4,476 research outputs found
Symmetry breaking and other phenomena in the optimization of eigenvalues for composite membranes
We consider the following eigenvalue optimization problem: Given a bounded
domain and numbers , ,
find a subset of area for which the first Dirichlet
eigenvalue of the operator is as small as possible.
We prove existence of solutions and investigate their qualitative properties.
For example, we show that for some symmetric domains (thin annuli and dumbbells
with narrow handle) optimal solutions must possess fewer symmetries than
; on the other hand, for convex reflection symmetries are
preserved.
Also, we present numerical results and formulate some conjectures suggested
by them.Comment: 24 pages; 3 figures (as separate files); (shortened previous
version); to appear in Comm. Math. Phy
INCORPORATION OF QUANTUM STATISTICAL FEATURES IN MOLECULAR DYNAMICS
We formulate a method for incorporating quantum fluctuations into molecular-
dynamics simulations of many-body systems, such as those employed for energetic
nuclear collision processes. Based on Fermi's Golden Rule, we allow spontaneous
transitions to occur between the wave packets which are not energy eigenstates.
The ensuing diffusive evolution in the space of the wave packet parameters
exhibits appealing physical properties, including relaxation towards quantum-
statistical equilibrium.Comment: 8 latex pages + 1 uuencoded ps figur
Epitaxial growth and transport properties of Nb-doped SrTiO thin films
Nb-doped SrTiO epitaxial thin films have been prepared on (001)
SrTiO substrates using pulsed laser deposition. A high substrate
temperature () was found to be necessary to achieve
2-dimensional growth. Atomic force microscopy reveals atomically flat surfaces
with 3.9 \AA steps. The films show a metallic behavior, residual
resistivity ratios between 10 and 100, and low residual resistivity of the
order of 10cm. At 0.3 K, a sharp superconducting transition,
reaching zero resistance, is observed.Comment: 4 pages, 4 figure
Indication of intrinsic spin Hall effect in 4d and 5d transition metals
We have investigated spin Hall effects in 4 and 5 transition metals,
Nb, Ta, Mo, Pd and Pt, by incorporating the spin absorption method in the
lateral spin valve structure; where large spin current preferably relaxes into
the transition metals, exhibiting strong spin-orbit interactions. Thereby
nonlocal spin valve measurements enable us to evaluate their spin Hall
conductivities. The sign of the spin Hall conductivity changes systematically
depending on the number of electrons. This tendency is in good agreement
with the recent theoretical calculation based on the intrinsic spin Hall
effect.Comment: 5 pages, 4 figure
Few body Calculation of Neutrino Neutral Inelastic scattering on 4He
The inelastic neutral reaction of neutrino on 4He is calculated using two
modern nucleon--nucleon potentials. Full final state interaction among the four
nucleons is considered, via the Lorentz integral transform (LIT) method. The
effective interaction hyperspherical-harmonic (EIHH) approach is used to solve
the resulting Schrodinger like equations. A detailed energy dependent
calculation is given in the impulse approximation.Comment: 4 pages; talk at 18th International Conference on Few-Body Problems
in Physics (FB18), Santos, SP, Brazil, August 200
Possibility of s-wave pion condensates in neutron stars revisited
We examine possibilities of pion condensation with zero momentum (s-wave
condensation) in neutron stars by using the pion-nucleus optical potential U
and the relativistic mean field (RMF) models. We use low-density
phenomenological optical potentials parameterized to fit deeply bound pionic
atoms or pion-nucleus elastic scatterings. Proton fraction (Y_p) and electron
chemical potential (mu_e) in neutron star matter are evaluated in RMF models.
We find that the s-wave pion condensation hardly takes place in neutron stars
and especially has no chance if hyperons appear in neutron star matter and/or
b_1 parameter in U has density dependence.Comment: 4 pages, 3 figures, REVTe
Thermoacoustic effects in supercritical fluids near the critical point: Resonance, piston effect, and acoustic emission and reflection
We present a general theory of thermoacoustic phenomena in supercritical
fluids near the critical point in a one-dimensional cell. We take into account
the effects of the heat conduction in the boundary walls and the bulk viscosity
near the critical point. We introduce a coefficient characterizing
reflection of sound with frequency at the boundary. As applications,
we examine the acoustic eigenmodes in the cell, the response to time-dependent
perturbations, sound emission and reflection at the boundary. Resonance and
rapid adiabatic changes are noteworthy. In these processes, the role of the
thermal diffusion layers is enhanced near the critical point because of the
strong critical divergence of the thermal expansion.Comment: 15 pages, 7 figure
Epidemiology, Surveillance and Laboratory Diagnosis of Leptospirosis in the WHO South-East Asia Region
A Mathematical Study of the One-Dimensional Keller and Rubinov Model for Liesegang Bands
Our purpose is to start understanding from a mathematical viewpoint experiments in which regularized structures with spatially distinct bands or rings of precipitated material are exhibited, with clearly visible scaling properties. Such patterns are known as Liesegang bands or rings. In this paper, we study a one-dimensional version of the Keller and Rubinow model and present conditions ensuring the existence of Liesegang bands
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