ is the Schwarzschild radius, $r$ is the radial coordinate, $\ell _{P}$ is the Planck length. This uncertainty relation is another form of the Heisenberg uncertainty principle between momentum and coordinate applied to the Planck scale. Indeed, this ratio can be written in the following form: $\Delta (2Gm/c^{2})\Delta r\geq G\hbar /c^{3}$, where $G$ is the gravitational constant, $m$ - body mass, $c$ - speed of light, $\hbar$ - Dirac constant. Reducing identical constants from two sides, we get Heisenberg's uncertainty principle $\Delta (mc)\Delta r\geq \hbar /2$. The uncertainty relation $\Delta r_{s}\Delta r\geq \ell _{P}^{2}$ predicts the appearance of virtual black holes (quantum foam) on the Planck scale and indicates that fluctuations in the photon velocity $\Delta c$ as they propagate through the entire Metagalaxy are determined not by the Planck length $\ell _{P}$, but by the square of the Planck length $\ell _{P}^{2}$, so that these fluctuations will be immeasurably small and images of distant sources will be sharp even at metagalactic distances. In this case, the appearance of virtual black holes and wormholes (fluctuations of quantum foam, the basis of the "fabric" of the Universe) on the Planck scale is energetically most favorable in three-dimensional space, which most likely predetermined the three dimensionality of the observed space. For more details, see On the fundamental role of massless form of matter in physics, Philosophy Documentation Center, Western University-Canada, pp.25-30. It can be seen from the paper that the basic equation of quantum gravity will be the equation: $-2i\ell _{P}^{2}{\frac {\partial }{\partial x^{\mu }}}|\Psi (x_{\mu })\rangle ={\hat {R}}_{\mu }|\Psi (x_{\mu })\rangle$, similar to the basic equation of quantum mechanics. Here $R_{\mu }$ is the component of the Schwarzschild radius.178.120.19.48 (talk) 10:34, 31 August 2020 (UTC)

spacetime vs space-time

Both spacetime and space-time are used throughout this article. Let's decide which is correct (or preferred) and be consistent throughout. — Preceding unsigned comment added by Rettik (talk • contribs) 12:28, 18 October 2020 (UTC)