5,009 research outputs found
Phase structure of Abelian Chern-Simons gauge theories
We study the effect of a Chern-Simons (CS) term in the phase structure of two
different Abelian gauge theories. For the compact Maxwell-Chern-Simons theory,
we obtain that for values of the CS coupling with ,
the theory is equivalent to a gas of closed loops with contact interaction,
exhibiting a phase transition in the universality class. We also employ
Monte Carlo simulations to study the noncompact U(1) Abelian Higgs model with a
CS term. Finite size scaling of the third moment of the action yields critical
exponents and that vary continuously with the strength of the CS
term, and a comparison with available analytical results is made.Comment: RevTex4, 4 pages, 1 figure; v3: improvements and corrections made in
the first part of the paper; references added. To be published in Europhysics
Letter
Compact U(1) gauge theories in 2+1 dimensions and the physics of low dimensional insulating materials
Compact abelian gauge theories in dimensions arise often as an
effective field-theoretic description of models of quantum insulators. In this
paper we review some recent results about the compact abelian Higgs model in
in that context.Comment: 5 pages, 3 figures; based on talk by F.S. Nogueira in the Aachen
HEP2003 conferenc
Abuse, proportionality and the burden of proof in CJEU’s case law on direct taxation
info:eu-repo/semantics/publishedVersio
Quantum critical scaling behavior of deconfined spinons
We perform a renormalization group analysis of some important effective field
theoretic models for deconfined spinons. We show that deconfined spinons are
critical for an isotropic SU(N) Heisenberg antiferromagnet, if is large
enough. We argue that nonperturbatively this result should persist down to N=2
and provide further evidence for the so called deconfined quantum criticality
scenario. Deconfined spinons are also shown to be critical for the case
describing a transition between quantum spin nematic and dimerized phases. On
the other hand, the deconfined quantum criticality scenario is shown to fail
for a class of easy-plane models. For the cases where deconfined quantum
criticality occurs, we calculate the critical exponent for the decay of
the two-spin correlation function to first-order in . We also
note the scaling relation connecting the exponent
for the decay to the correlation length exponent and the crossover
exponent .Comment: 4.1 pages, no figures, references added; Version accepted for
publication in PRB (RC
Gauge dependenceof the order parameter anomalous dimension in the Ginzburg-Landau model and the critical fluctuations in superconductors
The critical fluctuations of superconductors are discussed in a fixed
dimension scaling suited to describe the type II regime. The gauge dependence
of the anomalous dimension of the scalar field is stablished exactly from the
Ward-Takahashi identities. Its fixed point value gives the critical
exponent and it is shown that is gauge independent, as expected on
physical grounds. In the scaling considered, is found to be zero at
1-loop order, while . This result is just the 1-loop values
for the XY model obtained in the fixed dimension renormalization group
approach. It is shown that this XY behavior holds at all orders. The result
should be contrasted with the negative values frequently
reported in the literature.Comment: EuroLaTex, 7 pages, 2 figures, reference updated; version to be
published in Europhysics Letter
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
Avaliação das sementes do nim (Azadirachta indica) no controle de nematódeos gastrintestinais de caprinos criados em sistema de base agroecológica: resultados preliminares.
O objetivo desse trabalho foi avaliar a eficácia das sementes do nim (Azadiracht indica A. Juss) no controle das verminoses gastrintestinais de caprinos criados no sistema de produção do Cabrito Ecológico da Embrapa Semi-Árido. O trabalho foi realizado durante a época chuvosa (fevereiro a março), utilizando 18 caprinos ser padrão racial definido, divididos em três grupos homogêneos de acordo com os seguintes tratamentos: T1 controle (água); T2 (1,0 glkg) e T3 (3,0 glkg). Foram realizadas três aplicações com intervalo de 13 dias. Para avaliar a eficácia dos tratamentos, foi realizada a contagem do número de ovos de nematódeos pc gramas de fezes (OPG) antes e sete dias após as dosificações. Foi observado aumento do OPG em quase todos os tratamentos. Nas condições desse trabalho, a sementes do nim não foram eficazes no controle de nematódeos gastrintestinais de caprinos
Avaliação de plantas medicinais no controle de nematódeos gastrintestinais de caprinos criados em sistema de base agroecológica.
Este trabalho objetivou avaliar a eficácia de plantas medicinais no controle de nematódeos gastrintestinais. Foram utilizados 36 caprinos distribuídos em seis grupos de seis animais, nos seguintes tratamentos: T1 água (50 mL/animal); T2 closantel (10 mg/kg); T3 Curcubita sp. (3 g/kg); T4 Operculina sp. (8 g/kg); T5 Azadirachta indica (1 g/kg) e T6 Azadirachta indica (3 g/kg). As dosagens foram administradas após 12 horas de jejum, sob a forma de suco, por via oral. A eficácia dos tratamentos foi obtida pela contagem do OPG antes e sete dias após os tratamentos. A média do número de OPG antes dos tratamentos em todas as avaliações foi de 2.500 ovos. Apesar da discreta redução do OPG causada pelo T3 (41,0%) e T4 (34,9%) após a primeira administração, o OPG ainda permaneceu bastante elevado. Nos tratamentos T1, T5 e T6 foi observado aumento do OPG. A eficiência do closantel (T2) foi de 75,9%. Portanto, as dosagens utilizadas não apresentaram eficácia na redução do OPG
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