Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userScalar and tensor perturbation in vacuum inflation
82
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Recently, it was proposed that a small true vacuum universe can inflate spontaneously, in principle. Furthermore, there should be matter creation in vacuum inflation due to quantum fluctuations, and the matter created will influence the inflation simultaneously. In this paper, scalar and tensor perturbations in this model are analyzed and confronted with recent observations. These perturbations are derived and expressed with Hubble flow-functions. By comparing our calculations with experimental results, we can determine all the parameters in this model. Finally, with the determined parameters, we compute the evolution of the matter density and show that the matter produced in inflation roughly fits the observations at present.
rate research
Read More
We investigate the scalar perturbation of the inflation model driven by a massive-scalar field in Eddington-inspired Born-Infeld gravity. We focus on the perturbation at the attractor stage in which the first and the second slow-roll conditions are satisfied. The scalar perturbation exhibits the corrections to the chaotic inflation model in general relativity. We find that the tensor-to-scalar ratio becomes smaller than that of the usual chaotic inflation.
We study the scalar induced tensor perturbations at second order during matter domination in seven different gauges. Considering the obtained solution from the Newtonian gauge, we use the gauge transformation law of the scalar induced tensor perturbation to derive the solution in six other gauges. After identifying and eliminating the residual gauge modes in the synchronous and comoving orthogonal gauges, we obtain the same analytical results of the kernel function $I_{chi}$ for these two gauges as those obtained from the gauge transformation. For the scalar induced gravitational waves oscillating as $sin x$ and $cos x$, we find that $rho_{text{GW}}propto a^{-4}$, and $Omega_{text{GW}}propto 1/a$ in the matter dominated era, so the oscillating gravitational waves behave as radiation.
We investigate cosmological scenarios containing one canonical scalar field with an exponential potential in the context of bouncing models, where the bounce happens due to quantum cosmological effects. The only possible bouncing solutions in this scenario (discarding an infinitely fine tuned exception) must have one and only one dark energy phase, either occurring in the contracting era or in the expanding era. Hence,these bounce solutions are necessarily asymmetric. We calculate the spectral indexes and amplitudes of scalar and tensor perturbations numerically, considering the whole history of the model, including the bounce phase itself, without making any approximation or using any matching condition on the perturbations. As the background model is necessarily dust dominated in the far past, the usual adiabatic vacuum initial conditions can be easily imposed in this era. Hence, this is a cosmological model where the presence of dark energy behavior in the Universe does not turn problematic the usual vacuum initial conditions prescription for cosmological perturbation in bouncing models. Scalar and tensor perturbations end up being almost scale invariant, as expected. The background parameters can be adjusted, without fine tunings, to yield the observed amplitude for scalar perturbations, and also for the ratio between tensor and scalar amplitudes, $r = T/S lesssim 0.1$. The amplification of scalar perturbations over tensor perturbations takes place only around the bounce, due to quantum effects, and it would not occur if General Relativity has remained valid throughout this phase. Hence, this is a bouncing model where a single field induces not only an expanding background dark energy phase, but also produces all observed features of cosmological perturbations of quantum mechanical origin at linear order.
In this letter we investigate gauge invariant scalar fluctuations of the metric in a non-perturbative formalism for a Higgs inflationary model recently introduced in the framework of a geometrical scalar-tensor theory of gravity. In this scenario the Higgs inflaton field has its origin in the Weyl scalar field of the background geometry. We found a nearly scale invariance of the power spectrum for linear scalar fluctuations of the metric. For certain parameters of the model we obtain values for the scalar spectral index $n_s$ and the scalar to tensor ratio $r$ that fit well with the Planck 2018 results. Besides we show that in this model the trans-planckian problem can be avoided.
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.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
