Questions tagged [cosmology]
The study of the large-scale structure, history, and future of the universe. Cosmology is about asking and answering questions about the "big picture" - the extent, origin, and fate of everything we know.
5,740 questions
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Can vacuum shift to a higher energy level?
From this, I gather that a false vacuum can decay to a false vacuum of a lower energy. AFAIU vacuum decay is always local, propagating at the speed of light (whence the reference to the expanding ...
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Perturbations in the inflaton field before inflation
The recent papers I've read concerning perturbations that generate cosmic structures later on were careful to state that these perturbations in the inflaton field are generated during inflation. But ...
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Dark matter freeze-out in the Early Universe
Let us consider an Early Universe scenario in which I have dark matter particles (DM) $\chi_1$ and $\chi_2$, with a small mass splliting $\delta \ (m_2 = m_1 + \delta, \quad \delta \ll m_1, m_2)$, ...
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Confusion regarding Weinberg's proof of constant tensor perturbation on superhorizon scales
In Weinberg's "Damping of Tensor Modes in Cosmology" arXiv:astro-ph/0306304, he claims to show in the appendix that "$h_{ij}$ becomes time-independent as the wavelength of a mode leaves ...
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Requesting recommendations to learn about $S_8$ tension [closed]
I want to understand the $S_8$ parameter and the $S_8$ tension in full technical detail. Can someone recommend books, papers that go into detail on these topics, including the required background, ...
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Massive "Photon" on de Sitter (Inflation) Reference
I am trying to find a reference for massive $U(1)$ or "massive photon" during inflation (or de Sitter space) that derives or at least shows the mode functions for massive photon (with the ...
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Hubble's Law and the age of universe
Hubble's Law says that galaxies are moving away from Earth at speeds proportional to their distance. The resolution of Olbers' Paradox is that the universe is of finite age. However, Hubble's ...
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What does Newton's laws say about the geometry of spacetime?
Follow up to this question. Einstein's equation describes not only the motion of particles but also the geometry of spacetime. So far I understand, from the equations we can also make inferences of ...
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How to get the table of the sensitivity curves of DECIGO experiment
Any help how to find the text file of the table of graph Fig: 3 In paper for the blue curves? which are the Sensitivity Curves of The Japanese space gravitational wave antenna: DECIGO Or if there any ...
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Finite volume of the spherical FLRW metric
I am currently Reading Mukhanov: Physical Foundations of Cosmology. However, I am confused about the calculations on p.18f The FLRW metric for $k=1$ is given by $ds^2=dt^2-a^2[d\chi^2+sin^2(\chi)d\...
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What part of redshift is due to blackbody radation?
While traveling billions of lightyears, photons lose their energy. During my physics degree, the question of where that energy goes was never answered. I always thought it must be losing it to ...
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$n$-point spin-1 vertex in de Sitter?
To setup the motivation for this question, consider the following $n$-point interaction vertex that we will take to be in de Sitter space so that we can make predictions during inflation, where we are ...
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If dark energy is evolving as DESI seems to indicate, shouldn't it be increasing instead of weakening?
In cosmology, DESI survey has found evidence that dark energy may be weakening over time. However, according to the Hubble tension, the early universe (according to CMB data) expanded at a lower rate ...
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Approximate effective potential for late time and early universe
In the article entanglement entropy of GCG effective potential in equation 16 is approximated for early universe and obtained equation 21 and for later time in equation 26. Some constraints are given ...
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What is the temperature dependence of the weak interaction which converts protons into neutrons in Big Bang Nucleosynthesis?
In section 4.2.1 of Dodelson's textbook "Modern Cosmology" (2nd edition, 2020), we consider the weak interaction $ p + e^{-} \to n + \nu_{e} $. In this section it claims, "as the ...
