Electrically detected interferometry of Majorana fermions in a topological insulator

We show how a chiral Dirac fermion (a massless electron or hole) can be converted into a pair of neutral chiral Majorana fermions (a particle equal to its own antiparticle). These two types of fermions exist on the metallic surface of a topological insulator, respectively, at a magnetic domain wall and at a magnet-superconductor interface. Interferometry of Majorana fermions is a key operation in topological quantum computation, but the detection is problematic since these particles have no charge. The Dirac-Majorana converter enables electrical detection of the interferometric signal.Comment: 4 pages, 2 figure

Three-dimensional topologically gauged N=6 ABJM type theories

In this paper we construct the $\mathcal N=6$ conformal supergravity in three dimensions from a set of Chern-Simons-like terms one for each of the graviton, gravitino, and R-symmetry gauge field and then couple this theory to the $\mathcal N=6$ superconformal ABJM theory. In a first step part of the coupled Lagrangian for this topologically gauged ABJM theory is derived by demanding that all terms of third and second order in covariant derivatives cancel in the supersymmtry variation of the Lagrangian. To achieve this the transformation rules of the two separate sectors must be augmented by new terms. In a second step we analyze all terms in $\delta L$ that are of first order in covariant derivatives. The cancelation of these terms require additional terms in the transformation rules as well as a number of new terms in the Lagrangian. As a final step we check that all remaining terms in $\delta L$ which are bilinear in fermions cancel which means that the presented Lagrangian and transformation rules constitute the complete answer. In particular we find in the last step new terms in the scalar potential containing either one or no structure constant. The non-derivative higher fermion terms in $\delta L$ that have not yet been completely analyzed are briefly discussed.Comment: 26 pages, v.2 minor corrections, comment on relation to chiral gravity added

Quantum memory for non-stationary light fields based on controlled reversible inhomogeneous broadening

We propose a new method for efficient storage and recall of non-stationary light fields, e.g. single photon time-bin qubits, in optically dense atomic ensembles. Our approach to quantum memory is based on controlled, reversible, inhomogeneous broadening. We briefly discuss experimental realizations of our proposal.Comment: 4 page

Light-cone analysis of ungauged and topologically gauged BLG theories

We consider three-dimensional maximally superconformal Bagger-Lambert-Gustavsson (BLG) theory and its topologically gauged version (constructed recently in arXiv:0809.4478 [hep-th]) in the light-cone gauge. After eliminating the entire Chern-Simons gauge field, the ungauged BLG theory looks more conventional and, apart from the order of the interaction terms, resembles N=4 super-Yang-Mills theory in four dimensions. The light-cone superspace version of the BLG theory is given to quadratic and quartic order and some problems with constructing the sixth order interaction terms are discussed. In the topologically gauged case, we analyze the field equations related to the three Chern-Simons type terms of N=8 conformal supergravity and discuss some of the special features of this theory and its couplings to BLG.Comment: 22 pages; v2 some typos correcte

Heat capacity mapping mission project HCM-051

There are no author-identified significant results in this report

An almost isotropic cosmic microwave temperature does not imply an almost isotropic universe

In this letter we will show that, contrary to what is widely believed, an almost isotropic cosmic microwave background (CMB) temperature does not imply that the universe is ``close to a Friedmann-Lemaitre universe''. There are two important manifestations of anisotropy in the geometry of the universe, (i) the anisotropy in the overall expansion, and (ii) the intrinsic anisotropy of the gravitational field, described by the Weyl curvature tensor, although the former usually receives more attention than the latter in the astrophysical literature. Here we consider a class of spatially homogeneous models for which the anisotropy of the CMB temperature is within the current observational limits but whose Weyl curvature is not negligible, i.e. these models are not close to isotropy even though the CMB temperature is almost isotropic.Comment: 5 pages (AASTeX, aaspp4.sty), submitted to Astrophysical Journal Letter

Rotational states in deformed nuclei: An analytic approach

The consequences of the spontaneous breaking of rotational symmetry are investigated in a field theory model for deformed nuclei, based on simple separable interactions. The crucial role of the Ward-Takahashi identities to describe the rotational states is emphasized. We show explicitly how the rotor picture emerges from the isoscalar Goldstone modes, and how the two-rotor model emerges from the isovector scissors modes. As an application of the formalism, we discuss the M1 sum rules in deformed nuclei, and make connection to empirical information.Comment: 19 pages, 9 figure

The nature of z ~ 2.3 Lyman-alpha emitters

We study the multi-wavelength properties of a set of 171 Ly-alpha emitting candidates at redshift z = 2.25 found in the COSMOS field, with the aim of understanding the underlying stellar populations in the galaxies. We especially seek to understand what the dust contents, ages and stellar masses of the galaxies are, and how they relate to similar properties of Ly-alpha emitters at other redshifts. The candidates here are shown to have different properties from those of Ly-alpha emitters found at higher redshift, by fitting the spectral energy distributions (SEDs) using a Monte-Carlo Markov-Chain technique and including nebular emission in the spectra. The stellar masses, and possibly the dust contents, are higher, with stellar masses in the range log M_* = 8.5 - 11.0 M_sun and A_V = 0.0 - 2.5 mag. Young population ages are well constrained, but the ages of older populations are typically unconstrained. In 15% of the galaxies only a single, young population of stars is observed. We show that the Ly-alpha fluxes of the best fit galaxies are correlated with their dust properties, with higher dust extinction in Ly-alpha faint galaxies. Testing for whether results derived from a light-weighted stack of objects correlate to those found when fitting individual objects we see that stellar masses are robust to stacking, but ages and especially dust extinctions are derived incorrectly from stacks. We conclude that the stellar properties of Ly-alpha emitters at z = 2.25 are different from those at higher redshift and that they are diverse. Ly-alpha selection appears to be tracing systematically different galaxies at different redshifts.Comment: 15 pages, 11 figures, 8 tables, accepted in A&A. Table 6 available in full from the author