Questions tagged [cosmological-inflation]

Questions regarding the phenomenon in the early universe characterized by an extreme expansion of space.

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24
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1answer
677 views

Future of CMB observations: How will our knowledge of the early universe change?

The Planck satellite has been presented and awaited for a long time as the ultimate experiments for measuring temperature fluctuations in the cosmic microwave background (CMB) over the full sky. One ...
16
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1answer
425 views

How exactly does inflation convert random gravity fluctuations into coherent gravitational waves?

In the course of this very enjoyable press announcement, it is mentioned that inflation can create gravity waves by amplifying gravity fluctuations. I do not properly understand this statement. I ...
11
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1answer
922 views

Inflation cosmology: slow-roll inflation versus tunneling between two vacua

In slow-roll inflation models, the early inflation of the universe is driven by the flat non-zero part of the inflaton potential, and it ends as the ball rolls down the cliff and the potential energy ...
9
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4answers
736 views

Is the Universe really expanding at an increasing rate?

Here's what I just read from Wikipedia's page on the Hubble Space Telescope: While Hubble helped to refine estimates of the age of the universe, it also cast doubt on theories about its future. ...
8
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2answers
370 views

Expansion again: where does the energy come from?

Is it sensible to ask for the overall increase in potential energy when looking at the baryonic mass in the universe moving away from each other, that is, moving against the direction of the force ...
8
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1answer
255 views

Dark Energy Expansion

The new Cosmos extra features mentions that at about 6,771,500,000 years ago the universe began an accelerated expansion. How do we know this? What evidence do we have for this renewed and accelerated ...
7
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2answers
426 views

Why do we have the cosmological constant?

Since the cosmological constant is not required to explain that the universe seem to be expanding, why do we have it? What other factors cause us to have that constant? Background: Without the ...
7
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1answer
91 views

How distant were the furthest currently-observable cosmic events when their currently-observed radiation was emitted?

(Edited for clarity. Thanks to James K and Connor Garcia.) This question about the most distant, observable cosmic objects made me wonder if we know the distance that was between us and them at the ...
7
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1answer
124 views

Does the accelerating expansion of spacetime mean that the pace of time is changing?

Space expands everywhere, also here. And time is inseparable from space. Does this mean that time also "expands" as in changing its pace? Is the changing rate of time also astronomically observable? ...
6
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4answers
713 views

Can it be inferred that our cosmological horizon has increased over time?

If I am right, we can see only those stars that lie within our cosmological horizon, and there may or may not be any stars beyond that. Given last 150 years of using telescopes, and since then our ...
6
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1answer
544 views

How can the equation of state for cosmic strings and domain walls be derived?

In this article which nicely explains why it is really the quantity $\rho + 3p$ which is relevant to determine if the expansion of the universe is accelerating or decelerating by making use of the for ...
6
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1answer
140 views

What was the age of the universe when the average density was one atmosphere?

How long did it take after the Big Bang for the average density of the universe to reach one Earth atmosphere at sea level? How about the density of water? Is there a chart of densities that relate to ...
6
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2answers
4k views

Our universe the surface of a 4-dimensional sphere?

The cosmic microwave background that we observe uniformly around us is usually explained by assuming that our universe is the surface of a four dimensional sphere. That way the uniformity makes sense ...
5
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3answers
7k views

Does time slow down because the universe is expanding at an accelerating rate?

If the universe is expanding at an accelerating rate, such that the galaxies' moving away from each other is accelerated, then time should also slow down. And when universe will accelerate to the ...
5
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1answer
2k views

Does the universe expand at the same rate everywhere in the universe?

Specifically, I am wondering if some areas of the universe expand faster than other areas and whether the faster expanding areas diffuse the expansion through the slower expanding areas or does the ...
5
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2answers
119 views

What is the difference between the way light travels in a gravitational field and the way it travels through an expanding universe?

A photon is travelling through space. As it travels, the space through which it travels is expanding Does this describe A - a photon travelling from a distant galaxy to earth B - a photon travelling ...
5
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1answer
98 views

Understanding better the factors on $C_l$ in Angular power spectrum and Relation with Matter power spectrum

I am looking for an explanation on the angular power spectrum. I found this extract that is interesting but not fully understood for me (I will cite the step that I didn't understand) "what is ...
5
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1answer
176 views

Is dark energy constant?

Does the "amount" of dark energy in the universe change over time, or is it constant? The dark energy I am asking about is the rate of acceleration of the universe's expansion.
5
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1answer
141 views

Were parts of the Universe deflating during Inflation?

I was reading about the history of the early universe in Carroll & Ostlie and specifically looking at Inflation, which, as I understand, occurred because our [observable] part of the universe ...
5
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1answer
126 views

Red shifting galaxies

I am an amateur astronomer please correct if any of my understandings are wrong. We all know that from the Hubble's ultra deep field image the most distant galaxies which were created shortly after ...
4
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3answers
238 views

Did cosmological inflation occur at speeds greater than $c$?

If cosmological inflation occurred at speeds less than $c$, wouldn't we see the CMB right in front of our noses (or not at all) instead of at 13.7 billion light years? And if it happened faster than $...
4
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1answer
248 views

How can cosmic inflation make an infinite universe homogeneous?

As it is explained in this video, one of cosmic inflation's observable effects is the homogeneity of our universe. Inflation allows two points on the different sides of the observable universe to be ...
4
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2answers
229 views

A black "superhole" possibility?

When matter crosses the event horizon, it is easy to imagine that matter is torn apart into their individual components by tidal wave effects. Atoms would be ripped apart eventually. At one time, the ...
4
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2answers
119 views

Does Flat Universe mean even distribution?

I've read through all the other related answers to "flatness" questions but I need a bit more clarification. I understand that a triangle in a 2D universe would not equal 180 degrees in both a closed ...
4
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1answer
58 views

Problem with denoising the BICEP2 data?

This question pertains to this article which talks about why the BICEP2 measurements of B-mode polarization in Cosmic microwave background radiation turned out to be noise from galactic stardust. They ...
4
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4answers
310 views

What is our universe expanding into?

From inflation theory and other theories explaining the birth of the universe, the universe is expanding and recently it's been discovered that the expansion has been accelerating. My question is ...
4
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3answers
467 views

Distinction between metric expansion and objects just moving apart from each other?

I see explanations likes this: Galaxies and other sources, then, are not strictly expanding away from each other but rather are attached to the fixed grid on the expanding fabric of spacetime. Thus, ...
4
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1answer
271 views

What is the explanation for rapid inflation just after the big bang?

I often hear about cosmic inflation occurring rapidly after the Big Bang, but have never came across any explanation for it. What supposedly caused this inflationary period in the early universe? Also,...
4
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0answers
203 views

Is cosmic inflation still a hypothesis?

Is Cosmological inflation still considered as hypothesis? Is CMBR evidence not enough?
3
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2answers
202 views

BIg Bang Happened everywhere

According to the Friedmann equations big bang happened everywhere, but if we account for inflation theory, big bang did not happened everywhere. How ? Anyone please explain. Please see the video for ...
3
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2answers
359 views

Is the Big Bang inflation caused by Dark Energy

The rate of expansion of the universe after the Big Bang is described as Inflation. It is stated as being initially very fast then slowed. But the expansion is still continuing. Some say expansion is ...
3
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2answers
505 views

Are there ways to estimate size of the "whole universe"?

Words escape me, but by "whole universe" (I think) I mean everything that's spatially connected to the observable universe in a conventional sense. If there is a better term for it, please let me know!...
3
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1answer
217 views

Time dilation due to the expansion of the universe

This is not a homework question. I want some help in being able to clearly perceive the expansion of the universe and the consequences thereof. We know that the universe is expanding in an ...
3
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1answer
1k views

What will the universe be like in a googolplex years time?

It will be cold and dark in 10^(10^100) years. What else can be said of the state of things in the far distant future? Will everything have fallen into supermassive black holes and then radiated ...
3
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1answer
80 views

Does wavelength affect redshift caused by the metric expansion of space?

Does wavelength play a role in cosmological redshift? Do we see certain wavelengths affected less by expansion or notice any delay in arrival of certain wavelengths? How accurate are any observations?...
3
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4answers
371 views

What is the acceleration for the expansion of the Universe?

I've found that the speed of expansion is about $70\frac{km}{s\cdot 10^{6}pc}$. But what is the acceleration of expansion in terms of $\frac{km}{s^{2}\cdot 10^{6}pc}$ ? I want to know how fast this ...
3
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2answers
414 views

How could universe inflate itself out of the very dense and curved early spacetime? Could it happen in a black hole too?

Wasn't spacetime as much curved as a black hole directly after Big Bang, because mass was so densly packed? Wasn't everything like an event horizon and how could things expand across it? Could ...
3
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1answer
170 views

The universe is dying vs the universe is ever expanding

How does the idea that the universe is dying (trumpeted as some big new revelation the past few days on several new sites I keep seeing pop up on google news) square with the idea that the universe is ...
3
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1answer
252 views

How long was the hyper inflation phase?

How long was the hyper inflation phase? Haw can we know that it lasted for a period of time and not more or les time?
3
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1answer
139 views

Is the expansion of the universe greater than the speed of light?

If the rate of expansion of the universe is increasing , won't it eventually become greater than c? Also, after inflation, did the rate of expansion slow down and then start to accelerate again?
3
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1answer
153 views

Are there expanding-universe cosmological models that do not include inflation?

I'm happy that the universe is expanding, because we have good scientific evidence in the form of galactic redshift. The Wikipedia Hubble's law article gives what I think is a fair explanation of that....
3
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1answer
142 views

Standard Big Bang model and space curvature

Why it is said that in standard Big Bang model space curvature grows with time when the Universe expands? My intuition is that it should be the opposite. I saw this in a book talking about the ...
3
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1answer
241 views

What happened before, Big Bang or inflation?

I always thought that the cosmic inflation happened after the big bang (10-36 sec) and lasted for a very tiny fraction of time). Now, I recently came across a couple of articles (links below) claiming ...
3
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1answer
79 views

Was Guth inflation propelled by what we now call "Dark Energy"?

The more powerful our telescopes become, the more we are able to see earlier and earlier remnants of Guth Inflation. Assuming that it makes sense to associate a location, BB, in space-time where the ...
3
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1answer
151 views

Could the expansion of universe be a side effect of gravity?

Could the expansion of universe be a side effect of gravity? I mean maybe gravity "attracts things" at a "small" distances and repells them at "larger" distances? Do we have any theory/hypothesis/...
3
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1answer
290 views

Does the holographic principle contradict eternal inflation?

As it is for example explained here, Andrei Linde's chaotic inflation is among the potential winners or survivors of the spring cleaning induced by the potential detection of primoridal gravitational ...
3
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1answer
126 views

What are the concrete technical arguments supporting the idea that the wave function of the universe can be written as partition function?

In this talk, the not yet settled down idea that the wave function of the universe could potentially be written as the partition function of a scale invariant statistical field theory is mentioned: $...
3
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2answers
183 views

Was the Universe expanding before the beginning of inflation?

My point of view is that first there was the Big Bang singularity, and then the period of inflation which resulted in the observable Universe becoming many times bigger. But was the Universe expanding ...
3
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0answers
86 views

The nature of cosmological inflation — unfolding dimensions?

While the paradigm of cosmological inflation is well established, the nature of the inflation is not known and is tackled by introduction of a hypothetical "inflaton" field. I was wondering if there ...
3
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0answers
103 views

What is the difference between Steinhardt's and Neil Turok's cyclic cosmology and Guth's inflationary model and Hartle, Hawking no boundry cosmology?

I have been reading some cosmology and need to ask the experts at this point some specific points. I must admit I am a little confused. There are a few models of the universe and may be necessary at ...