40,441 research outputs found
Large-Scale Synchrony in Weakly Interacting Automata
We study the behavior of two spatially distributed (sandpile) models which
are weakly linked with one another. Using a Monte-Carlo implementation of the
renormalization group and algebraic methods, we describe how large-scale
correlations emerge between the two systems, leading to synchronized behavior.Comment: 6 pages, 3 figures; to appear PR
Predicting the relativistic periastron advance of a binary without curving spacetime
Relativistic Newtonian Dynamics, the simple model used previously for
predicting accurately the anomalous precession of Mercury, is now applied to
predict the periastron advance of a binary. The classical treatment of a binary
as a two-body problem is modified to account for the influence of the
gravitational potential on spacetime. Without curving spacetime, the model
predicts the identical equation for the relativistic periastron advance as the
post-Newtonian approximation of general relativity formalism thereby providing
further substantiation of this model.Comment: 6 pages, 2 figure
A Trackable Model of Reciprocity and Fairness.
We introduced a parametric model of other-regarding preferences in which my emotional state determines the marginal rate of substitution between my own and other' payoffs, and thus my subsequent choices. In turn, my emotional state responds to relative status and to the kindness or unkindness of others' choices. Structural estimations of this model with six existing data sets demonstrate that other-regarding preferences depend on status, reciprocity, and perceived property rights.RECIPROCITY ; MARGINAL RATE OF SUBSTITUTION ; PAYOFFS
Experience in feeding coal into a liquefaction process development unit
A system for preparing coal slurry and feeding it into a high pressure liquefaction plant is described. The system was developed to provide supporting research and development for the Bureau of Mines coal liquefaction pilot plant. Operating experiences are included
A numerical study of the r-mode instability of rapidly rotating nascent neutron stars
The first results of numerical analysis of classical r-modes of {\it rapidly}
rotating compressible stellar models are reported. The full set of linear
perturbation equations of rotating stars in Newtonian gravity are numerically
solved without the slow rotation approximation. A critical curve of
gravitational wave emission induced instability which restricts the rotational
frequencies of hot young neutron stars is obtained. Taking the standard cooling
mechanisms of neutron stars into account, we also show the `evolutionary
curves' along which neutron stars are supposed to evolve as cooling and
spinning-down proceed. Rotational frequencies of stars suffering
from this instability decrease to around 100Hz when the standard cooling
mechanism of neutron stars is employed. This result confirms the results of
other authors who adopted the slow rotation approximation.Comment: 4 pages, 2 figures; MNRAS,316,L1(2000
Necrotic tumor growth: an analytic approach
The present paper deals with a free boundary problem modeling the growth
process of necrotic multi-layer tumors. We prove the existence of flat
stationary solutions and determine the linearization of our model at such an
equilibrium. Finally, we compute the solutions of the stationary linearized
problem and comment on bifurcation.Comment: 14 pages, 3 figure
Quantum Brownian motion in a quasiperiodic potential
We consider a quantum particle subject to Ohmic dissipation, moving in a
bichromatic quasiperiodic potential. In a periodic potential the particle
undergoes a zero-temperature localization-delocalization transition as
dissipation strength is decreased. We show that the delocalized phase is absent
in the quasiperiodic case, even when the deviation from periodicity is
infinitesimal. Using the renormalization group, we determine how the effective
localization length depends on the dissipation. We show that {a similar problem
can emerge in} the strong-coupling limit of a mobile impurity moving in a
periodic lattice and immersed in a one-dimensional quantum gas.Comment: 5+6 pages, 1 figur
The Quantum Propagator for a Nonrelativistic Particle in the Vicinity of a Time Machine
We study the propagator of a non-relativistic, non-interacting particle in
any non-relativistic ``time-machine'' spacetime of the type shown in Fig.~1: an
external, flat spacetime in which two spatial regions, at time and
at time , are connected by two temporal wormholes, one leading from
the past side of to t the future side of and the other from the
past side of to the future side of . We express the propagator
explicitly in terms of those for ordinary, flat spacetime and for the two
wormholes; and from that expression we show that the propagator satisfies
completeness and unitarity in the initial and final ``chronal regions''
(regions without closed timelike curves) and its propagation from the initial
region to the final region is unitary. However, within the time machine it
satisfies neither completeness nor unitarity. We also give an alternative proof
of initial-region-to-final-region unitarity based on a conserved current and
Gauss's theorem. This proof can be carried over without change to most any
non-relativistic time-machine spacetime; it is the non-relativistic version of
a theorem by Friedman, Papastamatiou and Simon, which says that for a free
scalar field, quantum mechanical unitarity follows from the fact that the
classical evolution preserves the Klein-Gordon inner product
Quasi-Adiabatic Continuation in Gapped Spin and Fermion Systems: Goldstone's Theorem and Flux Periodicity
We apply the technique of quasi-adiabatic continuation to study systems with
continuous symmetries. We first derive a general form of Goldstone's theorem
applicable to gapped nonrelativistic systems with continuous symmetries. We
then show that for a fermionic system with a spin gap, it is possible to insert
-flux into a cylinder with only exponentially small change in the energy
of the system, a scenario which covers several physically interesting cases
such as an s-wave superconductor or a resonating valence bond state.Comment: 19 pages, 2 figures, final version in press at JSTA
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