23 research outputs found
Possible resolution of the domain wall problem in the NMSSM
We discuss a possibility that the domain wall problem in the next-to-minimal supersymmetric standard model is alleviated without introducing a small explicit Z3 breaking term by analyzing the evolution of the singlet scalar field within an inflationary paradigm. The singlet scalar field which explains the μ-term tracks a time-varying minimum of the effective potential after inflation and slowly rolls down to its global minimum if there exist sufficiently large negative Hubble-induced corrections on the effective potential for the singlet field, which arise through supergravity. As a consequence, the whole Universe is confined within a single domain during and after inflation, which prevents the formation of domain walls. This will further constrain the history of the early Universe along with the Higgs-singlet coupling
Evolution of Anemone AR NOAA 10798 and the Related Geo-Effective Flares and CMEs
We present a detailed examination of the features of the Active Region (AR)
NOAA 10798. This AR generated coronal mass ejections (CMEs) that caused a large
geomagnetic storm on 24 August 2005 with the minimum Dst index of -216 nT. We
examined the evolution of the AR and the features on/near the solar surface and
in the interplanetary space. The AR emerged in the middle of a small coronal
hole, and formed a {\it sea anemone} like configuration. H filaments
were formed in the AR, which have southward axial field. Three M-class flares
were generated, and the first two that occurred on 22 August 2005 were followed
by Halo-type CMEs. The speeds of the CMEs were fast, and recorded about 1200
and 2400 km s, respectively. The second CME was especially fast, and
caught up and interacted with the first (slower) CME during their travelings
toward Earth. These acted synergically to generate an interplanetary
disturbance with strong southward magnetic field of about -50 nT, which was
followed by the large geomagnetic storm.Comment: 32 pages, 9 figures, JGR accepte
GEOTAIL observation of the SGR1806-20 Giant Flare: The first 600 ms
On December 27, 2004, plasma particle detectors on the GEOTAIL spacecraft
detected an extremely strong signal of hard X-ray photons from the giant flare
of SGR1806-20, a magnetar candidate. While practically all gamma-ray detectors
on any satellites were saturated during the first ~500 ms interval after the
onset, one of the particle detectors on GEOTAIL was not saturated and provided
unique measurements of the hard X-ray intensity and the profile for the first
600 ms interval with 5.48 ms time resolution. After ~50 ms from the initial
rapid onset, the peak photon flux (integrated above ~50 keV) reached the order
of 10^7 photons sec^{-1} cm^{-2}. Assuming a blackbody spectrum with kT=175
keV, we estimate the peak energy flux to be 21 erg sec^{-1} cm^{-2} and the
fluence (for 0-600 ms) to be 2.4 erg cm^{-2}. The implied energy release
comparable to the magnetic energy stored in a magnetar (~10^{47} erg) suggests
an extremely efficient energy release mechanism.Comment: 6 pages, 2 color figures, submitted to Natur
Observation results by the TAMA300 detector on gravitational wave bursts from stellar-core collapses
We present data-analysis schemes and results of observations with the TAMA300
gravitational-wave detector, targeting burst signals from stellar-core collapse
events. In analyses for burst gravitational waves, the detection and
fake-reduction schemes are different from well-investigated ones for a
chirp-wave analysis, because precise waveform templates are not available. We
used an excess-power filter for the extraction of gravitational-wave
candidates, and developed two methods for the reduction of fake events caused
by non-stationary noises of the detector. These analysis schemes were applied
to real data from the TAMA300 interferometric gravitational wave detector. As a
result, fake events were reduced by a factor of about 1000 in the best cases.
The resultant event candidates were interpreted from an astronomical viewpoint.
We set an upper limit of 2.2x10^3 events/sec on the burst gravitational-wave
event rate in our Galaxy with a confidence level of 90%. This work sets a
milestone and prospects on the search for burst gravitational waves, by
establishing an analysis scheme for the observation data from an
interferometric gravitational wave detector