For more than twenty years, it has been argued that the Weyl anomaly of quantum electrodynamics sources cosmological magnetic fields in the early universe. If true, this would be a natural way to produce the seed magnetic fields of our universe within the Standard Model. In this talk, I will examine this long-standing claim and show that there is actually no production of coherent magnetic...
The primordial magnetic fields (PMFs) are expected to be generated in the early universe, and they are a possible origin of the present galactic magnetic fields. In this talk, we suggest a novel method to investigate the PMFs with 21-cm line observation. The recent observation of the 21-cm global absorption signal by EDGES suggests that the intergalactic medium (IGM) gas has been cooler than...
It has been found that baryon asymmetry of the Universe (BAU) can be generated without introducing any new physical ingredients beyond the Standard Model (SM) from the chiral asymmetry of the SM, if there exist helical hypermagnetic fields before the electroweak symmetry breaking. Then in order to explain the BAU, we need the physics beyond the SM to generate large-scale hypermagnetic fields....
Although it is commonly assumed that the physics of inflation and the subsequent reheating epoch can be understood by means of simple effective field theories, there is no guarantee that this reductionist point of view is realized. In fact, some UV completions of inflation tend to involve many fields, with complicated interactions that can lead to significant elements of randomness in the...
Multiple scalar fields nonminimally interacting through pure affine gravity are considered to generate primordial perturbations during an inflationary phase. The couplings considered give rise to two distinct sources of entropy perturbations that may not be suppressed in the long wavelength limit. The first is merely induced by the presence of more than one scalar and arises even in the...
In this talk I will show that a simple model of Dirac neutrinos that self-interact only through their right-handed components can naturally realize the self-interacting neutrino solution of the Hubble tension while evading all the cosmological or laboratory bounds.
It has been discussed by Gregory et al. that small blackholes would catalyze vacuum phase transitions. We investigate such phase transition including the (inhomogeneous) thermal effect of Hawking radiation and calculate the bounce action numerically. I will show that the transition rate can be slightly suppressed by the thermal effect of Hawking radiation. I will also mention an application to...
The Minimal Dark Matter (MDM) model suggested by Cirelli et al. is an extended model that introduces one SU (2) _L multiplet to the Standard Model so that the neutral component of the multiplet plays as the role of dark matter (DM). On the other hand, the stability of DM is not guaranteed because there is no mechanism to inhibit the DM decay process. We have built a model that makes DM...
In this paper, we investigate the dark energy phenomenon by studying the Tsallis holographic dark energy within the framework of Brans–Dicke (BD) scalar–tensor theory of gravity (Brans and Dicke in Phys. Rev. 124:925, 1961). In this context, we choose the BD scalar field ϕ as a logarithmic function of the average scale factor a(t) and Hubble horizon as the IR cutoff ( L=H^{−1} ). We...
In this paper, the stability analysis of an anisotropic dark energy cosmological model in a two fluid situations has been investigated. We have assumed that the dark energy pressure to be anisotropic in different spatial directions. several diagnostic analysis such as Om diagnostic, state finder analysis has also been incorporated and analysed. The results obtained are in accordance with the...
We discuss probes of dark matter with chirping GWs. The example dark matter candidates include primordial black holes and axion-like particles. We first discuss lensing observables of primordial black holes: GW fringes and GRB lensing parallax. They finally allow probing a whole range of the PBH mass range with lensing. Then we discuss the disturbance due to dark matter waves in the...
We revisit the gravitational leptogenesis scenario in which the lepton asymmetry is generated by circularly polarized gravitational waves during inflation, through the gravitational anomaly in the lepton number current. We consider a specific model in which the inflaton is coupled to gravity by the Chern-Simons term, and constrain the possible model parameter space by requiring the absence of...
