30,777 research outputs found
Electron screening in the liquid-gas mixed phases of nuclear matter
Screening effects of electrons on inhomogeneous nuclear matter, which
includes spherical, slablike, and rodlike nuclei as well as spherical and
rodlike nuclear bubbles, are investigated in view of possible application to
cold neutron star matter and supernova matter at subnuclear densities. Using a
compressible liquid-drop model incorporating uncertainties in the surface
tension, we find that the energy change due to the screening effects broadens
the density region in which bubbles and nonspherical nuclei appear in the phase
diagram delineating the energetically favorable shape of inhomogeneous nuclear
matter. This conclusion is considered to be general since it stems from a
model-independent feature that the electron screening acts to decrease the
density at which spherical nuclei become unstable against fission and to
increase the density at which uniform matter becomes unstable against proton
clustering.Comment: 12 pages, 8 figures, accepted for publication in Physical Review
Photoionization yield and absorption coeffi- cient of xenon in the region 860-1022 deg angstrom
Photoionization yield and absorption coefficient of xenon gas measured by photoelectric method
Universal Features of Quantized Thermal Conductance of Carbon Nanotubes
The universal features of quantized thermal conductance of carbon nanotubes
(CNTs) are revealed through theoretical analysis based on the Landauer theory
of heat transport. The phonon-derived thermal conductance of semiconducting
CNTs exhibits a universal quantization in the low temperature limit,
independent of the radius or atomic geometry. The temperature dependence
follows a single curve given in terms of temperature scaled by the phonon
energy gap. The thermal conductance of metallic CNTs has an additional
contribution from electronic states, which also exhibits quantized behavior up
to room temperature.Comment: 4 pages, 5 figures. accepted for publication in Phys. Rev. Let
Apparatus for time‐resolved measurements of acoustic birefringence in particle dispersions
An apparatus for time‐resolved measurements of the birefringence induced in a particle suspension by an acoustic wave pulse is described. Efficient acoustic coupling is obtained by operating near the transducer resonant frequency and by matching the acoustic impedances of the cell constituents. An almost‐overdamped acoustic configuration can alternatively be employed whenever a faster response is needed. Careful design of the optical setup and of the detection unit minimize diffraction and stress‐birefringence parasitic effects and yields a good responsivity at fairly low acoustic intensities. A test of the apparatus on a colloidal suspension of PTFE rodlike particles is presented and discussed
Potential inversion with subbarrier fusion data revisited
We invert experimental data for heavy-ion fusion reactions at energies well
below the Coulomb barrier in order to directly determine the internucleus
potential between the colliding nuclei. In contrast to the previous
applications of the inversion formula, we explicitly take into account the
effect of channel couplings on fusion reactions, by assuming that fusion cross
sections at deep subbarrier energies are governed by the lowest barrier in the
barrier distribution. We apply this procedure to the O +Sm and
O +Pb reactions, and find that the inverted internucleus
potential are much thicker than phenomenological potentials. A relation to the
steep fall-off phenomenon of fusion cross sections recently found at deep
subbarrier energies is also discussed.Comment: 5 pages, 3 eps figure
Quantum Effects in Small-Capacitance Single Josephson Junctions
We have measured the current-voltage (I-V) characteristics of
small-capacitance single Josephson junctions at low temperatures (T=0.02-0.6
K), where the strength of the coupling between the single junction and the
electromagnetic environment was controlled with one-dimensional arrays of dc
SQUIDs. The single-junction I-V curve is sensitive to the impedance of the
environment, which can be tuned IN SITU. We have observed Coulomb blockade of
Cooper-pair tunneling and even a region of negative differential resistance,
when the zero-bias resistance R_0' of the SQUID arrays is much higher than the
quantum resistance R_K = h/e^2 = 26 kohm. The negative differential resistance
is evidence of coherent single-Cooper-pair tunneling within the theory of
current-biased single Josephson junctions. Based on the theory, we have
calculated the I-V curves numerically in order to compare with the experimental
ones at R_0' >> R_K. The numerical calculation agrees with the experiments
qualitatively. We also discuss the R_0' dependence of the
single-Josephson-junction I-V curve in terms of the superconductor-insulator
transition driven by changing the coupling to the environment.Comment: 11 pages with 14 embedded figures, RevTeX4, final versio
Novel Charge Order and Superconductivity in Two-Dimensional Frustrated Lattice at Quarter Filling
Motivated by the various physical properties observed in
-(BEDT-TTF)X, we study the ground state of extended Hubbard model
on two-dimensional anisotropic triangular lattice at 1/4-filling with
variational Monte Carlo method. It is shown that the nearest-neighbor Coulomb
interaction enhances the charge fluctuation and it induces the anomalous state
such as charge-ordered metallic state and the triplet next-nearest-neighbor
-wave superconductivity. We discuss the relation to the real materials and
propose the unified view of the family of -(BEDT-TTF)X.Comment: 4 pages, 5 figure
Lower Critical Field Hc1(T) and Pairing Symmetry Based on Eilenberger Theory
We quantitatively estimate different T-dependences of Hc1 between s wave and
d wave pairings by Eilenberger theory. The T-dependences of Hc1(T) show
quantitative deviation from those in London theory. We also study differences
of Hc1(T) between p+ and p- wave pairing in chiral p wave superconductors.
There, Hc1(T) is lower in p- wave pairing, and shows the same T-dependence as
in s wave pairing.Comment: 2 pages, 1 figur
Hysteresis of spectral evolution in the soft state of black-hole binary LMC X-3
We report the discovery of hysteresis between the x-ray spectrum and
luminosity of black-hole binary LMC X-3. Our observations, with the
Proportional Counter Array on the Rossi X-ray Timing Explorer, took place
entirely within the soft spectral state, dominated by a spectral component that
was fitted well with a multicolor disk blackbody. A power-law component was
seen only during times when the luminosity of the disk blackbody was declining.
The x-ray luminosity at these times was comparable to that seen in transient
systems (x-ray novae) when they return to the hard state at the end of an
outburst. Our observations may represent partial transitions to the hard state;
complete transitions have been seen in this system by Wilms et al. (2001). If
they are related to the soft-to-hard transition in transients, then they
demonstrate that hysteresis effects can appear without a full state transition.
We discuss these observations in the context of earlier observations of
hysteresis within the hard state of binaries 1E 1740.7-2942 and GRS 1758-258
and in relation to published explanations of hysteresis in transients.Comment: 14 pages, 6 figures, accepted by The Astrophysical Journa
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