Perturbation theories and wave functions for calculation of electronic polarizabilities application to DNA bases

Three different forms of perturbation theories, variational perturbation, finite perturbation and second-order, are evaluated regarding their value for calculation of electronic polarizabilities of small and intermediate size molecules. It is concluded that with the practical constraint of a small basis set the variational perturbation method is the most promising alternative for calculation of polarizabilities. For several small molecules, our calculated polarizabilities indicate that both IEHT and ab initio wave functions give values in close agreement with each other. Variational perturbation calculations of polarizabilities with IEHT wave functions also include the DNA bases.     

Ground state wave functions in the hyperspherical formalism for nuclei with A>4

The general formulation of a technically advantageous method to find the ground state solution of the Schrödinger equation in configuration space for systems with a number of particles A greater than 4 is presented. The wave function is expanded in pair-correlated hyperspherical harmonics beyond the lowest order approximation and then calculated in the Faddeev approach. A recent efficient recursive method to construct antisymmetric A-particle hyperspherical harmonics is used. The accuracy is tested for the bound state energies of nuclei with A = 6–12. The high quality of the obtained results becomes evident from a comparison with other approaches.     

Suppression of thermal lensing effects in intra-cavity coherent combining of lasers

An efficient approach to suppress thermal lensing, when coherently combining several laser distributions, is presented. It is based on incorporating a compensating lens inside the laser cavity. The results reveal that with compensation the overall efficiencies can be more than 80% when combining four laser distributions and more than 90% when combining two laser distributions even at relatively high pulse repetition rates. A model for analyzing coherent combining is developed, where predicted results are in good agreement with the experimental results.     

Leptogenesis from supersymmetry breaking

We show that soft supersymmetry breaking terms involving the heavy sneutrinos can lead to sneutrino-antisneutrino mixing and to new sources of CP violation, which are present even if a single generation is considered. These terms are naturally present in supersymmetric versions of leptogenesis scenarios, and they induce indirect CP violation in the decays of the heavy sneutrinos, eventually generating a baryon asymmetry. This new contribution can be comparable to or even dominate over the asymmetry produced in traditional leptogenesis scenarios.     

Dicke photon trapping effects in molecular beam-foil experiments

The phenomena of delayed spontaneous emission in molecular beam-foil experiments, is interpreted as Dicke photon trapping.     

Axisymmetric motion of a pair of deformable heavy drops in an upward temperature gradient

The axisymmetric deformation and motion of interacting droplets under the combined influence of the gravitational force and a vertical temperature gradient is considered using boundary-integral techniques for creeping flow. The focus is on the case when the net thermocapillary and buoyancy forces acting on the drops are directed oppositely. When these forces are almost balanced our analysis shows that, though the deformations of the drops are apparently small, their influence on the motion is considerable. For highly deformable drops moving in a gravity field, even a small temperature gradient that almost does not effect the drops velocity may drastically change the deformation pattern and prevent the drops from breakup.     

Regularization of diffusion tensor MRI via local coordinates

We propose a novel framework for regularization of symmetric positive-definite (SPD) tensors (e.g., diffusion tensors). This framework is based on differential geometry. The space of SPD matrices, P_n, is described as a Riemannian manifold that is parameterized via the Iwasawa coordinate system. Then, distances on P_n are measured in terms of a natural GL (n)-invariant Riemannian metric. Using the Beltrami framework we construct a set of coupled geometric PDEs with respect to the Iwasawa coordinates. Then, by means of the gradient descent method these equations define the regularization flow over P_n. It appears to be that the local coordinate approach via that coordinate system results in very simple numerics that leads to fast convergence of the algorithm. We demonstrate the efficiency of this algorithm on real volumetric DTI datasets. Results of fibers tractography before and afterthe regularization process arepresented. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Israeli queue with retrials

The so-called “Israeli queue” (Boxma et al. in Stoch Model 24(4):604–625, 2008; Perel and Yechiali in Probab Eng Inf Sci, 2013; Perel and Yechiali in Stoch Model 29(3):353–379, 2013) is a multi-queue polling-type system with a single server. Service is given in batches, where the batch sizes are unlimited and the service time of a batch does not depend on its size. After completing service, the next queue to be visited by the server is the one with the most senior customer. In this paper, we study the Israeli queue with retrials, where the system is comprised of a “main” queue and an orbit queue. The main queue consists of at most \(M\) groups, where a new arrival enters the main queue either by joining one of the existing groups, or by creating a new group. If an arrival cannot join one of the groups in the main queue, he goes to a retrial (orbit) queue. The orbit queue dispatches orbiting customers back to the main queue at a constant rate. We analyze the system via both probability generating functions and matrix geometric methods, and calculate analytically various performance measures and present numerical results.     

Generation of macroscopic superpositions of quantum states by linear coupling to a bath

We demonstrate through an exactly solvable model that collective coupling to any thermal bath induces effectively nonlinear couplings in a quantum many-body (multispin) system. The resulting evolution can drive an uncorrelated large-spin system with high probability into a macroscopic quantum-superposition state. We discuss possible experimental realizations.