Competing cosmologies

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Re: Competing cosmologies

#181  Postby Calilasseia » Aug 26, 2021 7:43 pm

Meanwhile, would someone care to present some of the competing cosmologies extant in the physics literature?

I'm aware of two - Steinhardt & Turok's braneworld collision cosmology, and Hawking's No Boundary Theorem (which is bloody hard to understand even if you've had a decent science education) ... are there others? Ideally with peer reviewed papers attached?
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Re: Competing cosmologies

#182  Postby Spearthrower » Aug 26, 2021 7:48 pm

Calilasseia wrote:Meanwhile, would someone care to present some of the competing cosmologies extant in the physics literature?



Gooooooooooooooooooooooooooooooooooooood


Oh sorry, you said physics.
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Re: Competing cosmologies

#183  Postby newolder » Aug 27, 2021 8:35 am

Calilasseia wrote:Meanwhile, would someone care to present some of the competing cosmologies extant in the physics literature?

I'm aware of two - Steinhardt & Turok's braneworld collision cosmology, and Hawking's No Boundary Theorem (which is bloody hard to understand even if you've had a decent science education) ... are there others? Ideally with peer reviewed papers attached?


Not exhaustive but here's a start:

The folk at wikipedia have built an incomplete table of historical cosmologies: Cosmology but it needs further work especially in literature search. Some of the ideas mentioned in this RatSkep topic are also incomplete works in progress. For examples:

Inflation:

Wiki inflation cosmology & references

Guth, Alan H.; Kaiser, David I.; Nomura, Yasunori (2014). "Inflationary paradigm after Planck 2013". Physics Letters B. 733: 112–119. arXiv:1312.7619. Bibcode: 2014 PhLB..733..112G

Linde, Andrei (2014). "Inflationary cosmology after Planck 2013". arXiv:1402.0526

Conformal cyclic cosmology:

Wiki CCC & references

Penrose, R. Cycles of Time: An Extraordinary New View of the Universe, pub. Bodley Head 2010

Tod, P. The equations of Conformal Cyclic Cosmology. Gen Relativ Gravit 47, 17 (2015). https://doi.org/10.1007/s10714-015-1859-7, arXiv

Gurzadyan, V. G.; Penrose, R. (2018). "Apparent evidence for Hawking points in the CMB Sky". Monthly Notices Roy.Astron.Soc. 495 (2020) 3, 3403-3408 arXiv:1808.01740 DOI: 10.1093/mnras/staa1343

String gas cosmology:

STRING GAS COSMOLOGY AND STRUCTURE FORMATION
ROBERT H. BRANDENBERGER, ALI NAYERI, SUBODH P. PATIL and CUMRUN VAFA

International Journal of Modern Physics A Vol. 22, No. 21, pp. 3621-3642 (2007)

https://doi.org/10.1142/S0217751X07037159

ETA
Just to note that Paul J. Steinhardt has moved on from inflation and ekpyrotic ideas to a 'new' Bouncing Cosmology - as posted earlier in the topic. His web and links to papers anent is here
Last edited by newolder on Aug 27, 2021 12:32 pm, edited 1 time in total.
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Re: Competing cosmologies

#184  Postby hackenslash » Aug 27, 2021 10:15 am

I really must get back to cosmology. I'm well behind. Haven't even read Sean Carroll's blog in over a year.

I was doing some boning up on complex maths in the context of QM to try to get a handle on Hawking-Hartle, but I'm not there yet. TBF, I haven't added to my pre-Planck material since my piece on branes in 2016.
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Re: Competing cosmologies

#185  Postby newolder » Aug 27, 2021 2:52 pm

Physicists Debate Hawking’s Idea That the Universe Had No Beginning is the title of a "good read" Quanta Magazine article by Natalie Wolchover from 2019 that brought the Hartle-Hawking/Neil Turok* et al debate to no kind of resolution...
...
No matter how things go, perhaps we’ll be left with some essence of the picture Hawking first painted at the Pontifical Academy of Sciences 38 years ago. Or perhaps, instead of a South Pole-like non-beginning, the universe emerged from a singularity after all, demanding a different kind of wave function altogether. Either way, the pursuit will continue. “If we are talking about a quantum mechanical theory, what else is there to find other than the wave function?” asked Juan Maldacena, an eminent theoretical physicist at the Institute for Advanced Study in Princeton, New Jersey, who has mostly stayed out of the recent fray. The question of the wave function of the universe “is the right kind of question to ask,” said Maldacena, who, incidentally, is a member of the Pontifical Academy. “Whether we are finding the right wave function, or how we should think about the wave function — it’s less clear.”

Much fun.

* e.g. "No smooth beginning for spacetime", Job Feldbrugge, Jean-Luc Lehners, Neil Turok arXiv link
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Re: Competing cosmologies

#186  Postby newolder » Aug 31, 2021 4:10 pm

Haven't read this yet but it looks topic relevant...
Limitations of an Effective Field Theory Treatment of Early Universe Cosmology

Robert Brandenberger (McGill University)

Assuming that superstring theory is the fundamental theory which unifies all forces of Nature at the quantum level, I argue that there are key limitations on the applicability of effective field theory techniques in describing early universe cosmology.

Invited review for the special issue "The future of mathematical cosmology" of Philosophical Transactions A

arXiv link
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Re: Competing cosmologies

#188  Postby newolder » Nov 15, 2021 11:22 am

A couple more recent tubes to put into the mix...

The first, by Dr. Brian Keating of the original BICEP team, brings us up to date on the state of play with regards to tensor/scalar ratio measurements from BICEP3 and the BICEP array, and the ability to rule out some, but not all, inflationary scenarios.


The second is another presentation by Sir Roger Penrose on his Weyl curvature/conformal cyclic cosmology ideas for the Tencent-WE summit in 2021.


If I cut the https to http then the tubes don't show up in my (safari) browser (hackenslash's latest here does not show up either but his tube in the tensors topic uses https and is visible). Is this a browser/apple fail or a separate known issue? I thought the forum software didn't work with the https prefix :???:
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Re: Competing cosmologies

#189  Postby hackenslash » Nov 15, 2021 11:47 am

They're all showing for me in Chrome, with or without.

ETA: Also in Firefox.
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Re: Competing cosmologies

#190  Postby newolder » Nov 15, 2021 12:01 pm

Thanks. If the secure sockets layer works, I'll stick with that. :thumbup:
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Re: Competing cosmologies

#191  Postby newolder » Jan 15, 2022 8:26 pm

A fine review article:
The Road to Precision Cosmology
Michael S. Turner

Abstract

The past 50 years has seen cosmology go from a field known for the errors being in the exponents to precision science. The transformation, powered by ideas, technology, a paradigm shift and culture change, has revolutionized our understanding of the Universe, with the ΛCDM paradigm as its crowning achievement. I chronicle the journey of precision cosmology and finish with my thoughts about what lies ahead.

Published in: Annu. Rev. Nucl. Part. Sci. 2022. 72:1–33
https://doi.org/10.1146/annurev-nucl- 111119-041046
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Re: Competing cosmologies

#192  Postby newolder » May 19, 2022 6:21 pm

Riddles of Reality: From Quarks to the Cosmos


Brian Greene & Frank Wilczek in a live presentation from the World Science Foundation starting at the top of the hour...

I'll attempt to use the permalink after the event finishes...

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Re: Competing cosmologies

#193  Postby newolder » May 25, 2022 8:53 pm

Another livestream about to drop in couple of minutes...
Adam Riess: The Hubble Tension is Getting WORSE!
17 waiting Scheduled for 25 May 2022



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Re: Competing cosmologies

#194  Postby Chief Engineer » May 27, 2022 10:29 am

Hello all:

I have nothing to add to this word salad about the competing theories except:

I think the term Hypothesis should be used to describe the Ideas. Inflation, cyclical universe, steady state, infinite universe, String/Brane, No boundary, et al. Like the God hypothesis, they remain difficult to prove in a way science dictates for them to be a Theory like General Relativity itself.

Image


When you can satisfy this chart to proving the hypothesis, and when your work is verified, your hypothesis moves to a Theory. So far nothing in science has moved beyond this point, to something a Theist my label as "Truth".

Thanks for the video links. some I have not seen.
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Re: Competing cosmologies

#195  Postby newolder » May 27, 2022 10:56 am

Hi Mark,
Theists may label anything they like as "Truth", it makes no difference to science and its methods. The ideas presented in this topic are models that are tested against the best observations humans have made - this sometimes leads to arguments/discussions and progress may follow. As the observations improve, models are refined as predictions are falsified - and maybe a revolution in thought is required. So it goes.

Flowcharts are also models:
Image
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Re: Competing cosmologies

#196  Postby Chief Engineer » May 27, 2022 12:42 pm

newolder wrote:Hi Mark,
Theists may label anything they like as "Truth", it makes no difference to science and its methods. The ideas presented in this topic are models that are tested against the best observations humans have made - this sometimes leads to arguments/discussions and progress may follow. As the observations improve, models are refined as predictions are falsified - and maybe a revolution in thought is required. So it goes.

Flowcharts are also models:
Image



I see no conflict with what I said. You're simply adding more word salad to the thread. I am pointing out that the thread uses the term theory too loosely, as Theists do. You are simply restating it in a way that suits you
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Re: Competing cosmologies

#197  Postby newolder » May 27, 2022 1:24 pm

I'm not in conflict with what you (Mark) wrote. I added to your word salad with a definition of "theory" that fits the scientific method. A theory accounts for all observations hitherto and is used to generate hypotheses that should be tested by future experiment.
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Re: Competing cosmologies

#198  Postby Chief Engineer » May 27, 2022 2:23 pm

Seeing you are only 1 you do pretty well.

If we want to get very specific a good theory will also provide ways it could be disproved in its structure.
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Re: Competing cosmologies

#199  Postby Spearthrower » May 27, 2022 4:17 pm

Or rather, in its consequences.

If X, then Y.
Not Y?
Then not X.

Were our hypothesis/theory held to be correct, whatever follows from that can, through experimentation and direct observation, corroborate or falsify the original contention.

The power, of course, is that while it can completely demolish, once and for all, any falsity, it can never pretend to have presented proof absolute. The door remains open to seek new vistas.
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Re: Competing cosmologies

#200  Postby newolder » May 28, 2022 7:40 am

The current "most favoured" model is known as the Big Bang Inflation +ΛCDM (cosmological constant, Cold Dark Matter) scenario that has been moulded to accommodate almost all of the most recent of observations. Professor George Efstathiou of the University of Cambridge hosted the 22nd Hintze lecture, posted to the internet at the end of 2021, and asks: the legacy from Planck: do we have a standard model of cosmology? He gathers data, provides explanations and finishes with a Q&A that brings forward some of the competing ideas. An hour and a quarter presentation...

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