7,967 research outputs found
Topological Speed Limits to Network Synchronization
We study collective synchronization of pulse-coupled oscillators interacting
on asymmetric random networks. We demonstrate that random matrix theory can be
used to accurately predict the speed of synchronization in such networks in
dependence on the dynamical and network parameters. Furthermore, we show that
the speed of synchronization is limited by the network connectivity and stays
finite, even if the coupling strength becomes infinite. In addition, our
results indicate that synchrony is robust under structural perturbations of the
network dynamics.Comment: 5 pages, 3 figure
The Physical Projector and Topological Quantum Field Theories: U(1) Chern-Simons Theory in 2+1 Dimensions
The recently proposed physical projector approach to the quantisation of
gauge invariant systems is applied to the U(1) Chern-Simons theory in 2+1
dimensions as one of the simplest examples of a topological quantum field
theory. The physical projector is explicitely demonstrated to be capable of
effecting the required projection from the initially infinite number of degrees
of freedom to the finite set of gauge invariant physical states whose
properties are determined by the topology of the underlying manifold.Comment: 24 pages, no figures, plain LaTeX file; one more reference added.
Final version to appear in Jour. Phys.
Knowledge, Attitudes, and Beliefs Regarding Breast and Cervical Cancer Screening among Cambodian, Laotian, Thai, and Tongan Women
Asian American Pacific Islander (AAPI) groups have low rates of breast and cervical cancer screening. This study examined knowledge, attitudes, and beliefs (KABs) regarding breast and cervical cancer on AAPI women. A cross-sectional survey of 1,808 AAPI women was included. Descriptive statistics and chi-square tests were provided and 55.3%, 68.6%, and 71.9% had received mammograms, clinical breast exam, and Pap smears, respectively. KABs on breast and cervical cancer varied between the four ethnic groups. Understanding the KABs toward cancer screening among AAPI women holds promise for identifying barriers to early detection and could aid in the creation of interventions
Hamiltonian reduction of SU(2) Dirac-Yang-Mills mechanics
The SU(2) gauge invariant Dirac-Yang-Mills mechanics of spatially homogeneous
isospinor and gauge fields is considered in the framework of the generalized
Hamiltonian approach. The unconstrained Hamiltonian system equivalent to the
model is obtained using the gaugeless method of Hamiltonian reduction. The
latter includes the Abelianization of the first class constraints, putting the
second class constraints into the canonical form and performing a canonical
transformation to a set of adapted coordinates such that a subset of the new
canonical pairs coincides with the second class constraints and part of the new
momenta is equal to the Abelian constraints. In the adapted basis the pure
gauge degrees of freedom automatically drop out from the consideration after
projection of the model onto the constraint shell. Apart from the elimination
of these ignorable degrees of freedom a further Hamiltonian reduction is
achieved due to the three dimensional group of rigid symmetry possessed by the
system.Comment: 25 pages Revtex, no figure
Theory of friction: contribution from fluctuating electromagnetic field
We calculate the friction force between two semi-infinite solids in relative
parallel motion (velocity ), and separated by a vacuum gap of width . The
friction force result from coupling via a fluctuating electromagnetic field,
and can be considered as the dissipative part of the van der Waals interaction.
We consider the dependence of the friction force on the temperature , and
present a detailed discussion of the limiting cases of small and large and
.Comment: 15 pages, No figure
Counterintuitive transitions in multistate curve crossing involving linear potentials
Two problems incorporating a set of horizontal linear potentials crossed by a
sloped linear potential are analytically solved and compared with numerical
results: (a) the case where boundary conditions are specified at the ends of a
finite interval, and (b) the case where the sloped linear potential is replaced
by a piecewise-linear sloped potential and the boundary conditions are
specified at infinity. In the approximation of small gaps between the
horizontal potentials, an approach similar to the one used for the degenerate
problem (Yurovsky V A and Ben-Reuven A 1998 J. Phys. B 31,1) is applicable for
both problems. The resulting scattering matrix has a form different from the
semiclassical result obtained by taking the product of Landau-Zener amplitudes.
Counterintuitive transitions involving a pair of successive crossings, in which
the second crossing precedes the first one along the direction of motion, are
allowed in both models considered here.Comment: LaTeX 2.09 using ioplppt.sty and psfig.sty, 16 pages with 5 figures.
Submitted to J. Phys.
Phase Fluctuations and Single Fermion Spectral Density in 2D Systems with Attraction
The effect of static fluctuations in the phase of the order parameter on the
normal and superconducting properties of a 2D system with attractive
four-fermion interaction is studied. Analytic expressions for the fermion
Green's function, its spectral density, and the density of states are derived
in the approximation where the coupling between the spin and charge degrees of
freedom is neglected. The resulting single-particle Green's function clearly
demonstrates a non-Fermi liquid behavior. The results show that as the
temperature increases through the 2D critical temperature, the width of the
quasiparticle peaks broadens significantly.Comment: 29 pages, ReVTeX, 12 EPS figures; references added, typos corrected,
new comments adde
Bursts in the Chaotic Trajectory Lifetimes Preceding the Controlled Periodic Motion
The average lifetime () it takes for a randomly started trajectory
to land in a small region () on a chaotic attractor is studied. is
an important issue for controlling chaos. We point out that if the region
is visited by a short periodic orbit, the lifetime strongly deviates
from the inverse of the naturally invariant measure contained within that
region (). We introduce the formula that relates
to the expanding eigenvalue of the short periodic orbit
visiting .Comment: Accepted for publication in Phys. Rev. E, 3 PS figure
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