Cosmologies with Light Massive Relics (LiMRs) as a subdominant component of the dark sector are w... more Cosmologies with Light Massive Relics (LiMRs) as a subdominant component of the dark sector are well-motivated from a particle physics perspective, and can also have implications for the σ8 tension between early and late time probes of clustering. The effects of LiMRs on the cosmic microwave background (CMB) and structure formation on large (linear) scales have been investigated extensively. In this paper, we initiate a systematic study of the effects of LiMRs on smaller, non-linear scales using cosmological N-body simulations; focusing on quantities relevant for photometric galaxy surveys. For most of our study, we use a particular model of non-thermal LiMRs but the methods developed generalizing to a large class of LiMR models – we explicitly demonstrate this by considering the Dodelson–Widrow velocity distribution. We find that, in general, the effects of LiMR on small scales are distinct from those of a ΛCDM universe, even when the value of σ8 is matched between the models. We s...
Recently there have been reports of finding a lower bound on the neutrino mass parameter (Σm ν ) ... more Recently there have been reports of finding a lower bound on the neutrino mass parameter (Σm ν ) when using the Atacama Cosmology Telescope (ACT) and SPTpol data; however, these bounds on the Σm ν are still weaker for most cases around the 1σ level. In this context, here in this work, we study the consequences of using an enlarged four parameter dynamical dark energy equation of state on the neutrino mass parameter as well as on the Hubble and S8 tensions. The four parameter dark energy equation of state incorporates a generic nonlinear monotonic evolution of the dark energy equation of state, where the four parameters are the early and the present value of the equation of state, the transition scale factor, and the sharpness of the transition. We report that with lensing-marginalized Planck + BAO + Pantheon and prior on absolute magnitude M B , and KIDS/Viking S 8 prior, the model favors a nonzero value for the neutrino mass parameter at most at the 1σ level ( Σ m ν = 0.1847 − 0.16...
We study the consequences of an enlarged 4 parameter dynamical dark energy (4pDE) equation of sta... more We study the consequences of an enlarged 4 parameter dynamical dark energy (4pDE) equation of state using the latest Planck, BAO, and Pantheon supernovae data. This parameterization of the dark energy equation of state incorporates a generic non-linear monotonic evolution of the dark energy equation of state, where the four parameters are the early and the present value of the equation of state, the transition scale factor, and the sharpness of the transition. In this study, we use SH0ES $M_B$ prior and the KIDS/Viking $S_8$ prior while keeping the neutrino mass $Σm_ν$ as a free parameter. We show that in this case, the dynamical dark energy 4pDE model can bring down the Hubble tension to $\sim 2.5 σ$ level and the $S_8$ tension to $\sim 1.5 σ$ level when tested against Planck, BAO, and Pantheon supernovae data together. We also compare our results with the well-explored CPL model. We find that the present data can not constrain all the four dark energy equations of state parameters...
arXiv: Cosmology and Nongalactic Astrophysics, 2021
The $\Lambda$CDM prediction of $S_8\equiv\sigma_8(\Omega_m/0.3)^{0.5}$ -- where $\sigma_8$ is the... more The $\Lambda$CDM prediction of $S_8\equiv\sigma_8(\Omega_m/0.3)^{0.5}$ -- where $\sigma_8$ is the root mean square of matter fluctuations on a 8 $h^{-1}$Mpc scale -- once calibrated on Planck CMB data is $2-3\sigma$ lower than its direct estimate by a number of weak lensing surveys. In this paper, we explore the possibility that the '$S_8$-tension' is due to a non-thermal hot dark matter (HDM) fractional contribution to the universe energy density leading to a power suppression at small-scales in the matter power spectrum. Any HDM models can be characterized by its effective mass $ m_{sp}^{\rm eff}$ and its contribution to the relativistic degrees of freedom at CMB decoupling $\Delta N_{\rm eff}$. Taking the specific example of a sterile particle produced from the decay of the inflaton during a matter dominated era, we find that from Planck only the tension can be reduced below $2\sigma$, but Planck does not favor a non-zero ${m_{sp}^{\rm eff},\Delta N_{\rm eff}}$. In combin...
Cosmologies with Light Massive Relics (LiMRs) as a subdominant component of the dark sector are w... more Cosmologies with Light Massive Relics (LiMRs) as a subdominant component of the dark sector are well-motivated from a particle physics perspective, and can also have implications for the σ8 tension between early and late time probes of clustering. The effects of LiMRs on the cosmic microwave background (CMB) and structure formation on large (linear) scales have been investigated extensively. In this paper, we initiate a systematic study of the effects of LiMRs on smaller, non-linear scales using cosmological N-body simulations; focusing on quantities relevant for photometric galaxy surveys. For most of our study, we use a particular model of non-thermal LiMRs but the methods developed generalizing to a large class of LiMR models – we explicitly demonstrate this by considering the Dodelson–Widrow velocity distribution. We find that, in general, the effects of LiMR on small scales are distinct from those of a ΛCDM universe, even when the value of σ8 is matched between the models. We s...
Recently there have been reports of finding a lower bound on the neutrino mass parameter (Σm ν ) ... more Recently there have been reports of finding a lower bound on the neutrino mass parameter (Σm ν ) when using the Atacama Cosmology Telescope (ACT) and SPTpol data; however, these bounds on the Σm ν are still weaker for most cases around the 1σ level. In this context, here in this work, we study the consequences of using an enlarged four parameter dynamical dark energy equation of state on the neutrino mass parameter as well as on the Hubble and S8 tensions. The four parameter dark energy equation of state incorporates a generic nonlinear monotonic evolution of the dark energy equation of state, where the four parameters are the early and the present value of the equation of state, the transition scale factor, and the sharpness of the transition. We report that with lensing-marginalized Planck + BAO + Pantheon and prior on absolute magnitude M B , and KIDS/Viking S 8 prior, the model favors a nonzero value for the neutrino mass parameter at most at the 1σ level ( Σ m ν = 0.1847 − 0.16...
We study the consequences of an enlarged 4 parameter dynamical dark energy (4pDE) equation of sta... more We study the consequences of an enlarged 4 parameter dynamical dark energy (4pDE) equation of state using the latest Planck, BAO, and Pantheon supernovae data. This parameterization of the dark energy equation of state incorporates a generic non-linear monotonic evolution of the dark energy equation of state, where the four parameters are the early and the present value of the equation of state, the transition scale factor, and the sharpness of the transition. In this study, we use SH0ES $M_B$ prior and the KIDS/Viking $S_8$ prior while keeping the neutrino mass $Σm_ν$ as a free parameter. We show that in this case, the dynamical dark energy 4pDE model can bring down the Hubble tension to $\sim 2.5 σ$ level and the $S_8$ tension to $\sim 1.5 σ$ level when tested against Planck, BAO, and Pantheon supernovae data together. We also compare our results with the well-explored CPL model. We find that the present data can not constrain all the four dark energy equations of state parameters...
arXiv: Cosmology and Nongalactic Astrophysics, 2021
The $\Lambda$CDM prediction of $S_8\equiv\sigma_8(\Omega_m/0.3)^{0.5}$ -- where $\sigma_8$ is the... more The $\Lambda$CDM prediction of $S_8\equiv\sigma_8(\Omega_m/0.3)^{0.5}$ -- where $\sigma_8$ is the root mean square of matter fluctuations on a 8 $h^{-1}$Mpc scale -- once calibrated on Planck CMB data is $2-3\sigma$ lower than its direct estimate by a number of weak lensing surveys. In this paper, we explore the possibility that the '$S_8$-tension' is due to a non-thermal hot dark matter (HDM) fractional contribution to the universe energy density leading to a power suppression at small-scales in the matter power spectrum. Any HDM models can be characterized by its effective mass $ m_{sp}^{\rm eff}$ and its contribution to the relativistic degrees of freedom at CMB decoupling $\Delta N_{\rm eff}$. Taking the specific example of a sterile particle produced from the decay of the inflaton during a matter dominated era, we find that from Planck only the tension can be reduced below $2\sigma$, but Planck does not favor a non-zero ${m_{sp}^{\rm eff},\Delta N_{\rm eff}}$. In combin...
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Papers by Ravi Kumar Sharma