510 research outputs found
Determinant Structure of the Rational Solutions for the Painlev\'e IV Equation
Rational solutions for the Painlev\'e IV equation are investigated by Hirota
bilinear formalism. It is shown that the solutions in one hierarchy are
expressed by 3-reduced Schur functions, and those in another two hierarchies by
Casorati determinant of the Hermite polynomials, or by special case of the
Schur polynomials.Comment: 19 pages, Latex, using theorem.st
Vectorial Control of Magnetization by Light
Coherent light-matter interactions have recently extended their applications
to the ultrafast control of magnetization in solids. An important but
unrealized technique is the manipulation of magnetization vector motion to make
it follow an arbitrarily designed multi-dimensional trajectory. Furthermore,
for its realization, the phase and amplitude of degenerate modes need to be
steered independently. A promising method is to employ Raman-type nonlinear
optical processes induced by femtosecond laser pulses, where magnetic
oscillations are induced impulsively with a controlled initial phase and an
azimuthal angle that follows well defined selection rules determined by the
materials' symmetries. Here, we emphasize the fact that temporal variation of
the polarization angle of the laser pulses enables us to distinguish between
the two degenerate modes. A full manipulation of two-dimensional magnetic
oscillations is demonstrated in antiferromagnetic NiO by employing a pair of
polarization-twisted optical pulses. These results have lead to a new concept
of vectorial control of magnetization by light
Global diagnostics of ionospheric absorption during X-ray solar flares based on 8-20MHz noise measured by over-the-horizon radars
An analysis of noise attenuation during eighty solar flares between 2013 and
2017 was carried out at frequencies 8-20 MHz using thirty-four SuperDARN radars
and the EKB ISTP SB RAS radar. The attenuation was determined on the basis of
noise measurements performed by the radars during the intervals between
transmitting periods. The location of the primary contributing ground sources
of noise was found by consideration of the propagation paths of radar
backscatter from the ground. The elevation angle for the ground echoes was
determined through a new empirical model. It was used to determine the paths of
the noise and the location of its source. The method was particularly well
suited for daytime situations which had to be limited for the most part to only
two crossings through the D region. Knowing the radio path was used to
determine an equivalent vertical propagation attenuation factor. The change in
the noise during solar flares was correlated with solar radiation lines
measured by GOES/XRS, GOES/EUVS, SDO/AIA, SDO/EVE, SOHO/SEM and PROBA2/LYRA
instruments. Radiation in the 1 to 8 and and near
100 are shown to be primarily responsible for the increase in the
radionoise absorption, and by inference, for an increase in the D and E region
density. The data are also shown to be consistent with a radar frequency
dependence having a power law with an exponent of -1.6. This study shows that a
new dataset can be made available to study D and E region.Comment: 30 pages, 5 figures, 2 tables. Submitted to Space Weathe
Scintillation-only Based Pulse Shape Discrimination for Nuclear and Electron Recoils in Liquid Xenon
In a dedicated test setup at the Kamioka Observatory we studied pulse shape
discrimination (PSD) in liquid xenon (LXe) for dark matter searches. PSD in LXe
was based on the observation that scintillation light from electron events was
emitted over a longer period of time than that of nuclear recoil events, and
our method used a simple ratio of early to total scintillation light emission
in a single scintillation event. Requiring an efficiency of 50% for nuclear
recoil retention we reduced the electron background to 7.7\pm1.1(stat)\pm1.2
0.6(sys)\times10-2 at energies between 4.8 and 7.2 keVee and to
7.7\pm2.8(stat)\pm2.5 2.8(sys)\times10-3 at energies between 9.6 and 12 keVee
for a scintillation light yield of 20.9 p.e./keV. Further study was done by
masking some of that light to reduce this yield to 4.6 p.e./keV, the same
method results in an electron event reduction of 2.4\pm0.2(stat)\pm0.3
0.2(sys)\times10-1 for the lower of the energy regions above. We also observe
that in contrast to nuclear recoils the fluctuations in our early to total
ratio for electron events are larger than expected from statistical
fluctuations.Comment: 25 pages, 15 figure
Search for solar axions in XMASS, a large liquid-xenon detector
XMASS, a low-background, large liquid-xenon detector, was used to search for
solar axions that would be produced by bremsstrahlung and Compton effects in
the Sun. With an exposure of 5.6ton days of liquid xenon, the model-independent
limit on the coupling for mass 1keV is
(90% C.L.), which is a factor of two stronger than the existing experimental
limit. The bounds on the axion masses for the DFSZ and KSVZ axion models are
1.9 and 250eV, respectively. In the mass range of 10-40keV, this study produced
the most stringent limit, which is better than that previously derived from
astrophysical arguments regarding the Sun to date
- …