Late-time entropy production from scalar decay and the relic neutrino temperature

Adhya, Paramita; Chaudhuri, Dwaipayan; Hannestad, Steen

doi:10.1103/physrevd.68.083519

Cited by 13 publications

(23 citation statements)

References 46 publications

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“…The general trend is to increase the discrepancy between predictions and observations, since 7 Li/H increases with η BBN , with a low N eff and a high n n /n p at BBN. This observation disfavours any reasonable attempt of solving the Li problem with decaying ALPs.…”

Section: Constraintsmentioning

confidence: 91%

“…A number of excellent papers have considered the cosmological implications of decaying massive relics, see for instance [7][8][9]. Our work focuses on ALPs and deals with particles in an intermediate mass range (keV-GeV), which is often not considered.…”

Section: Overviewmentioning

confidence: 99%

“…5 we can see that the low D/H trend of low mass ALPs is drastically changed when the mass gets above 2m π + and the effect on 4 He gets strongly boosted when crossing this boundary. The effects of pions are hampered if the ALPs decay very early (τ 10 −2 s), when the electroweak reactions p + + e − ↔ n + ν e can still re-establish the n n /n p equilibrium; or very late (above τ ∼ 10 2 s), because pions fail to interact before decaying 7 .…”

Section: Large Massesmentioning

confidence: 99%

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Cosmological bounds on pseudo Nambu-Goldstone bosons

Cadamuro¹,

Redondo²

2012

J. Cosmol. Astropart. Phys.

260

287

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Abstract. We review the cosmological implications of a relic population of pseudo NambuGoldstone bosons (pNGB) with an anomalous coupling to two photons, often called axion-like particles (ALPs). We establish constraints on the pNGB mass and two-photon coupling by considering big bang nucleosynthesis, the physics of the cosmic microwave background, and the diffuse photon background. The bounds from WMAP7 and other large-scale-structure data on the effective number of neutrino species can be stronger than the traditional bounds from the primordial helium abundance. These bounds, together with those from primordial deuterium abundance, constitute the most stringent probes of early decays.

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Section: Constraintsmentioning

confidence: 91%

Section: Overviewmentioning

confidence: 99%

Section: Large Massesmentioning

confidence: 99%

See 1 more Smart Citation

Cosmological bounds on pseudo Nambu-Goldstone bosons

Cadamuro¹,

Redondo²

2012

J. Cosmol. Astropart. Phys.

260

287

View full text Add to dashboard Cite

show abstract

“…The responsible physical mechanisms could be, though are not limited to, heating from decays of massive particles or fields, e.g. [27][28][29][30], such as expected in thermal inflation [31,32], or cooling by thermal contact with other species, Refs. [28,33].…”

Section: Introductionmentioning

confidence: 99%

Signatures of relativistic neutrinos in CMB anisotropy and matter clustering

2004

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We present a detailed analytical study of ultra-relativistic neutrinos in cosmological perturbation theory and of the observable signatures of inhomogeneities in the cosmic neutrino background. We note that a modification of perturbation variables that removes all the time derivatives of scalar gravitational potentials from the dynamical equations simplifies their solution notably. The used perturbations of particle number per coordinate, not proper, volume are generally constant on superhorizon scales. In real space an analytical analysis can be extended beyond fluids to neutrinos.The faster cosmological expansion due to the neutrino background changes the acoustic and damping angular scales of the cosmic microwave background (CMB). But we find that equivalent changes can be produced by varying other standard parameters, including the primordial helium abundance. The low-l integrated Sachs-Wolfe effect is also not sensitive to neutrinos. However, the gravity of neutrino perturbations suppresses the CMB acoustic peaks for the multipoles with l 200 while it enhances the amplitude of matter fluctuations on these scales. In addition, the perturbations of relativistic neutrinos generate a unique phase shift of the CMB acoustic oscillations that for adiabatic initial conditions cannot be caused by any other standard physics. The origin of the shift is traced to neutrino free-streaming velocity exceeding the sound speed of the photonbaryon plasma. We find that from a high resolution, low noise instrument such as CMBPOL the effective number of light neutrino species can be determined with an accuracy of σ(Nν ) ≃ 0.05 to 0.09, depending on the constraints on the helium abundance.

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“…For instance, neutrinos could violate the Pauli exclusion principle and obey Bose-Einstein statistics with important cosmological and astrophysical implications [16,17]. Nonequilibrium neutrino spectra are also produced in lowreheating scenarios [18,19,20], from the decays of massive neutrinos into relativistic products (see for instance [21,22]) or as the result of active-sterile neutrino oscillations after decoupling (see [23] and references therein). A full list of references can be found in [24].…”

Section: Introductionmentioning

confidence: 99%

Do observations prove that cosmological neutrinos are thermally distributed?

et al. 2005

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It is usually assumed that relic neutrinos possess a Fermi-Dirac distribution, acquired during thermal equilibrium in the Early Universe. However, various mechanisms could introduce strong distortions in this distribution. We perform a Bayesian likelihood analysis including the first moments of the three active neutrino distributions as free parameters, and show that current cosmological observations of light element abundances, Cosmic Microwave Background (CMB) anisotropies and Large Scale Structures (LSS) are compatible with very large deviations from the standard picture. We also calculate the bounds on non-thermal distortions which can be expected from future observations, and stress that CMB and LSS data alone will not be sensitive enough in order to distinguish between non-thermal distortions in the neutrino sector and extra relativistic degrees of freedom. This degeneracy could be removed by additional constraints from primordial nucleosynthesis or independent neutrino mass scale measurements.

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Late-time entropy production from scalar decay and the relic neutrino temperature

Cited by 13 publications

References 46 publications

Cosmological bounds on pseudo Nambu-Goldstone bosons

Cosmological bounds on pseudo Nambu-Goldstone bosons

Signatures of relativistic neutrinos in CMB anisotropy and matter clustering

Do observations prove that cosmological neutrinos are thermally distributed?

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