scholarly journals The Background Radiation in Isotropic World Models

1969 ◽  
Vol 22 (1) ◽  
pp. 59 ◽  
Author(s):  
AD Payne
Keyword(s):  
Thermal History ◽  
General Equation ◽  
Background Radiation ◽  
Radio Spectrum ◽  
Numerical Results ◽  
Background Intensity ◽  
Background Spectrum ◽  
History Of ◽  
Homogeneous Universe ◽  
The Universe

A general equation for the extragalactic background intensity is derived for the general case of an isotropic homogeneous universe. The extragalactic radio spectrum depends critically on the thermal history of the universe and numerical results have been obtained for different possible models. A brief discussion is given on the conclusions drawn from the comparison of these results with the observed background spectrum.

scholarly journals Cosmic Microwave Background Anisotropy at Degree Angular Scales and the Thermal History of the Universe

1997 ◽  
Vol 480 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Paolo de Bernardis ◽  
Amedeo Balbi ◽  
Giancarlo De Gasperis ◽  
Alessandro Melchiorri ◽  
Nicola Vittorio
Keyword(s):  
Cosmic Microwave Background ◽  
Thermal History ◽  
Microwave Background ◽  
Cosmic Microwave Background Anisotropy ◽  
History Of ◽  
The Universe

scholarly journals A dark clue to seesaw and leptogenesis in a pseudo-Dirac singlet doublet scenario with (non)standard cosmology

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Partha Konar ◽  
Ananya Mukherjee ◽  
Abhijit Kumar Saha ◽  
Sudipta Show
Keyword(s):  
Dark Matter ◽  
Thermal History ◽  
Direct Detection ◽  
Critical Role ◽  
Mass Term ◽  
Baryon Asymmetry ◽  
Dark Sector ◽  
Lepton Asymmetry ◽  
History Of ◽  
The Universe

Abstract We propose an appealing alternative scenario of leptogenesis assisted by dark sector which leads to the baryon asymmetry of the Universe satisfying all theoretical and experimental constraints. The dark sector carries a non minimal set up of singlet doublet fermionic dark matter extended with copies of a real singlet scalar field. A small Majorana mass term for the singlet dark fermion, in addition to the typical Dirac term, provides the more favourable dark matter of pseudo-Dirac type, capable of escaping the direct search. Such a construction also offers a formidable scope to radiative generation of active neutrino masses. In the presence of a (non)standard thermal history of the Universe, we perform the detailed dark matter phenomenology adopting the suitable benchmark scenarios, consistent with direct detection and neutrino oscillations data. Besides, we have demonstrated that the singlet scalars can go through CP-violating out of equilibrium decay, producing an ample amount of lepton asymmetry. Such an asymmetry then gets converted into the observed baryon asymmetry of the Universe through the non-perturbative sphaleron processes owing to the presence of the alternative cosmological background considered here. Unconventional thermal history of the Universe can thus aspire to lend a critical role both in the context of dark matter as well as in realizing baryogenesis.

scholarly journals A Scale at 10 MeV, Gravitational Topological Vacuum, and Large Extra Dimensions

Universe ◽  
2018 ◽  
Vol 4 (7) ◽  
pp. 80
Author(s):  
Ufuk Aydemir
Keyword(s):  
Thermal History ◽  
Extra Dimensions ◽  
Weak Interactions ◽  
Large Extra Dimensions ◽  
Big Bang ◽  
Length Scale ◽  
Big Bang Nucleosynthesis ◽  
History Of ◽  
The Universe ◽  
Bonnet Term

We discuss a possible scale of gravitational origin at around 10 MeV, or 10−12 cm, which arises in the MacDowell–Mansouri formalism of gravity due to the topological Gauss–Bonnet term in the action, as pointed out by Bjorken several years ago. A length scale of the same size emerges also in the Kodama solution in gravity, which is known to be closely related to the MacDowell–Mansouri formulation. We particularly draw attention to the intriguing incident that the existence of six compact extra dimensions originated from TeV-scale quantum gravity as well points to a length scale of 10−12 cm, as the compactification scale. The presence of six such extra dimensions is also in remarkable consistency with the MacDowell–Mansouri formalism; it provides a possible explanation for the factor of ∼10120 multiplying the Gauss–Bonnet term in the action. We also comment on the relevant implications of such a scale regarding the thermal history of the universe motivated by the fact that it is considerably close to 1–2 MeV below which the weak interactions freeze out, leading to Big Bang Nucleosynthesis.

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