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T Prosen

Publications and source records attributed to T Prosen.

11 recordsLinked to original sources
PubMed2006

Anomalous slow fidelity decay for symmetry-breaking perturbations.

Symmetries as well as other special conditions can cause anomalous slowing down of fidelity decay. These situations will be characterized, and a family of random matrix models to emulate them generically presented. An analytic solution based on exponentiated linear response will be given. For one representative case the exact solution is obtained from a supersymmetric calculation. The results agree well with dynamical calculations for a kicked top.

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PubMed2005

Uniform semiclassical approach to fidelity decay in the deep Lyapunov regime.

We use the uniform semiclassical approximation in order to derive the fidelity decay in the regime of large perturbations. Numerical computations are presented which agree with our theoretical predictions. Moreover, our theory allows us to explain previous findings, such as the deviation from the Lyapunov decay rate in cases where the classical finite-time instability is nonuniform in phase space.

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PubMed2001

Anomalous diffusion and dynamical localization in polygonal billiards.

We study numerically classical and quantum dynamics of a piecewise parabolic area preserving map on a cylinder which emerges from the bounce map of elongated triangular billiards. The classical map exhibits anomalous diffusion. Quantization of the same map results in a system with dynamical localization and pure point spectrum.

Journal Article↗
PubMed2001

Dimer decimation and intricately nested localized-ballistic phases of a kicked Harper model.

A new decimation scheme is introduced to study localization transitions in tight binding models with long range interaction. Within this scheme, the lattice models are mapped to a vectorized dimer where an asymptotic dissociation of the dimer is shown to correspond to the vanishing of the transmission coefficient through the system. When applied to the kicked Harper model, the method unveils an intricately nested extended and localized phases in two-dimensional parameter space. In addition to computing transport characteristics with extremely high precision, the renormalization tools also provide a new method to compute quasienergy spectrum.

Journal Article↗
PubMed2001

A novel X chromosome-linked genetic cause of recurrent spontaneous abortion.

OBJECTIVE: Unexplained recurrent spontaneous abortion is a common women's health problem that affects approximately 1 of every 200 women who wish to have children. It has long been assumed that a large proportion of recurrent spontaneous abortion results from genetic problems, but no causative genes have been identified to date. Here, we tested the hypothesis that a subset of women with recurrent spontaneous abortion are carriers of X-linked recessive disorders that result in the loss of male pregnancies. STUDY DESIGN: X chromosome inactivation patterns, an assay used to detect women who are likely to be carriers of X-linked recessive cell-lethal traits, were compared between 105 female patients with idiopathic recurrent pregnancy loss and 101 women (control subjects) with a single successful pregnancy and no history of pregnancy loss. Inheritance patterns and gender of offspring were studied in relevant subsets of participants. RESULTS: Female patients showed a highly statistically significant increase in the frequency of skewed X chromosome inactivation (90%; P < .0005). Female patients with highly skewed X chromosome inactivation showed a significant decrease in male children. Four of 6 families that were studied showed maternal inheritance of the skewed inactivation trait. CONCLUSION: We found the 14% of women with unexplained recurrent pregnancy loss show highly skewed X inactivation, which suggests that they are carriers of X-linked recessive lethal traits. Furthermore, the observed gender bias among women with highly skewed X inactivation suggests selective loss of male conceptions, which is consistent with an X chromosome-linked genetic defect that leads to cell death or growth disadvantage. Identification of such female carriers is important for the reproductive counseling and treatment of these women.

Abortion, Habitual↗
PubMed2000

Triangle map: A model of quantum chaos

We study an area preserving parabolic map which emerges from the Poincare map of a billiard particle inside an elongated triangle. We provide numerical evidence that the motion is ergodic and mixing. Moreover, when considered on the cylinder, the motion appears to follow a Gaussian diffusive process.

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PubMed2000

Momentum conservation implies anomalous energy transport in 1D classical lattices

Under quite general conditions, we prove that for classical many-body lattice Hamiltonians in one dimension (1D) total momentum conservation implies anomalous conductivity in the sense of the divergence of the Kubo expression for the coefficient of thermal conductivity, kappa. Our results provide rigorous confirmation and explanation of many of the existing "surprising" numerical studies of anomalous conductivity in 1D classical lattices, including the celebrated Fermi-Pasta-Ulam problem.

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PubMed2000

Quantization of a billiard model for interacting particles

We consider a billiard model of a self-bound, interacting three-body system in two spatial dimensions. Numerical studies show that the classical dynamics is chaotic. The corresponding quantum system displays spectral fluctuations that exhibit small deviations from random matrix theory predictions. These can be understood in terms of a new type of scarring caused by a one-parameter family of orbits inside the collinear manifold.

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PubMed1999

Ergodic properties of a generic nonintegrable quantum many-body system in the thermodynamic limit.

We study a generic but simple nonintegrable quantum many-body system of locally interacting particles, namely, a kicked-parameter (t,V) model of spinless fermions on a one-dimensional lattice (equivalent to a kicked Heisenberg XX-Z chain of 1/2 spins). The statistical properties of the dynamics (quantum ergodicity and quantum mixing) and the nature of quantum transport in the thermodynamic limit are considered as the kick parameters (which control the degree of nonintegrability) are varied. We find and demonstrate ballistic transport and nonergodic, nonmixing dynamics (implying infinite conductivity at all temperatures) in the integrable regime of zero or very small kick parameters, and more generally and importantly, also in the nonintegrable regime of intermediate values of kicked parameters, whereas only for sufficiently large kick parameters do we recover quantum ergodicity and mixing implying normal (diffusive) transport. We propose an order parameter (charge stiffness D) which controls the phase transition from nonmixing and nonergodic dynamics (ordered phase, D>0) to mixing and ergodic dynamics (disordered phase, D=0) in the thermodynamic limit. Furthermore, we find exponential decay of time correlation functions in the regime of mixing dynamics. The results are obtained consistently within three different numerical and analytical approaches: (i) time evolution of a finite system and direct computation of time correlation functions, (ii) full diagonalization of finite systems and statistical analysis of stationary data, and (iii) algebraic construction of quantum invariants of motion of an infinite system, in particular the time-averaged observables.

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