We consider the SN1987A supernova cooling bound on axions and other light particles. Core collapse simulations used in the literature to substantiate the bound omitted from the calculation the envelope exterior to the proto-neutron star (PNS). As a result, the only source of neutrinos in these simulations was, by construction, a cooling PNS. We show that if the delayed neutrino mechanism...
After reviewing basic aspects of 21cm brightness temperature observation from the epoch of reionization, we will discuss the 21cm forest, that is, systems of narrow absorption lines due to intervening, cold neutral hydrogen in the spectra of high-redshift background radio sources in the cosmic reionization epoch. We will show that the 21cm forest observations are very sensitive to the mass of...
I discuss how one can probe the primordial Universe by using the neutral hydrogen 21 cm line, particularly focusing on primordial fluctuations. After briefly reviewing the physics of 21cm line, I discuss how the 21cm global signal, such as observed by EDGES, can probe small-scale primordial power spectrum. I also discuss the prospect of probing primordial non-Gaussianities with 21cm line. I...
Strong gravitational lens systems with time delays between the multiple images are a powerful probe of cosmology, particularly of the Hubble constant (H0) that is key to probing dark energy, neutrino physics, and the spatial curvature of the Universe, as well as discovering new physics. The H0 Lenses In COSMOGRAIL’s Wellspring (H0LiCOW) project has measured H0 from lensed quasars using deep...
In this talk, we propose a model for a dark matter (and dark sector) which is in complete decoupling with the Standard model sector. In an effort to identify DM's stability, mass and interaction type it does, we pay a special attention to two arguments that concern the Hubble tension and the core-cusp problem. Thereby, we aim at presenting a possibility of having a light decaying fermion DM...
The nature of dark matter (DM) is still a big mystery. Among the varieties of candidates, Weakly Interacting Massive Particle (WIMP) is one of the most promising ones. Gamma-ray observations of dwarf spheroidal galaxies (dSphs) by Fermi satellites put the strongest constraints at mDM~ < a few hundreds of GeV. In the near future, Cherenkov Telescope Array (CTA) starts its operations and expect...
Gravitational wave sources accompanied by electromagnetic counterparts
offer an independent standard siren measurement of the Hubble constant as
demonstrated following the discovery of the first neutron star merger, GW170817.
This measurement does not assume a cosmological model and is independent of
a cosmic distance ladder. I will talk about the first result of the Hubble constant...
