All Questions
Tagged with space-expansion cosmological-inflation
152
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How to find the relation between flow-parameters and number of e-folds?
In models of single field inflation the Friedmann equation reads
$$ H(t)^2 = \frac{8\pi G}{3} \big(V(\varphi) + \frac{\dot{\varphi}^2}{2}\big) \tag{1}\label{eq1}. $$
In the slow-roll approximation one ...
- 126
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A problem on cosmic inflation
I analyze inflation in this following scenario: Suppose that at some very early epoch, $t_1 ��� t ≤ t_2$ (where $t_1 ≪ t_2 ≪ t_r$ and $t_r$ is the time at the recombination epoch), the universe resides ...
- 131
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Horizon problem, what if our observable universe is roughly equal to the whole universe, especially in early times?
How do we know that at a time of 380.000 years, when CMB got free, the observable universe was not equal to the actual universe? Maybe they were roughly the same and couldn't that explain the horizon ...
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Is time inflating proportionally to space?
We know space is expanding at a rate of roughly 432 miles/light-year/year. Since Einstein showed that time was intrinsically linked into the 4 dimensional structure of spacetime one would logically ...
- 341
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Does dark energy get used up in the expansion of the universe?
Now, I am a beginner in Cosmology, so I am not sure if this makes sense.
Since the universe is expanding at an accelerating rate, and thus distant objects are also accelerating away. In that sense, ...
- 109
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What means Alan Guth's Free Lunch Principle for the universe?
Alan Guth calls the universe the ultimate free lunch. What does he mean by this?
Does he mean that the total energy of the universe is zero? So the total energy of all particles is the negative of the ...
- 450
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Intuitive explanation of COSMIC TIME?
I came across the following statement, while studying a Newtonian model for cosmic expansion:
"If $R(t)$ is the scaling factor, we can define the Hubble parameter as $H(t)=\frac{\dot{R(t)}}{R(t)}...
- 152
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Difference between new inflation and chaotic inflation
I'm trying to understand the difference between new inflation and Linde's chaotic inflation. From what I understand, according to the old inflation, during inflation empty space remains empty, so its ...
- 67
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Does inflation theory assume a finite universe?
Inflation theory has it that the early universe was causally connected, and could “mix”, hence explaining relative homogeneity of the CMB. The universe then rapidly expanded and became causally ...
- 139
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What causes a big rip?
If dark energy has $w<-1$ you get the Big rip scenario, where dark energy becomes more and more powerful until it eventually rips all matter apart. Why does this occur? Why does having $w<-1$ ...
- 2,908
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What if the cosmological principle does not hold at larger scales?
Quite naturally, the observable Universe is the only bit of the Universe we can extract information from, as light from farther away has not reached us yet, and there are zones from which we'll never ...
- 1,616
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What's so "quantum" about quantum fluctuations in the CMB?
I've heard that fluctuations in the CMB provide support for inflationary theory, as they are thought to be amplified quantum fluctuations of the inflaton field. My question is, what is so "...
- 373
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Duration of inflationary epoch
Why is it thought that the inflationary epoch of the universe lasted approximately $10^{-30}$ seconds and why did it take the inflaton (assuming its existence) to release the energy contained itself ...
- 495
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Visualizing the Hubble Sphere
I have viewed the definitions of the Hubble Sphere and related cosmological concepts, as well as various explanations, yet Im still struggling to comprehend a full visualisation of this, which I would ...
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How is the universe becoming increasingly unreachable for things traveling at speed of light?
I've seen a few articles like this that say the majority of the universe is practically unreachable to us, even if we were to travel at the speed of light. My understanding is that there is enough ...
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