Boosted Simon-Wolff Spectral Criterion and Resonant Delocalization

Discussed here are criteria for the existence of continuous components in the spectra of operators with random potential. First, the essential condition for the Simon-Wolff criterion is shown to be measurable at infinity. By implication, for the iid case and more generally potentials with the K-property the criterion is boosted by a zero-one law. The boosted criterion, combined with tunneling estimates, is then applied for sufficiency conditions for the presence of continuous spectrum for random Schr\"odinger operators. The general proof strategy which this yields is modeled on the resonant delocalization arguments by which continuous spectrum in the presence of disorder was previously established for random operators on tree graphs. In another application of the Simon-Wolff rank-one analysis we prove the almost sure simplicity of the pure point spectrum for operators with random potentials of conditionally continuous distribution.Comment: In version 2 the presentation was somewhat streamlined, and a related new (/improved) result was added (Appendix B

On the ubiquity of the Cauchy distribution in spectral problems

We consider the distribution of the values at real points of random functions which belong to the Herglotz-Pick (HP) class of analytic mappings of the upper half plane into itself. It is shown that under mild stationarity assumptions the individual values of HP functions with singular spectra have a Cauchy type distribution. The statement applies to the diagonal matrix elements of random operators, and holds regardless of the presence or not of level repulsion, i.e. applies to both random matrix and Poisson-type spectra.Comment: Slightly revised version: presentation was made more explicit in places, and additional references were provide

Complete Dynamical Localization in Disordered Quantum Multi-Particle Systems

We present some recent results concerning the persistence of dynamical localization for disordered systems of n particles under weak interactions.Comment: For the proceedings of the XVI International Congress of Mathematical Physics, Prague 2009. Lecture presented by S. Warze

Kac-Ward formula and its extension to order-disorder correlators through a graph zeta function

A streamlined derivation of the Kac-Ward formula for the planar Ising model's partition function is presented and applied in relating the kernel of the Kac-Ward matrices' inverse with the correlation functions of the Ising model's order-disorder correlation functions. A shortcut for both is facilitated by the Bowen-Lanford graph zeta function relation. The Kac-Ward relation is also extended here to produce a family of non planar interactions on $\mathbb{Z}^2$ for which the partition function and the order-disorder correlators are solvable at special values of the coupling parameters/temperature.Comment: An extension of the Kac-Ward determinantal formula beyond planarity was added (Section 5). To appear in Journal of Statistical Physic