13,066 research outputs found
Competition between hidden order and antiferromagnetism in URu_2Si_2 under uniaxial stress studied by neutron scattering
We have performed elastic neutron scattering experiments under uniaxial
stress sigma applied along the tetragonal [100], [110] and [001] directions for
the heavy electron compound URu2Si2. We found that antiferromagnetic (AF) order
with large moment is developed with sigma along the [100] and [110] directions.
If the order is assumed to be homogeneous, the staggered ordered moment mu_o
continuously increases from 0.02 mu_B (sigma=0) to 0.22 mu_B (0.25 GPa). The
rate of increase partial mu_o/partial sigma is ~ 1.0 mu_B/GPa, which is four
times larger than that for the hydrostatic pressure (partial mu_o/partial P sim
0.25 mu_B/GPa). Above 0.25 GPa, mu_o shows a tendency to saturate, similar to
the hydrostatic pressure behavior. For sigma||[001], mu_o shows only a slight
increase to 0.028 mu_B (sigma = 0.46 GPa) with a rate of ~ 0.02 mu_B/GPa,
indicating that the development of the AF state highly depends on the direction
of sigma. We have also found a clear hysteresis loop in the isothermal
mu_o(sigma) curve obtained for sigma||[110] under the zero-stress-cooled
condition at 1.4 K. This strongly suggests that the sigma-induced AF phase is
metastable, and separated from the "hidden order" phase by a first-order phase
transition. We discuss these experimental results on the basis of crystalline
strain effects and elastic energy calculations, and show that the c/a ratio
plays a key role in the competition between these two phases.Comment: 9 pages, 7 figures, to appear in Physical Review
Recording Leaf Movements with a Strain Gauge
Lightweight strain gauge sensing unit for recording circadian leaf movements in space environmen
Reconstruction of the primordial fluctuation spectrum from the five-year WMAP data by the cosmic inversion method with band-power decorrelation analysis
The primordial curvature fluctuation spectrum is reconstructed by the cosmic
inversion method using the five-year WMAP data of the cosmic microwave
background temperature anisotropy. We apply the covariance matrix analysis and
decompose the reconstructed spectrum into statistically independent
band-powers. The statistically significant deviation from a simple power-law
spectrum suggested by the analysis of the first-year data is not found in the
five-year data except possibly at one point near the border of the wavenumber
domain where accurate reconstruction is possible.Comment: 9page
Metric perturbation from inflationary magnetic field and generic bound on inflation models
There is an observational indication of extragalactic magnetic fields. No
known astrophysical process can explain the origin of such large scale magnetic
fields, which motivates us to look for their origin in primordial inflation. By
solving the linearized Einstein equations, we study metric perturbations
sourced by magnetic fields that are produced during inflation. This leads to a
simple but robust bound on the inflation models by requiring that the induced
metric perturbation should not exceed the observed value 10^-5. In case of the
standard single field inflation model, the bound can be converted into a lower
bound on the Hubble parameter during inflation.Comment: 14 page
Hiding cosmic strings in supergravity D-term inflation
The influence of higher-order terms in the K\"{a}hler potential of the
supergravity D-term inflation model on the density perturbation is studied. We
show that these terms can make the inflaton potential flatter, which lowers the
energy scale of inflation under the COBE/WMAP normalization. As a result, the
mass per unit length of cosmic strings, which are produced at the end of
inflation, can be reduced to a harmless but detectable level without
introducing a tiny Yukawa coupling. Our scenario can naturally be implemented
in models with a low cut-off as in Type I or Type IIB orientifold models.Comment: 15 pages, 4 figure
Description of two new actinosporean types from a brook of Fuji Mountain, Honshu, and from Chitose River, Hokkaido, Japan
Actinospore infection of oligochaetes living in the mud of 3 freshwater biotopes in Japan was studied. Using the cell-well plate method, a new aurantiactinomyxon type was found in 0.77 % of the examined Tubifex tubifex oligochaete specimens from a brook near Yamanashi Prefectural Fisheries Experimental Station on Fuji Mountain. In 0.14 % of Lumbriculus variagetus collected from Chitose River, near Chitose Salmon Hatchery, a new siedleckiella type was found, while at the same time 8.1 % of the Lumbriculus spp. oligochaetes released triactinomyxons of Myxobolus arcticus. Of the examined Rhyacodrilus komarovi oligochaetes collected from the Mena River system, Hokkaido, 0.2, 0.6, 0.5 and 0.8% were infected with echinactinomyxon, neoactinomyxum and 2 types of triactinomyxon spores, respectively, and described in our previous paper. The oligochaetes released actinospores for several weeks. Actinospore infection showed high intensity in positive oligochaetes in the case of all the actinosporean types. Two of the actinospore types (aurantiactinomyxon and siedleckiella) presented here have not been previously described
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