Fermion zero modes at the boundary of superfluid 3He-B

Superfluid 3He-B belongs to the important special class of time-reversal invariant topological superfluids. It has Majorana fermions as edge states on the surface of bulk 3He-B. On the rough wall these fermion zero modes have finite density of states at E=0. It is possible that Lancaster experiments with a wire vibrating in 3He-B have already probed Majorana fermions living on the surface of the wire.Comment: 4 pages, no Figures, JETP Letters style, version to be published in JETP Letter

Spin Berry phase in the Fermi arc states

Unusual electronic property of a Weyl semi-metallic nanowire is revealed. Its band dispersion exhibits multiple subbands of partially flat dispersion, originating from the Fermi arc states. Remarkably, the lowest energy flat subbands bear a finite size energy gap, implying that electrons in the Fermi arc surface states are susceptible of the spin Berry phase. This is shown to be a consequence of spin-to-surface locking in the surface electronic states. We verify this behavior and the existence of spin Berry phase in the low-energy effective theory of Fermi arc surface states on a cylindrical nanowire by deriving the latter from a bulk Weyl Hamiltonian. We point out that in any surface state exhibiting a spin Berry phase pi, a zero-energy bound state is formed along a magnetic flux tube of strength, hc/(2e). This effect is highlighted in a surfaceless bulk system pierced by a dislocation line, which shows a 1D chiral mode along the dislocation line.Comment: 9 pages, 9 figure

Evolution of edge states in topological superfluids during the quantum phase transition

The quantum phase transition between topological and non-topological insulators or between fully gapped superfluids/superconductors can occur without closing the gap. We consider the evolution of the Majorana edge states on the surface of topological superconductor during transition to the topologically trivial superconductor on example of non-interacting Hamiltonian describing the spin-triplet superfluid 3He-B. In conventional situation when the gap is nullified at the transition, the spectrum of Majorana fermions shrinks and vanishes after the transition to the trivial state. If the topological transition occurs without the gap closing, the Majorana fermion spectrum disappears by escaping to ultraviolet, where Green's function approaches zero. This demonstrates the close connection between the topological transition without closing the gap and zeroes in the Green's function. Similar connection takes place in interacting systems where zeroes may occur due to interaction.Comment: 5 pages, 2 figures, JETP Letters style, version submitted to JETP Letter

Localization dynamics of fluids in random confinement

The dynamics of two-dimensional fluids confined within a random matrix of obstacles is investigated using both colloidal model experiments and molecular dynamics simulations. By varying fluid and matrix area fractions in the experiment, we find delocalized tracer particle dynamics at small matrix area fractions and localized motion of the tracers at high matrix area fractions. In the delocalized region, the dynamics is subdiffusive at intermediate times, and diffusive at long times, while in the localized regime, trapping in finite pockets of the matrix is observed. These observations are found to agree with the simulation of an ideal gas confined in a weakly correlated matrix. Our results show that Lorentz gas systems with soft interactions are exhibiting a smoothening of the critical dynamics and consequently a rounded delocalization-to-localization transition.Comment: 5 pages, 3 figure

Combinatorial Properties of Triangle-Free Rectangle Arrangements and the Squarability Problem

We consider arrangements of axis-aligned rectangles in the plane. A geometric arrangement specifies the coordinates of all rectangles, while a combinatorial arrangement specifies only the respective intersection type in which each pair of rectangles intersects. First, we investigate combinatorial contact arrangements, i.e., arrangements of interior-disjoint rectangles, with a triangle-free intersection graph. We show that such rectangle arrangements are in bijection with the 4-orientations of an underlying planar multigraph and prove that there is a corresponding geometric rectangle contact arrangement. Moreover, we prove that every triangle-free planar graph is the contact graph of such an arrangement. Secondly, we introduce the question whether a given rectangle arrangement has a combinatorially equivalent square arrangement. In addition to some necessary conditions and counterexamples, we show that rectangle arrangements pierced by a horizontal line are squarable under certain sufficient conditions.Comment: 15 pages, 13 figures, extended version of a paper to appear at the International Symposium on Graph Drawing and Network Visualization (GD) 201

Electromagnetic and gravitational responses and anomalies in topological insulators and superconductors

One of the defining properties of the conventional three-dimensional ("$\mathbb{Z}_2$-", or "spin-orbit"-) topological insulator is its characteristic magnetoelectric effect, as described by axion electrodynamics. In this paper, we discuss an analogue of such a magnetoelectric effect in the thermal (or gravitational) and the magnetic dipole responses in all symmetry classes which admit topologically non-trivial insulators or superconductors to exist in three dimensions. In particular, for topological superconductors (or superfluids) with time-reversal symmetry which lack SU(2) spin rotation symmetry (e.g. due to spin-orbit interactions), such as the B phase of $^3$He, the thermal response is the only probe which can detect the non-trivial topological character through transport. We show that, for such topological superconductors, applying a temperature gradient produces a thermal- (or mass-) surface current perpendicular to the thermal gradient. Such charge, thermal, or magnetic dipole responses provide a definition of topological insulators and superconductors beyond the single-particle picture. Moreover we find, for a significant part of the 'ten-fold' list of topological insulators found in previous work in the absence of interactions, that in general dimensions the effective field theory describing the space-time responses is governed by a field theory anomaly. Since anomalies are known to be insensitive to whether the underlying fermions are interacting or not, this shows that the classification of these topological insulators is robust to adiabatic deformations by interparticle interactions in general dimensionality. In particular, this applies to symmetry classes DIII, CI, and AIII in three spatial dimensions, and to symmetry classes D and C in two spatial dimensions.Comment: 16 pages, 2 figure

Mental health professionals' attitudes toward patients with PTSD and depression

Background: To date, mental health professionals' attitudes toward posttraumatic stress disorder (PTSD), compared to other psychiatric disorders such as schizophrenia or depression, have rarely been studied. Objective: We assessed mental health professionals' attitudes toward patients with PTSD compared to patients suffering from depression. Method: Case vignettes of a patient with either PTSD or depression were presented to two samples of mental health professionals: attendees of a conference on posttraumatic stress (N = 226) or of a lecture for psychiatry residents (N = 112). Participants subsequently completed a questionnaire that assessed their attitude reactions to the presented case. Results: Participants showed similarly positive attitudes toward depression and PTSD. PTSD elicited a more favorable attitude with regard to prosocial reactions, estimated dependency, attributed responsibility, and interest in the case, particularly in mental health professionals specializing in psychotraumatology. Across diagnoses, higher age and longer professional experience were associated with more positive attitudes toward patients. Conclusions: Mental health professionals' positive attitudes toward patients with depression and PTSD correlate with their specific knowledge about the disorder, their level of professional training, and their years of professional experience. Limitations: The instruments used, although based on established theoretical concepts in attitude research, were not validated in their present versions

Seroepidemiological survey for canine angiostrongylosis in dogs from Germany and the UK using combined detection of Angiostrongylus vasorum antigen and specific antibodies

Dogs infected with Angiostrongylus vasorum, a potentially lethal parasite parasitizing the heart and pulmonary arteries, may present severe respiratory, haematological and neurological signs. In this first large-scale seroepidemiological survey, 4003 sera originating from Germany and 4030 from the UK were tested by an ELISA for the detection of circulating antigen of A. vasorum, and by a separate ELISA detecting specific antibodies. In Germany, where mainly western federal states were sampled, 0·3% (n = 13, CI: 0·2-0·6%) of dogs were positive in both ELISAs, whereas in total 0·5% (n = 20, CI: 0·3-0·8%) were antigen-positive and 2·25% (n = 90, CI: 1·8-2·8%) were positive for specific antibodies. Regions with antigen- and antibody-positive animals were overlapping. In the UK, where mainly the south of the country was sampled, 0·97% (n = 39, CI: 0·7-1·3%) of dogs were antigen- and antibody positive. In total, 1·32% (n = 53, CI: 1·0-1·7%) were antigen-positive, and 3·2% (n = 129, CI: 2·7-3·8%) were positive for specific antibodies, again in overlapping regions. These results confirm the occurrence of A. vasorum in a random dog population originating from large parts of the countries investigated. The use of the tests alone or in combination was considered as a function of their sensitivities and specificities, in order to guide efficient clinical and epidemiological applicatio

Using Cosmic Rays detected by HST as Geophysical Markers I: Detection and Characterization of Cosmic Rays

The Hubble Space Telescope (HST) has been operational for over 30 years and throughout that time it has been bombarded by high energy charged particles colloquially referred to as cosmic rays. In this paper, we present a comprehensive study of more than 1.2 billion cosmic rays observed with HST using a custom written python package, \texttt{HSTcosmicrays}, that is available to the astronomical community. We analyzed $75,908$ dark calibration files taken as part of routine calibration programs for five different CCD imagers with operational coverage of Solar Cycle 23 and 24. We observe the expected modulation of galactic cosmic rays by solar activity. For the three imagers with the largest non-uniformity in thickness, we independently confirm the overall structure produced by fringing analyses by analyzing cosmic ray strikes across the detector field of view. We analyze STIS/CCD observations taken as HST crosses over the South Atlantic Anomaly and find a peak cosmic ray flux of $\sim1100$ $CR/s/cm^2$. We find strong evidence for two spatially confined regions over North America and Australia that exhibit increased cosmic ray fluxes at the $5\sigma$ level.Comment: 48 pages, 30 figures, submitted to Ap

Experimental erosion of microbial diversity decreases soil CH4_4 consumption rates

Biodiversity‐ecosystem functioning (BEF) experiments have predominantly focused on communities of higher organisms, in particular plants, with comparably little known to date about the relevance of biodiversity for microbially driven biogeochemical processes. Methanotrophic bacteria play a key role in Earth's methane (CH$_{4}$) cycle by removing atmospheric CH$_{4}$ and reducing emissions from methanogenesis in wetlands and landfills. Here, we used a dilution‐to‐extinction approach to simulate diversity loss in a methanotrophic landfill cover soil community. Replicate samples were diluted 10$^{1}$–10$^{7}$‐fold, preincubated under a high CH$_{4}$ atmosphere for microbial communities to recover to comparable size, and then incubated for 86 days at constant or diurnally cycling temperature. We hypothesize that (1) CH$_{4}$ consumption decreases as methanotrophic diversity is lost, and (2) this effect is more pronounced under variable temperatures. Net CH$_{4}$ consumption was determined by gas chromatography. Microbial community composition was determined by DNA extraction and sequencing of amplicons specific to methanotrophs and bacteria (pmoA and 16S gene fragments). The richness of operational taxonomic units (OTU) of methanotrophic and nonmethanotrophic bacteria decreased approximately linearly with log‐dilution. CH$_{4}$ consumption decreased with the number of OTUs lost, independent of community size. These effects were independent of temperature cycling. The diversity effects we found occured in relatively diverse communities, challenging the notion of high functional redundancy mediating high resistance to diversity erosion in natural microbial systems. The effects also resemble the ones for higher organisms, suggesting that BEF relationships are universal across taxa and spatial scales