Endstates in multichannel spinless p-wave superconducting wires

Multimode spinless p-wave superconducting wires with a width W much smaller than the superconducting coherence length \xi are known to have multiple low-energy subgap states localized near the wire's ends. Here we compare the typical energies of such endstates for various terminations of the wire: A superconducting wire coupled to a normal-metal stub, a weakly disordered superconductor wire and a wire with smooth confinement. Depending on the termination, we find that the energies of the subgap states can be higher or lower than for the case of a rectangular wire with hard-wall boundaries.Comment: 10 pages, 7 figure

Interacting non-Abelian anyons as Majorana fermions in the honeycomb lattice model

We study the collective states of interacting non-Abelian anyons that emerge in Kitaev's honeycomb lattice model. Vortex-vortex interactions are shown to lead to the lifting of the topological degeneracy and the energy is discovered to exhibit oscillations that are consistent with Majorana fermions being localized at vortex cores. We show how to construct states corresponding to the fusion channel degrees of freedom and obtain the energy gaps characterizing the stability of the topological low energy spectrum. To study the collective behavior of many vortices, we introduce an effective lattice model of Majorana fermions. We find necessary conditions for it to approximate the spectrum of the honeycomb lattice model and show that bi-partite interactions are responsible for the degeneracy lifting also in many vortex systems.Comment: 22 pages, 12 figures, published versio

Multi-wavelength Observations of Dusty Star Formation at Low and High Redshift

This paper examines what can be learned about high-redshift star formation from the small fraction of high-redshift galaxies' luminosities that is emitted at accessible wavelengths. We review and quantify empirical correlations between bolometric luminosities produced by star formation and the UV, mid-IR, sub-mm, and radio luminosities of galaxies in the local universe. These correlations suggest that observations of high-redshift galaxies at any of these wavelengths should constrain their star-formation rates to within 0.2--0.3 dex. We assemble the limited evidence that high-redshift galaxies obey these locally calibrated correlations. The characteristic luminosities and dust obscurations of galaxies at z ~ 0, z ~ 1, and z ~ 3 are reviewed. After discussing the relationship between the high-redshift populations selected in surveys at different wavelengths, we calculate the contribution to the 850um background from each. The available data show that a correlation between star-formation rate and dust obscuration L_dust/L_UV exists at low and high redshift. This correlation plays a central role in the major conclusion of this paper: most star formation at high redshift occurred in galaxies with 1 < L_dust/L_UV < 100 similar to those that host the majority of star formation in the local universe and to those that are detected in UV-selected surveys. (abridged)Comment: Scheduled for publication in ApJ v544 Dec 2000. Significant changes to section 4. Characteristic UV and dust luminosities of star-forming galaxies at redshifts z~0, z~1, and z~3 presented. Existence of extremely obscured galaxies more clearly acknowledged. Original conclusions reinforced by the observed correlation between bolometric luminosity and dust obscuration at 0<z<

Kaleidoscope of topological phases with multiple Majorana species

Exactly solvable lattice models for spins and non-interacting fermions provide fascinating examples of topological phases, some of them exhibiting the localized Majorana fermions that feature in proposals for topological quantum computing. The Chern invariant $\nu$ is one important characterization of such phases. Here we look at the square-octagon variant of Kitaev's honeycomb model. It maps to spinful paired fermions and enjoys a rich phase diagram featuring distinct abelian and nonabelian phases with $\nu= 0,\pm1,\pm2,\pm3$ and $\pm4$. The $\nu=\pm1$ and $\nu=\pm3$ phases all support localized Majorana modes and are examples of Ising and $SU(2)_2$ anyon theories respectively.Comment: 6 pages, 5 figures. The second version has a new title, reflecting a change of focus of the presentation in this version. The third version contains minor changes and is essentially the one published in New Journal of Physic

M\"ossbauer Antineutrinos: Recoilless Resonant Emission and Absorption of Electron Antineutrinos

Basic questions concerning phononless resonant capture of monoenergetic electron antineutrinos (M\"ossbauer antineutrinos) emitted in bound-state beta-decay in the 3H - 3He system are discussed. It is shown that lattice expansion and contraction after the transformation of the nucleus will drastically reduce the probability of phononless transitions and that various solid-state effects will cause large line broadening. As a possible alternative, the rare-earth system 163Ho - 163Dy is favoured. M\"ossbauer-antineutrino experiments could be used to gain new and deep insights into several basic problems in neutrino physics

Zero-voltage conductance peak from weak antilocalization in a Majorana nanowire

We show that weak antilocalization by disorder competes with resonant Andreev reflection from a Majorana zero-mode to produce a zero-voltage conductance peak of order e^2/h in a superconducting nanowire. The phase conjugation needed for quantum interference to survive a disorder average is provided by particle-hole symmetry - in the absence of time-reversal symmetry and without requiring a topologically nontrivial phase. We identify methods to distinguish the Majorana resonance from the weak antilocalization effect.Comment: 13 pages, 8 figures. Addendum, February 2014: Appendix B shows results for weak antilocalization in the circular ensemble. (This appendix is not in the published version.

A finite model of two-dimensional ideal hydrodynamics

A finite-dimensional su($N$) Lie algebra equation is discussed that in the infinite $N$ limit (giving the area preserving diffeomorphism group) tends to the two-dimensional, inviscid vorticity equation on the torus. The equation is numerically integrated, for various values of $N$, and the time evolution of an (interpolated) stream function is compared with that obtained from a simple mode truncation of the continuum equation. The time averaged vorticity moments and correlation functions are compared with canonical ensemble averages.Comment: (25 p., 7 figures, not included. MUTP/92/1

Stability of corn (\u3ci\u3eZea mays\u3c/i\u3e)- foxtail (\u3ci\u3eSetaria\u3c/i\u3e spp.) interference relationships

Variation in interference relationships have been shown for a number of crop-weed associations and may have an important effect on the implementation of decision support systems for weed management. Multiyear field experiments were conducted at eight locations to determine the stability of corn-foxtail interference relationships across years and locations. Two coefficients (I and A) of a rectangular hyperbola equation were estimated for each data set using nonlinear regression procedures. The I and A coefficients represent percent corn yield loss as foxtail density approaches zero and maximum percent corn yield loss, respectively. The coefficient I was stable across years at two locations and varied across years at four locations. Maximum yield loss (A) varied between years at one location. Both coefficients varied among locations. Although 3 to 4 foxtail plants m-1 row was a conservative estimate of the single-year economic threshold (Te) of foxtail density, variation in I and A resulted in a large variation in Te. Therefore, the utility of using common coefficient estimates to predict future crop yield loss from foxtail interference between years or among locations within a region is limited

Stability of corn (\u3ci\u3eZea mays\u3c/i\u3e)- foxtail (\u3ci\u3eSetaria\u3c/i\u3e spp.) interference relationships

Variation in interference relationships have been shown for a number of crop-weed associations and may have an important effect on the implementation of decision support systems for weed management. Multiyear field experiments were conducted at eight locations to determine the stability of corn-foxtail interference relationships across years and locations. Two coefficients (I and A) of a rectangular hyperbola equation were estimated for each data set using nonlinear regression procedures. The I and A coefficients represent percent corn yield loss as foxtail density approaches zero and maximum percent corn yield loss, respectively. The coefficient I was stable across years at two locations and varied across years at four locations. Maximum yield loss (A) varied between years at one location. Both coefficients varied among locations. Although 3 to 4 foxtail plants m-1 row was a conservative estimate of the single-year economic threshold (Te) of foxtail density, variation in I and A resulted in a large variation in Te. Therefore, the utility of using common coefficient estimates to predict future crop yield loss from foxtail interference between years or among locations within a region is limited