Entropy Distance: New Quantum Phenomena

We study a curve of Gibbsian families of complex 3x3-matrices and point out new features, absent in commutative finite-dimensional algebras: a discontinuous maximum-entropy inference, a discontinuous entropy distance and non-exposed faces of the mean value set. We analyze these problems from various aspects including convex geometry, topology and information geometry. This research is motivated by a theory of info-max principles, where we contribute by computing first order optimality conditions of the entropy distance.Comment: 34 pages, 5 figure

Strongly birefringent cut-wire pair structure as negative index wave plates at THz frequencies

We report a new approach for the design and fabrication of thin wave plates with high transmission in the terahertz (THz) regime. The wave plates are based on strongly birefringent cut-wire pair metamaterials that exhibit refractive indices of opposite signs for two orthogonal polarization components of an incident wave. As specific examples, we fabricated and investigated a quarter- and a half-wave plate that revealed a peak intensity transmittance of 74% and 58% at 1.34 THz and 1.3 THz, respectively. Furthermore, the half wave plate displayed a maximum figure of merit (FOM) of 23 at 1.3 THz where the refractive index was -1.7. This corresponds to one of the highest FOMs reported at THz frequencies so far. The presented results evidence that negative index materials enter an application stage in terms of optical components for the THz technology.Comment: 4 pages, 3 figures, submitted to Appl. Phys. Let

Barrier-controlled carrier transport in microcrystalline semiconducting materials: Description within a unified model

A recently developed model that unifies the ballistic and diffusive transport mechanisms is applied in a theoretical study of carrier transport across potential barriers at grain boundaries in microcrystalline semiconducting materials. In the unified model, the conductance depends on the detailed structure of the band edge profile and in a nonlinear way on the carrier mean free path. Equilibrium band edge profiles are calculated within the trapping model for samples made up of a linear chain of identical grains. Quantum corrections allowing for tunneling are included in the calculation of electron mobilities. The dependence of the mobilities on carrier mean free path, grain length, number of grains, and temperature is examined, and appreciable departures from the results of the thermionic-field-emission model are found. Specifically, the unified model is applied in an analysis of Hall mobility data for n-type microcrystalline Si thin films in the range of thermally activated transport. Owing mainly to the effect of tunneling, potential barrier heights derived from the data are substantially larger than the activation energies of the Hall mobilities. The specific features of the unified model, however, cannot be resolved within the rather large uncertainties of the analysis.Comment: REVTex, 19 pages, 9 figures; to appear in J. Appl. Phy

Translating the Untranslatable : A Note on The Mystic Trumpeter

Commends Whitman\u27s achievement in his 1872 poem The Mystic Trumpeter, published in As a Strong Bird on Pinions Free, and argues that the poem extends Whitman\u27s exploration and celebration of the \u27eternal play\u27 of Man

"Translating the Untranslatable": A Note on "The Mystic Trumpeter"

Commends Whitman\u27s achievement in his 1872 poem "The Mystic Trumpeter," published in As a Strong Bird on Pinions Free, and argues that the poem "extends Whitman\u27s exploration and celebration of the \u27eternal play\u27 of Man.

Effective interactions and phase behaviour for a model clay suspension in an electrolyte

Since the early observation of nematic phases of disc-like clay colloids by Langmuir in 1938, the phase behaviour of such systems has resisted theoretical understanding. The main reason is that there is no satisfactory generalization for charged discs of the isotropic DLVO potential describing the effective interactions between a pair of spherical colloids in an electrolyte. In this contribution, we show how to construct such a pair potential, incorporating approximately both the non-linear effects of counter-ion condensation (charge renormalization) and the anisotropy of the charged platelets. The consequences on the phase behaviour of Laponite dispersions (thin discs of 30 nm diameter and 1 nm thickness) are discussed, and investigation into the mesostructure via Monte Carlo simulations are presented.Comment: LaTeX, 12 pages, 11 figure

Preliminary Design and Fabrication Assessment for Two Solar Sail Candidates

Primary emphasis is directed to the spinning sail design and fabrication assessment. Several methods of fabricating the spinning sail blades are presented and compared. Evaluations are made of each proposed design, as well as the baseline design. These efforts resulted in the recommendation of an apparent optimum design and fabrication plan with an assessment of the major advantages/disadvantages of each concept considered

Magneto-Rayleigh-Taylor Instability: Theory and Simulation in Planar and Cylindrical Pulsed Power Targets.

Cylindrical liner implosions in the Magnetized Liner Inertial Fusion (MagLIF) concept are susceptible to the magneto-Rayleigh-Taylor instability (MRT). The danger of MRT enters in two phases, (1) during the main implosion, the outer surface of the liner is MRT unstable, and (2) during the short time period when the liner decelerates onto the hot fuel, the inner surface becomes unstable. Growth of MRT on the outer surface may also feedthrough, which may seed the inner surface leading to high MRT growth in the second phase. If MRT growth becomes large enough, confinement of the fuel is lost. To characterize MRT, we solve the linearized, ideal MHD equations in both planar and cylindrical geometries, including an axial magnetic field and the effects of sausage and kink modes. To evaluate our analytic growth rates, 1D HYDRA MHD simulations are used to generate realistic, evolving profiles (in density, pressure, and magnetic field) during the implosion. In general, the total instability growth rates in cylindrical geometry are larger than those in planar geometry. MRT and feedthrough are suppressed by strong magnetic field line bending (tension). We apply our analytic MRT growth rates to experiments on the Z-machine at Sandia National Laboratories. Analytic MRT growth rates for a typical magnetized MagLIF-like implosion show the kink mode to be the fastest growing early and very late in the liner implosion (during deceleration). Sophisticated 2D HYDRA simulations show that highly compressed axial magnetic fields can reduce the growth of perturbations at the fuel/liner interface during the implosion phase, enhancing the stability of the implosion. HYDRA 2D simulations also show that a non-uniform shock, driven from the liner exterior, can seed the liner interior, leading to substantial growth of instability far in excess of feedthrough. Large-scale perturbations on the liner interior may also feedout to the liner exterior when a shock wave interacts with the surface, which further destabilizes the liner. These effects are reduced when shock compression is minimized or significant perturbations are not present during shock compression. The feedthrough effects then dominate.PhDNuclear ScienceUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113414/1/weisy_1.pd

Outflow or galactic wind: The fate of ionized gas in the halos of dwarf galaxies

Context: H\alpha images of star bursting irregular galaxies reveal a large amount of extended ionized gas structures, in some cases at kpc-distance away from any place of current star forming activity. A kinematic analysis of especially the faint structures in the halo of dwarf galaxies allows insights into the properties and the origin of this gas component. This is important for the chemical evolution of galaxies, the enrichment of the intergalactic medium, and for the understanding of the formation of galaxies in the early universe. Aims: We want to investigate whether the ionized gas detected in two irregular dwarf galaxies (NGC 2366 and NGC 4861) stays gravitationally bound to the host galaxy or can escape from it by becoming a freely flowing wind. Methods: Very deep H\alpha images of NGC 2366 and NGC 4861 were obtained to detect and catalog both small and large scale ionized gas structures down to very low surface brightnesses. Subsequently, high-resolution long-slit echelle spectroscopy of the H\alpha line was performed for a detailed kinematic analysis of the most prominent filaments and shells. To calculate the escape velocity of both galaxies and to compare it with the derived expansion velocities of the detected filaments and shells, we used dark matter halo models. Results: We detected a huge amount of both small scale (up to a few hundred pc) and large scale (about 1-2 kpc of diameter or length) ionized gas structures on our H\alpha images. Many of the fainter ones are new detections. The echelle spectra reveal outflows and expanding bubbles/shells with velocities between 20 and 110 km/s. Several of these structures are in accordance with filaments in the H\alpha images. A comparison with the escape velocities of the galaxies derived from the NFW dark matter halo model shows that all gas features stay gravitationally bound.Comment: 15 pages, 13 figures, accepted for publication in A&