相关论文: Probing Lepton Asymmetry with 21 cm Fluctuations
Amongst standard model parameters that are constrained by cosmic microwave background (CMB) observations, the optical depth $\tau$ stands out as a nuisance parameter. While $\tau$ provides some crude limits on reionization, it also degrades…
We use the Wilkinson Microwave Anisotropy Probe (WMAP) data on the spectrum of cosmic microwave background anisotropies to put constraints on the present amount of lepton asymmetry L, parameterized by the dimensionless chemical potential…
There can arise ubiquitous ultra-light scalar fields in the Universe, such as the pseudo-Goldstone bosons from the spontaneous breaking of an approximate symmetry, which can make a partial contribution to the dark matter and affect the…
Primordial Big-Bang Nucleosynthesis (BBN) tightly constrains the existence of any additional relativistic degrees of freedom at that epoch. However a large asymmetry in electron neutrino number shifts the chemical equilibrium between the…
We present new Big Bang Nucleosynthesis (BBN) limits on the cosmic expansion rate or relativistic energy density, quantified via the number $N_\nu$ of equivalent neutrino species. We use the latest light element observations, neutron mean…
The 21-cm line fluctuations and the cosmic microwave background (CMB) are powerful probes of the epoch of reionisation of the universe. We study the potential of the cross-correlation between 21-cm line fluctuations and CMB anisotropy to…
The 21-cm brightness temperature fluctuation from the Dark Ages ($z \simeq 30-100$) will allow us to probe the inflationary epoch on very small scales ($>0.1 \, \mbox{Mpc}^{-1}$), inaccessible to cosmic microwave background experiments.…
Neutral hydrogen is ubiquitous, absorbing and emitting 21 cm radiation throughout much of the Universe's history. Active sources of perturbations, such as cosmic strings, would generate simultaneous perturbations in the distribution of…
In this paper, we put constraints on neutrino properties such as mass $m_{\nu}$ and degeneracy parameters $\xi_i$ from WMAP5 data and light element abundances by using a Markov chain Monte Carlo (MCMC) approach. In order to take…
We present cosmological constraints on deviations of Newton's constant at large scales, analyzing latest cosmic microwave background (CMB) anisotropies and primordial abundances of light elements synthesized by big bang nucleosynthesis…
We focus on the ongoing and future observations for both the 21 cm line and the CMB B-mode polarization produced by a CMB lensing, and study their sensitivities to the effective number of neutrino species, the total neutrino mass, and the…
A large neutrino asymmetry is an interesting possibility for cosmology, which can have significant observable consequences for nucleosynthesis and the cosmic microwave background. However, although it is a possibility, there is no obvious…
In this article, we study the implications of the coupling between Axion-Like-Particles (ALPs) and Leptons to cosmology, in particular, the Big Bang Nucleosynthesis (BBN). We show that the BBN, through the constraint on the effective number…
We present constraints on the number of relativistic species from a joint analysis of cosmic microwave background (CMB) fluctuations and light element abundances (helium and deuterium) compared to big bang nucleosynthesis (BBN) predictions.…
Spectral distortions of the Cosmic Microwave Background (CMB) offer the possibility of probing processes which occurred during the evolution of our Universe going back up to Z$\simeq 10^7$. Unfortunately all the attempts so far carried out…
Physical models for the hemispherical power asymmetry in the cosmic microwave background (CMB) reported by the Planck Collaboration must satisfy CMB constraints to the homogeneity of the Universe and quasar constraints to power asymmetries.…
We provide a fresh look at the cosmological constraints on axion-like particles (ALPs) that couple predominantly to photons, focusing on lifetimes $\tau_{a} \lesssim 10^{4}\, {\rm s}$ and masses $m_a\lesssim 10\,{\rm GeV}$. We consider Big…
The increasing precision of Cosmic Microwave Background (CMB) observations has unveiled significant tensions between different datasets, notably between Planck and the Atacama Cosmology Telescope (ACT), as well as with the late-Universe…
The bounds on neutrino masses and mixing that follows from the data on light element abundances, large scale structure formation, and angular fluctuations of cosmic microwave background radiation are analyzed. The role of neutrino…
Massive neutrinos modify the expansion history of the universe and suppress the structure formation below their free streaming scale. Cosmic microwave background (CMB) observations at small angular scales can be used to constrain the total…