Related papers: Transient Parity Violation during Inflation: Impli…
By leveraging the limits on primordial magnetic fields (PMFs), their contributions to secondary gravitational waves (GWs), and the recent observations by the pulsar timing arrays (PTAs), we arrive at constraints on the epoch of reheating.…
The stochastic gravitational wave background (SGWB) detected recently by the pulsar timing arrays (PTAs) observations may have cosmological origins. In this work we consider a model of single field inflation containing an intermediate phase…
Arrays of precisely-timed millisecond pulsars are used to search for gravitational waves with periods of months to decades. Gravitational waves affect the path of radio pulses propagating from a pulsar to Earth, causing the arrival times of…
A series of pulsar timing arrays (PTAs) recently observed gravitational waves at the nanohertz frequencies. Motivated by this remarkable result, we present a novel class of Pati-Salam models that give rise to a network of metastable cosmic…
It is widely accepted that the primordial universe experienced a brief period of accelerated expansion called inflation. This scenario provides a plausible solution to the horizon and flatness problems. However, the particle physics…
Measurement of the pulsar timing residuals provides a direct way to detect relic gravitational waves at the frequency $f\sim 1/{\rm yr}$. In this paper, we investigate the constraints on the inflationary parameters, the tensor-to-scalar…
We investigate the cosmic microwave background (CMB) bispectra of the intensity (temperature) and polarization modes induced by the graviton non-Gaussianities, which arise from the parity-conserving and parity-violating Weyl cubic terms…
We investigate the properties of gravitational waves generated by heating induced phase transitions in warm inflation. In this scenario, the heating phase of inflation followed by subsequent cosmological cooling can trigger two associated…
Supersolid inflation is a class of inflationary theories that simultaneously breaks time and space reparameterization invariance during inflation, with distinctive features for the dynamics of cosmological fluctuations. We investigate…
Axion fluctuations generated during inflation lead to isocurvature and non-Gaussian temperature fluctuations in the cosmic microwave background radiation. Following a previous analysis for the model independent string axion we consider the…
We investigate Power-Law Plateau (PLP) inflation in standard gravity and its consistency with ACT DR6 data. While many inflationary models, including the Starobinsky inflation, are disfavored by ACT observations, the PLP potential remains…
Pulsar timing arrays probe isotropic stochastic gravitational wave (GW) backgrounds in the nanohertz band but are insensitive to its parity-violating component. Motivated by recent progress in pulsar polarization arrays, we study the…
We thoroughly study the induced gravitational wave interpretation of the possible gravitational wave background reported by PTA collaborations, considering the unknown equation of state $w$ of the early universe. We perform a Bayesian…
We study a mechanism to produce the circular polarization of primordial gravitational waves. The circular polarization is generated during the super-inflation driven by the Gauss-Bonnet term in the string-inspired cosmology. The instability…
Recent measurements of temperature fluctuations in the cosmic microwave background (CMB) indicate that the Universe is flat and that large-scale structure grew via gravitational infall from primordial adiabatic perturbations. Both of these…
We investigate the inhomogeneous inflation, in which the space exponentially expands with inhomogeneities, and its cosmological perturbations. The inhomogeneous inflation is realized by introducing scalar fields with spacelike gradients…
Recent observations by pulsar timing arrays (PTAs) indicate a potential detection of a stochastic gravitational wave (GW) background. Metastable cosmic strings have been recognized as a possible source of the observed signals. In this…
The behaviour of gravitational waves in the anomaly-induced inflationary phase is studied. The metric perturbations exhibit a stable behaviour, with a very moderate growth in the amplitude of the waves. The spectral indice is computed,…
We show that the recently reported cosmic gravitational wave background by the NANOGrav 15-year collaboration may be the result of resonant particle creation during inflation. For the appropriate amplitude and particle mass an enhancement…
Dark gauge fields have been discussed as candidates for dark matter recently. If they existed, primordial dark magnetic fields during inflation would have existed. It is believed that primordial gravitational waves (PGWs) arise out of…