Related papers: Einstein or Jordan: seeking answers from the rehea…
We initiate a study of the gravitational-wave signatures of a phase transition that occurs as the Universe's temperature increases during reheating. The gravitational-wave signatures of such a heating phase transition are different from…
We investigate the imprint of post-inflationary evolution on primordial cosmological correlators by relaxing the standard assumption of instantaneous reheating. We compute the power spectrum and bispectrum for a conformally coupled and…
We study cosmological perturbations in generalized Einstein scenarios and show the equivalence of inflationary observables both in the Jordan frame and the Einstein frame. In particular the consistency relation relating the tensor-to-scalar…
We describe a simple way of incorporating fluctuations of the Hubble scale during the horizon exit of scalar perturbations into the delta N formalism. The dominant effect comes from the dependence of the Hubble scale on low-frequency modes…
Scalar-tensor theories of gravity can be formulated in the Jordan or in the Einstein frame, which are conformally related. The issue of which conformal frame is physical is a contentious one; we provide a straightforward example based on…
Conservation of super-horizon tensor fluctuations is crucial for connecting inflation to observations. Starting from first principles, recent works have found violations of this conservation if free-streaming radiation is produced during…
The reconstruction of an inflationary universe in the context of one $f(\phi)T$ gravity, in which $T$ corresponds to the trace of energy momentum tensor is studied. To realize this reconstruction during the inflationary epoch, we consider…
We review the relation between the inflationary potential and the spectra of density (scalar) perturbations and gravitational waves (tensor perturbations) produced, with particular emphasis on the possibility of reconstructing the inflaton…
We discuss possible observational manifestations of static, spherically symmetric solutions of a class of multidimensional theories of gravity, which includes the low energy limits of supergravities and superstring theories as special…
We investigate a standard minimally-coupled scalar-field inflationary scenario, which is based on a new potential, with suitably generalized plateau features, that leads to extra small tensor-to-scalar ratios. In particular, we consider a…
Several alternative ways to quantize gravitational interactions seem to indicate that gravity at short distances is effectively two-dimensional. If this were true, and the energy scale at which the dimensional transition occurs is of the…
Thermal history of the Universe between inflation and big-bang nucleosynthesis has not yet been revealed observationally. It will be probed by the detection of primordial gravitational waves generated during inflation, which contain…
We explore the scenario that the observable universe emerged from the vicinity of a negative mass ring singularity, and all content of the universe travels at the same group velocity close to the speed of light on a geodesic trajectory…
Conformal scaling invariance should play an important role for understanding the origin and evolution of universe. During inflation period, it appears to be an approximate symmetry, but how it is broken remains uncertain. The appealing…
We analyze reheating scenarios where a hidden sector is populated during reheating along with the sector containing the Standard Model. We numerically solve the Boltzmann equations describing perturbative reheating of the two sectors,…
The conformal equivalence between Jordan frame and Einstein frame can be used in order to search for exact solutions in general theories of gravity in which scalar fields are minimally or nonminimally coupled with geometry. In the…
The recent Planck results and future releases on the horizon present a key opportunity to address a fundamental question in inflationary cosmology of whether primordial density perturbations have a quantum or thermal origin, i.e. whether…
Scalar-tensor theories of gravity are considered to be competitors to Einstein's theory of general relativity for the description of classical gravity, as they are used to build feasible models for cosmic inflation. These theories can be…
We show how to constrain inflationary models and reheating by using mixed constraints. In particular we study the physics of the reheating phase after inflation from observational constraints to the inflationary stage. We show that it is…
Reheating is a transition era after the end of inflation, during which the inflaton is converted into the particles that populate the Universe at later times. No direct cosmological observables are normally traceable to this period of…