The spectrum of energy density fluctuations, baryon asymmetry, and coherent large-scale magnetic fields are the three observables that provide crucial information on physics at very high energies. Inflation can only provide a mechanism to explain the density perturbations, and the origin of primordial magnetic fields and baryon asymmetry require physics beyond the standard models of cosmology and particle physics. In this work, we show that the mechanism that leads to primordial helical fields also leads to baryogenesis at the beginning of the radiation-dominated epoch. The model we consider here consists of mass dimension 6 operators that include Riemann coupling between gravity and electromagnetic field without extending the Standard Model of particle physics. We explicitly show that the generation of helical magnetic fields leads to baryogenesis.We further show that the model predicts the observed amount of baryon asymmetry of the Universe for a range of reheating temperatures consistent with the observations.

We construct a consistent model of Galileon scalar electrodynamics. The model satisfies three essential requirements: (1) The action contains higher-order derivative terms, and obey the Galilean symmetry, (2) Equations of motion also satisfy Galilean symmetry and contain only up to secondorder derivative terms in the matter fields and, hence do not suffer from instability, and (3) local U (1) gauge invariance is preserved. We show that the non-minimal coupling terms in our model are different from that of the real scalar Galileon models; however, they match with the Galileon real scalar field action. We show that the model can lead to an accelerated expansion in the early Universe. We discuss the implications of the model for cosmological inflation. * ashu712@iitb.ac.in † shanki@phy.iitb.ac.in

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We present a novel model that explains the origin of Fast Radio Bursts (FRBs) -short (< 1 s), bright (0.1 − 1000 Jy) bursts of GHz frequency radio waves. The model has three ingredients -compact object, progenitor with effective magnetic field strength around 10 10 Gauss, and GHz frequency gravitational waves (GWs). The energy conversion from GWs to electromagnetic waves occurs when GWs pass through the magnetosphere of such compact objects due to the Gertsenshtein-Zel'dovich effect. This conversion produces bursts of electromagnetic waves in the GHz range, leading to FRBs. Our model has three key features: (i) can generate peak-flux up to 1000 Jy, (ii) can naturally explain the pulse-width and (iii) predict FRB's random and repeating nature with a wide flux range. We thus conclude that the millisecond pulsars could be the progenitor of FRBs. Further, our model offers a novel perspective on the indirection detection of GWs at high-frequency beyond detection capabilities. Thus, transient events like FRBs are a rich source for the current era of multi-messenger astronomy.

There is growing evidence for high-frequency gravitational waves (HFGWs) ranging from MHz to GHz. Several HFGW detectors have been operating for over a decade, and two GHz events have been reported recently. However, a confirmed detection might take a decade. This essay argues that unexplained observed astrophysical phenomena, like Fast Radio Bursts (FRBs), might provide indirect evidence for HFGWs. In particular, using the Gertsenshtein–Zel’dovich effect, we show that our model can explain three key features of FRBs: generate peak-flux up to [Formula: see text], naturally explain the pulse width and the coherent nature of FRBs. In short, our model offers a novel perspective on the indirection detection of HFGWs beyond current detection capabilities. Thus, transient events like FRBs are a rich source for multi-messenger astronomy.