Current Ground-based Detectors Research Articles

Dark photon dark matter from cosmic strings and gravitational wave background

Dark photon dark matter may be produced by the cosmic strings in association with the dark U(1) gauge symmetry breaking. We perform three-dimensional lattice simulations of the Abelian-Higgs model and follow the evolution of cosmic strings. In particular, we simulate the case of (very) light vector boson and find that such vector bosons are efficiently produced by the collapse of small loops while the production is inefficient in the case of heavy vector boson. We calculate the spectrum of the gravitational wave background produced by the cosmic string loops for the light vector boson case and find characteristic features in the spectrum, which can serve as a probe of the dark photon dark matter scenario. In particular, we find that the current ground-based detectors may be sensitive to such gravitational wave signals and also on-going/future pulsar timing observations give stringent constraint on the dark photon dark matter scenario.

Earth’s spheroidal motion induced by a gravitational wave in flat spacetime

We revisit the theoretical modeling of astrophysical gravitational wave (GW) interaction with Earth's normal modes in the millihertz frequency band. We consider a force term associated with plane waves in a flat spacetime acting on a nonrotating anelastic Earth model. Our study confirms that the leading spheroidal induced displacement consists of an angular order-2 term, while the induced azimuthal order terms depend on the incident angles of the GW. We show that some of the previous estimates of the Earth's acceleration due to incoming gravitational waves were too optimistic. Current ground-based detectors are embedded in seismic and environmental noise that is several orders of magnitude larger than the expected GW signal. However, with the prospect of new technologies and improved noise reduction techniques, detection may become feasible.

Numerical studies on core collapse supernova in self-interacting massive scalar-tensor gravity

We investigate stellar core collapse in scalar-tensor theory with a massive self-interacting scalar field. In these theories, strong long-lived inverse chirp signals could be induced during the stellar core collapse, which provides us with several potential smoking-gun signatures that could be found using current ground-based detectors. We show that the existence of self-interaction in the potential of the scalar field can significantly suppress spontaneous scalarization and the amplitude of the monopole gravitational-wave radiation. Moreover, this suppression due to self-interaction is frequency dependent and may be discernible in LIGO/Virgo's sensitive band. Therefore, self-interaction should be considered when constraining scalar-tensor coupling parameters with gravitational-wave detections. Alternatively, if such monopole gravitational-wave signals are detected, then one may be able to infer the presence of self-interaction.

TeV gamma radiation of BL Lac objects Mkn 421 and Mkn 501

The current imaging atmospheric Cherenkov telescopes operating in the energy range from several hundred GeV to ≥20 TeV are nicely suited for study of high energy properties of nearby BL Lac objects. The ranges of timescales and flux variations of TeV flares oftwo representatives of this source population — Mkn 421 and Mkn 501 — are well-matched to the sensitivity of the best current ground-based detectors. On several occasions truly simultaneous observations of both sources in TeV and X-ray bands were available during last two years. These results contain unique information about the AGN jets, and provide meaningful constraints on the diffuse infrared extragalactic background.

TeV gamma radiation of BL Lac objects Mkn 421 and Mkn 501

The current imaging atmospheric Cherenkov telescopes operating in the energy range from several hundred GeV to ≥20 TeV are nicely suited for study of high energy properties of nearby BL Lac objects. The ranges of timescales and flux variations of TeV flares oftwo representatives of this source population — Mkn 421 and Mkn 501 — are well-matched to the sensitivity of the best current ground-based detectors. On several occasions truly simultaneous observations of both sources in TeV and X-ray bands were available during last two years. These results contain unique information about the AGN jets, and provide meaningful constraints on the diffuse infrared extragalactic background.