Questions tagged [dark-matter]
Questions about astrophysical observations, experimental searches, and theoretical models related to dark matter and its quanta.
934 questions
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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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Perturbation of a spinor field and energy-momentum tensor in curved backgrounds
I am interested in computing the stress-energy tensor of a Dirac fermion field in arbitrary curved spacetime, but it seems a complicated problem. The result is included in textbooks and articles, but ...
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Red Shift Uncertainties
From a very amateur astronomer seeking enlightenment: I often read that "red shift" proves the universe is expanding and that the farther away the source, the more red-shifted and therefore ...
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What is the Timescape Model of Cosmology?
I am seeing some articles about timescape and comparisons to ΛCDM. In particular there is an article in the Monthly Notices of the Royal Astronomical Society: Supernovae evidence for foundational ...
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Is there a model for the synthesis of light-sector heavy hadron formation during a first order phase transition?
I've recently been reading some research on theories of dark matter. So, I read about Fermi-balls (https://arxiv.org/abs/2008.04430), or non-topological solitons bound inside their own domain walls. ...
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In the beginning of time, regular and dark matter were strongly coupled?
It was mentioned during this lecture at this moment that in the early universe regular and dark matter were strongly coupled. This explains the existence of supermassive black holes in the beginning ...
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Galaxies observed as spinning faster than they should be due to relativistic effects?
When learning about dark matter, one of the reasons given that shows that it exists is that some galaxies are spinning faster than they should be able to without falling apart. So there needs to be ...
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Sterile neutrino dark matter candidate - mass eigenstate or Majorana?
If we consider the SM by adding right-handed neutrinos $\nu_R$ and Majorana-mass terms $$ \mathcal{L}_{M_{\nu}} = -\overline{\nu_L}m_D\nu_R - \frac{1}{2}\overline{\nu}_Rm_R\nu_R^c - \frac{1}{2}\...
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Majorana sterile neutrino interaction terms and Feynman rules
I am currently doing some investigation on sterile neutrinos charged under an additional $U(1)_X$ gauge group as a proposal for dark matter. As I am mostly doing this alone, I seek some confirmation/...
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Calculation of freeze-out temperature
I'm struggling with an exercise that asks me to calculate the freeze-out temperature in term of $x_f = \frac{m_{\chi}}{T_f}$ of a Dark Matter fermion $\chi$ using the relation $ \left< \sigma v \...
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Do symmetry assumptions determine galaxy rotation curves?
This paper https://arxiv.org/abs/2405.04933 claims - not yet peer reviewed though - that assuming cylindrical symmetry the vacuum solution yields flat galactic rotation curves without dark matter. Two ...
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Does scalar field dark matter behave like dust in cosmology?
A uniform scalar field has pressure equal to its energy density (equation of state $w=1$) and so dilutes very rapidly as the universe expands, $\rho \approx a^{-6}$. However, some theories of dark ...
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How does MOND explain ‘low dark matter’ galaxies?
MOND attempts to solve the rotation curve problem of galaxies by modifying the law of gravitation. However, there are galaxies (notably NGC 1277) where the rotation curves do more-or-less agree with ...
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Can a galaxy's rotational energy account for dark matter?
I have heard that a wound clock weighs more than an unwound clock, because the energy stored in the winding gives the clock more mass: $E=mc^2$. ChatGPT calculates that the rotational energy of a ...
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Derive relic abandence of Dark Matter
I am reading Dodelson's Modern Cosmology and I have a question about how to derive equation 3.60 from equation 3.59. Equation 3.59 is $$\Omega_X = \left[\frac{4\pi^3 G g_*(m)}{45}\right]^{1/2} \frac{...
