4 ms·

The work press-release-announced in the link at the top, the preprint for which is at <https://arxiv.org/abs/2305.18521 https://arxiv.org/abs/2305.18521>, has n

The work press-release-announced in the link at the top, the preprint for which is at <https://arxiv.org/abs/2305.18521 https://arxiv.org/abs/2305.18521>, has nothing to do with cosmic inflation. At all. The authors are at pains to contain the dynamical aspect of the spacetimes they investigate. In particular they write, "... we also expect our particle production mechanism to backreact on the spacetime. However, the spacetime background we have used here is constant by construction". Their investigation works on asymptotically flat spacetimes and so (a) are manifestly not cosmological in itself and (b) can be "knitted" into a wide variety suitable comsological metrics by procedures like Israel-Darmois. Possibly including the (family of) cosmological spacetimes at the links you supplied. However... I can't imagine even an exceptionally generous reading of only the link at the top (terse as it is) being relevant to any of the four in-English links you push in your comment. Those papers are particularly interested in background gravitational waves and the bulk expansion and contraction of space, all of which are a signature of a dynamical spacetime, quite the opposite of the background in the work at the top. The fifth, in Russian, focuses on black holes and neutron stars in but (a) in a dynamical spacetime and (b) not in a way that is (even trying to be generous) remotely related to the work discussed at the link at the top of the page. [However, I did note the 2021 Astrophysics Bulletin paper's authors' reference 38, which is Hawking's 1975 "Particle creations by black holes", and tried to take that one citation into account. It's raised in §2 around eqn (1) in the context of estimating a whole-universe distribution of black holes. Unfortunately this feels to me a bit like a conversation about laboratory mice swerving into commentary about quaking aspen groves being assessed as OK or not on the basis that both organisms share a distant common ancestor. The connection turns out to be less than tenuous.] Lastly, I note via <https://hn.algolia.com/?dateRange=all&page=0&prefix=true&query=https%3A%2F%2Fpos.sissa.it%2F335%2F039%2F&sort=byPopularity&type=comment https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...> that you have posted these links to HN at least twice before, and this is the second time they do not fit the context in a reasonable way. I don't think your repetitive posting is doing a service to anyone, including Н. Н. Горькавый and his coauthors.

sesm 3y ago
I disagree, 'everything will evaporate' assumes a model of one-time ever-expanding universe.
- raattgift 3y ago
  "Everything will evaporate" is the press-release title, and does not fairly capture the Schwarzschild-black-hole-focused work in the paper press-released by the university. The PR title overemphasizes and mischaracterizes the last paragraph of the paper's conclusion as something more than an appeal for further investigation of central masses other than black holes. Their analysis does not rely on the presence of a (particular family of) horizons (cf. Visser Phys. Rev. D 90, 127502 (2014)), and therefore other spherically symmetric non-rotating central masses (possibly even noncompact ones) might induce this gravitational analogue of the Schwinger effect. > assumes ... ever-expanding universe No it does not. I already gave the link to the preprint in your parent comment, but for ease of access <https://arxiv.org/abs/2305.18521 https://arxiv.org/abs/2305.18521>. Equation (5) therein is the line element, standard Schwarzschild, and in particular you'll notice a lack of \Lambda or any other expansion term. I drew explicit attention to the asymptotic flatness and Israel-Darmois junction conditions in my comment you replied to. We can "knit" (using junction conditions) an asymptotically flat solution into a cyclical spacetime like the Gorkavyi model in your set of links. Because the re-collapse timescales there are a lot shorter than the black hole era of the standard model, large black holes may not even stop accreting, but they will however still induce the gravitational pair production that is the topic of the paper. This seems at first glance to be comparable to the outgoing gravitational radiation induced by compact objects that Gorkavyi considers. If one takes the gravitational backreaction of the gravitational pair production idea into account, the incoming gravitational radiation might even make it and Gorkayvi roughly compatible (the idea being that it would induce a small acceleration on the BH similar to the "anti-gravity" idea raised in the appendix of his Astro. Bull. 76, 229-247, 2021 paper, contributing to the "Big Bounce"). A generalization of the Vaidya metric seems like it might be helpful. One might even wonder if there could be a gravitational analogue of the Stark effect induced upon close binaries (esp. with his relict neutron stars with large mass ratios) in a Gorkavyi cyclical model. Unfortunately, since you engage with the title at the top and practically nothing else, you missed an opportunity for taking this type of synthesis seriously.

sesm 3y ago

I disagree, 'everything will evaporate' assumes a model of one-time ever-expanding universe.

raattgift 3y ago
"Everything will evaporate" is the press-release title, and does not fairly capture the Schwarzschild-black-hole-focused work in the paper press-released by the university. The PR title overemphasizes and mischaracterizes the last paragraph of the paper's conclusion as something more than an appeal for further investigation of central masses other than black holes. Their analysis does not rely on the presence of a (particular family of) horizons (cf. Visser Phys. Rev. D 90, 127502 (2014)), and therefore other spherically symmetric non-rotating central masses (possibly even noncompact ones) might induce this gravitational analogue of the Schwinger effect. > assumes ... ever-expanding universe No it does not. I already gave the link to the preprint in your parent comment, but for ease of access <https://arxiv.org/abs/2305.18521 https://arxiv.org/abs/2305.18521>. Equation (5) therein is the line element, standard Schwarzschild, and in particular you'll notice a lack of \Lambda or any other expansion term. I drew explicit attention to the asymptotic flatness and Israel-Darmois junction conditions in my comment you replied to. We can "knit" (using junction conditions) an asymptotically flat solution into a cyclical spacetime like the Gorkavyi model in your set of links. Because the re-collapse timescales there are a lot shorter than the black hole era of the standard model, large black holes may not even stop accreting, but they will however still induce the gravitational pair production that is the topic of the paper. This seems at first glance to be comparable to the outgoing gravitational radiation induced by compact objects that Gorkavyi considers. If one takes the gravitational backreaction of the gravitational pair production idea into account, the incoming gravitational radiation might even make it and Gorkayvi roughly compatible (the idea being that it would induce a small acceleration on the BH similar to the "anti-gravity" idea raised in the appendix of his Astro. Bull. 76, 229-247, 2021 paper, contributing to the "Big Bounce"). A generalization of the Vaidya metric seems like it might be helpful. One might even wonder if there could be a gravitational analogue of the Stark effect induced upon close binaries (esp. with his relict neutron stars with large mass ratios) in a Gorkavyi cyclical model. Unfortunately, since you engage with the title at the top and practically nothing else, you missed an opportunity for taking this type of synthesis seriously.