The origin of the accelerated expansion of the Universe remains an unsolved mystery in Cosmology. In this work we consider a spatially flat Friedmann-Robertson-Walker (FRW) Universe with non-relativistic matter and a single scalar field contributing to the energy density of the Universe. Properties of this scalar field, like potential, kinetic energy, equation of state etc. are reconstructed from Supernovae and BAO data using Gaussian processes. We also reconstruct energy conditions and kinematic variables of expansion, such as the jerk and the slow roll parameter. We find that the reconstructed scalar field variables and the kinematic quantities are consistent with a flat Lambda-CDM Universe. Further we find that the null energy condition is satisfied for the redshift range of the Supernovae data considered in the paper but, the strong energy condition is violated.
We detail a novel theoretical prediction that a geometric torsion model for scalar field dark matter could lead to oscillations, on readily probeable timescales, in the time evolution of cosmological redshifts of astronomical sources with qualitatively distinct behavior at different redshift scales (larger or smaller than z ~ 0.1). We present an analysis of extant spectroscopy data from the Australian Dark Energy Survey (OzDES) to assess whether such signals are present across a wide array of cosmological sources and baseline redshifts on the six-year timescale of OzDES. While a simple Fourier…
There is a growing expectation that the gravitational wave detectors will start probing the stochastic gravitational wave backgrounds in the following years. We explore the spectral shapes of gravitational waves induced to second order by scalar perturbations and presumably have been produced in the early universe. We calculate the gravitational wave spectra generated during radiation and kination eras together with the associated primordial black hole counterpart. We employ power spectra for the primordial curvature perturbation generated by $α$-attractors and nonminimal derivative coupling i…
While large scale primordial non-Gaussianity is strongly constrained by present-day data, there are no such constraints at Mpc scales. Here we investigate the effect of significant small-scale primordial non-Gaussianity on structure formation and the galaxy formation process with collisionless simulations: specifically, we explore four different types of non-Gaussianities. All of these prescriptions lead to a distinct and potentially detectable feature in the matter power spectrum around the non-linear scale. The feature might have interesting consequences for the $S_8$ tension. We then show i…
We study the parameter space of the effective (with two scalars) models of cosmological inflation and primordial black hole (PBH) formation in the modified $(R+R^2)$ supergravity. Our models describe double inflation, whose first stage is driven by Starobinsky's scalaron coming from the $R^2$ gravity, and whose second stage is driven by another scalar belonging to the supergravity multiplet. The ultra-slow-roll regime between the two stages leads a large peak (enhancement) in the power spectrum of scalar perturbations, which results in efficient PBH formation. Both inflation and PBH formation …
Inflation without an Inflaton III: non-Gaussian signatures
Scuola Superiore Meridionale（南方高等学院）；INFN, Sezione di Napoli（意大利国家核物理研究所那不勒斯分部）；Cairo University（开罗大学）；ICC, University of Barcelona（巴塞罗那大学天文研究中心）；ICREA（加泰罗尼亚高级研究学院）；Dipartimento di Fisica e Astronomia Galileo Galilei, Università degli Studi di Padova（帕多瓦大学伽利略·伽利莱物理与天文学系）；INFN, Sezione di Padova（意大利国家核物理研究所帕多瓦分部）；INAF-Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）；Gran Sasso Science Institute（格兰萨索科学研究所）；Università di Pisa（比萨大学）
We study the cosmology of the dark sector consisting of (ultra) light scalars. Since the scalar mass is radiatively unstable, a special explanation is required to make the mass much smaller than the UV scale. There are two well-known mechanisms for the origin of scalar mass. The scalar can be identified as a pseudo-Goldstone boson, whose shift symmetry is explicitly broken by non-perturbative corrections, like the axion. Alternatively, it can be identified as a composite particle like the glueball, whose mass is limited by the confinement scale of the theory. In both cases, the scalar can be n…
We study primordial non-gaussianity in supersolid inflation. The dynamics of supersolid is formulated in terms of an effective field theory based on four scalar fields with a shift symmetric action minimally coupled with gravity. In the scalar sector, there are two phonon-like excitations with a kinetic mixing stemming from the completely spontaneous breaking of diffeomorphism. In a squeezed configuration, $f_{\text{NL}}$ of scalar perturbations is angle dependent and not proportional to slow-roll parameters showing a blunt violation of the Maldacena consistency relation. Contrary to solid inf…
