Inflationary interpretation of the stochastic gravitational wave background signal detected by pulsar timing array experiments

PBHs and GWs from 𝕋2-inflation and NANOGrav 15-year data

“…Furthermore, we try to show the possibility that the recent PTA data can be interpreted by the induced GW sourced by EMSG term during inflation. Several other studies, for example [62][63][64][65][66][67][68][69][70][71][72][73][74], have been carried out on SIGWs as an explanation of the PTAs data.…”

Can the Gravitational Wave Background Feel Wiggles in Spacetime?

“…Due to the weakness of the gravitational interaction, gravitational waves (GWs), and the GWB as well, are thought to be insensitive to any environmental physics they propagate through, unless such physics has strength beyond the linear regime, which is typically only true near the GW source. As a result, most theoretical studies of the PTA signal have focused on the possible sources such as supermassive black holes (see Agazie et al 2023b;Antoniadis et al 2023b for some up-todate constraints, and also Huang et al 2023;Konoplya & Zhidenko 2023;Yang et al 2023b), inflation (Starobinsky 1979;Rubakov et al 1982;Guzzetti et al 2016;Vagnozzi 2021Vagnozzi , 2023Borah et al 2023;Choudhury 2023;Datta 2023;Firouzjahi & Talebian 2023;Niu & Rahat 2023;Unal et al 2023), scalar-induced GWs (Tomita 1967;Matarrese et al 1993Matarrese et al , 1994Domènech 2021; Abe & Tada 2023;Cai et al 2023;Ebadi et al 2023;Franciolini et al 2023;Liu et al 2023a;Wang et al 2023a;Yi et al 2023;Zhu et al 2023), and collision of bubbles of first-order phase transitions (Kosowsky et al 1992;Caprini et al 2008;Huber & Konstandin 2008;Arzoumanian et al 2021;Li et al 2021;Ashoorioon et al 2022;Addazi et al 2023;Bringmann et al 2023;…”

Prospects for Taiji to detect a gravitational-wave background from cosmic strings

“…Recently, several pulsar timing array (PTA) collaborations, including NANOGrav [16,17], PPTA [18,19], EPTA [20,21], and CPTA [22], have independently announced compelling evidence for a stochastic signal in their latest data sets, displaying the Hellings-Downs [23] spatial correlations consistent with an SGWB as predicted by general relativity. While the PTA window encompasses a wide range of potential sources [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38], the nature of the observed signal, whether it originates from astrophysical phenomena or cosmological processes, remains the subject of ongoing investigation [39][40][41][42][43][44][45][46][47]. The PTA signal can potentially be attributed to various sources [48][49][50][51], such as the SGWB produced by supermassive black hole binaries [52][53][54][55][56], scalar-induced GWs associated with the formation of primordial black holes [81][82]…”