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.
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Decoherent vacuum fluctuations in Minkowski spacetime?
I was reading a paper (https://arxiv.org/abs/1008.0808) on whether observers (like Boltzmann Brains) arising from vacuum fluctuations could occur in a Minkowski vacuum. I had a couple of questions on ...
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New theory of everything [closed]
I've developed a TOE and would like feedback on it. I'd particularly like comments on a proposed a modified atomic model. In the new model an electron in a hydrogen atom collapses to a particle at ...
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Two questions about the expansion of the universe and matter?
I have a couple of questions about the consequences that the expansion of the universe (being an accelerated expansion or a linear one) would have on matter and structures in the universe
1. Neutrinos:...
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Why didn't inflation happen right after creation and it had to wait $10^{-36}$ seconds to occur?
What caused this minimum delay in the universe faster than light expansion?
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How can the ions in intergalactic and interstellar gas held together?
The interstellar and intergalactic medium contain huge amounts of free ions (both free protons and electrons).
However, when these particles are not stabilized in an atom because they are excited, as ...
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Singularities and Casorati-Weirstrass theorem [closed]
The Casorati-Weirstrass theorem states that if there exists an Essential Singularity of a function $f$ at some point $z_0$ in the complex plane, Then the function assumes values close to any complex ...
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Equation of motion for a Proca field in Robertson Walker metric
this is my very first question, I hope to do everything in a proper way.
The problem I have is about a vector field in a flat-Robertson metric:
\begin{equation}
d s^2=d t^2-a^2(t)d\vec{x}^2,\quad \...
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Does an expanding de-Sitter bubble create mass from nothing?
Dear Physics Stack Exchange Community,
I am experimenting a bit with different kinds of FLRW solutions to the Einstein equations, in particular with the de-Sitter solution, which comes from choosing $...
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Do the equations $T_{\nu}(t)=\frac{T_{\nu ,0}}{a(t)}$ and $T_{\gamma}(t)=\frac{T_{\gamma,0}}{a(t)}$ actually hold at all times?
I’ve always been under the impression that $T_{\nu}(t)=\frac{T_{\nu ,0}}{a(t)}$ and $T_{\gamma}(t)=\frac{T_{\gamma,0}}{a(t)}$ describe the neutrino and photon temperatures (respectively) throughout ...
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Are relic neutrinos gravitationally bound to large scale structures?
I have been interested in how neutrinos arrange themselves around gravitational potentials. However, I found contradictory claims and I would like to clarify this
After reading a bit into this paper (...
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Assuming that proton decay occurs, will all types of particles be dispersed without exception?
Proton decay is a theoretical possibility, as it is predicted to happen by some GUTs, so the proton may not be stable and could decay into lighter particles considering enormous time scales.
If proton ...
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Why is it necessary the inflaton field?
The Friedmann equations read $(+---)$:
$$\frac{\dot{a}^2+kc^2}{a^2} = \frac{8\pi G\rho + \Lambda c^2}{3}$$
$$3\frac{\ddot{a}}{a} = \Lambda c^2 - 4\pi G \left(\rho + \frac{3p}{c^2}\right)$$
$$\dot{\rho}...
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Density fluctuations in a homogeneous and isotropic linearly expanding universe? [closed]
I would like to ask a question about an interesting paper back from the late 90's
There, the authors propose how the universe may evolve from the near future to extremely far time scales
Near the end ...
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Vacuum bubble nucleation by cosmic rays suppressed? [closed]
There are models of vacuum bubble nucleation events that would be cause by high energy density zones like cosmic rays collisions
However, one paper argues that this process is suppressed. I asked the ...
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Why is the universe depicted as elliptical in all images? [duplicate]
Is there a physical equation that describes the ellipse of the Universe? It seems to me that this is not the case, as most of the motions within it are chaotic (with the exception of the many motions ...
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