All Questions
Tagged with cosmology cosmological-inflation
515
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Spatial Curvature of Universe at recombination vs now
From my understanding, we use the CMB data to measure the spatial curvature of the universe today. Why is it the value for today if the CMB data reflects the universe at recombination (380K years ...
- 25
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Are vacuum "up-tunneling" phase transition in AdS and Minkowski spaces impossible?
I am interested in the topic of vacuum phase transitions in models of the universe. One popular instance of this is a vacuum decay from a metastable vacuum energy level to a "true" one (in ...
- 2,462
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Cosmological numerical computations
I am unsure where to ask this question, whether here or in the Mathematica stackexchange, but either way, I was wondering what are some recommendations for cosmological computations specifically using ...
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Inflation in background free models of the universe
There are many authors who are attempting to construct a model of physics that doesn't rely on the objective existence of spacetime. This is part of the work in quantum gravity. This leads to things ...
- 1,430
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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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Feynman rule from dynamical Chern-Simons
Consider the following action that
\begin{equation}
S = \int d^4x\sqrt{-g}\left(-\frac{1}{2}(\partial\phi)^2 + V(\phi) + \frac{2R}{\kappa^2}
- \frac{\phi}{4f}{}^*RR\right)
\end{equation}
where
\...
- 704
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88
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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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What would an inter-universal medium be like?
I don't really believe in the Multiverse Theory, but hypothetically, if universes were like soap bubbles in a foam, what might that foam be like? I know this seems like an opinion-based question but ...
- 143
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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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Cosmological Scalar Field Density Dilution
Consider a homogeneous free scalar field $\phi$ of mass m which has a
potential
$$V(\phi) = \frac{1}{2}m^2\phi^2$$
Show that, for $m ≫ H$, the scalar field undergoes oscillations with
frequency given ...
- 191
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If dark energy has constant density, would it still be subject to quantum variations; would increase/decrease be symmetrical, or would one take over?
There are different suggestions, but it stills seems like the basic scenario is for dark energy to have constant density, as a property of space (and as represented by the cosmological constant in ...
- 15
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43
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Why is the comoving Hubble radius always increasing without inflation?
I have been told that the comoving Hubble radius $r_{H}(t)\equiv\frac{c}{\dot{a}}$ is increasing without inflation (and inflation was introduced as a period of time with decreasing $r_{H}$ in order to ...
- 475
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A question from a paper on general relativity
I try to read a paper on general relativity and perturbation theory:
https://arxiv.org/abs/2109.01398 page16
My question is about equation (3.16) in section (3.2):
$$
\delta \phi = -\sqrt{\frac{2}{\...
- 395
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How low can the scale of cosmological inflation be?
Usually, when we think of inflation we think of it happening at high energy scales, close to the bound set by CMB polarization measurements (with a Hubble scale of $H_I\sim 10^{14}$ GeV). However, ...
- 11
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Model of Quintessential Inflation
I have a question about how the potential for an inflaton field is selected. It is clear that there are limitations associated with number of e-folds, scalar-to-tensor relation and scalar spectral ...
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