1,751 research outputs found
Ground State Property of an Alternating Spin Ladder Involving Two Kinds of Inter-Chain Interactions
The ground state property of the alternating spin ladder is studied in the
case that the system involves an antiferromagnetic intra-chain interaction as
well as two kinds of inter-chain interactions; one is between spins of the same
magnitude and the other is between spins with different magnitudes. The
calculation has been carried out by the exact diagonalization method. As a
consequence of the competition among interactions, the system is revealed to
show an interesting variety of phases in the ground state property. Its phase
diagram is exhibited in the parameter space of the system. We find that,
however small the total amount of the inter-chain interactions is, the
ferrimagnetic ground state becomes unstable in a certain region. In this case,
which of the ferrimagnetic and the singlet ground state to appear is determined
only by the ratio between the inter-chain interactions regardless of their
total amount. The nature of two phases appearing in the singlet region of the
phase diagram and the type of the phase transition between them are also
discussed. The results are ensured by comparing with those of obtained in other
models which are contained in our model as special limiting cases.Comment: 12 pages, 9 PostScript figure
Mutual first order coherence of phase-locked lasers
We argue that (first-order) coherence is a relative, and not an absolute,
property. It is shown how feedforward or feedback can be employed to make two
(or more) lasers relatively coherent. We also show that after the relative
coherence is established, the two lasers will stay relatively coherent for some
time even if the feedforward or feedback loop has been turned off, enabling,
e.g., demonstration of unconditional quantum teleportation using lasers.Comment: 9 pages, 6 figure
In-gap state and effect of light illumination in CuIrS probed by photoemission spectroscopy
We have studied disorder-induced in-gap states and effect of light
illumination in the insulating phase of spinel-type CuIrS using
ultra-violet photoemission spectroscopy (UPS). The Ir/Ir
charge-ordered gap appears below the metal-insulator transition temperature.
However, in the insulating phase, in-gap spectral features with are
observed in UPS just below the Fermi level (), corresponding to the
variable range hopping transport observed in resistivity. The spectral weight
at is not increased by light illumination, indicating that the
Ir-Ir dimer is very robust although the long-range octamer order
would be destructed by the photo-excitation. Present results suggest that the
Ir-Ir bipolaronic hopping and disorder effects are responsible
for the conductivity of CuIrS.Comment: 14 pages, 5 figure
Search for Cosmic-Ray Antideuterons
We performed a search for cosmic-ray antideuterons using data collected
during four BESS balloon flights from 1997 to 2000. No candidate was found. We
derived, for the first time, an upper limit of 1.9E-4 (m^2 s sr
GeV/nucleon)^(-1) for the differential flux of cosmic-ray antideuterons, at the
95% confidence level, between 0.17 and 1.15 GeV/nucleon at the top of the
atmosphere.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Measurement of Low-Energy Cosmic-Ray Antiprotons at Solar Minimum
The absolute fluxes of the cosmic-ray antiprotons at solar minimum are
measured in the energy range 0.18 to 1.4 GeV, based on 43 events unambiguously
detected in BESS '95 data. The resultant energy spectrum appears to be flat
below 1 GeV, compatible with a possible admixture of primary antiproton
component with a soft energy spectrum, while the possibility of secondary
antiprotons alone explaining the data cannot be excluded with the present
accuracy. Further improvement of statistical accuracy and extension of the
energy range are planned in future BESS flights.Comment: REVTeX, 4 pages including 4 eps figures. Submitted to PR
Measurements of Atmospheric Antiprotons
We measured atmospheric antiproton spectra in the energy range 0.2 to 3.4
GeV, at sea level and at balloon altitude in the atmospheric depth range 4.5 to
26 g/cm^2. The observed energy spectra, including our previous measurements at
mountain altitude, were compared with estimated spectra calculated on various
assumptions regarding the energy distribution of antiprotons that interacted
with air nuclei.Comment: Accepted for publication in PL
Measurements of Primary and Atmospheric Cosmic-Ray Spectra with the BESS-TeV Spectrometer
Primary and atmospheric cosmic-ray spectra were precisely measured with the
BESS-TeV spectrometer. The spectrometer was upgraded from BESS-98 to achieve
seven times higher resolution in momentum measurement. We report absolute
fluxes of primary protons and helium nuclei in the energy ranges, 1-540 GeV and
1-250 GeV/n, respectively, and absolute flux of atmospheric muons in the
momentum range 0.6-400 GeV/c.Comment: 26 pages, 9 figures, 3 tables, Submitted to Phys. Lett.
Discovery of possible molecular counterparts to the infrared Double Helix Nebula in the Galactic center
We have discovered two molecular features at radial velocities of -35 km/s
and 0 km/s toward the infrared Double Helix Nebula (DHN) in the Galactic center
with NANTEN2. The two features show good spatial correspondence with the DHN.
We have also found two elongated molecular ridges at these two velocities
distributed vertically to the Galactic plane over 0.8 degree. The two ridges
are linked by broad features in velocity and are likely connected physically
with each other. The ratio between the 12CO J=2-1 and J=1-0 transitions is 0.8
in the ridges which is larger than the average value 0.5 in the foreground gas,
suggesting the two ridges are in the Galactic center. An examination of the K
band extinction reveals a good coincidence with the CO 0 km/s ridge and is
consistent with a distance of 8 +/-2 kpc. We discuss the possibility that the
DHN was created by a magnetic phenomenon incorporating torsional Alfv\'en waves
launched from the circumnuclear disk (Morris, Uchida & Do 2006) and present a
first estimate of the mass and energy involved in the DHN.Comment: 32 pages, 23 figures, Accepted by Ap
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