Spin Glass Field Theory with Replica Fourier Transforms

We develop a field theory for spin glasses using Replica Fourier Transforms (RFT). We present the formalism for the case of replica symmetry and the case of replica symmetry breaking on an ultrametric tree, with the number of replicas $n$ and the number of replica symmetry breaking steps $R$ generic integers. We show how the RFT applied to the two-replica fields allows to construct a new basis which block-diagonalizes the four-replica mass-matrix, into the replicon, anomalous and longitudinal modes. The eigenvalues are given in terms of the mass RFT and the propagators in the RFT space are obtained by inversion of the block-diagonal matrix. The formalism allows to express any $i$-replica vertex in the new RFT basis and hence enables to perform a standard perturbation expansion. We apply the formalism to calculate the contribution of the Gaussian fluctuations around the Parisi solution for the free-energy of an Ising spin glass.Comment: 39 pages, 3 figure

On the two-point function of the one-dimensional KPZ equation

In this short communication we show that basic tools from Malliavin calculus can be applied to derive the two-point function of the slope of the one-dimensional KPZ equation, starting from an arbitrary two-sided Brownian motion, in terms of the polymer end-point annealed distribution associated to the stochastic heat equation. We also prove that this distribution is given in terms of the derivative of the variance of the solution of the KPZ equation.Comment: 10 pages, 1 figure, typos correcte

Destruction of long-range antiferromagnetic order by hole doping

We study the renormalization of the staggered magnetization of a two-dimensional antiferromagnet as a function of hole doping, in the framework of the t-J model. It is shown that the motion of holes generates decay of spin waves into ''particle-hole'' pairs, which causes the destruction of the long-range magnetic order at a small hole concentration. This effect is mainly determined by the coherent motion of holes. The value obtained for the critical hole concentration, of a few percent, is consistent with experimental data for the doped copper oxide high-Tc superconductors.Comment: 12 pages, 2 figure

Atividades degradativas de celulose e de fenóis por fungos isolados de acículas de Pinus taeda.

Oito fungos isolados de acículas de Pinus taeda em decomposição, da região de Três Barras, SC, Brasil, foram analisados quanto ao potencial de degradarem celulose e lignina. Utilizou-se a técnica de coloração com vermelho congo em meio carboximetilcelulose-ágar (CMCA) para a presença de celulase, e o teste de Bavendamm em meio extrato de malte-ácido tânico-ágar (EMATA) para a presença de fenoloxidase. Aspergillus sp. e Cladosporium sp. produziram maior atividade em meio CMCA, enquanto que Trichoderma sp., Pestalotia sp., Exophiala sp. e Phomopsis sp. produziram maior atividade em meio EMATA. Os fungos Stachybotrys sp. e Rhizopus sp. se desenvolveram em CMCA e EMATA, mas não apresentaram atividade, indicando que não possuem capacidade para degradar celulose ou fenóis em acículas de pínus