Related papers: Gravitational waves from cosmic strings associated…
This study explores a dark matter model in which a pseudo-Nambu-Goldstone boson arises as a viable dark matter candidate from the spontaneous and soft breaking of global $\mathrm{U}(1)$ symmetries and stabilized by a residual $\mathbb{Z}_3$…
Gravitational waves offer a new window to probe the nature of gravity, including answering if the mediating particle, graviton, has a non-zero mass or not. Pulsar timing arrays measure stochastic gravitational wave background (SGWB) at…
The longitudinal components of massive vector fields generated during inflation constitute a well-motivated dark matter candidate, with interesting phenomenological implications. During the epoch of radiation domination following inflation,…
We discuss the appearance of topological structures from the spontaneous breaking of $E_6$ to the Standard Model via its maximal subgroup $SO(10) \times U(1)_\psi$. They include dumbbells, metastable strings, as well as domain walls bounded…
In a recent paper, the NANOGrav collaboration studied new physics explanations of the observed pulsar timing residuals consistent with a stochastic gravitational wave background (SGWB), including cosmic strings in the Nambu-Goto (NG)…
We demonstrate that novel types of gravitational wave signatures arise in theories with new gauge symmetries broken at high energy scales. For concreteness, we focus on models with gauged baryon number and lepton number, in which neutrino…
Proton decay is a smoking gun signature of Grand Unified Theories (GUTs). Searches by Super-Kamiokande have resulted in stringent limits on the GUT symmetry breaking scale. The large-scale multipurpose neutrino experiments DUNE,…
The spontaneous breaking of a $U(1)$ symmetry via an intermediate discrete symmetry may yield a hybrid topological defect of \emph{domain walls bounded by cosmic strings}. The decay of this defect network leads to a unique gravitational…
Pre--big bang models of inflation based on string cosmology produce a stochastic gravitational wave background whose spectrum grows with decreasing wavelength, and which may be detectable using interferometers such as LIGO. We point out…
Cosmic strings are generic cosmological predictions of many extensions of the Standard Model of particle physics, such as a $U(1)^\prime$ symmetry breaking phase transition in the early universe or remnants of superstring theory. Unlike…
The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration has recently reported strong evidence for a signal at nanohertz, potentially the first detection of the stochastic gravitational-wave background…
Supersymmetric grand unification based on $SO(10)$ is one of the most attractive paradigms in physics beyond the Standard Model. Inspired by the recent NANOGrav signal, we discuss the implications of detecting a stochastic gravitational…
In type I seesaw models, the right-handed neutrinos are typically super-heavy, consistent with the generation of baryon asymmetry via standard leptogenesis. Primordial gravitational waves of cosmological origin provides a new window to…
Primordial gravitational waves provide a very important stochastic background that could be detected soon with interferometric gravitational wave antennas or indirectly via the induced patterns in the polarization anisotropies of the cosmic…
We describe a unique gravitational wave signature for a class of models with a vast hierarchy between the symmetry breaking scales. The unusual shape of the signal is a result of the overlapping contributions to the stochastic gravitational…
While topologically stable cosmic strings are disfavoured by the recent observation of nHz stochastic gravitational waves (GW) by Pulsar Timing Arrays (PTA), e.g., NANOGrav, cosmic metastable strings and superstrings are not. However,…
We investigate the problem of metric fluctuations in the presence of the vacuum fluctuations of matter fields and critically assess the usual assertion that vacuum energy implies a Planckian cosmological constant. A new stochastic classical…
In recent years, several pulsar timing array collaborations have reported first hints for a stochastic gravitational wave background at nano-Hertz frequencies. Here we elaborate on the possibility that this signal comes from new physics…
We compare the spectrum of the stochastic gravitational wave background produced in several models of cosmic strings with the common-spectrum process recently reported by NANOGrav. We discuss theoretical uncertainties in computing such a…
Cosmic domain walls are harmless, provided that their tension decreases with expansion of the Universe. This setup can be realized, if the scale of spontaneous symmetry breaking is induced dynamically through the interaction with hot…