Register to reply 
Flat Universe, dark energy and accelerating expansion 
Share this thread: 
#1
Jan213, 10:36 PM

P: 20

The CMB data suggests that the Universe is flat with in 0.4%. CMB data also shows that the expansion of the Universe is accelerating (from the sum of angles of triangle formed by distant hot spots Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess). The pushing out dark energy is about 74% of the energy/mass of the Universe. Question  (a) is 74% dark 26% dark+real matter arrived from the experimental results of observed expansion acceleration to give a flat Universe? (b) If the expansion is accelerating, what does it mean for the curvature  should it have a slight negative curvature from FLRW equations?
If the Universe is flat and infinite, why do people (like Roger Penrose) continue to talk about big bang big crunch cycles? 


#2
Jan313, 12:44 AM

Astronomy
Sci Advisor
PF Gold
P: 23,274

What people do you mean? Please give examples of people who in 2012 were talking about the bang, crunch, bang, crunch...type of cycle. Penrose pet cosmic model he's been promoting since 2005 does not involve a crunch. About half of the "quantum cosmology" papers since 2009 (a Stanford search engine finds) are Loop. Loop models are typically fit to observations and have have a positive COSMOLOGICAL CONSTANT. (dark energy is a bad name since we don't know it is an energy, behaves simply like a constant curvature, recently some people have begun calling it "vacuum curvature" instead of "dark energy") Such models are not CYCLIC, the have a single bounce. A long contraction followed by a long expansion. 


#3
Jan313, 10:30 AM

P: 20




#4
Jan313, 11:24 AM

Astronomy
Sci Advisor
PF Gold
P: 23,274

Flat Universe, dark energy and accelerating expansion
In case anyone is really confused about it, those are not the words of Roger Penrose and are in contradiction with what he has been saying especially since 2005 what you quote here appear to be the words of a SPIRIT MEDIUM named Jorge Oguin transcribed in December 2007 when the medium believed he was "channeling" a "Thetan" being. The cosmological ideas presented by the medium are delightfully wacko, have no scientific content, and no relation to the actual ideas of Roger Penrose. Since 2005 Penrose has promoted the "conformal cyclic" model which has no crunch, it's a rather odd variant of the continuous expansion picture. Almost no one in the scientific community has gone along with Penrose on that however. He seems to have given up on the "conformal cyclic" idea, or anyway just quieted down. His ideas since 2005 have not been influential, though he is a wonderful speaker and has a high public media profile. 


#5
Jan313, 03:11 PM

P: 20

Apologize for giving that link on Penrose. But there seem to be other allusions to big crunch and big bounce of Penrose in several places. You can google it if you like. No matter. You answered that question.
But my main question is does an accelerating expansion imply negative curvature? 


#6
Jan313, 05:23 PM

P: 453

Penrose suggests our universe is cyclic but his idea is not based on the traditional big crunch. The big crunch would occur if the amount of stuff in the universe exerts a gravitational break on the expansion of the universe such that it turns it around and causes it to contract. Thats not what Penrose is saying. What he argues is that the universe will continue to expand forever but eventually all mass will decay away. when this happens its impossible to build a ruler or a clock and so the universe rescales itself back to 0 size. Read the wiki article here:
http://en.wikipedia.org/wiki/Conformal_cyclic_cosmology Whilst this is a cyclic model, it is quite different to the big crunch models of the past. 


#7
Jan313, 05:36 PM

P: 453

The initial arxiv papers produced , supposedly showing ring like patterns in the CMB confirming Penrose theories was shot down very quickly by the community. However I have noticed this paper recently supporting it in a new analysis on the CMb.
http://arxiv.org/pdf/1207.2498v1.pdf Given one of the authors is from the the MAX pLanck Institute for Gravitational Physics I would hope they are more careful than previously, but the best thing to do is wait for Planck data and see what that has to say, should be only a few months away now. 


#8
Jan313, 07:06 PM

Astronomy
Sci Advisor
PF Gold
P: 23,274

Thanks for the arxiv.org/abs/1207.2498 reference! I hadn't seen it.
I respect Meissner a lot, and the authors do not say that the Penrose CCC model would be the ONLY quantum cosmological explanation for ringtype patterns of statistical correlation. Instead they say on page 2: ==quote== It is commonly taken for granted (with the notable exception of [8]) that the Cosmic Microwave Background is purely statistical being produced by the quantum fluctuations usually assumed to have taken place during inflation (as the solution in De Sitter space suggests). ==endquote== But in Ashtekar and others' recent LQC work it is NOT true that CMB anisotropy is entirely due to "the quantum fluctuations usually assumed to have taken place during inflation". So [8] is not the only exception. LQC focus has shifted towards preinflation and in some cases prebounce. Ed WilsonEwing's paper even includes matter coming into the bounce, which would I guess include black holes from previous. So I think the examination of structure in CMB is just beginning. Nobody should get the idea that Penrose has a monopoly on explaining any structures which are not readily attributable to fluctuation during the inflation stage. Merely because his [8] could be considered the most NOTABLE, does not mean it is the only model with possibility of preinflation structure 


#9
Jan413, 02:55 AM

P: 453

BTW what do you think of the paper? do you think they have been more thorough than Penrose and Gurzadyan's previous effort? 


#10
Jan413, 12:37 PM

Astronomy
Sci Advisor
PF Gold
P: 23,274

In case anyone else is reading and unfamiliar with some of this, Nicolai is a division head at Albert Einstein Institute (MPIGolm), directs the Unified Theories and Quantum Gravity program at AEI. One of the foremost/influential European string and field theorists. Has wisely supported both Loop and String research at AEI since before 2004 (like a scientist rather than a partisan), making the institute unique in Europe. http://inspirehep.net/author/K.A.Meissner.1/ (average cites per published paper 35) http://inspirehep.net/author/H.Nicolai.1/ (average cites per published paper 47) They are highly respected firstrate scientists. Completely focused on research, not publicity. And those are good numbers. Meissner is Nicolai's close and frequent collaborator, in particular on a nonstring QFT unification idea called Conformal Standard Model. Latest paper was August 2012 http://arxiv.org/abs/1208.5653 An early paper on the CSM, December 2006 http://arxiv.org/abs/hepth/0612165 note where they say in 2006 "...there exists a set of parameters for which the model may remain viable even up to the Planck scale. The decay modes of the extra scalar field provide a unique signature of this model which can be tested at LHC." well that is what they are talking about seen signs of in the August 2012 paper. What can I say, my impression of the PAPER is good, for what that's worth. My impression of the people is gold standardcareful, they don't make mistakes. There's a great talk by Nicolai at the 2009 Max Born conferenceI'd recommend anybody to watch the video if they haven't. ================= To respond to the other question, suppose Meissner's work is confirmed, about the circular patterns. That would be a great triumph and encouragement to Penrose. But would still not prove that his CCC model is right. Penrose model depends on making some very strange assumptions. The first thing people would do is see what other explanations there might be. AFAIK the Loop cosmology people have NOT specifically predicted that kind of patterning in the CMB, but they are just getting started looking at nonuniformities that might arise preinflation. If there is a bounce (with gravity turning repellent at high density) then supermassive black holes must explode, I would imagine, in the collapsing prebounce phase. Maybe the bounce occurs in a nonuniform way, with places where the density is much higher beginning to expand earlier. Scattered explosions. This is too handwavy to pursue further. But the main thing is Penrose model would get a lot of competition, when push comes to shove. That is not inconsistent with it being a major moral victory for Penrosean enormously creative guy! Here's the link to this very interesting Meissner et al paper, again http://arxiv.org/abs/1207.2498 I notice that they thank (Ezra) Ted Newman (born 1929) in the acknowledgements. 


#11
Jan1213, 08:26 AM

P: 453

http://arxiv.org/abs/1104.3688 Here they claim that if such circles do exist they will have different properties in eahc of these four models: 1CCC 2 Ekpyrotic 3 LQC without inflation 4 LQC with inflation It seem this could really help distinguish between models IF such circles are found and with PLanck data due out in (April?) maybe we could really learn something profound. Not betting on it but an exciting prospect I think. 


#12
Jan1213, 11:06 AM

Sci Advisor
PF Gold
P: 9,488

I remain concerned about systematic effects of procedures used to produce CMB maps. Obviously this was also considered by Meissner, et al, given they specifically addressed such an issue in section 3 of the paper. I agree that Planck data should be helpful in clarifying matters. For discussion of some of the obstacles that need to be addressed: Observational Scan Induced Artificial CMB Anisotropy, http://arxiv.org/abs/1101.2720.



Register to reply 
Related Discussions  
How can the Universe be flat and accelerating in its expansion?  Cosmology  2  
Dark Energy & Expansion of the Universe; Really ?  Astronomy & Astrophysics  12  
Dark energy  Expansion of the universe  Astronomy & Astrophysics  10  
Accelerating Universe, Relativistic Mass and Dark Energy  Astronomy & Astrophysics  2  
Dark Energy and the Accelerating Universe (survey)  Cosmology  2 