5,991 research outputs found
Propagation of mesons in asymmetric nuclear matter in a density dependent coupling model
We study the propagation of the light mesons sigma, omega, rho, and a0(980)
in dense hadronic matter in an extended derivative scalar coupling model.
Within the scheme proposed it is possible to unambiguously define effective
density-dependent couplings at the Lagrangian level. We first apply the model
to study asymmetric nuclear matter with fixed isospin asymmetry, and then we
pay particular attention to hypermatter in beta-equilibrium. The equation of
state and the potential contribution to the symmetry coefficient arising from
the mean field approximation are investigated.Comment: 17 pages, 15 PostScript figure
Observability and Synchronization of Neuron Models
Observability is the property that enables to distinguish two different
locations in -dimensional state space from a reduced number of measured
variables, usually just one. In high-dimensional systems it is therefore
important to make sure that the variable recorded to perform the analysis
conveys good observability of the system dynamics. In the case of networks
composed of neuron models, the observability of the network depends
nontrivially on the observability of the node dynamics and on the topology of
the network. The aim of this paper is twofold. First, a study of observability
is conducted using four well-known neuron models by computing three different
observability coefficients. This not only clarifies observability properties of
the models but also shows the limitations of applicability of each type of
coefficients in the context of such models. Second, a multivariate singular
spectrum analysis (M-SSA) is performed to detect phase synchronization in
networks composed by neuron models. This tool, to the best of the authors'
knowledge has not been used in the context of networks of neuron models. It is
shown that it is possible to detect phase synchronization i)~without having to
measure all the state variables, but only one from each node, and ii)~without
having to estimate the phase
APPROXIMATE MODEL MATCHING WITH RELAXED CONSTRAINTS ON THE REFERENCE MODEL
It is suggested that if the overall transfer function, O( s), of a certain control system is allowed to match approximately a reference model, H(s), that is O(jω)≈ H(jω), then several constraints on the structure of H( s) can be relaxed. The main ideas are illustrated by means of examples
Grassmanian and Bosonic Thirring Models with Jump Defects
In this paper we discuss the Lax formulation of the Grassmanian and Bosonic
Thirring models in the presence of jump defects. For the Grassmanian case, the
defect is described by B\"acklund transformation which is responsible for
preserving the integrability of the model.
We then propose an extension of the B\"acklund transformation for the Bosonic
Thirring model which is verified by some B\"acklund transitions like
Vacuum-One soliton, One soliton - One soliton, One soliton - Two solitons and
Two solitons - Two solitons. The Lax formulation within the space split by the
defect leads to the integrability of Bosonic Thirring model.Comment: Latex 21 page
Thirring Model with Jump Defect
The purpose of our work is to extend the formulation of classical affine Toda
Models in the presence of jump defects to pure fermionic Thirring model. As a
first attempt we construct the Lagrangian of the Grassmanian Thirring model
with jump defect (of Backlund type) and present its conserved modified momentum
and energy expressions giving a first indication of its integrability.Comment: Poster contribution to the 5th International School on Field Theory
and Gravitation, Cuiaba, MT, Brazil, 20-24 Apr 2009. to be published in PoS
ISFTG(2009
Defects in the supersymmetric mKdV hierarchy via Backlund transformations
The integrability of the supersymmetric modified Korteweg
de-Vries (smKdV) hierarchy in the presence of defects is investigated through
the construction of its super B\"acklund transformation. The construction of
such transformation is performed by using essentially two methods: the
B\"acklund-defect matrix approach and the superfield approach. Firstly, we
employ the defect matrix associated to the hierarchy which turns out to be the
same for the supersymmetric sinh-Gordon (sshG) model. The method is general for
all flows and as an example we derive explicitly the B\"acklund equations in
components for the first few flows of the hierarchy, namely and .
Secondly, the supersymmetric extension of the B\"acklund transformation in the
superspace formalism is constructed for those flows. Finally, this super
B\"acklund transformation is employed to introduce type I defects for the
supersymmetric mKdV hierarchy. Further integrability aspects by considering
modified conserved quantities are derived from the defect matrix.Comment: 40 pages. Some comments and references added. Version accepted for
publication in JHE
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