Universal Parametric correlations at the soft edge of the spectrum of random matrix ensembles

We extend a recent theory of parametric correlations in the spectrum of random matrices to study the response to an external perturbation of eigenvalues near the soft edge of the support. We demonstrate by explicit non-perturbative calculation that the two-point function for level density fluctuations becomes, after appropriate rescaling, a universal expression.Comment: 8 pages, written in TeX, Preprint OUTP-94-10S (University of Oxford

Quantum dot to disordered wire crossover: A complete solution in all length scales for systems with unitary symmetry

We present an exact solution of a supersymmetric nonlinear sigma model describing the crossover between a quantum dot and a disordered quantum wire with unitary symmetry. The system is coupled ideally to two electron reservoirs via perfectly conducting leads sustaining an arbitrary number of propagating channels. We obtain closed expressions for the first three moments of the conductance, the average shot-noise power and the average density of transmission eigenvalues. The results are complete in the sense that they are nonperturbative and are valid in all regimes and length scales. We recover several known results of the recent literature by taking particular limits.Comment: 4 page

Path Integral Approach to the Scattering Theory of Quantum Transport

The scattering theory of quantum transport relates transport properties of disordered mesoscopic conductors to their transfer matrix \bbox{T}. We introduce a novel approach to the statistics of transport quantities which expresses the probability distribution of \bbox{T} as a path integral. The path integal is derived for a model of conductors with broken time reversal invariance in arbitrary dimensions. It is applied to the Dorokhov-Mello-Pereyra-Kumar (DMPK) equation which describes quasi-one-dimensional wires. We use the equivalent channel model whose probability distribution for the eigenvalues of \bbox{TT}^{\dagger} is equivalent to the DMPK equation independent of the values of the forward scattering mean free paths. We find that infinitely strong forward scattering corresponds to diffusion on the coset space of the transfer matrix group. It is shown that the saddle point of the path integral corresponds to ballistic conductors with large conductances. We solve the saddle point equation and recover random matrix theory from the saddle point approximation to the path integral.Comment: REVTEX, 9 pages, no figure

Universal Transport Properties of Disordered Quantum Wires

For disordered quantum wires which belong to all ten universality classes, the universal quantities of transport properties are obtained through DMPK approach. Calculated are the universal parts of one- and two-point correlation functions for probability distribution functions of transmission eigenvalues. In this analysis, the asymptotic solution of DMPK equation is used. Transport properties for new universality classes(chiral and Bogoliubov-de Gennes classes) are discussed comparing with those for standard class.Comment: 22 pages, 2 figure

Universal parametric correlations in the transmission eigenvalue spectra of disordered conductors

We study the response of the transmission eigenvalue spectrum of disordered metallic conductors to an arbitrary external perturbation. For systems without time-reversal symmetry we find an exact non-perturbative solution for the two-point correlation function, which exhibits a new kind of universal behavior characteristic of disordered conductors. Systems with orthogonal and symplectic symmetries are studied in the hydrodynamic regime.Comment: 10 pages, written in plain TeX, Preprint OUTP-93-36S (University of Oxford), to appear in Phys. Rev. B (Rapid Communication

Deviations from the Gaussian distribution of mesoscopic conductance fluctuations

The conductance distribution of metallic mesoscopic systems is considered. The variance of this distribution describes the universal conductance fluctuations, yielding a Gaussian distribution of the conductance. We calculate diagrammatically the third cumulant of this distribution, the leading deviation from the Gaussian. We confirm random matrix theory calculations that the leading contribution in quasi-one dimension vanishes. However, in quasi two dimensions the third cumulant is negative, whereas in three dimensions it is positive.Comment: 9 pages, Revtex, with eps figures,to appear in Phys Rev

Condensed Tannins and Total Phenols in \u3ci\u3eStylosanthes\u3c/i\u3e spp.

Rangelands, such as the species of the genus Stylosanthes, are plants highly selected by animals and represent an important forage source for livestock in the Northeast region of Brazil. Plants of this genus are naturally occurring in several places in Brazil and other semi-arid areas. The variability of condensed tannins and total phenols in different Stylosanthes accessions is still poorly characterized. Based on that, the objective of this study was to quantify the content of condensed tannins and total phenols of Stylosanthes accessions collected in different physiographic zones of the State of Pernambuco and cultivated in germplasm banks. The work was carried out in two germplasm banks in the municipalities of Serra Talhada and Carpina in Pernambuco-Brazil. These regions have different edaphoclimatic characteristics. The analyzes were performed on samples of the whole plant (leaves and stems) collected at 20 cm height. The design was completely randomized, with accessions representing the fixed effects treatments. The data were submitted for analysis of variance, and the means were compared by the Scott-Knott test at a level of 5%. The Stylosanthes accessions cultivated in the active germplasm banks of the municipalities of Carpina and Serra Talhada showed statistically significant differences (P \u3c 0.05) among accessions in their concentrations of condensed tannins and total phenols. For the accessions cultivated in the active germplasm bank of Serra Talhada, six groups were formed. The concentrations of condensed tannins ranged from 5.6 to 63.3 mg g-1, and the total phenols ranged from 13.7 to 100.0 mg g-1in the cultivars from Serra Talhada. Likewise, condensed tannins ranged between 16.6 and 142.1 mg g-1, and total phenols ranged from 38.4 and 294.1 mg g-1 for the three groups from the municipality of Carpina. There is variability in the contents of condensed tannins and total phenols among accessions of Stylosanthes spp

Transmission through a many-channel random waveguide with absorption

We compute the statistical distribution of the transmittance of a random waveguide with absorption in the limit of many propagating channels. We consider the average and fluctuations of the conductance T = tr t^{\dagger} t, where t is the transmission matrix, the density of transmission eigenvalues \tau (the eigenvalues of t^{\dagger} t), and the distribution of the plane-wave transmittances T_a and T_{ab}. For weak absorption (length L smaller than the exponential absorption length \xi_a), we compute moments of the distributions, while for strong absorption (L >> \xi_a), we can find the complete distributions. Our findings explain recent experiments on the transmittance of random waveguides by Stoytchev and Genack [Phys. Rev. Lett. 79, 309 (1997)].Comment: 13 pages, RevTeX; 9 figures include