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We perform the first search for an isotropic non-tensorial gravitational-wave background (GWB) allowed in general metric theories of gravity in the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 12.5-year data set.…

Cosmology and Nongalactic Astrophysics · Physics 2025-03-28 Zu-Cheng Chen , Chen Yuan , Qing-Guo Huang

We use direct numerical simulations of decaying primordial hydromagnetic turbulence with helicity to compute the resulting gravitational wave (GW) production and its degree of circular polarization. We find a clear dependence of the…

General Relativity and Quantum Cosmology · Physics 2022-04-20 Alberto Roper Pol , Sayan Mandal , Axel Brandenburg , Tina Kahniashvili

We analyze the polarization content of gravitational waves in Horndeski theory. Besides the familiar plus and cross polarizations in Einstein's General Relativity, there is one more polarization state which is the mixture of the transverse…

General Relativity and Quantum Cosmology · Physics 2018-05-15 Shaoqi Hou , Yungui Gong , Yunqi Liu

The International Pulsar Timing Array (IPTA) is a galactic-scale gravitational-wave observatory that monitors an array of millisecond pulsars. The timing precision of these pulsars is such that one can measure the correlated changes in…

Instrumentation and Methods for Astrophysics · Physics 2019-03-04 Jeffrey S. Hazboun , Chiara M. F. Mingarelli , Kejia Lee

We combine new analysis of the stochastic gravitational wave background to be expected from cosmic strings with the latest pulsar timing array (PTA) limits to give an upper bound on the energy scale of the possible cosmic string network,…

Cosmology and Nongalactic Astrophysics · Physics 2020-04-21 Jose J. Blanco-Pillado , Ken D. Olum , Xavier Siemens

We study an inflation model with nonminimal derivative coupling that features a coupling between the derivative of the inflaton field and the Einstein tensor. This model naturally amplifies curvature perturbations at small scales via…

The Chinese Pulsar Timing Array (CPTA) has collected observations from 57 millisecond pulsars using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) for close to three years, for the purpose of searching for gravitational…

The recent announcement of evidence for a stochastic background of gravitational waves (GWB) in pulsar timing array (PTA) data has piqued interest across the scientific community. A combined analysis of all currently available data holds…

Instrumentation and Methods for Astrophysics · Physics 2025-09-01 Serena Valtolina , Rutger van Haasteren

Pulsar Timing Array (PTA) experiments exploit the clock-like behaviour of an array of millisecond pulsars, with the goal of detecting low-frequency gravitational waves. PTA experiments have been in operation over the last decade, led by…

Instrumentation and Methods for Astrophysics · Physics 2018-03-28 Caterina Tiburzi

Pulsar timing arrays (PTAs) can be used to detect and study gravitational waves in the nanohertz band (i.e., wavelengths of order light-years). This requires high-precision, decades-long data sets from sensitive, instrumentally stable…

Instrumentation and Methods for Astrophysics · Physics 2018-10-17 NANOGrav Collaboration

We extend the recently introduced Bayesian framework `Generative Pulsar Timing Analysis' to incorporate both pulse jitter (high frequency variation in the arrival time of the pulse) and epoch to epoch stochasticity in the shape of the pulse…

Instrumentation and Methods for Astrophysics · Physics 2015-09-28 L. Lentati , R. M. Shannon

We present an analysis of high-precision pulsar timing data taken as part of the North American Nanohertz Observatory for Gravitational waves (NANOGrav) project. We have observed 17 pulsars for a span of roughly five years using the Green…

The stochastic signal detected by pulsar timing arrays (PTAs) has raised great interest in understanding its physical origin. Assuming the signal is a cosmological gravitational-wave background produced by overly large primordial curvature…

Cosmology and Nongalactic Astrophysics · Physics 2025-03-31 Jia-Heng Jin , Zu-Cheng Chen , Zhu Yi , Zhi-Qiang You , Lang Liu , You Wu

After NANOGrav, the IPTA collaboration also reports a strong evidence of a stochastic gravitation wave background. This hint has very important implications for fundamental physics. With the recent IPTA data release two, we attempt to…

Cosmology and Nongalactic Astrophysics · Physics 2022-03-22 Deng Wang

The recent astronomical milestone by the pulsar timing arrays (PTA) has revealed galactic-size gravitational waves (GW) in the form of a stochastic gravitational wave background (SGWB), correlating the radio pulses emitted by millisecond…

General Relativity and Quantum Cosmology · Physics 2024-11-08 Reginald Christian Bernardo , Kin-Wang Ng

The null hypothesis in Pulsar Timing Array (PTA) analyses includes assumptions about ensemble properties of pulsar time-correlated noise. These properties are encoded in prior probabilities for the amplitude and the spectral index of the…

High Energy Astrophysical Phenomena · Physics 2025-02-06 Boris Goncharov , Shubhit Sardana

We present the results of simulated injections testing the first Bayesian search-pipeline capable of investigating the angular-structure of a gravitational-wave (GW) background influencing pulsar signals. A stochastic background of GWs from…

General Relativity and Quantum Cosmology · Physics 2013-10-30 Stephen R. Taylor , Jonathan R. Gair

The stochastic gravitational wave background for pulsar timing arrays is often modeled by a Gaussian ensemble which is isotropic and unpolarized. However, the Universe has a discrete set of polarized gravitational wave sources at specific…

General Relativity and Quantum Cosmology · Physics 2024-05-02 Bruce Allen , Serena Valtolina