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Large-scale primordial perturbations have been well constrained by current cosmological observations, but the properties of small-scale perturbations remain elusive. This study focuses on second-order induced gravitational waves generated…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-11 Di Wu , Zhi-Chao Li , Peng-Yu Wu , Fei-Yu Chen , Jing-Zhi Zhou

Compared to primordial perturbations on large scales, roughly larger than $1$ megaparsec, those on smaller scales are not severely constrained. We revisit the issue of probing small-scale primordial perturbations using gravitational waves…

Cosmology and Nongalactic Astrophysics · Physics 2019-02-20 Keisuke Inomata , Tomohiro Nakama

The detection of the Stochastic Gravitational Wave Background (SGWB) is one of the most challenging tasks for both current and next-generation detectors. Successfully distinguishing the SGWB from instrumental noise and environmental effects…

Instrumentation and Methods for Astrophysics · Physics 2025-07-22 Ilaria Caporali , Angelo Ricciardone

We present an effective numerical method that can be used to straightforwardly calculate the full spectrum of primordial gravitational waves produced during inflation and reheating. Our method is based on the Bogoliubov approach with…

High Energy Physics - Phenomenology · Physics 2026-04-21 Yubing Wang , Quan-feng Wu , Xun-Jie Xu

We introduce $\texttt{GWFAST}$, a novel Fisher-matrix code for gravitational-wave studies, tuned toward third-generation gravitational-wave detectors such as Einstein Telescope (ET) and Cosmic Explorer (CE). We use it to perform a…

General Relativity and Quantum Cosmology · Physics 2023-01-02 Francesco Iacovelli , Michele Mancarella , Stefano Foffa , Michele Maggiore

We consider the production of secondary gravity waves in Galileon inflation with an ultra-slow roll (USR) phase and show that the spectrum of scalar-induced gravitational waves (SIGWs) in this case is consistent with the recent NANOGrav…

Cosmology and Nongalactic Astrophysics · Physics 2024-09-23 Sayantan Choudhury , Ahaskar Karde , Sudhakar Panda , M. Sami

Unmodelled searches and reconstruction is a critical aspect of gravitational wave data analysis, requiring sophisticated software tools for robust data analysis. This paper introduces PycWB, a user-friendly and modular Python-based…

General Relativity and Quantum Cosmology · Physics 2024-03-05 Yumeng Xu , Shubhanshu Tiwari , Marco Drago

The stochastic gravitational-wave background (SGWB) is expected to arise from the superposition of many independent and unresolved gravitational-wave signals of either cosmological or astrophysical origin. The spectral content of the SGWB…

Cosmology and Nongalactic Astrophysics · Physics 2013-08-27 Vuk Mandic , Eric Thrane , Stefanos Giampanis , Tania Regimbau

Gravitational wave astrophysics requires accurate evaluation of the Signal-to-Noise Ratio (SNR) and the Probability of Detection (Pdet) for applications such as population simulations and hierarchical Bayesian inference with selection…

Instrumentation and Methods for Astrophysics · Physics 2025-10-30 Hemantakumar Phurailatpam , Otto Akseli Hannuksela

The stochastic gravitational wave (GW) background is secondarily and inevitably induced by the primordial curvature perturbations beyond the first order of the cosmological perturbation theory. We analytically calculate the integration…

General Relativity and Quantum Cosmology · Physics 2026-01-15 Takahiro Terada

Context. As the importance of Gravitational Wave (GW) Astrophysics increases rapidly, astronomers in different fields and with different backgrounds can have the need to get a quick idea of which GW source populations can be detected by…

A stochastic gravitational-wave background (SGWB) is expected from the superposition of a wide variety of independent and unresolved astrophysical and cosmological sources from different stages in the evolution of the Universe. Radiometric…

General Relativity and Quantum Cosmology · Physics 2018-07-25 Anirban Ain , Jishnu Suresh , Sanjit Mitra

We investigate the scalar induced gravitational waves (SIGWs) in the Chern-Simons (CS) modified gravity during the radiation dominated era. The SIGWs are circularly polarized, which provide us a tool to test the possible parity violation in…

General Relativity and Quantum Cosmology · Physics 2022-10-19 Fengge Zhang , Jia-Xi Feng , Xian Gao

We investigate the scalar induced gravitational waves (SIGWs) in the Chern-Simons (CS) gravity with a dynamical scalar field during slow roll inflation. Due to the parity violation in the CS term, the SIGWs are generally polarized, which…

General Relativity and Quantum Cosmology · Physics 2023-07-26 Jia-Xi Feng , Fengge Zhang , Xian Gao

Superposition of unresolved sources of gravitational waves (GW) is expected to create a persistent background of stochastic gravitational wave background (SGWB). Different types of astrophysical and cosmological sources are however likely…

General Relativity and Quantum Cosmology · Physics 2019-04-11 Abhishek Parida , Jishnu Suresh , Sanjit Mitra , Sanjay Jhingan

The primordial gravitational waves (\textbf{PGW}) have been generated by inflationary amplification of the primordial (quantum) fluctuations. It is true that they have not been recorded directly so far, but their spectrum can help a lot in…

General Relativity and Quantum Cosmology · Physics 2022-02-23 Taimur Mohammadi , Behrooz Malekolkalami , Khabat Ghamari

The standard model of particle physics is known to be intriguingly successful. However their rich phenomena represented by the phase transitions (PTs) have not been completely understood yet, including the possibility of the existence of…

Cosmology and Nongalactic Astrophysics · Physics 2021-07-07 Katsuya T. Abe , Yuichiro Tada , Ikumi Ueda

Parity-violation leaves tell-tale trails in many cosmological observables. We illustrate parity-odd primordial scalar trispectra, that despite being of modest strength, impart detectable chirality to scalar-induced gravitational waves…

Cosmology and Nongalactic Astrophysics · Physics 2025-07-08 H. V. Ragavendra , Nicola Bartolo

The extraction of the gravitational wave signal, within the context of a characteristic numerical evolution is revisited. A formula for the gravitational wave strain is developed and tested, and is made publicly available as part of the…

General Relativity and Quantum Cosmology · Physics 2013-12-18 Nigel T Bishop , Christian Reisswig

We investigate the scalar induced gravitational waves (SIGWs) in metric teleparallel gravity with the Nieh-Yan (NY) term, which results in parity violation during the radiation-dominated era. By solving the equations of motion of linear…

General Relativity and Quantum Cosmology · Physics 2024-07-24 Fengge Zhang , Jia-Xi Feng , Xian Gao