Related papers: Fundamental quantum limits for detecting ultrahigh…
Primordial gravitational waves (GWs) with frequencies > 10^{-15} Hz contribute to the radiation density of the Universe at the time of decoupling of the cosmic microwave background (CMB). The effects of this GW background on the CMB and…
In this paper, we present an upper limit of $\Omega_{\rm GW}<1.2\times 10^{8}$ on an isotropic stochastic gravitational-wave (GW) background integrated over a year in the frequency range 0.05 Hz - 1 Hz, which improves current upper limits…
Primordial density perturbations in the radiation-dominated era of the early Universe are expected to generate stochastic gravitational waves (GWs) due to nonlinear mode coupling. In this \emph{Letter}, we report on a search for such a…
The gravitational wave (GW) spectrum at frequencies above a kHz is a largely unexplored frontier. We show that detectors with sensitivity to single-phonon excitations in crystal targets can search for GWs with frequencies, $\mathrm{THz}…
As one of the primary detection targets for contemporary gravitational wave (GW) observatories, the stochastic gravitational wave background (SGWB) holds significant potential for enhancing our understanding of the early universe's…
The first direct measurement of gravitational waves by the LIGO and Virgo collaborations has opened up new avenues to explore our Universe. This white paper outlines the challenges and gains expected in gravitational wave searches at…
The quantum nature of the electromagnetic field imposes a fundamental limit on the sensitivity of optical precision measurements such as spectroscopy, microscopy, and interferometry. The so-called quantum limit is set by the zero-point…
We study the graviton-photon conversion in the magnetic fields of the Earth, the Milky Way Galaxy, and intergalactic regions. Requiring that the photon flux converted from gravitons does not exceed the observed photon flux with telescopes,…
Third generation ground-based gravitational wave (GW) detectors, such as Einstein Telescope and Cosmic Explorer, will operate in the $(\text{few}-10^4)$ Hz frequency band, with a boost in sensitivity providing an unprecedented reach into…
The canonical methods for gravitational wave detection are ground- and space-based laser interferometry, pulsar timing, and polarization of the cosmic microwave background. But as has been suggested by numerous investigators, astrometry…
Global cosmic strings are generically predicted in particle physics beyond the Standard Model, e.g., a post-inflationary global $U(1)$ symmetry breaking which may associate with axion-like dark matter. We demonstrate that although…
The advent of gravitational-wave (GW) astronomy has presented us with a completely new means for observing the Universe, allowing us to probe its structure and evolution like never before. In this thesis, we explore three distinct but…
Gravitational wave experiments will play a key role in the investigation of the frontiers of cosmology and the structure of fundamental fields at high energies, by detecting, or setting strong upper-limits to, the primordial gravitational…
Gravitational wave (GW) backgrounds of cosmological origin are expected to be nearly isotropic, with small anisotropies resembling those of the cosmic microwave background. We analyse the case of a scalar-induced GW background and clarify…
The collection of individually resolvable gravitational wave (GW) events makes up a tiny fraction of all GW signals which reach our detectors, while most lie below the confusion limit and go undetected. Like voices in a crowded room, the…
A stochastic background of gravitational waves is expected to arise from a superposition of many incoherent sources of gravitational waves, of either cosmological or astrophysical origin. This background is a target for the current…
This article aims at clarifying the situation about astrophysical sources that might be observed with haloscope experiments sensitive to gravitational waves in the 1-10 GHz band. The GrAHal setup is taken as a benchmark. We follow a very…
The spectrum of primordial gravitational waves (GWs), especially its tilt $n_T$, carries significant information about the primordial universe. Combining recent aLIGO and Planck2015+BK14 data, we find that the current limit is…
Primordial magnetic fields (PMFs) can source gravitational wave background (GWB). In this paper, we investigate the possible constraints on small-scale PMF considering the ongoing and forthcoming direct detection observations of GWB. In…
We report on the possibility of detecting a submillimetre-sized extra dimension by observing gravitational waves (GWs) emitted by pointlike objects orbiting a braneworld black hole. Matter in the `visible' universe can generate a discrete…