arXiv subjects

J. Yokoyama

Publications and source records attributed to J. Yokoyama.

7 recordsLinked to original sources

arXiv2022

Response of the underground environment of the KAGRA observatory against the air-pressure disturbance from the Tonga volcano eruption on January 15th, 2022

On January 15, 2022, at 04:14:45 (UTC), the Hunga Tonga-Funga Ha'apai, a submarine volcano in the Tongan archipelago in the southern Pacific Ocean, erupted and generated global seismic, shock, and electromagnetic waves, which also reached Japan, situated more than 8,000 km away. KAGRA is a gravitational wave telescope located in an underground facility in Kamioka, Japan. It has a wide variety of auxiliary sensors to monitor environmental disturbances which obstruct observation of gravitational waves. The effects of the volcanic eruption were observed by these environmental sensors both inside and outside of the underground facility. In particular, the shock waves made it possible to evaluate the transfer functions from the air pressure wave in the atmosphere to the underground environmental disturbances (air pressure and seismic motion).

astro-ph.IM↗

arXiv2021

Method for environmental noise estimation via injection tests for ground-based gravitational wave detectors

Environmental noise is one of the critical issues for the observation of gravitational waves, but is difficult to predict in advance. Therefore, to evaluate the adverse impact of environmental noise on the detector sensitivity, understanding the detector response to the environmental noise in actual setup is crucial, for both the observation and future upgrades. In this paper, we introduce and verify a new method of the environmental noise injection test based on the post-observation commissioning of KAGRA. This new method (response function model) includes the frequency conversion and nonlinearity of power, which are the effects that are not considered in the current model (coupling function model) used in LIGO and Virgo. We also confirmed the validity of our method by applying it to an environmental noise-enriched dataset and successfully reproducing them.

gr-qc↗

arXiv2009

On the realization of the MSSM inflation

We study the fine-tuning problem on the initial condition of inflation in the minimal supersymmetric standard model (MSSM), associated with the narrowness of the slow-roll region. We consider two cases before the onset of the MSSM inflation, namely, the radiation dominated era and preceding inflationary era. We find thermal dissipation does not induce additional friction to the inflaton, so that it does not help enlarge the slow-roll region. We argue thermal correction to the potential in the preceding radiation dominated era and quantum fluctuations in the preceding inflationary era disturb field configuration and prevent the MSSM inflation unless some specific preinflation history is realized.

hep-ph↗

arXiv2006

D-term Inflation and Leptogenesis by Right-handed Sneutrino

We discuss a D-term inflation scenario where a right-handed sneutrino can be an inflaton field leading to a viable inflation and leptogenesis, with a minimal form of Kähler potential. The decay of an inflaton sneutrino can non-thermally create large enough lepton asymmetry. Its entropy production is also big enough to ameliorate the gravitino problem caused by too high a reheating temperature from the decay of a symmetry breaking field.

hep-ph↗

arXiv2005

Generation of Large-Scale Magnetic Fields from Dilaton Inflation in Noncommutative Spacetime

Generation of large-scale magnetic fields is studied in dilaton electromagnetism in noncommutative inflationary cosmology, taking into account the effects of the spacetime uncertainty principle motivated by string theory. We show that it is possible to generate large-scale magnetic fields with sufficient strength to account for the observed fields in galaxies and clusters of galaxies through only adiabatic compression without dynamo amplification mechanism in models of power-law inflation based on spacetime noncommutativity without introducing a huge hierarchy between the dilaton's potential and its coupling to the electromagnetic fields.

hep-ph↗

arXiv2004

Large-scale magnetic fields from dilaton inflation in noncommutative spacetime

The generation of large-scale magnetic fields is studied in dilaton electromagnetism in noncommutative inflationary cosmology taking into account the effects of the spacetime uncertainty principle motivated by string theory. We show that it is possible to generate large-scale magnetic fields with sufficient strength to account for the observed fields in galaxies and clusters of galaxies through only adiabatic compression without dynamo amplification mechanism in models of power-law inflation based on spacetime noncommutativity without introducing a huge hierarchy between the dilaton's potential and its coupling to the electromagnetic fields.

hep-ph↗

arXiv2004

Large-scale magnetic fields from inflation in dilaton electromagnetism

The generation of large-scale magnetic fields is studied in dilaton electromagnetism in inflationary cosmology, taking into account the dilaton's evolution throughout inflation and reheating until it is stabilized with possible entropy production. It is shown that large-scale magnetic fields with observationally interesting strength at the present time could be generated if the conformal invariance of the Maxwell theory is broken through the coupling between the dilaton and electromagnetic fields in such a way that the resultant quantum fluctuations in the magnetic field has a nearly scale-invariant spectrum. If this condition is met, the amplitude of the generated magnetic field could be sufficiently large even in the case huge amount of entropy is produced with the dilution factor $\sim 10^{24}$ as the dilaton decays.

astro-ph↗