4,354 research outputs found
Moduli Spaces of Abelian Vortices on Kahler Manifolds
We consider the self-dual vortex equations on a positive line bundle L --> M
over a compact Kaehler manifold of arbitrary dimension. When M is simply
connected, the moduli space of vortex solutions is a projective space. When M
is an abelian variety, the moduli space is the projectivization of the
Fourier-Mukai transform of L. We extend this description of the moduli space to
the abelian GLSM, i.e. to vortex equations with a torus gauge group acting
linearly on a complex vector space. After establishing the Hitchin-Kobayashi
correspondence appropriate for the general abelian GLSM, we give explicit
descriptions of the vortex moduli space in the case where the manifold M is
simply connected or is an abelian variety. In these examples we compute the
Kaehler class of the natural L^2-metric on the moduli space. In the simplest
cases we compute the volume and total scalar curvature of the muduli space.
Finally, we note that for abelian GLSM the vortex moduli space is a
compactification of the space of holomorphic maps from M to toric targets, just
as in the usual case of M being a Riemann surface. This leads to various
natural conjectures, for instance explicit formulae for the volume of the space
of maps CP^m --> CP^n.Comment: v2: 48 pages; significant changes; description of the vortex moduli
spaces of the GLSM extended to allow general values of the parameters, beyond
the generic values of v
Vortex equations in abelian gauged sigma-models
We consider nonlinear gauged sigma-models with Kahler domain and target. For
a special choice of potential these models admit Bogomolny (or self-duality)
equations -- the so-called vortex equations. We find the moduli space and
energy spectrum of the solutions of these equations when the gauge group is a
torus T^n, the domain is compact, and the target is C^n or CP^n. We also obtain
a large family of solutions when the target is a compact Kahler toric manifold.Comment: v2: 60 pages, more details than in CMP versio
Network Mutual Information and Synchronization under Time Transformations
We investigate the effect of general time transformations on the phase
synchronization (PS) phenomenon and the mutual information rate (MIR) between
pairs of nodes in dynamical networks. We demonstrate two important results
concerning the invariance of both PS and the MIR. Under time transformations PS
can neither be introduced nor destroyed and the MIR cannot be raised from zero.
On the other hand, for proper time transformations the timing between the
cycles of the coupled oscillators can be largely improved. Finally, we discuss
the relevance of our findings for communication in dynamical networks.Comment: 15 p
Optimal network topologies for information transmission in active networks
This work clarifies the relation between network circuit (topology) and
behavior (information transmission and synchronization) in active networks,
e.g. neural networks. As an application, we show how to determine a network
topology that is optimal for information transmission. By optimal, we mean that
the network is able to transmit a large amount of information, it possesses a
large number of communication channels, and it is robust under large variations
of the network coupling configuration. This theoretical approach is general and
does not depend on the particular dynamic of the elements forming the network,
since the network topology can be determined by finding a Laplacian matrix (the
matrix that describes the connections and the coupling strengths among the
elements) whose eigenvalues satisfy some special conditions. To illustrate our
ideas and theoretical approaches, we use neural networks of electrically
connected chaotic Hindmarsh-Rose neurons.Comment: 20 pages, 12 figure
The quantum equivariant cohomology of toric manifolds through mirror symmetry
Using mirror symmetry as described by Hori and Vafa, we compute the quantum
equivariant cohomology ring of toric manifolds. This ring arises naturally in
topological gauged sigma-models and is related to the Hamiltonian Gromov-Witten
invariants of the target manifold.Comment: 13 pages; v2: added comments and references, published versio
Experimental observation of a complex periodic window
The existence of a special periodic window in the two-dimensional parameter
space of an experimental Chua's circuit is reported. One of the main reasons
that makes such a window special is that the observation of one implies that
other similar periodic windows must exist for other parameter values. However,
such a window has never been experimentally observed, since its size in
parameter space decreases exponentially with the period of the periodic
attractor. This property imposes clear limitations for its experimental
detection.Comment: 4.2 pages, 4 figure
A spiral structure in the disk of EX Draconis on the rise to outburst maximum
We report on the R-band eclipse mapping analysis of high-speed photometry of
the dwarf nova EX Dra on the rise to the maximum of the November 1995 outburst.
The eclipse map shows a one-armed spiral structure of ~180 degrees in azimuth,
extending in radius from R ~0.2 to 0.43 R_{L1} (where R_{L1} is the distance
from the disk center to the inner Lagrangian point), that contributes about 22
per cent of the total flux of the eclipse map. The spiral structure is
stationary in a reference frame co-rotating with the binary and is stable for a
timescale of at least 5 binary orbits. The comparison of the eclipse maps on
the rise and in quiescence suggests that the outbursts of EX Dra may be driven
by episodes of enhanced mass-transfer from the secondary star. Possible
explanations for the nature of the spiral structure are discussed.Comment: To appear in the Astrophysical Journal Letters; 8 pages, 2 figures;
coded with AAS latex styl
Bronquiolite: Avanços Recentes
A bronquiolite e a infecção respiratória aguda das vias aéreas inferiores mais frequente em criançascom idade inferior a 24 meses, responsável por morbimortalidade significativa, incluindo complicações
frequentes na fase aguda e a longo prazo. A
heterogeneidade da abordagem desta patologia e a dificuldade em reduzir o seu peso nos indices de saúde pública, vem motivando investigação contínua e legitimou a publicação recente (2006) pela
Academia Americana de Pediatria (AAP) de normas de actuação, chamando-se a atenção para os resultados de uma metanálise realizada pela Cochrane Collaboration e para a existência de diversos fenotipos
de apresentação c1ínica.Os autores abordam alguns aspectos epidemiológicos,
c1ínicos (nomeadamente as complicações)
e, sobretudo, de terapêutica, com base em estudos recentes, elaborando uma proposta concretade actuação
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