Topological invariants for spin-orbit coupled superconductor nanowires

We show that a spin-orbit coupled semiconductor nanowire with Zeeman splitting and s-wave superconductivity is in symmetry class BDI (not D as is commonly thought) of the topological classification of band Hamiltonians. The class BDI allows for an integer Z topological invariant equal to the number of Majorana fermion (MF) modes at each end of the quantum wire protected by the chirality symmetry (reality of the Hamiltonian). Thus it is possible for this system (and all other d=1 models related to it by symmetry) to have an arbitrary integer number, not just 0 or 1 as is commonly assumed, of MFs localized at each end of the wire. The integer counting the number of MFs at each end reduces to 0 or 1, and the class BDI reduces to D, in the presence of terms in the Hamiltonian that break the chirality symmetry.Comment: 4+ pages, no figure

Diamagnetic susceptibility obtained from the six-vertex model and its implications for the high-temperature diamagnetic state of cuprate superconductors

We study the diamagnetism of the 6-vertex model with the arrows as directed bond currents. To our knowledge, this is the first study of the diamagnetism of this model. A special version of this model, called F model, describes the thermal disordering transition of an orbital antiferromagnet, known as d-density wave (DDW), a proposed state for the pseudogap phase of the high-Tc cuprates. We find that the F model is strongly diamagnetic and the susceptibility may diverge in the high temperature critical phase with power law arrow correlations. These results may explain the surprising recent observation of a diverging low-field diamagnetic susceptibility seen in some optimally doped cuprates within the DDW model of the pseudogap phase.Comment: 4.5 pages, 2 figures, revised version accepted in Phys. Rev. Let

Review of geographical stocks of tropical dolphins (Stenella spp. and Delphinus delphis) in the eastern Pacific

Information on geographical variation is reviewed for Stenella attenuata, S. longirostris, S. coeruleoalba, and Delphinus delphis in the eastern tropical Pacific, and boundaries for potential management units are proposed. National Marine Fisheries Service and Inter-American Tropical Tuna Commission sighting records made from 1979 to 1983 which were outside boundaries used in a 1979 assessment were examined for validity. Tagging returns and morphological data were also analyzed. Several stock ranges are expanded or combined. Three management units are proposed for S. attenuata: the coastal, northern offshore, and southern offshore spoiled dolphins. Four management units are proposed for S. longirostris: the Costa Rican, eastern, northern whitebelly, and southern whitebelly spinner dolphins. Two provisional management units are proposed for S. coeruleoalba: the northern and southern striped dolphins. Five management units (two of which are provisional) are proposed for D. delphis: the Baja neritic, northern, central, southern, and Guerrero common dolphins. Division into management units was based on morphological stock differences and distributional breaks. (PDF file contains 34 pages.

NASA/MSFC Large Stretch Press Study

The purpose of this study was to: A. assess and document the advantages/disadvantages of a government agency investment in a large stretch form press on the order of 5000 tons capacity (per jaw); B. develop a procurement specification for the press; and C. provide trade study data that will permit an optimum site location. Tasks were separated into four major elements: cost study, user survey, site selection, and press design/procurement specification

Oyster Mortality Studies In Virginia. II. The Fungus Disease Caused By Dermocystidium Marinum In Oysters Of Chesapeake Bay

A high death rate of oysters in Virginia waters during the warm months of summer and fall was reported by Hewatt & Andrews (1954b). One of the most important causes of this warm-season mortality is the fungus Dermocystidium marinum, a pathogen discovered in the Gulf of Mexico by Mackin, Owen & Collier (1950). The fungus is found along the coast of the Western Atlantic from Delaware Bay to Florida and on the coast of the Gulf of Mexico from Florida to Texas. In Chesapeake Bay the disease was studied for pathogenicity to oysters, seasonal occurrence, distribution, and its effect on the oyster industry. Over 3000 dead or dying oysters and 7000 live oysters were examined. Most of the dead or dying oysters were obtained from trays suspended in the York River at Gloucester Point, Virginia, but the live oysters came from many localities in Chesapeake Bay

Temperature Control Experiments on the Fungus Disease, Dermocystidium marinum, of Oysters

In 1950 Mackin, Owen, and Collier described a fungus parasite, Dermocystidium marinim, found in oysters of Louisiana coastal waters. Since that, time numerous studies have been conducted on the nature of the fungus and its effects upon the host. It has been definitely established that the pathogen is the main contributor to the causes of mortality of oysters in some areas. Ray and Chandler (1955) have adequately reviewed the literature on the subject. Among the various observations that have been made on the fungus disease there is very positive evidence that the incidence and intensity of the infection are primarily controlled by the temperature of the water. Mackin (1953) found that mortality rates and intensity of the infection were greatly depressed during the winter months in Barataria Bay, Louisiana. Hewatt and Andrews (1953) reported a high mortality period extending from June through October in the lower York River, Virginia., Ray and Chandler (1955) stated that temperatures exceeding 20°c. favor the development of Dermocystidium marinum in waters of the Gulf of Mexico. During the summer of 1954 we conducted a series of experiments in an effort to determine the effects of relatively low and high temperatures on the development of the fungus disease. Oysters were collected from two different sources. One group of oysters, estimated to be three years of age, was collected from Wreck Shoal of the James River, where no evidence of the fungus has been found. This group \u27Will be referred to as the Nonendemic Oysters & The other group of oysters came from the Rappahannock River, where fungus infections have been found. This group will be designated Endemic Oysters .

Phenomenology of Electroweak Symmetry Breaking from Theory Space

Recently, a new class of realistic models for electroweak symmetry breaking have been constructed, without supersymmetry. These theories have naturally light Higgs bosons and perturbative new physics at the TeV scale. We describe these models in detail, and show that electroweak symmetry breaking can be triggered by a large top quark Yukawa coupling. A rich spectrum of particles is predicted, with a pair of light Higgs doublets accompanied by new light weak triplet and singlet scalars. The lightest of these new scalars is charged under a geometric discrete symmetry and is therefore stable, providing a new candidate for WIMP dark matter. At TeV energies, a plethora of new heavy scalars, gauge bosons and fermions are revealed, with distinctive quantum numbers and decay modes.Comment: 22 pages, latex, 6 figures. Numerical results corrected, clarifications added, conclusions unchange