Related papers: Primordial Gravitational Waves in Quadratic Gravit…
We give a rigorous and mathematically clear presentation of the Covariant and Gauge Invariant theory of gravitational waves in a perturbed Friedmann-Lemaitre-Robertson-Walker universe for Fourth Order Gravity, where the matter is described…
We investigate a model of inflationary cosmology where the minimally coupled scalar field theory is modified by additional correction terms. Among the most general ten correction terms remarked by Weinberg in context of effective field…
A new effect is described by which primordial gravity waves leave a permanent signature in the large scale structure of the Universe. The effect occurs at second order in perturbation theory and is sensitive to the order in which…
Inflation predicts a primordial gravitational wave spectrum that is slightly ``red,'' i.e., nearly scale-invariant with slowly increasing power at longer wavelengths. In this paper, we compute both the amplitude and spectral form of the…
In this paper, we construct a bounce inflation cosmological scenario in the framework of the modified symmetric teleparallel gravity, namely f(Q) theory, and investigate the tensor perturbations therein. As is well-known, the tensor…
We revisit the old (fourth-order or quadratically generated) gravity model of Starobinsky in four space-time dimensions, and derive the (inflaton) scalar potential in the equivalent scalar-tensor gravity model via a Legendre-Weyl transform.…
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…
The swampland conjectures seek to distinguish effective field theories which can be consistently embedded in a theory of quantum gravity from those which can not (and are hence referred to as being in the swampland). We consider two such…
We study second order gravitational perturbations on plane wave spacetimes from both the metric and curvature perturbation points of view. For the former, we explicitly use the isometries of the background to introduce tensor oscillator…
We study the tensor perturbations in a class of non-local, purely gravitational models which naturally end inflation in a distinctive phase of oscillations with slight and short violations of the weak energy condition. We find the usual…
We discuss the implications of purely classical, instead of quantum, theory of gravity for the gravitational wave spectrum generated during inflation. We show that a positive detection of primordial gravitational waves will no longer…
Theories with curvature squared terms in the action are known to contain ghost modes in general. However, if we regard curvature squared terms as quantum corrections to the original theory, the emergence of ghosts may be simply due to the…
"The self-induced collapse hypothesis" was introduced by D. Sudarsky and collaborators to explain the origin of cosmic structure from a perfect isotropic and homogeneous universe during the inflationary regime. In this paper, we calculate…
Quadratic gravity is a well-motivated extension of general relativity~(GR) wherein the Einstein-Hilbert action is augmented by quadratic curvature terms. This theory is equivalent to GR in an effective-field-theory framework, while the two…
The primordial spectrum of fluctuations may present a large peak as a result of enhancing features during inflation. This may include, but is not limited to, bumps in the inflaton's potential, phases of ultra-slow-roll or turns in…
In this work we study a modified version of $f(R)$ gravity in which higher order kinetic terms of a scalar field are added in the action of vacuum $f(R)$ gravity. This type of theory is a type of $k$-essence $f(R)$ gravity, and it belongs…
Primordial non-Gaussianities of the scalar(tensor)-tensor-tensor type supporting a non-trivial squeezed component are known to induce anisotropies in the stochastic gravitational wave background. We derive the explicit form of such…
We propose a mechanism to evade the Lyth bound in models of inflation. We minimally extend the conventional single-field inflation model in general relativity (GR) to a theory with non-vanishing graviton mass in the very early universe. The…
In the framework of asymptotic safety, we study quantum quadratic gravity in the presence of the Higgs field considered as non-separable from the vacuum. The theory flows to a high energy fixed point where the Higgs field is strongly…
The primordial spectrum of cosmological tensor perturbations is considered as a possible probe of quantum gravity effects. Together with string theory, loop quantum gravity is one of the most promising frameworks to study quantum effects in…