2,669 research outputs found
Intrinsic chaos and external noise in population dynamics
We address the problem of the relative importance of the intrinsic chaos and
the external noise in determining the complexity of population dynamics. We use
a recently proposed method for studying the complexity of nonlinear random
dynamical systems. The new measure of complexity is defined in terms of the
average number of bits per time-unit necessary to specify the sequence
generated by the system. This measure coincides with the rate of divergence of
nearby trajectories under two different realizations of the noise. In
particular, we show that the complexity of a nonlinear time-series model
constructed from sheep populations comes completely from the environmental
variations. However, in other situations, intrinsic chaos can be the crucial
factor. This method can be applied to many other systems in biology and
physics.Comment: 13 pages, Elsevier styl
Trio-One: Layering Uncertainty and Lineage on a Conventional DBMS
Trio is a new kind of database system that supports data, uncertainty, and lineage in a fully integrated manner. The first Trio prototype, dubbed Trio-One, is built on top of a conventional DBMS using data and query translation techniques together with a small number of stored procedures. This paper describes Trio-One's translation scheme and system architecture, showing how it efficiently and easily supports the Trio data model and query language
Electron spin phase relaxation of phosphorus donors in nuclear spin enriched silicon
We report a pulsed EPR study of the phase relaxation of electron spins bound
to phosphorus donors in isotopically purified 29^Si and natural abundance Si
single crystals measured at 8 K.Comment: 5 pages, 3 figure
Density matrix renormalization group in a two-dimensional Hamiltonian lattice model
Density matrix renormalization group (DMRG) is applied to a (1+1)-dimensional
model. Spontaneous breakdown of discrete symmetry is
studied numerically using vacuum wavefunctions. We obtain the critical coupling
and the critical exponent
, which are consistent with the Monte Carlo and the
exact results, respectively. The results are based on extrapolation to the
continuum limit with lattice sizes , and 1000. We show that the
lattice size L=500 is sufficiently close to the the limit .Comment: 16 pages, 10 figures, minor corrections, accepted for publication in
JHE
The anomalous behavior of coefficient of normal restitution in the oblique impact
The coefficient of normal restitution in an oblique impact is theoretically
studied. Using a two-dimensional lattice models for an elastic disk and an
elastic wall, we demonstrate that the coefficient of normal restitution can
exceed one and has a peak against the incident angle in our simulation.
Finally, we explain these phenomena based upon the phenomenological theory of
elasticity.Comment: 4 pages, 4 figures, to be appeared in PR
Quantum Nernst effect in a bismuth single crystal
We report a theoretical calculation explaining the quantum Nernst effect
observed experimentally in a bismuth single crystal. Generalizing the
edge-current picture in two dimensions, we show that the peaks of the Nernst
coefficient survive in three dimensions due to a van Hove singularity. We also
evaluate the phonon-drag effect on the Nernst coefficient numerically. Our
result agrees with the experimental result for a bismuth single crystal.Comment: 4 pages, 4 figures, to be published in Proceedings of ISQM-Tokyo '0
Kinks in Discrete Light Cone Quantization
We investigate non-trivial topological structures in Discrete Light Cone
Quantization (DLCQ) through the example of the broken symmetry phase of the two
dimensional theory using anti periodic boundary condition (APBC). We
present evidence for degenerate ground states which is both a signature of
spontaneous symmetry breaking and mandatory for the existence of kinks. Guided
by a constrained variational calculation with a coherent state ansatz, we then
extract the vacuum energy and kink mass and compare with classical and semi -
classical results. We compare the DLCQ results for the number density of bosons
in the kink state and the Fourier transform of the form factor of the kink with
corresponding observables in the coherent variational kink state.Comment: 10 pages, 3 figure
Nernst effect in semi-metals: the meritorious heaviness of electrons
We present a study of electric, thermal and thermoelectric transport in
elemental Bismuth, which presents a Nernst coefficient much larger than what
was found in correlated metals. We argue that this is due to the combination of
an exceptionally low carrier density with a very long electronic
mean-free-path. The low thermomagnetic figure of merit is traced to the
lightness of electrons. Heavy-electron semi-metals, which keep a metallic
behavior in presence of a magnetic field, emerge as promising candidates for
thermomagnetic cooling at low temperatures.Comment: 4 pages, including 4 figure
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