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Register a new userGravitational mechanism for baryogenesis in the cosmological QCD phase transition
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One of the biggest puzzles in modern cosmology is the observed baryon asymmetry in the universe. In current models of baryogenesis gravity plays a secondary role, although the process is believed to have happened in the early universe, under the influence of an intense gravitational field. In the present work we resume Sakharovs original program for baryogenesis and propose a central role for gravity in the process. This is achieved through a non-minimal coupling (NMC) between the gravitational field and both the strong interaction field and the quark fields. When in action, the present mechanism leads to baryon number non-conservation and CP violation. Moreover, the NMC induces reduced effective quark masses, which favours a first order QCD phase transition. As a consequence, a baryon asymmetry can be attained in the transition from the quark epoch to the hadron epoch.
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We investigate how baryogenesis can occur by the presence of an $f(T)$-related gravitational term. We study various cases of $f(T)$ gravity and we discuss in detail the effect of the novel terms on the baryon-to-entropy ratio. Additionally, we study the constraints imposed by the observational values of the baryon-to-entropy ratio and we discuss how more generalized cosmologies can contribute successfully, in a viable and consistent way, in the gravitational baryogenesis mechanism.
We explore the possibility of baryogenesis in the framework of quintessential inflation. We focus on the model independent features of the underlying paradigm and demonstrate that the required baryon asymmetry can successfully be generated in this scenario. To this effect, we use the effective field theory framework with desired terms in the Lagrangian necessary to mimic baryon number violation textit{`{a} la} spontaneous baryogenesis which can successfully evade Sakharovs requirement allowing us to generate the observed baryon asymmetry in the equilibrium process. Our estimates are independent of the underlying physical process responsible for baryon number violation. The underlying framework of quintessential inflation essentially includes the presence of kinetic regime after inflation which gives rise to blue spectrum of gravitational wave background at high frequencies. In addition to baryogenesis, we discuss the prospects of detection of relic gravitational wave background, in the future proposed missions, sticking to model independent treatment.
We show that in the vacuum inflation model, the gravitational baryogenesis mechanism will produce the baryon asymmetry. We analyze the evolution of entropy and baryon number in the vacuum inflation model. The comparison between dilution speed and the chemical potential may give a natural interpretation for decouple temperature of the gravitational baryogenesis interaction. From the result, the mechanism can give acceptable baryon-to-entropy ratio in the vacuum inflation model.
The standard model of particle physics is known to be intriguingly successful. However their rich phenomena represented by the phase transitions (PTs) have not been completely understood yet, including the possibility of the existence of unknown dark sectors. In this Letter, we investigate the measurement of the equation of state parameter $w$ and the sound speed $c_{rm s}$ of the PT plasma with use of the gravitational waves (GWs) of the universe. Though the propagation of GW is insensitive to $c_{rm s}$ in itself, the sound speed value affects the dynamics of primordial density (or scalar curvature) perturbations and the induced GW by their horizon reentry can then be an indirect probe both $w$ and $c_{rm s}$. We numerically reveal the concrete spectrum of the predicted induced GW with two simple examples of the scalar perturbation spectrum: the monochromatic and scale-invariant spectra. In the monochromatic case, we see that the resonant amplification and cancellation scales of the induced GW depend on the $c_{rm s}$ values at different time respectively. The scale-invariant case gives a more realistic spectrum and its specific shape will be compared with observations. In particular, the QCD phase transition corresponds with the frequency range of the pulsar timing array (PTA) observations. If the amplitude of primordial scalar power is in the range of $10^{-4}lesssim A_zetalesssim10^{-2}$, the induced GW is consistent with current observational constraints and detectable in the future observation in Square Kilometer Array. Futhermore the recent possible detection of stochastic GWs by NANOGrav 12.5 yr analysis~[1] can be explained by the induced GW if $A_zetasimsqrt{7}times10^{-3}$.
A dynamical resolution to the cosmological constant fine-tuning problem has been previously put forward, based on a scalar-tensor gravitational theory possessing de Sitter attractor solutions characterized by a small Hubble expansion rate, irrespective of an initially large vacuum energy. We show that a technically natural subregion of the parameter space yields a cosmological evolution through radiation- and matter-dominated eras that is essentially indistinguishable from that predicted by General Relativity. Similarly, the proposed model automatically satisfies the observational constraints on a fifth force mediated by the new scalar degree of freedom.
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