Flat Universe, dark energy and accelerating expansion

In summary, 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.
  • #1
say_cheese
41
1
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?
 
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  • #2
say_cheese said:
...
If the Universe is flat and infinite, why do people (like Roger Penrose) continue to talk about big bang- big crunch cycles?

You can't take for granted "flat and infinite". Most recent batch of CMB data (SPT) suggested not flat, and finite. We have a thread about that.

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
marcus said:
You can't take for granted "flat and infinite". Most recent batch of CMB data (SPT) suggested not flat, and finite. We have a thread about that.

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.

Roger Penrose - http://unveiledsecretsandmessagesoflight.blogspot.com/2009/05/big-crunch-theory.html
 
  • #4
say_cheese said:
:rolleyes::smile:
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
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
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.
 
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  • #7
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
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 ring-type 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 pre-inflation and in some cases pre-bounce.

Ed Wilson-Ewing'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 pre-inflation structure
 
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  • #9
marcus said:
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 ring-type 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 pre-inflation and in some cases pre-bounce.

Ed Wilson-Ewing'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 pre-inflation structure

Sure, I just note that Meissner had referenced Penrose model as a theorietical motivation for such rings. The only other model I was aware of that predicts circular strucutre was the collding bubbles in eternal inflation but i believe these are a different type than Penrose's model. It would be interesting to see how many models out there are predicting this sort of strucutre and how they differ from one to other, especially before Planck data released. Imagine if circular strucutres were discovered, might wer have very different models all claiming victory?
BTW what do you think of the paper? do you think they have been more thorough than Penrose and Gurzadyan's previous effort?
 
  • #10
skydivephil said:
Imagine if circular strucutres were discovered, might we have very different models all claiming victory?
BTW what do you think of the paper? do you think they have been more thorough than Penrose and Gurzadyan's previous effort?

Second question first. As I said earlier, I have very high opinion of Meissner. I don't think I'm qualified to give more than a subjective judgement of the methodology. The paper *looks* real solid to me. This is in line with my earlier impression of his work with Hermann Nicolai.

In case anyone else is reading and unfamiliar with some of this, Nicolai is a division head at Albert Einstein Institute (MPI-Golm), 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 first-rate scientists. Completely focused on research, not publicity. And those are good numbers.
Meissner is Nicolai's close and frequent collaborator, in particular on a non-string 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/hep-th/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 standard--careful, they don't make mistakes. There's a great talk by Nicolai at the 2009 Max Born conference---I'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 non-uniformities that might arise pre-inflation. 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 non-uniform 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 Penrose---an 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 acknowledgments.
 
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  • #11
marcus said:
Second question first. As I said earlier, I have very high opinion of Meissner. I don't think I'm qualified to give more than a subjective judgement of the methodology. The paper *looks* real solid to me. This is in line with my earlier impression of his work with Hermann Nicolai.

In case anyone else is reading and unfamiliar with some of this, Nicolai is a division head at Albert Einstein Institute (MPI-Golm), 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 first-rate scientists. Completely focused on research, not publicity. And those are good numbers.
Meissner is Nicolai's close and frequent collaborator, in particular on a non-string 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/hep-th/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 standard--careful, they don't make mistakes. There's a great talk by Nicolai at the 2009 Max Born conference---I'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 non-uniformities that might arise pre-inflation. 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 non-uniform 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 Penrose---an 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 acknowledgments.

I have found a paper that is quite interesting with regards to circles in the CMb;
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
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.
 

Related to Flat Universe, dark energy and accelerating expansion

1. What is a "Flat Universe"?

A Flat Universe refers to the geometric shape of the universe on a large scale. In a Flat Universe, the spatial geometry is flat, meaning that the angles of a triangle add up to 180 degrees and parallel lines never meet. This is in contrast to a closed universe, where the geometry is curved like a sphere, or an open universe, where the geometry is curved like a saddle.

2. What is dark energy?

Dark energy is a hypothetical form of energy that is believed to be the driving force behind the accelerating expansion of the universe. It is thought to make up approximately 68% of the total energy in the universe and is characterized by its ability to push galaxies apart, counteracting the force of gravity. Dark energy is still not fully understood, and its exact nature and origin are still the subject of ongoing research and debate.

3. What is accelerating expansion?

Accelerating expansion refers to the observed phenomenon that the universe is expanding at an increasing rate. This means that the distances between galaxies are getting larger at a faster and faster rate. This acceleration was first discovered in the late 1990s and is thought to be caused by dark energy, which is counteracting the force of gravity and pushing galaxies apart.

4. How do we know that the universe is flat?

Scientists have determined that the universe is flat through multiple methods, including measurements of the cosmic microwave background radiation, observations of the large-scale structure of the universe, and analysis of the apparent brightness of Type Ia supernovae. These methods all converge on the conclusion that the universe is flat within a margin of error of less than 1%.

5. What are the implications of a Flat Universe and accelerating expansion?

The discovery of a Flat Universe and accelerating expansion has significant implications for our understanding of the universe and its evolution. It suggests that the universe will continue to expand at an increasing rate, eventually leading to the "heat death" of the universe. It also supports the idea that dark energy is a dominant force in the universe and may lead to new theories and models for the nature of the universe.

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