2,529 research outputs found
A channel Brownian pump powered by an unbiased external force
A Brownian pump of particles in an asymmetric finite tube is investigated in
the presence of an unbiased external force. The pumping system is bounded by
two particle reservoirs. It is found that the particles can be pumped through
the tube from a reservoir at low concentration to one at the same or higher
concentration. There exists an optimized value of temperature (or the amplitude
of the external force) at which the pumping capacity takes its maximum value.
The pumping capacity decreases with increasing the radius at the bottleneck of
the tube.Comment: 14 pages, 9 figure
The Collective Excitation Spectra of and Mesons in Nuclear Matter
The recent progress on the study of the collective excitation in relativistic
nuclear matter is reviewed. The collective excitation modes are derived by
meson propagators in nuclear matter. The mesons we study are and mesons. For pion, we derived not only the relativistic
particle - hole, delta - hole excitations but also antiparticle excitations,
such as particle - antiparticle, antidelta - particle, delta - antiparticle
excitations. By calculating the dispersion relation and the spin - isospin
dependent response function, the effects of all these excitation are studied.Comment: 14 pages, 6 eps file, Latex; Talk at the Symposium of the Thermo
Field Dynamics and its application, May 5-8, CCAST, Beijing, P. R. Chin
Weak Topological Insulators in PbTe/SnTe Superlattices
It is desirable to realize topological phases in artificial structures by
engineering electronic band structures. In this paper, we investigate
superlattices along [001] direction and find a robust
weak topological insulator phase for a large variety of layer numbers m and
2n-m. We confirm this topologically non-trivial phase by calculating Z2
topological invariants and topological surface states based on the
first-principles calculations. We show that the folding of Brillouin zone due
to the superlattice structure plays an essential role in inducing topologically
non-trivial phases in this system. This mechanism can be generalized to other
systems in which band inversion occurs at multiple momenta, and gives us a
brand-new way to engineer topological materials in artificial structures.Comment: 6 pages, 4 figures, another author adde
Stellar Parameters and Chemical Abundances of G Giants
We present basic stellar parameters of 99 late-type G giants based on high
resolution spectra obtained by the High Dispersion Spectrograph attached to
Subaru Telescope. These stars are targets of a Doppler survey program searching
for extra-solar planets among evolved stars, with a metallicity of
-0.8<[Fe/H]<+0.2. We also derived their abundances of 15 chemical elements,
including four -elements (Mg, Si, Ca, Ti), three odd-Z light elements
(Al, K, Sc), four iron peak elements (V, Cr, Fe, Ni), and four neutron-capture
elements (Y, Ba, La, Eu). Kinematic properties reveal that most of the program
stars belong to the thin disk.Comment: 21 pages, 15 figures, PASJ accepte
Covariant Hamiltonian boundary term: Reference and quasi-local quantities
The Hamiltonian for dynamic geometry generates the evolution of a spatial
region along a vector field. It includes a boundary term which determines both
the value of the Hamiltonian and the boundary conditions. The value gives the
quasi-local quantities: energy-momentum, angular-momentum and center-of-mass.
The boundary term depends not only on the dynamical variables but also on their
reference values; the latter determine the ground state (having vanishing
quasi-local quantities). For our preferred boundary term for Einstein's GR we
propose 4D isometric matching and extremizing the energy to determine the
reference metric and connection values.Comment: 6 pages, contribution to the Proceedings of the Second LeCosPA
Symposium "Everything about Gravity", Taipei, 14-18 Dec., 201
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