Silicon spin diffusion transistor: materials, physics and device characteristics

The realisation that eaveryday electronics has ignored the spin of the carrier in favour of its charge is the foundation of the field of spintronics. Starting with simple two-terminal devices based on GMR and tunnel magnetoresistance, the technology has advanced to consider three-terminal devices that aim to combine spin sensitivity with a high current gain and a large current output. These devices require both efficient spin injection and semiconductor fabrication. In this paper, a discussion is presented of the design, operation and characteristics of the only spin transistor that has yielded a current gain greater than one in combination with reasonable output current

Space-variant filtering for correction of wavefront curvature effects in spotlight-mode SAR imagery formed via polar formatting

Wavefront curvature defocus effects can occur in spotlight-mode SAR imagery when reconstructed via the well-known polar formatting algorithm (PFA) under certain scenarios that include imaging at close range, use of very low center frequency, and/or imaging of very large scenes. The range migration algorithm (RMA), also known as seismic migration, was developed to accommodate these wavefront curvature effects. However, the along-track upsampling of the phase history data required of the original version of range migration can in certain instances represent a major computational burden. A more recent version of migration processing, the Frequency Domain Replication and Downsampling (FReD) algorithm, obviates the need to upsample, and is accordingly more efficient. In this paper the authors demonstrate that the combination of traditional polar formatting with appropriate space-variant post-filtering for refocus can be as efficient or even more efficient than FReD under some imaging conditions, as demonstrated by the computer-simulated results in this paper. The post-filter can be pre-calculated from a theoretical derivation of the curvature effect. The conclusion is that the new polar formatting with post filtering algorithm (PF2) should be considered as a viable candidate for a spotlight-mode image formation processor when curvature effects are present

Non-adiabatic corrections to elastic scattering of halo nuclei

We derive the formalism for the leading order corrections to the adiabatic approximation to the scattering of composite projectiles. Assuming a two-body projectile of core plus loosely-bound valence particle and a model (the core recoil model) in which the interaction of the valence particle and the target can be neglected, we derive the non-adiabatic correction terms both exactly, using a partial wave analysis, and using the eikonal approximation. Along with the expected energy dependence of the corrections, there is also a strong dependence on the valence-to-core mass ratio and on the strength of the imaginary potential for the core-target interaction, which relates to absorption of the core in its scattering by the target. The strength and diffuseness of the core-target potential also determine the size of the corrections. The first order non-adiabatic corrections were found to be smaller than qualitative estimates would expect. The large absorption associated with the core-target interaction in such halo nuclei as Be11 kills off most of the non-adiabatic corrections. We give an improved estimate for the range of validity of the adiabatic approximation when the valence-target interaction is neglected, which includes the effect of core absorption. Some consideration was given to the validity of the eikonal approximation in our calculations.Comment: 14 pages with 10 figures, REVTeX4, AMS-LaTeX v2.13, submitted to Phys. Rev.

Electromagnetic Form Factors of the SU(3) Octet Baryons in the semibosonized SU(3) Nambu-Jona-Lasinio Model

The electromagnetic form factors of the SU(3) octet baryons are investigated in the semibosonized SU(3) Nambu--Jona-Lasinio model (chiral quark-soliton model). The rotational $1/N_c$ and strange quark mass corrections in linear order are taken into account. The electromagnetic charge radii of the nucleon and magnetic moments are also evaluated. It turns out that the model is in a remarkable good agreement with the experimental data.Comment: RevTex is used. 37 pages. The final version to appear in Phys. Rev. D. 13 figures are include

Flux Backgrounds in 2D String Theory

We study RR flux backgrounds in two dimensional type 0 string theories. In particular, we study the relation between the 0A matrix model and the extremal black hole in two dimensions. Using T-duality we find a dual flux background in type 0B theory and propose its matrix model description. When the Fermi level is set to zero this system remains weakly coupled and exhibits a larger symmetry related to the structure of flux vacua. Finally, we construct a two dimensional type IIB background as an orbifold of the 0B background.Comment: Harvmac, 40 pages, 6 figs, minor changes, references adde

Dioctahedral mixed K-Na-micas and paragonite in diagenetic to low-temperature metamorphic terrains: bulk rock chemical, thermodynamic and textural constraints

Abstract Metamorphic mineral assemblages in low-temperature metaclastic rocks often contain paragonite and/or its precursor metastable phase (mixed K-Na-white mica). Relationships between the bulk rock major element chemistries and the formation of paragonite at seven localities from Central and SE-Europe were studied, comparing the bulk chemical characteristics with mineral assemblage, mineral chemical and metamorphic petrological data. Considerable overlaps between the projection fields of bulk chemistries of the Pg-free and Pg-bearing metaclastic rocks indicate significant differences between the actual (as analyzed) and effective bulk chemical compositions. Where inherited, clastic, inert phases/constituents were excluded, it was found that a decrease in Na/(Na+Al*) and in K/(K+Al*) ratios of rocks favors the formation and occurrence of Pg and its precursor phases (Al* denotes here the atomic quantity of aluminum in feldspars, white micas and “pure” hydrous or anhydrous aluminosilicates). In contrast to earlier suggestions, enrichment in Na and/or an increase in Na/K ratio by themselves do not lead to formation of paragonite. Bulk rock chemistries favorable to formation of paragonite and its precursor phases are characterized by enrichment in Al and depletion in Na, K, Ca (and also, Mg and Fe2+). Such bulk rock chemistries are characteristic of chemically “mature” (strongly weathered) source rocks of the pelites and may also be formed by synand post-sedimentary magmatism-related hydrothermal (leaching) activity. What part of the whole rock is active in determining the effective bulk chemistry was investigated by textural examination of diagenetic and anchizone-grade samples. It is hypothesized that although solid phases act as local sources and sinks, transport of elements such as Na through the grain boundaries have much larger communication distances. Sodium-rich white micas nucleate heterogeneously using existing phyllosilicates as templates and are distributed widely on the thin section scale. The results of modeling by THERMOCALC suggest that paragonite preferably forms at higher pressures in low-T metapelites. The stability fields of Pg-bearing assemblages increase, the Pg-in reaction line is shifted towards lower pressures, while the stability field of the Chl-Ms-Ab-Qtz assemblage decreases and is shifted towards higher temperatures with increasing Al* content and decreasing Na/(Na+Al*) and K/(K+Al*) ratios

Inverse magnetic catalysis in field theory and gauge-gravity duality

We investigate the surface of the chiral phase transition in the three-dimensional parameter space of temperature, baryon chemical potential and magnetic field in two different approaches, the field-theoretical Nambu-Jona-Lasinio (NJL) model and the holographic Sakai-Sugimoto model. The latter is a top-down approach to a gravity dual of QCD with an asymptotically large number of colors and becomes, in a certain limit, dual to an NJL-like model. Our main observation is that, at nonzero chemical potential, a magnetic field can restore chiral symmetry, in apparent contrast to the phenomenon of magnetic catalysis. This "inverse magnetic catalysis" occurs in the Sakai-Sugimoto model and, for sufficiently large coupling, in the NJL model and is related to the physics of the lowest Landau level. While in most parts our discussion is a pedagogical review of previously published results, we include new analytical results for the NJL approach and a thorough comparison of inverse magnetic catalysis in the two approaches.Comment: 37 pages, 11 figures, to appear in Lect. Notes Phys. "Strongly interacting matter in magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A. Schmitt, H.-U. Ye

Occupational Communication as Boundary Mechanism

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69000/2/10.1177_073088847400100404.pd

A Review of Magnetic Phenomena in Probe-Brane Holographic Matter

Gauge/gravity duality is a useful and efficient tool for addressing and studying questions related to strongly interacting systems described by a gauge theory. In this manuscript we will review a number of interesting phenomena that occur in such systems when a background magnetic field is turned on. Specifically, we will discuss holographic models for systems that include matter fields in the fundamental representation of the gauge group, which are incorporated by adding probe branes into the gravitational background dual to the gauge theory. We include three models in this review: the D3-D7 and D4-D8 models, that describe four-dimensional systems, and the D3-D7' model, that describes three-dimensional fermions interacting with a four-dimensional gauge field.Comment: 35 pages, 27 figures, to appear in Lect. Notes Phys. "Strongly interacting matter in magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A. Schmitt, H.-U. Yee; references adde