Equivalent Definitions of the Quantum Nonadiabatic Entropy Production

The nonadiabatic entropy production is a useful tool for the thermodynamic analysis of continuously dissipating, nonequilibrium steady states. For open quantum systems, two seemingly distinct definitions for the nonadiabatic entropy production have appeared in the literature, one based on the quantum relative entropy and the other based on quantum trajectories. We show that these two formulations are equivalent. Furthermore, this equivalence leads us to a proof of the monotonicity of the quantum relative entropy under a special class of completely-positive, trace-preserving quantum maps, which circumvents difficulties associated with the noncommuntative structure of operators.     

Ethidium and proflavine binding to a 2',5'-linked RNA duplex

Despite over 40 years of physical investigations, fundamental questions persist regarding the energetics of RNA and DNA intercalation. The dramatic unwinding of a nucleic acid duplex upon intercalation immediately suggests that the nucleic acid backbone should play a significant role in dictating the free energy of intercalation. However, the contribution of the backbone to intercalation free energy is difficult to appreciate given the intertwined energetics associated with intercalation (e.g., pi-pi stacking and solvent effects). Fluorescence titrations were used to determine the association constants of two known intercalators, proflavine and ethidium, for duplex 2',5'-linked RNA. Proflavine was found to bind 2',5' RNA with an association constant 25-fold greater than that measured for standard, 3',5'-linked RNA. In contrast, ethidium binds 2',5' RNA less favorably than standard RNA.     

Links between heavy ion and astrophysics

Heavy-ion experiments provide important data to test astrophysical models. The high-density equation of state can be probed in HI collisions and applied to the hot protoneutron star formed in core collapse supernovae. The parity radius experiment (PREX) aims to accurately measure the neutron radius of ²⁰⁸Pb with parity-violating electron scattering. This determines the pressure of neutron-rich matter and the density dependence of the symmetry energy. Competition between nuclear attraction and Coulomb repulsion can form exotic shapes called nuclear pasta in neutron star crusts and supernovae. This competition can be probed with multifragmentation HI reactions. We use large-scale semiclassical simulations to study nonuniform neutron-rich matter in supernovae. We find that the Coulomb interactions in astrophysical systems suppress density fluctuations. As a result, there is no first-order liquid-vapor phase transition. Finally, the virial expansion for low-density matter shows that the nuclear vapor phase is complex with significant concentrations of alpha particles and other light nuclei in addition to free nucleons.     

Kohn-Sham exchange potential for a metallic surface

The behavior of the surface barrier that forms at the metal-vacuum interface is important for several fields of surface science. Within the density functional theory framework, this surface barrier has two nontrivial components: exchange and correlation. Exact results are provided for the exchange component, for a jellium metal-vacuum interface, in a slab geometry. The Kohn-Sham exact-exchange potential V(x)(z) has been generated by using the optimized effective potential method, through an accurate numerical solution, imposing the correct boundary condition. It has been proved analytically, and confirmed numerically, that V(x)(z--> infinity) --> -e(2)/z; this conclusion is not affected by the inclusion of correlation effects. Also, the exact-exchange potential develops a shoulderlike structure close to the interface, on the vacuum side. The issue of the classical image potential is discussed.     

Forcing axioms and the Galvin number

Periodica Mathematica Hungarica - We study the Galvin property. We show that various square principles imply that the cofinality of the Galvin number is uncountable (or even greater than $$aleph...     

Some limit theorems for Markov processes

The aim of this paper is to prove some limit theorems for Markov processes using only functional analytic methods. Some of our results were proved in [7], [8] and [5] by probabilistic methods. We prove in the Appendix a theorem on Markov processes that have no finite invariant measure. This paper is a part of the author’s Ph.D. thesis to be submitted to the Hebrew University of Jerusalem. The author wishes to express his thanks to Professor S. R. Foguel for much valuable advice and encouragement.     

Beam coupling induced transparency in a bacteriorhodopsin-based saturable absorber

The nonlinear coupling of two beams in a saturable absorber is shown to cause a strong enhancement of the beams' transmissivity. An analysis of this beam-coupling effect and its experimental demonstration with bacteriorhodopsin are given.     

Self-similar amplification in fiber Bragg gratings written in fiber amplifiers

We show, by using numerical simulations, that self-similar pulses with a duration on the order of few nanoseconds and an energy on the order of 10?μJ can be obtained at the output of a fiber Bragg grating (FBG) written in a fiber amplifier. The evolution of the amplified pulses is determined by the combined effect of Kerr nonlinearity, normal-dispersion, gain, and gain saturation, which limit the pulse energy. The output pulse mainly depends on the initial pulse energy rather than on the initial pulse profile. The reduced group velocity in FBGs can significantly increase the total gain for a given amplifier length. Hence we find that the proposed amplification scheme can be highly advantageous for amplification of nanosecond-scale pulses in fiber amplifiers.