6,398 research outputs found
A note on the phase transition in a topologically massive Ginzburg-Landau theory
We consider the phase transition in a model which consists of a
Ginzburg-Landau free energy for superconductors including a Chern-Simons term.
The mean field theory of Halperin, Lubensky and Ma [Phys. Rev. Lett. 32, 292
(1974)] is applied for this model. It is found that the topological mass,
, drives the system into different regimes of phase transition. For
instance, there is a such that for a
fluctuation induced first order phase transition occurs. On the other hand, for
only the second order phase transition exists. The 1-loop
renormalization group analysis gives further insight to this picture. The fixed
point structure exhibits tricritical and second order fixed points.Comment: Revised version; uses a more physical parametrization of the
renormalization group equations; new references added; one figure added;
EuroLatex, 6 page
A non-perturbative approach to the Coleman- Weinberg mechanism in massless scalar QED
We rederive non-perturbatively the Coleman-Weinberg expression for the
effective potential for massless scalar QED. Our result is not restricted to
small values of the coupling constants. This shows that the Coleman- Weinberg
result can be established beyond the range of validity of perturbation theory.
Also, we derive it in a manifestly renormalization group invariant way. It is
shown that with the derivation given no Landau ghost singularity arises. The
finite temperature case is discussed.
Pacs number: 11.10.Ef,11.10.Gh
Towards a knowledge-based system to assist the Brazilian data-collecting system operation
A study is reported which was carried out to show how a knowledge-based approach would lead to a flexible tool to assist the operation task in a satellite-based environmental data collection system. Some characteristics of a hypothesized system comprised of a satellite and a network of Interrogable Data Collecting Platforms (IDCPs) are pointed out. The Knowledge-Based Planning Assistant System (KBPAS) and some aspects about how knowledge is organized in the IDCP's domain are briefly described
On the Integrability and Chaos of an N=2 Maxwell-Chern-Simons-Higgs Mechanical Model
We apply different integrability analysis procedures to a reduced (spatially
homogeneous) mechanical system derived from an off-shell non-minimally coupled
N=2 Maxwell-Chern-Simons-Higgs model that presents BPS topological vortex
excitations, numerically obtained with an ansatz adopted in a special -
critical coupling - parametric regime. As a counterpart of the regularity
associated to the static soliton-like solution, we investigate the possibility
of chaotic dynamics in the evolution of the spatially homogeneous reduced
system, descendant from the full N=2 model under consideration. The originally
rich content of symmetries and interactions, N=2 susy and non-minimal coupling,
singles out the proposed model as an interesting framework for the
investigation of the role played by (super-)symmetries and parametric domains
in the triggering/control of chaotic behavior in gauge systems.
After writing down effective Lagrangian and Hamiltonian functions, and
establishing the corresponding canonical Hamilton equations, we apply global
integrability Noether point symmetries and Painleveproperty criteria to both
the general and the critical coupling regimes. As a non-integrable character is
detected by the pair of analytical criteria applied, we perform suitable
numerical simulations, as we seek for chaotic patterns in the system evolution.
Finally, we present some Comments on the results and perspectives for further
investigations and forthcoming communications.Comment: 18 pages, 5 figure
Fidelity Between Partial States as Signature of Quantum Phase Transitions
We introduce a partial state fidelity approach to quantum phase transitions.
We consider a superconducting lattice with a magnetic impurity inserted at its
centre, and look at the fidelity between partial (either one-site or two-site)
quantum states. In the vicinity of the point of the quantum phase transition,
we observe a sudden drop of the fidelity between two one-site partial states
corresponding to the impurity location and its close vicinity. In the case of
two-site states, the fidelity reveals the transition point as long as one of
the two electron sites is located at the impurity, while the other lies
elsewhere in the lattice. We also determine the Uhlmann mixed state geometric
phase, recently introduced in the study of the structural change of the system
state eigenvectors in the vicinity of the lines of thermal phase transitions,
and find it to be trivial, both for one- and two-site partial states, except
when an electron site is at the impurity. This means that the system partial
state eigenvectors do not contribute significantly to the enhanced state
distinguishability around the point of this quantum phase transition. Finally,
we use the fidelity to analyze the total amount of correlations contained
within a composite system, showing that, even for the smallest two-site states,
it features an abrupt quantitative change in the vicinity of the point of the
quantum phase transition.Comment: 11 pages, 5 figure
Perceção da cultura estratégica por docentes, funcionários e alunos nas instituições de ensino superior público: estudo de caso
As Instituições de Ensino Superior Público, que tentam responder a desafios como a internacionalização e a excelência no ensino e na investigação, começam, por todo o mundo, a utilizar a gestão estratégica. Será fundamental que todos os agentes estejam envolvidos nesta nova filosofia, pelo que neste estudo se pretende estudar o envolvimento e as opiniões de docentes, funcionários e alunos, em relação à gestão estratégica da Escola Superior de Tecnologia e de Gestão de Bragança - Instituto Politécnico de Bragança. Para esse efeito elaborou-se um questionário aos referidos agentes, apresentando-se neste estudo os resultados
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