Talk:Conformal cyclic cosmology

Null hypothesis?

The article cited regarding "low probability of null hypothesis" does not mention the null hypothesis anywhere. How is that conclusion drawn from the paper cited? —Preceding unsigned comment added by 76.102.204.31 (talk) 07:09, 1 December 2010 (UTC)

While not using the phrase "null hypothesis", starting on the bottom of page 4 and continuing on most of page 5, it discusses possible other causes of the claimed phenomena, e.g. instrument noise etc. Lenborje (talk) 08:05, 8 December 2010 (UTC)

Perspective

It doesn't appear to offer any perspective from other physicists in terms of secondary sources. Instead we have an article which appears to be based on a popular non-fiction book. IRWolfie- (talk) 10:01, 27 June 2012 (UTC)

I agree. Specifically, the current article makes it appear that CCC is a mainstream cosmological theory, or even the prevailing viewpoint, when it does not appear to be taken seriously by the cosmological community. The predictive failures and disagreement with evidence quoted in the article are framed as though to suggest they don't actually discredit the theory. It feels like the article is trying to present a fringe viewpoint in the best possible light.TricksterWolf (talk) 19:16, 8 October 2020 (UTC)

Spacelike ??

This phrase: "the boundary between aeons is not a boundary at all, but just a spacelike surface that can be passed across like any other" used in the Property section is confusing to me. I thought there is no possibility of connecting space-like separated events in General Relativity??? Shouldn't it be time-like?71.31.148.44 (talk) 18:08, 15 July 2012 (UTC)

External Link doesn't exist.

"The Cyclic Universe - A conversation with Roger Penrose", Ideas Roadshow, 2013 70.53.60.158 (talk) 13:17, 26 August 2015 (UTC)

Misrepresentation of empirical evidence

User:Alex39K recently replaced the section

However, the statistical significance of the claimed detection has since been questioned. Three groups have independently attempted to reproduce these results, but found that the detection of the concentric anomalies was not statistically significant, in the sense that such circles would appear in a proper Gaussian simulation of the anisotropy in the CMB data. The reason for the disagreement was tracked down to an issue of how to construct the simulations that are used to determine the significance: The three independent attempts to repeat the analysis all used simulations based on the standard Lambda-CDM model, while Penrose and Gurzadyan used an undocumented non-standard approach (cites 3 papers here).

with

Presence of structures in CMB sky reported by Gurzadyan and Penrose have been confirmed by independent study using Planck satellite data (cites DeAbreu here). In 2013 Gurzadyan and Penrose published the further development of their work, also introducing a new method, the sky-twist transformation (not using simulations), and in 2015 they published the results of Planck data analysis confirming those of WMAP.

where I've omitted the references to avoid cluttering the talk page. I think this was an extremely questionable edit. First of all, it leaves out all mention of failures to reproduce the empirical evidence Gurzadian et al. claim they have. But perhaps even worse, it then goes on to give the very misleading impression that DeAbreu supports their claim of empirical evidence. But in fact, DeAbreu is yet another paper that finds no statistically significant excess of structures in the CMB, as one can see directly in the abstract:

In a recent paper, Gurzadyan & Penrose claim to have found directions in the sky around which there are multiple concentric sets of annuli with anomalously low variance in the cosmic microwave background (CMB). These features are presented as evidence for a particular theory of the pre-Big Bang Universe. We are able to reproduce the analysis these authors presented for data from the WMAP satellite and we confirm the existence of these apparently special directions in the newer Planck data. However, we also find that these features are present at the same level of abundance in simulated Gaussian CMB skies, i.e., they are entirely consistent with the predictions of the standard cosmological model.

I have undone this edit, and added the DeAbreu paper to the list of citations for papers that find no empirical evidence for CCC.

@Alex39K: Why did you remove the mention of independent refutations, and why did you present DeAbreu's article as supporting Gurzadyan when in fact it comes to the opposite conclusion? Amaurea (talk) 14:21, 29 September 2016 (UTC)

Need to mention Penrose's ideas about mass decay

This story has hit the news with an article in New Scientist, 15th August 2018 - which is how I ended up on this page, to find out more about how Roger Penrose deals with all particles, including electrons, eventually decaying. If I understand right his paper actually suggests that eventually all particles lose mass, including electrons, and including presumably the massive bosons too. Writing:

"A much more satisfying possibility, from my own perspective, is that the electron’s mass will eventually decay away—and, again, there is all of eternity for this to happen, so the possibility may not be too outrageous to contemplate"

It is his preferred solution of two possibilities, the other being that the electron eventually loses its charge

"It is not too unconventional to assume that protons will ultimately decay, or even that there is one variety of neutrino that is massless, but the real problem lies with electrons. A good many of them will annihilate with positively charged particles, but there will be a relatively small number of “stray” charged particles which become trapped in their ultimate event horizons, being unable to come in contact with other particles of opposite charge. There are various possible ways out of this, none of which is part of conventional particle physics. One possibility is that electric charge is not exactly conserved, so that within the span of eternity, electric charge would eventually disappear. A much more satisfying possibility, from my own perspective, is that the electron’s mass will eventually decay away—and, again, there is all of eternity for this to happen, so the possibility may not be too outrageous to contemplate. "

Also in the section Conformal cyclic cosmology#Empirical tests I think we should have some explanation of the "excess of concentric circles" which is likely to be puzzling to the reader as no explanation is given of why this theory would predict such a thing. Going back to his paper he introduces the idea there:

“This has the implication that gravitational radiation actually survives at the future boundary ... This gives rise to density fluctuations at the Big bang, and possibly primordial gravitational radiation.”

It is covered in more detail in the cited paper as

"The clearest observational signal of CCC results from numerous supermassive black-hole encounters occurring within clusters of galaxies in the aeon previous to ours. These encounters should yield huge energy releases in the form of gravitational radiation bursts. From the perspective of our own aeon (see[3]), these would appear not in the form of gravitational waves, but as spherical,largely isotropic, impulsive bursts of energy in the initial material in the universe, which we take to be some primordial form of dark matter, the impulse moving outwards with the speed of light up to our last-scattering surface"

I think we need a brief one or two sentence summary of this in that section. I am happy to provide this - or other editors may like to do it first. It is my habit as an editor to do DB and BDR rather than BRD for any edit of significance so I have posted to the talk page first. This is just to check in case the existing editors of the article have preferred ways of doing things and not to step on anyone's toes here, on what is the only article on this significant topic. Robert Walker (talk) 12:55, 15 August 2018 (UTC)

• I attended a lecture by Penrose on this theory at the Conway Hall. His requirement for all particles with mass to vanish seemed quite a stretch and I asked a question about the spontaneous recreation of particles as a result of quantum fluctuation which implied that there would always be some particles with mass. He seemed to take my point and didn't have a good answer to it. The article now states that "In his Nobel Prize Lecture video, Roger Penrose moderated his previous requirement for no mass ... allowing some mass particles to be present as long as the amounts are insignificant..." I suppose that he has arrived at that position as a result of such objections. Andrew🐉(talk) 09:00, 18 November 2024 (UTC)

Conformal cyclic cosmology vs non-conformal cyclic cosmology (almost the same as the Penrosean theory, but the universe always expands but the rate of expansion is not stable [usually, because alternative subtheories exist])

Penrose is wrong on claiming that the void with low enegy photons cannot measure time and re-defaults the whole universe; because outside Hubble volumes causality is broken (not entirely, due to intermediate Hubble volumes, which are infinite... but after a big amount of Hubble volumes, decoherence is nearly 100% thus we have almost perfect causal disconnection... so Roger Penrose is NECESSARILY WRONG, because simply THE FULL UNIVERSE IS NOT ACCECIBLE TO A SPECIFIC OBSERVER TO REDEFAULT IN SIZE (that idea has no meaning/it is senseless).

If the actual universe of today continues to acceleratingly expand, it will explode superluminally pointwise. Each point will be causally disconnected from the other points if all spacetime expands superluminally. Thus each point will become a separate Hubble volume. The full universe will not be accessible to redefault as a coherent whole. And if it does that would have to affect the wave function of the universe as a whole, but we do not have the math for that (suggested theories have gaps). — Preceding unsigned comment added by 2A02:2149:8704:6400:9C2B:E746:E41C:316A (talk) 15:30, 19 November 2021 (UTC)

References

What's that?

Are you serious? This page doesn't talk about the theory at all, just about its issues. Can you please explain the theory in details before talking about the issues? By the way, what's happening to wikipedia since a couple of years? It's becoming dry as hell and it's deleting all interesting debates and suggestions. 37.163.238.75 (talk) 19:24, 13 January 2023 (UTC)

funny, I think it has gotten better. de gustibus... 2A02:A44E:E127:1:FC95:6954:AFC3:6463 (talk) 13:56, 16 October 2024 (UTC)

fermions must be irreversibly converted into radiation during black hole evaporation, to preserve the smoothness of the boundary between aeons

This way of putting things suggest that P is putting the cart before the horse: the fermions have to behave in such and such a way in order that the boundary has the mathematical Property P would like it to have. P is smart enough to know that mathematical wishes do not impose convenient physics on particles, so I am going to blame the phrasing here rather than P himself... 2A02:A44E:E127:1:FC95:6954:AFC3:6463 (talk) 13:58, 16 October 2024 (UTC)

CCC and the Fermi paradox

This section is fine, except that it fails to address the obvious question: if information can be transmitted from aeon to aeon, the paradox ought to become more pressing, not less 2A02:A44E:E127:1:FC95:6954:AFC3:6463 (talk) 14:00, 16 October 2024 (UTC)