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The gravitational wave emission by a distorted rotating fluid star is computed. The distortion is supposed to be symmetric around some axis inclined with respect to the rotation axis. In the general case, the gravitational radiation is…

Astrophysics · Physics 2014-10-13 S. Bonazzola , E. Gourgoulhon

High time-resolution observations of pulsars were carried out at 35 MHz, using the Gauribidanur Radio Telescope (India), to study the spectra of intrinsic pulse-to-pulse fluctuations. Our sample consists of a few bright pulsars, each of…

Astrophysics · Physics 2007-05-23 Ashish Asgekar , A. A. Deshpande

Following up on our recent study, we consider the regime of graviton masses and gravitational wave propagation distances at which decoherence of the wave packets plays a major role for phenomenology. This regime is of particular interest,…

General Relativity and Quantum Cosmology · Physics 2018-03-21 Kevin Max , Moritz Platscher , Juri Smirnov

Interstellar scintillation analysis of pulsars allows us to probe the small-scale distribution and inhomogeneities of the ionized interstellar medium. Our priority is to present the data set and the basic measurements of scintillation…

We study observational implications of the stochastic gravitational wave background and a non-Gaussian feature of scalar perturbations on the curvaton mechanism of the generation of density/curvature fluctuations, and show that they can…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-20 Kazunori Nakayama , Jun'ichi Yokoyama

We propose to use pulsar scintillation measurements to test predictions of alternative theories of gravity. Comparing to single-path pulsar timing measurements, the scintillation measurements can achieve a factor of 10^5 improvement in…

General Relativity and Quantum Cosmology · Physics 2017-05-03 Huan Yang , Atsushi Nishizawa , Ue-Li Pen

The curvaton and the inhomogeneous reheating scenarios for the generation of the cosmological curvature perturbation on large scales represent an alternative to the standard slow-roll scenario where the observed density perturbations are…

Astrophysics · Physics 2009-11-10 L. Pilo , A. Riotto , A. Zaffaroni

We study graviton-photon conversion in magnetosphere of a pulsar and explore the possibility of detecting high frequency gravitational waves with pulsar observations. It is shown that conversion of one polarization mode of photons can be…

General Relativity and Quantum Cosmology · Physics 2023-05-24 Asuka Ito , Kazunori Kohri , Kazunori Nakayama

We discuss metric perturbations of the relativistic diffusion equation around the homogeneous Juttner equilibrium of massless particles in a homogeneous expanding universe. The metric perturbation describes matter distribution and the…

General Relativity and Quantum Cosmology · Physics 2015-02-27 Z. Haba

We give the initial spectrum of quantized gravitational waves in the context of the one-bubble open inflationary universe scenario. In determining the quantum state after the bubble nucleation we adopt the prescription to require the…

Astrophysics · Physics 2009-10-09 Takahiro Tanaka , Misao Sasaki

We present here a method to study the distribution of electron density fluctuations in pulsar directions as well as to estimate pulsar distances. The method, based on a simple two-component model of the scattering medium discussed by Gwinn…

Astrophysics · Physics 2009-10-30 A. A. Deshpande , R. Ramachandran

This article reviews our current understanding of modelling convection dynamics in stars. Several semi-analytical time-dependent convection models have been proposed for pulsating one-dimensional stellar structures with different…

Solar and Stellar Astrophysics · Physics 2016-01-18 Günter Houdek , Marc-Antoine Dupret

Being able to reliably track perturbations across bounces and turnarounds in cyclic and bouncing cosmology lies at the heart of being able to compare the predictions of these models with the Cosmic Microwave Background observations. This…

General Relativity and Quantum Cosmology · Physics 2016-03-23 Tirthabir Biswas , Riley Mayes , Colleen Lattyak

We study the effects of various phenomena which may have happened in the early universe on the spectrum of inflationary gravitational waves. The phenomena include phase transitions, entropy productions from non-relativistic matter, the…

High Energy Physics - Phenomenology · Physics 2015-06-16 Ryusuke Jinno , Takeo Moroi , Kazunori Nakayama

The curvaton scenario for the generation of the cosmological curvature perturbation on large scales represents an alternative to the standard slow-roll scenario of inflation in which the observed density perturbations are due to…

Astrophysics · Physics 2008-12-18 N. Bartolo , S. Matarrese , A. Riotto , A. Vaihkonen

We present a novel mechanism for gravitational wave generation in the early Universe. Light spectator scalar fields during inflation can acquire a blue-tilted power spectrum due to stochastic effects. We show that this effect can lead to…

Cosmology and Nongalactic Astrophysics · Physics 2023-07-06 Reza Ebadi , Soubhik Kumar , Amara McCune , Hanwen Tai , Lian-Tao Wang

The direct detection of gravitational waves by ground-based interferometers opened an unprecedented channel to probe alternative theories of gravitation. Several theories predict a dispersion of the gravitational waves during their…

General Relativity and Quantum Cosmology · Physics 2021-06-30 Leïla Haegel

The emission of gravitational waves from a system of massive objects interacting on elliptical, hyperbolic and parabolic orbits is studied in the quadrupole approximation. Analytical expressions are then derived for the gravitational wave…

Astrophysics · Physics 2010-04-21 Salvatore Capozziello , Mariafelicia De Laurentis

In this paper, we calculate the spectrum of scalar field fluctuations in a bouncing, asymptotically flat Universe, and investigate the dependence of the result on changes in the physics on length scales shorter than the Planck length which…

High Energy Physics - Theory · Physics 2009-11-07 Robert H Brandenberger , Sergio E. Joras , Jerome Martin