27,311 research outputs found
A New Form of Path Integral for the Coherent States Representation and its Semiclassical Limit
The overcompleteness of the coherent states basis leads to a multiplicity of
representations of Feynman's path integral. These different representations,
although equivalent quantum mechanically, lead to different semiclassical
limits. Two such semiclassical formulas were derived in \cite{Bar01} for the
two corresponding path integral forms suggested by Klauder and Skagerstan in
\cite{Klau85}. Each of these formulas involve trajectories governed by a
different classical representation of the Hamiltonian operator: the P
representation in one case and the Q representation in other. In this paper we
construct a third representation of the path integral whose semiclassical limit
involves directly the Weyl representation of the Hamiltonian operator, i.e.,
the classical Hamiltonian itself.Comment: 16 pages, no figure
Tecnologia para produção orgância de cenoura consorciada com alface em Sergipe.
bitstream/CPATC/19935/1/ct-50.pd
Coherent State Path Integrals in the Weyl Representation
We construct a representation of the coherent state path integral using the
Weyl symbol of the Hamiltonian operator. This representation is very different
from the usual path integral forms suggested by Klauder and Skagerstan in
\cite{Klau85}, which involve the normal or the antinormal ordering of the
Hamiltonian. These different representations, although equivalent quantum
mechanically, lead to different semiclassical limits. We show that the
semiclassical limit of the coherent state propagator in Weyl representation is
involves classical trajectories that are independent on the coherent states
width. This propagator is also free from the phase corrections found in
\cite{Bar01} for the two Klauder forms and provides an explicit connection
between the Wigner and the Husimi representations of the evolution operator.Comment: 23 page
Tecnologia para biodegradação da casca de coco sem gerar outros resíduos.
bitstream/CPATC/19770/1/f_07_2007.pdfExiste o documento impresso
Deformation method for generalized Abelian Higgs-Chern-Simons models
We present an extension of the deformation method applied to self-dual
solutions of generalized Abelian Higgs-Chern-Simons models. Starting from a
model defined by a potential and a non-canonical kinetic term
whose analytical domain wall solutions are
known, we show that this method allows to obtain an uncountable number of new
analytical solutions of new models defined by other functions
and . We present some examples of deformation functions
leading to new families of models and their associated analytic solutions.Comment: 6 pages, 10 figure
Analytical BPS Maxwell-Higgs vortices
We have established a prescription for the calculation of analytical vortex
solutions in the context of generalized Maxwell-Higgs models whose overall
dynamics is controlled by two positive functions of the scalar field. We have
also determined a natural constraint between these functions and the Higgs
potential allowing the existence of axially symmetric
Bogomol'nyi-Prasad-Sommerfield (BPS) solutions possessing finite energy.
Furthermore, when the generalizing functions are chosen suitably, the
nonstandard BPS equations can be solved exactly. We have studied some examples,
comparing them with the usual Abrikosov-Nielsen-Olesen (ANO) solution. The
overall conclusion is that the analytical self-dual vortices are well-behaved
in all relevant sectors, strongly supporting the generalized models they belong
themselves. In particular, our results mimic well-known properties of the usual
(numerical) configurations, as localized energy density, while contributing to
the understanding of topological solitons and their description by means of
analytical methods.Comment: 8 pages, 4 figure
Tecnologia para biodegradação da casca de coco seco e de outros resíduos do coqueiro.
bitstream/item/158629/1/ct-46.pd
Examining punishment at different explanatory levels.
Experimental studies on punishment have sometimes been over-interpreted not only for the reasons Guala lists, but also because of a frequent conflation of proximate and ultimate explanatory levels that Guala's review perpetuates. Moreover, for future analyses we may need a clearer classification of different kinds of punishment
Reputation based on punishment rather than generosity allows for evolution of cooperation in sizable groups
Cooperation among unrelated individuals can arise if decisions to help others can be based on reputation. While working for dyadic interactions, reputation-use in social dilemmas involving many individuals (e.g. public goods games) becomes increasingly difficult as groups become larger and errors more frequent. Reputation is therefore believed to have played a minor role for the evolution of cooperation in collective action dilemmas such as those faced by early humans. Here, we show in computer simulations that a reputation system based on punitive actions can overcome these problems and, compared to reputation system based on generous actions, (i) is more likely to lead to the evolution of cooperation in sizable groups, (ii) more effectively sustains cooperation within larger groups, and (iii) is more robust to errors in reputation assessment. Punishment and punishment reputation could therefore have played crucial roles in the evolution of cooperation within larger groups of humans
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