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We derive the effects of a non-zero cosmological constant $\Lambda$ on gravitational wave propagation in the linearized approximation of general relativity. In this approximation we consider the situation where the metric can be written as…

High Energy Physics - Theory · Physics 2012-09-17 José Bernabeu , Domènec Espriu , Daniel Puigdomènech

If we want to explain the recently discovered accelerated stage of the universe, one of the option we have is to modify the Einstein tensor. The simplest such modification, in agreement with all observations, is the positive cosmological…

General Relativity and Quantum Cosmology · Physics 2014-11-18 M. Nowakowski , I. Arraut

We analyze the propagation of gravitational waves (GWs) in an asymptotically de-Sitter space by expanding the perturbation around Minkowski and introducing the effects of the Cosmological Constant ($\Lambda$), first as an additional source…

General Relativity and Quantum Cosmology · Physics 2013-04-09 Ivan Arraut

Pulsar Timing Arrays (PTA) around the world are using the incredible consistency of millisecond pulsars to measure low frequency gravitational waves from (super)Massive Black Hole (MBH) binaries. We use comprehensive MBH merger models based…

High Energy Astrophysical Phenomena · Physics 2017-09-06 Luke Zoltan Kelley , Laura Blecha , Lars Hernquist , Alberto Sesana , Stephen R. Taylor

Pulsar timing arrays (PTAs) will be sensitive to a finite number of gravitational wave (GW) "point" sources (e.g. supermassive black hole binaries). N quiet pulsars with accurately known distances d_{pulsar} can characterize up to 2N/7…

High Energy Astrophysical Phenomena · Physics 2013-05-30 Latham Boyle , Ue-Li Pen

Gravitational wave (GW) searches using pulsar timing arrays (PTAs) are assumed to be limited by the typical average observational cadence of $1/(2~{\rm weeks})$ for a single pulsar to GW frequencies $\lesssim 4\times 10^{-7}$ Hz. We show…

High Energy Astrophysical Phenomena · Physics 2021-02-10 Yan Wang , Soumya D. Mohanty , Zhoujian Cao

One of the imminent science goals of pulsar timing arrays (PTAs) is the detection of a continuous gravitational wave (CGW) emitted by an individual supermassive black hole binary (SMBHB). SMBHBs that cause CGWs with GW frequencies…

High Energy Astrophysical Phenomena · Physics 2026-02-18 Kathrin Grunthal , Nataliya Porayko , David J. Champion , Michael Kramer

Pulsar timing arrays (PTAs) are searching for gravitational waves from supermassive black hole binaries (SMBHBs). Here we show how future PTAs could use a detection of gravitational waves from individually resolved SMBHB sources to produce…

Cosmology and Nongalactic Astrophysics · Physics 2022-10-13 Casey McGrath , Daniel J. D'Orazio , Jolien Creighton

In the nanohertz band, the spatial correlations in pulsar timing arrays (PTAs) produced by interfering gravitational waves (GWs) from multiple sources likely deviate from the traditional ones without interference under the assumption of an…

General Relativity and Quantum Cosmology · Physics 2025-10-01 Yu-Mei Wu , Yan-Chen Bi , Qing-Guo Huang

Pulsar Timing Array (PTA) observations have recently gathered substantial evidence for the existence of a gravitational wave background in the nHz frequency band. Searching for anisotropies in this signal is key to determining its origin,…

Cosmology and Nongalactic Astrophysics · Physics 2024-09-02 Paul Frederik Depta , Valerie Domcke , Gabriele Franciolini , Mauro Pieroni

The recent discovery of ultra-long wavelength gravitational waves through the advent of pulsar timing arrays (PTA) has opened up new avenues for fundamental science. Here we show that every PTA source will be diffractively lensed by…

Cosmology and Nongalactic Astrophysics · Physics 2024-07-04 Dylan L. Jow , Ue-Li Pen

Pulsar Timing Arrays (PTAs) have recently found strong evidence for low-frequency gravitational waves (GWs) in the nanohertz frequency regime. As GWs pass, they produce deviations in measured lengths and light-travel times. PTA experiments…

High Energy Astrophysical Phenomena · Physics 2025-05-05 Luke Zoltan Kelley

Several pulsar-timing array (PTA) collaborations are finding tantalising hints for a stochastic gravitational wave background signal in the nano-Hertz regime. So far, though, no convincing evidence for the expected Hellings-Downs…

General Relativity and Quantum Cosmology · Physics 2022-04-20 Gianmassimo Tasinato

Pulsar timing arrays (PTAs) can be used to search for very low frequency ($10^{-9}$--$10^{-7}$ Hz) gravitational waves (GWs). In this paper we present a general method for the detection and localization of single-source GWs using PTAs. We…

Instrumentation and Methods for Astrophysics · Physics 2015-03-27 Xing-Jiang Zhu , Linqing Wen , George Hobbs , Yilin Zhang , Yan Wang , Dustin R. Madison , Richard N. Manchester , Matthew Kerr , Pablo A. Rosado , Jingbo Wang

Evidence of a gravitational wave (GW) signal has emerged in pulsar timing array (PTA) data, opening a new window into the nanoHz GW Universe. We explore the physics of GW signals potentially explaining the data, with a primary focus on GW…

Cosmology and Nongalactic Astrophysics · Physics 2026-03-04 Alberto Sesana , Daniel G. Figueroa

Pulsar timing array (PTA) provides an excellent opportunity to detect the gravitational waves (GWs) in nanoHertz frequency band. In particular, due to the larger number of "arms" in PTA, it can be used to test gravity by probing the…

General Relativity and Quantum Cosmology · Physics 2019-03-29 Rui Niu , Wen Zhao

Pulsar timing arrays (PTAs) are searching for nanohertz-frequency gravitational waves (GWs) through cross-correlation of pulse arrival times from a set of radio pulsars. PTAs have relied upon a frequency-shift formula of the pulse, where…

High Energy Astrophysical Phenomena · Physics 2024-07-03 Ryousuke Kubo , Kakeru Yamahira , Hideki Asada

The detection of gravitational waves with Pulsar Timing Arrays (PTAs) requires precise measurement of the difference between the pulsars' timing models and their observed pulses, as well as dealing with numerous and sometimes hard to…

High Energy Astrophysical Phenomena · Physics 2025-05-07 Giulia Fumagalli , Golam Shaifullah , Alberto Sesana

In this study the effects of a non-zero cosmological constant $\Lambda$ on a quadrupole signal are studied. The linearized approximation of general relativity was used, so the metric can be written as…

General Relativity and Quantum Cosmology · Physics 2018-03-12 L. A. Somlai

Pulsar Timing Array (PTA) collaborations gather high-precision timing measurements of pulsars with the aim of detecting gravitational wave (GW) signals. A major challenge lies in the identification and characterization of the different…