Atom Lithography with Near-Resonant Light Masks: Quantum Optimization Analysis

We study the optimal focusing of two-level atoms with a near resonant standing wave light, using both classical and quantum treatments of the problem. Operation of the focusing setup is considered as a nonlinear spatial squeezing of atoms in the thin- and thick-lens regimes. It is found that the near-resonant standing wave focuses the atoms with a reduced background in comparison with far-detuned light fields. For some parameters, the quantum atomic distribution shows even better localization than the classical one. Spontaneous emission effects are included via the technique of quantum Monte Carlo wave function simulations. We investigate the extent to which non-adiabatic and spontaneous emission effects limit the achievable minimal size of the deposited structures.Comment: 10 pages including 11 figures in Revte

Molecular Frisbee: Motion of Spinning Molecules in Inhomogeneous Fields

Several laser techniques have been suggested and demonstrated recently for preparing polarizable molecules in rapidly spinning states with a disc-like angular distribution. We consider motion of these spinning discs in inhomogeneous fields, and show that the molecular trajectories may be precisely controlled by the tilt of the plane of the laser-induced rotation. The feasibility of the scheme is illustrated by optical deflection of linear molecules twirled by two delayed cross-polarized laser pulses. These results open new ways for many applications involving molecular focusing, guiding and trapping, and may be suitable for separating molecular mixtures by optical and static fields

Resonance Enhanced Tunneling

Time evolution of tunneling in thermal medium is examined using the real-time semiclassical formalism previously developed. Effect of anharmonic terms in the potential well is shown to give a new mechanism of resonance enhanced tunneling. If the friction from environment is small enough, this mechanism may give a very large enhancement for the tunneling rate. The case of the asymmetric wine bottle potential is worked out in detail.Comment: 12 pages, LATEX file with 5 PS figure

Nondegenerate parametric down conversion in coherently prepared two-level atomic gas

We describe parametric down conversion process in a two-level atomic gas, where the atoms are in a superposition state of relevant energy levels. This superposition results in splitting of the phase matching condition into three different conditions. Another, more important, peculiarity of the system under discussion is the nonsaturability of amplification coefficients with increasing pump wave intensity, under "sideband" generation conditions

Pneumatic compression devices for in-home management of lymphedema: two case reports

The two patients in this case series had experienced long-term difficulty controlling lymphedema at home. Both patients had used numerous home therapies, including older-generation intermittent pneumatic compression devices, without success. The Flexitouch® system, an advanced pneumatic device, was prescribed to assist them with in-home efforts by providing therapy to their affected limbs in addition to the lower trunk area for the patient with lymphedema of the lower extremity; and the trunk, chest wall, and shoulder areas for the patient with lymphedema of the upper extremity. Both patients achieved successful home maintenance of lymphedema, as judged by limb volume, clinical observations, and subjective patient impressions, after incorporating the Flexitouch® system. Neither patient experienced the deleterious effects (worsening genital edema; fibrotic cuff development) that they had experienced with the older-generation intermittent pneumatic compression devices they had previously used. Incorporating the Flexitouch® system as part of maintenance may improve success for lymphedema patients who have previously struggled with in-home management

Energy diffusion in strongly driven quantum chaotic systems

The energy evolution of a quantum chaotic system under the perturbation that harmonically depends on time is studied for the case of large perturbation, in which the rate of transition calculated from the Fermi golden rule exceeds the frequency of perturbation. It is shown that the energy evolution retains its diffusive character, with the diffusion coefficient that is asymptotically proportional to the magnitude of perturbation and to the square root of the density of states. The results are supported by numerical calculation. They imply the absence of the quantum-classical correspondence for the energy diffusion and the energy absorption in the classical limit $\hbar \to 0$.Comment: 12 pages, 3 figures, RevTe

Smearing of phase transition due to a surface effect or a bulk inhomogeneity in ferroelectric nanostructures

The boundary conditions, customarily used in the Landau-type approach to ferroelectric thin films and nanostructures, have to be modified to take into account that a surface of a ferroelectric (FE) is a defect of the ``field'' type. The surface (interface) field is coupled to a normal component of polarization and, as a result, the second order phase transitions are generally suppressed and anomalies in response are washed out. In FE films with a compositional (grading) or some other type of inhomogeneity, the transition into a monodomain state is suppressed, but a transition with formation of a domain structure may occur.Comment: 5 pages, 1 figure; the effective bias field is very large, the estimate is adde

Dynamics of barrier penetration in thermal medium: exact result for inverted harmonic oscillator

Time evolution of quantum tunneling is studied when the tunneling system is immersed in thermal medium. We analyze in detail the behavior of the system after integrating out the environment. Exact result for the inverted harmonic oscillator of the tunneling potential is derived and the barrier penetration factor is explicitly worked out as a function of time. Quantum mechanical formula without environment is modifed both by the potential renormalization effect and by a dynamical factor which may appreciably differ from the previously obtained one in the time range of 1/(curvature at the top of potential barrier).Comment: 30 pages, LATEX file with 11 PS figure

Ising model for distribution networks

An elementary Ising spin model is proposed for demonstrating cascading failures (break-downs, blackouts, collapses, avalanches, ...) that can occur in realistic networks for distribution and delivery by suppliers to consumers. A ferromagnetic Hamiltonian with quenched random fields results from policies that maximize the gap between demand and delivery. Such policies can arise in a competitive market where firms artificially create new demand, or in a solidary environment where too high a demand cannot reasonably be met. Network failure in the context of a policy of solidarity is possible when an initially active state becomes metastable and decays to a stable inactive state. We explore the characteristics of the demand and delivery, as well as the topological properties, which make the distribution network susceptible of failure. An effective temperature is defined, which governs the strength of the activity fluctuations which can induce a collapse. Numerical results, obtained by Monte Carlo simulations of the model on (mainly) scale-free networks, are supplemented with analytic mean-field approximations to the geometrical random field fluctuations and the thermal spin fluctuations. The role of hubs versus poorly connected nodes in initiating the breakdown of network activity is illustrated and related to model parameters