We present small-scale structure constraints on sterile dark matter produced from a heavy mediato... more We present small-scale structure constraints on sterile dark matter produced from a heavy mediator particle, inspired by models of moduli decay. Dark matter particles produced through this mechanism can contribute to the entire dark matter energy density but the particles have a nonthermal phase-space distribution; however, we show that the resulting linear matter power spectra can be mapped to effective thermal-relic warm dark matter models. This production mechanism is therefore subject to warm dark matter constraints from smallscale structure as probed by ultrafaint dwarf galaxy abundances and strong gravitational lensing flux ratio statistics. We use the correspondence to thermal-relic models to derive a lower bound on the nonthermal particle mass of 107 keV, at 95% confidence limits. These are the most stringent constraints derived on sterile dark matter produced via the heavy mediator decay scenario we consider.
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...
The ΛCDM prediction of S8 ≡ σ8(Ωm/0.3) 0.5-where σ8 is the root mean square of matter fluctuation... more The ΛCDM prediction of S8 ≡ σ8(Ωm/0.3) 0.5-where σ8 is the root mean square of matter fluctuations on 8 h −1 Mpc scale-once calibrated on Planck CMB data is 2 − 3σ lower than its direct estimate by a number of weak lensing surveys. In this paper, we explore the possibility that the 'S8-tension' is due to a fractional contribution of non-thermal hot dark matter (HDM) to the energy density of the universe leading to a power suppression at small-scales in the matter power spectrum. Any HDM model can be characterized by its effective mass m eff sp and its contribution to the relativistic degrees of freedom at CMB decoupling ∆N eff. Taking the specific example of a sterile particle produced from the decay of the inflaton during an early matter-dominated era, we find that the tension can be reduced below 2σ from Planck data only, but it does not favor a nonzero {m eff sp , ∆N eff }. In combination with a measurement of S8 from KIDS1000+BOSS+2dfLenS, the S8-tension would hint at the existence of a particle of mass m eff sp 0.67 +0.26 −0.48 eV with a contribution to ∆N eff 0.06 ± 0.05. However, Pantheon and BOSS BAO/f σ8 data restricts the particle mass to m eff sp 0.48 +0.17 −0.36 and contribution to ∆N eff 0.046 +0.004 −0.031. We discuss implications of our results for other canonical non-thermal HDM models-the Dodelson-Widrow model and a hidden sector model of a thermal sterile particle with a different temperature. We report competitive results on such hidden sector temperature which might have interesting implications for particle physics model building, in particular connecting the S8-tension to the longstanding short baseline oscillation anomaly.
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...
We present a novel scenario, in which light (∼ few eV) dark fermions (sterile neutrinos) interact... more We present a novel scenario, in which light (∼ few eV) dark fermions (sterile neutrinos) interact with a scalar field like in mass varying neutrino dark energy theories. As the eV sterile states naturally become non-relativistic before the Matter Radiation Equality (MRE), we show that the neutrino-scalar fluid develops strong perturbative instability followed by the formation of neutrino-nuggets and the early dark energy behaviour disappears around MRE. The stability of the nugget is achieved when the Fermi pressure balances the attractive scalar force and we numerically find the mass and radius of heavy cold nuggets by solving for the static configuration for the scalar field. We find that for the case when DM nugget density is subdominant and most of the early DE energy goes into scalar field dynamics, it can in principle relax the Hubble anomaly. Especially when a kinetic energy dominated phase appears after the phase transition, the DE density dilutes faster than radiation and satisfy the requirements for solving H 0 anomaly. In our scenario, unlike in originally proposed early dark energy theory, the dark energy density is controlled by (eV) neutrino mass and it does not require a fine tuned EDE scale. We perform a MCMC analysis and confront our model with Planck + SH0ES and BAO data and find an evidence for non-zero neutrino-scalar EDE density during MRE. Our analysis shows that this model is in agreement of nearly 1.3σ with SH0ES measurement which is H 0 = 74.03 ± 1.42 km/s/Mpc.
We present small-scale structure constraints on sterile dark matter produced from a heavy mediato... more We present small-scale structure constraints on sterile dark matter produced from a heavy mediator particle, inspired by models of moduli decay. Dark matter particles produced through this mechanism can contribute to the entire dark matter energy density but the particles have a nonthermal phase-space distribution; however, we show that the resulting linear matter power spectra can be mapped to effective thermal-relic warm dark matter models. This production mechanism is therefore subject to warm dark matter constraints from smallscale structure as probed by ultrafaint dwarf galaxy abundances and strong gravitational lensing flux ratio statistics. We use the correspondence to thermal-relic models to derive a lower bound on the nonthermal particle mass of 107 keV, at 95% confidence limits. These are the most stringent constraints derived on sterile dark matter produced via the heavy mediator decay scenario we consider.
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...
The ΛCDM prediction of S8 ≡ σ8(Ωm/0.3) 0.5-where σ8 is the root mean square of matter fluctuation... more The ΛCDM prediction of S8 ≡ σ8(Ωm/0.3) 0.5-where σ8 is the root mean square of matter fluctuations on 8 h −1 Mpc scale-once calibrated on Planck CMB data is 2 − 3σ lower than its direct estimate by a number of weak lensing surveys. In this paper, we explore the possibility that the 'S8-tension' is due to a fractional contribution of non-thermal hot dark matter (HDM) to the energy density of the universe leading to a power suppression at small-scales in the matter power spectrum. Any HDM model can be characterized by its effective mass m eff sp and its contribution to the relativistic degrees of freedom at CMB decoupling ∆N eff. Taking the specific example of a sterile particle produced from the decay of the inflaton during an early matter-dominated era, we find that the tension can be reduced below 2σ from Planck data only, but it does not favor a nonzero {m eff sp , ∆N eff }. In combination with a measurement of S8 from KIDS1000+BOSS+2dfLenS, the S8-tension would hint at the existence of a particle of mass m eff sp 0.67 +0.26 −0.48 eV with a contribution to ∆N eff 0.06 ± 0.05. However, Pantheon and BOSS BAO/f σ8 data restricts the particle mass to m eff sp 0.48 +0.17 −0.36 and contribution to ∆N eff 0.046 +0.004 −0.031. We discuss implications of our results for other canonical non-thermal HDM models-the Dodelson-Widrow model and a hidden sector model of a thermal sterile particle with a different temperature. We report competitive results on such hidden sector temperature which might have interesting implications for particle physics model building, in particular connecting the S8-tension to the longstanding short baseline oscillation anomaly.
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...
We present a novel scenario, in which light (∼ few eV) dark fermions (sterile neutrinos) interact... more We present a novel scenario, in which light (∼ few eV) dark fermions (sterile neutrinos) interact with a scalar field like in mass varying neutrino dark energy theories. As the eV sterile states naturally become non-relativistic before the Matter Radiation Equality (MRE), we show that the neutrino-scalar fluid develops strong perturbative instability followed by the formation of neutrino-nuggets and the early dark energy behaviour disappears around MRE. The stability of the nugget is achieved when the Fermi pressure balances the attractive scalar force and we numerically find the mass and radius of heavy cold nuggets by solving for the static configuration for the scalar field. We find that for the case when DM nugget density is subdominant and most of the early DE energy goes into scalar field dynamics, it can in principle relax the Hubble anomaly. Especially when a kinetic energy dominated phase appears after the phase transition, the DE density dilutes faster than radiation and satisfy the requirements for solving H 0 anomaly. In our scenario, unlike in originally proposed early dark energy theory, the dark energy density is controlled by (eV) neutrino mass and it does not require a fine tuned EDE scale. We perform a MCMC analysis and confront our model with Planck + SH0ES and BAO data and find an evidence for non-zero neutrino-scalar EDE density during MRE. Our analysis shows that this model is in agreement of nearly 1.3σ with SH0ES measurement which is H 0 = 74.03 ± 1.42 km/s/Mpc.
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Papers by Ravi Kumar Sharma