Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userBounds on very low reheating scenarios after Planck
103
0
0.0
(
0
)
Added by
Massimiliano Lattanzi
Publication date
2015
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We consider the case of very low reheating scenarios ($T_{rm RH}simmathcal{O}({rm MeV})$) with a better calculation of the production of the relic neutrino background (with three-flavor oscillations). At 95% confidence level, a lower bound on the reheating temperature $T_{rm RH}>4.1$ MeV is obtained from Big Bang Nucleosynthesis, while $T_{rm RH}>4.3$ MeV from Planck data for very light ($sum m_i = 0.06$ eV) neutrinos. If neutrino masses are allowed to vary, Planck data yield $T_{rm RH}>4.7$ MeV, the most stringent bound on the reheating temperature to date. Neutrino masses as large as 1 eV are possible for very low reheating temperatures.
rate research
Read More
We use cosmological observations in the post-Planck era to derive limits on thermally produced cosmological axions. In the early universe such axions contribute to the radiation density and later to the hot dark matter fraction. We find an upper limit m_a < 0.67 eV at 95% C.L. after marginalising over the unknown neutrino masses, using CMB temperature and polarisation data from Planck and WMAP respectively, the halo matter power spectrum extracted from SDSS-DR7, and the local Hubble expansion rate H_0 released by the Carnegie Hubble Program based on a recalibration of the Hubble Space Telescope Key Project sample. Leaving out the local H_0 measurement relaxes the limit somewhat to 0.86 eV, while Planck+WMAP alone constrain the axion mass to 1.01 eV, the first time an upper limit on m_a has been obtained from CMB data alone. Our axion limit is therefore not very sensitive to the tension between the Planck-inferred H_0 and the locally measured value. This is in contrast with the upper limit on the neutrino mass sum, which we find here to range from 0.27 eV at 95% C.L. combining all of the aforementioned observations, to 0.84 eV from CMB data alone.
We revise cosmological mass bounds on hadronic axions in low-reheating cosmological scenarios, with a reheating temperature $T_{rm RH}~le 100$ MeV, in light of the latest cosmological observations. In this situation, the neutrino decoupling would be unaffected, while the thermal axion relic abundance is suppressed. Moreover, axions are colder in low-reheating temperature scenarios, so that bounds on their abundance are possibly loosened. As a consequence of these two facts, cosmological mass limits on axions are relaxed. Using state-of-the-art cosmological data and characterizing axion-pion interactions at the leading order in chiral perturbation theory, we find in the standard case an axion mass bound $m_a < 0.26$ eV. However, axions with masses $m_a simeq 1$ eV, or heavier, would be allowed for reheating temperatures $T_{rm RH} lesssim 80$ MeV. Multi-eV axions would be outside the mass sensitivity of current and planned solar axion helioscopes and would demand new experimental approaches to be detected.
The Planck collaboration has recently published maps of the Cosmic Microwave Background radiation with the highest precision. In the standard flat $Lambda$CDM framework, Planck data show that the Hubble constant $H_0$ is in tension with that measured by the several direct probes on $H_0$. In this paper, we perform a global analysis from the current observational data in the general dark energy models and find that resolving this tension on $H_0$ requires the dark energy model with its equation of state (EoS) $w eq-1$. Firstly, assuming the $w$ to be a constant, the Planck data favor $w < -1$ at about $2,sigma$ confidence level when combining with the supernovae SNLS compilation. And consequently the value derived on $H_0$, $H_0=71.3pm2.0$ ${rm km,s^{-1},Mpc^{-1}}$ (68% C.L.), is consistent with that from direct $H_0$ probes. We then investigate the dark energy model with a time-evolving $w$, and obtain the 68% C.L. constraints $w_0=-0.81pm0.19$ and $w_a=-1.9pm1.1$ from the Planck data and the SNLS compilation. Current data still slightly favor the Quintom dark energy scenario with EoS across the cosmological constant boundary $wequiv-1$.
We present strong bounds on the sum of three active neutrino masses ($sum m_{ u}$) in various cosmological models. We use the following baseline datasets: CMB temperature data from Planck 2015, BAO measurements from SDSS-III BOSS DR12, the newly released SNe Ia dataset from Pantheon Sample, and a prior on the optical depth to reionization from 2016 Planck Intermediate results. We constrain cosmological parameters in $Lambda CDM$ model with 3 massive active neutrinos. For this $Lambda CDM+sum m_{ u}$ model we find a upper bound of $sum m_{ u} <$ 0.152 eV at 95$%$ C.L. Adding the high-$l$ polarization data from Planck strengthens this bound to $sum m_{ u} <$ 0.118 eV, which is very close to the minimum required mass of $sum m_{ u} simeq$ 0.1 eV for inverted hierarchy. This bound is reduced to $sum m_{ u} <$ 0.110 eV when we also vary r, the tensor to scalar ratio ($Lambda CDM+r+sum m_{ u}$ model), and add an additional dataset, BK14, the latest data released from the Bicep-Keck collaboration. This bound is further reduced to $sum m_{ u} <$ 0.101 eV in a cosmology with non-phantom dynamical dark energy ($w_0 w_a CDM+sum m_{ u}$ model with $w(z)geq -1$ for all $z$). Considering the $w_0 w_a CDM+r+sum m_{ u}$ model and adding the BK14 data again, the bound can be even further reduced to $sum m_{ u} <$ 0.093 eV. For the $w_0 w_a CDM+sum m_{ u}$ model without any constraint on $w(z)$, the bounds however relax to $sum m_{ u} <$ 0.276 eV. Adding a prior on the Hubble constant ($H_0 = 73.24pm 1.74$ km/sec/Mpc) from Hubble Space Telescope (HST), the above mentioned bounds further improve to $sum m_{ u} <$ 0.117 eV, 0.091 eV, 0.085 eV, 0.082 eV, 0.078 eV and 0.247 eV respectively. This substantial improvement is mostly driven by a more than 3$sigma$ tension between Planck 2015 and HST measurements of $H_0$ and should be taken cautiously. (abstract abridged)
We calculate high-precision constraints on Natural Inflation relative to current observational constraints from Planck 2018 + BICEP/Keck(BK15) Polarization + BAO on $r$ and $n_S$, including post-inflationary history of the universe. We find that, for conventional post-inflationary dynamics, Natural Inflation with a cosine potential is disfavored at greater than 95% confidence out by current data. If we assume protracted reheating characterized by $overline{w}>1/3,$ Natural Inflation can be brought into agreement with current observational constraints. However, bringing unmodified Natural Inflation into the 68% confidence region requires values of $T_{mathrm{re}}$ below the scale of electroweak symmetry breaking. The addition of a SHOES prior on the Hubble Constant $H_0$ only worsens the fit.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
