Magnetism in spin models for depleted honeycomb-lattice iridates: Spin-glass order towards percolation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A study of a relativistic quark-diquark model for the nucleon

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Teorias de Spin-1: decomposição em helicidades, redução dimensional e imersão de calibre

We have studied the physical content of the following models: Maxwell, Proca, Self-Dual and Maxwell-Chern-Simons. One method we have used is the decomposition in the so called helicity variables, which can be done in the Lagrangian formalism. It leads to the correct counting of degrees of freedom without choosing a gauge condition. The method separates the propagating modes from the non-propagating ones. The Hamiltonian of the MCS and the AD is calculated. The second method used here is the analysis of the sign of the imaginary part of the residues of the two-point amplitude of the theory, showing that the models analyzed are free of ghosts. We also carry the dimensional reduction of the Maxwell-Chern-Simons and Self-Dual models from D = 2+1 to D = 1 + 1 dimensions. Next, we show that the dimensional reduction of those equivalent models also leads to equivalent models in D=1+1. Even more interesting is the fact, demonstrated here, that those reduced models can also be connected via gauge embedding. So the gauge embedding of the Self-Dual model into the Maxwell-Chern-Simons theory is preserved by the dimensional reduction

Interaction of biologically-relevant peptides with membrane model systems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Spontaneous symmetry breaking in a spin-orbit-coupled f=2 spinor condensate

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Light-by-light scattering with intact protons at the LHC: from standard model to new physics

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Mobile vector soliton in a spin-orbit coupled spin-1 condensate

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Vector solitons in a spin-orbit-coupled spin-2 Bose-Einstein condensate

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The spin-orbit resonant problem including core-mantle gravitational coupling

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dual descriptions of massive spin-3 particles in D=2+1 via Noether gauge embedment

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A unified solution to the small scale problems of the Lambda CDM model II: introducing parent-satellite interaction

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Origin of spin incommensurability in hole-doped S=1 Y2-xCaxBaNiO5 chains

Spin incommensurability (IC) has been recently experimentally discovered in the hole-doped Ni-oxide chain compound Y2-xCaxBaNiO5 [G. Xu et al., Science 289, 419 (2000)]. Here a two orbital model for this material is studied using computational techniques. Spin IC is observed in a wide range of densities and couplings. The phenomenon originates in antiferromagnetic correlations across holes dynamically generated to improve hole movement, as it occurs in the one-dimensional Hubbard model and in recent studies of the two-dimensional extended t-J model. The close proximity of ferromagnetic and phase-separated states in parameter space is also discussed.

Conservation laws for Z(N) symmetric quantum spin models and their exact ground state energies

We derive an infinite set of conserved charges for some Z(N) symmetric quantum spin models by constructing their Lax pairs. These models correspond to the Potts model, Ashkin-Teller model and the particular set of self-dual Z(N) models solved by Fateev and Zamolodchikov [6]. The exact ground state energy for this last family of hamiltonians is also presented. © 1986.

Estudos de acoplamento spin-órbita em dinâmica do sistema solar

Pós-graduação em Física - FEG

On the question of neutrino spin precession in a magnetic field

Using the Feynman procedure of ordered exponential operators we solve the evolution equations for a two-neutrino system considering arbitrarily varying matter density and magnetic field along the neutrino trajectory. We show that a large geometrical phase velocity suppresses νL→νR transitions unless some stationary trajectory is found along the neutrino path. Concerning the solar neutrino case, if we admit the standard solar model matter distribution, no such trajectory can be found.