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2answers
245 views

How to concile flat spacetime and big bang?

After reading How do we resolve a flat spacetime and the cosmological principle? I still remain perplex. Please excuse my ignorance and try explaining to me : I thought that basically, when we ...
2
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2answers
186 views

What are the limitations of the FLRW metric?

I was wondering, given how in any other area of life making an explosion spherically symmetric is more or less impossible is there any reason to expect that the universe is? I appreciate that the FLRW ...
11
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2answers
283 views

How is causal patch complementarity compatible with behavior during inflation?

Causal patch complementarity is the conjecture that in de Sitter space with a positive cosmological constant, the states within the causal patch are sufficient to fully describe the universe with the ...
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1answer
159 views

Supermassive Black Holes = expansion origin?

(Sorry, couldn't resist the title) An article on Physics Today brings news that there is a new record for largest black hole (not) seen in space, some 300 million light-years away. It hints at ...
2
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0answers
75 views

Can composite field consists of two fermions cause cosmic inflation rather one scalar field?

Inflation is triggered by one scalar field, can a field composite of fermions do the same in the early universe
8
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2answers
431 views

Is eternal inflation and the multiverse compatible with causal patch complementarity?

The argument for eternal inflation is we have some patch of metastable vacuum with positive cosmological constant, and so it expands exponentially a la de Sitter. Most of the patch decays to something ...
2
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1answer
77 views

Cosmic bubble collision

I'm reading this review right now. The claim seems to be that when you have an expanding "false vacuum", finite size bubbles form due to phase transition (cause by finite action instantons) (which, in ...
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2answers
613 views

How long did inflation take to happen?

If inflation happened, it ended about 13.7 billion years ago. But how long was inflation going on before that? Was it just a short burst of time so that it's really okay to say that the age of the ...
2
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1answer
163 views

Does anisotropic expansion of the universe imply quintaessence?

a Recent paper establishes under solid grounds anisotropy in the expansion acceleration rate in the universe. My question is very simple: can this anomaly be explained entirely in terms of a ...
7
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2answers
986 views

photons in expanding space: how is energy conserved?

If a photon (wave package) redshifts (streches) traveling in our expanding universe, is it's energy reduced? If so, where does it go?
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2answers
182 views

Could dark matter be expanded atoms, and dark energy expanded radiation? [closed]

After watching Lawrence Krauss' lecture 'life, universe, and nothing', an interesting idea lighted up in my mind. Is it possible that dark matter is just spread out matter waves and dark energy ...
9
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1answer
938 views

How does Inflation solve the Magnetic Monopole problem?

Cosmological Inflation was proposed by Alan Guth to explain the flatness problem, the horizon problem and the magnetic monopole problem. I think I pretty much understand the first two, however I don't ...
6
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1answer
474 views

Inflation Scale via CMB Polarization

COBE, WMAP, and now PLANCK, have or are in the process of measuring anisotropies in the cosmic microwave background. WMAP has dectected E-mode polarization from electron Thomson scattering, but not ...
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1answer
407 views

Inflation factor and doubling time

I get the general idea about cosmic inflation, but the numbers associated with it seem to be pulled out at random. For example, in The Elegant Universe, Brian Greene says that the universe doubled ...
3
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2answers
316 views

How is perturbation theory applied to the Bunch-Davies state for an interacting quantum field theory?

Feynman diagrams are ordinarily the usual method of perturbative analysis for weakly interacting quantum field theories. However, over a de Sitter background, the total number of particles isn't even ...
10
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2answers
581 views

Can the Big Rip really rip apart an atomic nucleus?

Some scenarios describing the fate of the matter vs dark energy tug of war on the universe involve the acceleration of the universe increasing to the point that it ends up ripping apart even atoms. ...
7
votes
1answer
648 views

On Flatness problem, Inflation etc

I have a couple of naive questions from the topic of the title. We know \begin{eqnarray} \Omega-1=\frac{k}{a^2H^2}-\frac{\Lambda}{3H^2} \end{eqnarray} Now I read that from the standard big bang ...
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1answer
240 views

Inflation and string theory in general relativity

How can we relate inflation and string theory? We study some inflationary cosmological model or some string cosmological model under some specific assumptions or conditions. Is their any relation or ...
6
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4answers
537 views

de sitter cosmologic limit

It has been said that our universe is going to eventually become a de sitter universe. Expansion will accelerate until their relative speed become higher than the speed of light. So i want to ...
2
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1answer
179 views

Size of our inflationary bubble

Once again, an attempt to connect popular and real science. I have read that inflation implies our universe should look flat, or really close to flat, because our observable universe is only a really ...
5
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2answers
380 views

Undergraduate-friendly reading material on the multiverse?

I'll be teaching a seminar for first-year undergraduates next year. The idea of my university's first-year seminar program is to expose students to exciting ideas and important texts in a somewhat ...
5
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5answers
2k views

What is the evidence for Inflation of the early universe?

The theory of Inflation explains the apparent consistency of the universe by proposing that the early universe grew exponentially for a 1E-36 seconds. Isn't a simpler explanation that the universe is ...
5
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3answers
359 views

What current alternatives are there to the standard concordance model of cosmology?

The current "standard model" or concordance model of cosmology is Lambda CDM which includes late time acceleration due to a cosmological constant, cold dark matter as the missing matter component and ...