arXiv subjects
Publications and source records attributed to Marcelo M. Leite.
The critical exponents $ν_{L2}, η_{L2}$ and $γ_{L2}$ of a uniaxial Lifshitz point are calculated at two-loop level using renormalization group and $ε_{L}$-expansion techniques. We found a new constraint involving the loop momenta along the competition axis, which allows to solve the two-loop integrals. The exponent $γ_{L2}$ obtained using our method is in good agreement with numerical estimates based on Monte Carlo simulations.
We reply to a recent comment by H. W. Diehl and M. Shpot (cond-mat/0106502) criticizing our paper J. Phys. A: Math. Gen. 34 (2001) L327-332. We show that the approximation we use for evaluating higher-loop integrals is consistent with homogeneity. A new renormalization group approach is presented in order to compare the two methods with high-precision numerical data concerning the uniaxial case. We stress that the isotropic behaviour cannot be obtained from the anisotropic one.
We present the critical exponents $ν_{L2}$, $η_{L2}$ and $γ_{L}$ for an $m$-axial Lifshitz point at second order in an $ε_{L}$ expansion. We introduced a constraint involving the loop momenta along the $m$-dimensional subspace in order to perform two- and three-loop integrals. The results are valid in the range $0 \leq m < d$. The case $m=0$ corresponds to the usual Ising-like critical behavior.
A self-contained discussion of integral equations of scattering is presented in the case of centrally-symmetric potentials in one dimension, which will facilitate the understanding of more complex scattering integral equations in two and three dimensions. The present discussion illustrates in a simple fashion the concept of partial-wave decomposition, Green's function, Lippmann-Schwinger integral equations of scattering for wave function and transition operator, optical theorem and unitarity relation. We illustrate the present approach with a Dirac delta potential.
A self-contained discussion of nonrelativistic quantum scattering is presented in the case of central potentials in one space dimension, which will facilitate the understanding of the more complex scattering theory in two and three dimensions. The present discussion illustrates in a simple way the concept of partial-wave decomposition, phase shift, optical theorem and effective-range expansion.
The susceptibility amplitude ratio in the neighborhood of a uniaxial Lifshitz point is calculated at one-loop level using field-theoretic and $ε_{L}$-expansion methods. We use the Schwinger parametrization of the propagator in order to split the quadratic and quartic part of the momenta, as well as a new special symmetry point suitable for renormalization purposes. For a cubic lattice (d = 3), we find the result $\frac{C_{+}}{C_{-}} = 3.85$.
We show that two-dimensional topological BF theories coupled to particles carrying non-Abelian charge admit a new coupling involving the Lagrange multiplier field. When applied to the gauge theoretic formulation of dilatonic gravity it gives rise to a source term for the gravitational field. We show that the system admits black hole solutions.