14,638 research outputs found
Peculiar Velocities of Nonlinear Structure: Voids in McVittie Spacetime
As a study of peculiar velocities of nonlinear structure, we analyze the
model of a relativistic thin-shell void in the expanding universe. (1) Adopting
McVittie (MV) spacetime as a background universe, we investigate the dynamics
of an uncompensated void with negative MV mass. Although the motion itself is
quite different from that of a compensated void, as shown by Haines & Harris
(1993), the present peculiar velocities are not affected by MV mass. (2) We
discuss how precisely the formula in the linear perturbation theory applies to
nonlinear relativistic voids, using the results in (1) as well as the previous
results for the homogeneous background (Sakai, Maeda, & Sato 1993). (3) We
re-examine the effect of the cosmic microwave background radiation. Contrary to
the results of Pim & Lake (1986, 1988), we find that the effect is negligible.
We show that their results are due to inappropriate initial conditions. Our
results (1)-(3) suggest that the formula in the linear perturbation theory is
approximately valid even for nonlinear voids.Comment: 12 pages, aastex, 4 ps figures separate, Fig.2 added, to appear in
Ap
The second phase transition in the pyrochlore oxide Cd2Re2O7
Evidence for another phase transition at 120 K in the metallic pyrochlore
oxide Cd2Re2O7, following the structural transition at 200 K and followed by
the superconducting transition at 1.0 K, is given through resistivity,
magnetoresistance, specific heat, and X-ray diffraction measurements. The
results indicate unique successive structural and electronic transitions
occurring in the pyrochlore compound, revealing an interesting interplay
between the crystal and electronic structures on the itinerant electron system
in the pyrochlore lattice
Charge Exchange Spin-Dipole Excitations of 90Zr and 208Pb and Neutron Matter Equation of State
Charge exchange spin-dipole (SD) excitations of Zr and Pb are
studied by using a Skyrme
Hartree-Fock(HF) + Random Phase approximation (RPA). The calculated
spin-dipole strength distributions are compared with experimental data obtained
by Zr (p,n) Nb and Zr (n,p) Nb reactions. The
model-independent SD sum rule values of various Skyrme interactions are studied
in comparison with the experimental values in order to determine the neutron
skin thickness of Zr. The pressure of the neutron matter equation of
state (EOS) and the nuclear matter symmetry energy are discussed in terms of
the neutron skin thickness and peak energies of SD strength distributions.Comment: 26pages, 10figure
Single Impurity Anderson Model with Coulomb Repulsion between Conduction Electrons on the Nearest-Neighbour Ligand Orbital
We study how the Kondo effect is affected by the Coulomb interaction between
conduction electrons on the basis of a simplified model. The single impurity
Anderson model is extended to include the Coulomb interaction on the
nearest-neighbour ligand orbital. The excitation spectra are calculated using
the numerical renormalization group method. The effective bandwidth on the
ligand orbital, , is defined to classify the state. This quantity
decreases as the Coulomb interaction increases. In the
region, the low energy properties are described by the Kondo state, where
is the hybridization width. As decreases in this region, the
Kondo temperature is enhanced, and its magnitude becomes comparable to
for . In the region, the local
singlet state between the electrons on the and ligand orbitals is formed.Comment: 5 pages, 3 figures, LaTeX, to be published in J. Phys. Soc. Jpn Vol.
67 No.
Metamagnetism of antiferromagnetic XXZ quantum spin chains
The magnetization process of the one-dimensional antiferromagnetic Heisenberg
model with the Ising-like anisotropic exchange interaction is studied by the
exact diagonalization technique. It results in the evidence of the first-order
spin flop transition with a finite magnetization jump in the N\'eel ordered
phase for . It implies that the S=1/2 chain is an exceptional case
where the metamagnetic transition becomes second-order due to large quantum
fluctuations.Comment: 4 pages, Revtex, with 6 eps figure
Topological Inflation with Multiple Winding
We analyze the core dynamics of critically coupled, superheavy gauge vortices
in the (2+1) dimensional Einstein-Abelian-Higgs system. By numerically solving
the Eistein and field equations for various values of the symmetry breaking
scale, we identify the regime in which static solutions cease to exist and
topological inflation begins. We explicitly include the topological winding of
the vortices into the calculation and extract the dependence on the winding of
the critical scale separating the static and inflating regimes. Extrapolation
of our results suggests that topological inflation might occur within high
winding strings formed at the Grand Unified scale.Comment: 13 pages, 4 figures, RevTe
Numerical Renormalization Group Study of non-Fermi-liquid State on Dilute Uranium Systems
We investigate the non-Fermi-liquid (NFL) behavior of the impurity Anderson
model (IAM) with non-Kramers doublet ground state of the f configuration
under the tetragonal crystalline electric field (CEF). The low energy spectrum
is explained by a combination of the NFL and the local-Fermi-liquid parts which
are independent with each other. The NFL part of the spectrum has the same form
to that of two-channel-Kondo model (TCKM). We have a parameter range that the
IAM shows the divergence of the magnetic susceptibility together with
the positive magneto resistance. We point out a possibility that the anomalous
properties of UThRuSi including the decreasing resistivity
with decreasing temperature can be explained by the NFL scenario of the TCKM
type. We also investigate an effect of the lowering of the crystal symmetry. It
breaks the NFL behavior at around the temperature, , where
is the orthorhombic CEF splitting. The NFL behavior is still expected above the
temperature, .Comment: 25 pages, 12 figure
Hierarchical fragmentation and collapse signatures in a high-mass starless region
Aims: Understanding the fragmentation and collapse properties of the dense
gas during the onset of high-mass star formation. Methods: We observed the
massive (~800M_sun) starless gas clump IRDC18310-4 with the Plateau de Bure
Interferometer (PdBI) at sub-arcsecond resolution in the 1.07mm continuum
andN2H+(3-2) line emission. Results: Zooming from a single-dish low-resolution
map to previous 3mm PdBI data, and now the new 1.07mm continuum observations,
the sub-structures hierarchically fragment on the increasingly smaller spatial
scales. While the fragment separations may still be roughly consistent with
pure thermal Jeans fragmentation, the derived core masses are almost two orders
of magnitude larger than the typical Jeans mass at the given densities and
temperatures. However, the data can be reconciled with models using
non-homogeneous initial density structures, turbulence and/or magnetic fields.
While most sub-cores remain (far-)infrared dark even at 70mum, we identify weak
70mum emission toward one core with a comparably low luminosity of ~16L_sun,
re-enforcing the general youth of the region. The spectral line data always
exhibit multiple spectral components toward each core with comparably small
line widths for the individual components (in the 0.3 to 1.0km/s regime). Based
on single-dish C18O(2-1) data we estimate a low virial-to-gas-mass ratio
<=0.25. We discuss that the likely origin of these spectral properties may be
the global collapse of the original gas clump that results in multiple spectral
components along each line of sight. Even within this dynamic picture the
individual collapsing gas cores appear to have very low levels of internal
turbulence.Comment: 8 pages, 4 figures, A&A in pres
Stepwise lowering of water-level caused by tectonic events occurred during 50-15 ka in the Paleo-Kathmandu Lake, central Nepal Himalaya
Abstract HKT-ISTP 2013
B
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