Renormalization Group
Mostrando 13-24 de 56 artigos, teses e dissertações.
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13. Teorema Central do Limite para o modelo O(N) de Heisenberg hierárquico na criticalidade e o papel do limite N ->infinito na dinâmica dos zeros de Lee-Yang / Central Limit Theorem for the hierarchical O(N) Heisenberg model at criticality and the role of the N ->infinity limit for the Lee-Yang zeros´s dynamics
In this work we stablish the Central Limit Theorem for the hierarchical O(N) Heisenberg model at criticality via partial differential equation in the limit N ->infinity. For simplicity we only treat the d = 4 case but the theorem is still valid for d >4. By studying a given partial differential equation (PDE) we determine for any d >2 the critical inverse te
Publicado em: 2008
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14. Estudos do transporte de partÃculas brownianas interagentes e de transiÃÃes de fases em modelos de spin quÃnticos
Nesta Tese, sÃo investigados dois temas de interesse atual, o transporte de partÃculas brownianas interagentes e as transiÃÃes de fase em sistemas magnÃticos quÃnticos. No primeiro, o transporte de partÃculas brownianas interagentes sujeitas a um potencial de substrato do tipo catraca foi investigado numericamente atravÃs da dinÃmica de Langevin. Me
Publicado em: 2008
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15. Equation of state of gluon plasma and renormalization of local action
We consider a local, renormalizable, BRST-invariant action for QCD in Coulomb gauge that contains auxiliary bose and fermi ghost fields. It possess a non-perturbative vacuum that spontaneously breaks BRST-invariance. The vacuum condition leads to a gap equation that introduces a mass scale. Calculations are done to one-loop order in a perturbative expansion
Brazilian Journal of Physics. Publicado em: 2007-03
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16. Exploring the infrared structure of QCD with the Gribov-Zwanziger Lagrangian
We review recent one and two loop ${\overline{\mbox{MS}}}$ Landau gauge calculations using the Gribov-Zwanziger Lagrangian. The behaviour of the gluon and Faddeev-Popov ghost propagators as well as the renormalization group invariant effective coupling constant is examined in the infrared limit.
Brazilian Journal of Physics. Publicado em: 2007-03
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17. A local non-Abelian gauge invariant action stemming from the nonlocal operator FmuN(D²)-1FmuN
We report on the nonlocal gauge invariant operator of dimension two, FµN (D²)-1 FµN. We are able to localize this operator by introducing a suitable set of (anti)commuting antisymmetric tensor fields. Starting from this, we succeed in constructing a local gauge invariant action containing a mass parameter, and we prove the renormalizability to all orders
Brazilian Journal of Physics. Publicado em: 2007-03
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18. Cold and dense perturbative Yukawa theory with massive fermions
Recent results for the two-loop thermodynamic potential of QCD at finite density have shown that nonzero quark mass corrections to the pressure are relevant and can dramatically affect the structure of compact stars. Motivated by these findings, we consider a simple toy model - cold and dense Yukawa theory - to study the effects of finite fermion masses on t
Brazilian Journal of Physics. Publicado em: 2007-03
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19. Analyzing dynamical gluon mass generation
We study the necessary conditions for obtaining infrared finite solutions from the Schwinger-Dyson equation governing the dynamics of the gluon propagator. The equation in question is set up in the Feynman gauge of the background field method, thus capturing a number of desirable features. Most notably, and in contradistinction to the standard formulation, t
Brazilian Journal of Physics. Publicado em: 2007-03
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20. Confinement by design?
The configuration space of SU(N) gauge theory is restricted to orbits with vanishing Polyakov loops of non-trivial N-ality. A practical method of constraining to this orbit space C0 is found by implementing a certain axial-type gauge. It is shown that the representative of an orbit in C0 is unique in this gauge up to time independent Abelian gauge transforma
Brazilian Journal of Physics. Publicado em: 2007-03
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21. Numerical renormalization group for asymmetric conduction band / Grupo de renormalização numérico com banda assimétrica
Este trabalho apresenta um tratamento do Grupo de Renormalização Numérico (GRN) que permite a inclusão de assimetrias na banda de condução, como a provocada por campo magnetostático aplicado a sistemas de spins localizados em metais. Resultados para calor específico e suscetibilidade magnética de spin são obtidos para os modelos de Kondo de dois ca
Publicado em: 2007
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22. The effective charge velocity of spin-¹/2 superlattices
We calculate the spin gap of homogeneous and inhomogeneous spin chains, using the White's density matrix renormalization group technique. We found that the spin gap is related to the ration between the spin velocity and the correlation exponent. We consider a spin superlattice, which is composed of a repeated pattern of two spin-¹/2 XXZ chains with differen
Brazilian Journal of Physics. Publicado em: 2006-09
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23. The temperature dependence of the QCD running coupling
We study the running of the QCD coupling with the momentum squared (Q²) and the temperature scales in the high temperature limit (T > Tc), using a mass dependent renormalization scheme to build the Renormalization Group Equations. The approach used guaranty gauge invariance, through the use of the Hard Thermal Loop approximation, and independence of the ver
Brazilian Journal of Physics. Publicado em: 2006-06
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24. Remarks on the dynamical mass generation in confining Yang-Mills theories
The dynamical mass generation for gluons is discussed in Euclidean Yang-Mills theories supplemented with a renormalizable mass term. The mass parameter is not free, being determined in a self-consistent way through a gap equation which obeys the renormalization group. The example of the Landau gauge is worked out explicitly at one loop order. A few remarks o
Brazilian Journal of Physics. Publicado em: 2006-03