Multicolored Temperley-Lieb lattice models. The ground state

Using inversion relation, we calculate the ground state energy for the lattice integrable models, based on a recently obtained baxterization of non trivial multicolored generalization of Temperley-Lieb algebras. The simplest vertex and IRF models are analyzed and found to have a mass gap.Comment: 15 pages 2 figure

Topological defects: A problem for cyclic universes?

We study the behaviour of cosmic string networks in contracting universes, and discuss some of their possible consequences. We note that there is a fundamental time asymmetry between defect network evolution for an expanding universe and a contracting universe. A string network with negligible loop production and small-scale structure will asymptotically behave during the collapse phase as a radiation fluid. In realistic networks these two effects are important, making this solution only approximate. We derive new scaling solutions describing this effect, and test them against high-resolution numerical simulations. A string network in a contracting universe, together with the gravitational radiation background it has generated, can significantly affect the dynamics of the universe both locally and globally. The network can be an important source of radiation, entropy and inhomogeneity. We discuss the possible implications of these findings for bouncing and cyclic cosmological models.Comment: 11 RevTeX 4 pages, 6 figures; version to appear in Phys. Rev.

Electron-Phonon Interactions in C28_{28}-derived Molecular Solids

We present {\it ab initio} density-functional calculations of molecular solids formed from C$_{28}$-derived closed-shell fullerenes. Solid C$_{28}$H$_4$ is found to bind weakly and exhibits many of the electronic structure features of solid C$_{60}$ with an enhanced electron-phonon interaction potential. We show that chemical doping of this structure is feasible, albeit more restrictive than its C$_{60}$ counterpart, with an estimated superconducting transition temperature exceeding those of the alkali-doped C$_{60}$ solids.Comment: Lower quality postscript file for Figure 1 is used in the manuscript in order to meet submission quota for pre-print server. Higher quality postscript file available from author: [email protected] This article has been updated to reflect changes incorporated during the peer review process. It is published in PRB 70, 140504(R) 200

Higher lattices, discrete two-dimensional holonomy and topological phases in (3+1)D with higher gauge symmetry

Higher gauge theory is a higher order version of gauge theory that makes possible the definition of 2-dimensional holonomy along surfaces embedded in a manifold where a gauge 2-connection is present. In this paper, we study Hamiltonian models for discrete higher gauge theory on a lattice decomposition of a manifold. We show that a construction for higher lattice gauge theory is well-defined, including in particular a Hamiltonian for topological phases of matter in 3+1 dimensions. Our construction builds upon the Kitaev quantum double model, replacing the finite gauge connection with a finite gauge 2-group 2-connection. Our Hamiltonian higher lattice gauge theory model is defined on spatial manifolds of arbitrary dimension presented by slightly combinatorialized CW-decompositions (2-lattice decompositions), whose 1-cells and 2-cells carry discrete 1-dimensional and 2-dimensional holonomy data. We prove that the ground-state degeneracy of Hamiltonian higher lattice gauge theory is a topological invariant of manifolds, coinciding with the number of homotopy classes of maps from the manifold to the classifying space of the underlying gauge 2-group. The operators of our Hamiltonian model are closely related to discrete 2-dimensional holonomy operators for discretized 2-connections on manifolds with a 2-lattice decomposition. We therefore address the definition of discrete 2-dimensional holonomy for surfaces embedded in 2-lattices. Several results concerning the well-definedness of discrete 2-dimensional holonomy, and its construction in a combinatorial and algebraic topological setting are presented

New symmetries of the chiral Potts model

In this paper a hithertho unknown symmetry of the three-state chiral Potts model is found consisting of two coupled Temperley-Lieb algebras. From these we can construct new superintegrable models. One realisation is in terms of a staggered isotropic XY spin chain. Further we investigate the importance of the algebra for the existence of mutually commuting charges. This leads us to a natural generalisation of the boost-operator, which generates the charges.Comment: 19 pages, improved notation, made the text easier to read, corrected some typo

Quantum tunneling of superconducting string currents

We investigate the decay of current on a superconducting cosmic string through quantum tunneling. We construct the instanton describing tunneling in a simple bosonic string model, and estimate the decay rate. The tunneling rate vanishes in the limit of a chiral current. This conclusion, which is supported by a symmetry argument, is expected to apply in general. It has important implications for the stability of chiral vortons.Comment: 16 pages, 2 figure

Risk assessment of wildlife-watching tourism in an important endangered loggerhead turtle rookery

T: Wildlife-watching tourism is a non-exploitative activity that can contribute to sustainable economic development of coastal communities. However, it is important to assess the potential impact and implement best practices to mitigate any negative effects of such tourism. We studied this issue on Boa Vista (Cabo Verde), which supports around 60% of nesting activity of one of the most endangered loggerhead turtle rookeries globally. Between 2013 and 2016, authorized turtle watching involved 4942 tourists, generating a mean annual direct income of >USD 289 000 and the direct creation of >250 jobs. On João Barrosa beach, which supports around 20% of nests and 48% of turtle-watching activity on the island, we tested the influence of turtle watching on nesting behavior, reproduction and nest-site fidelity. Nesting females observed by tourists spent significantly less time on nest-camouflaging behavior, although all other phases of nesting were unaffected. There were no statistically significant differences between the re-nesting frequency of females watched (n = 187) and non-watched (n = 972) by tourists. We found no evidence that the current turtle-watching intensity has an effect on turtle reproduction. Turtle poaching remains a severe threat on beaches with no turtle watching, although it has strongly decreased on beaches with tourist visits. We suggest tour guides follow best practice guidelines to minimize disturbance, specifically retreating from the immediate vicinity of a female during nest camouflaging to mitigate the observed impact.Peer reviewe

Planetary Nebula Abundances and Morphology: Probing the Chemical Evolution of the Milky Way

This paper presents a homogeneous study of abundances in a sample of 79 northern galactic planetary nebulae whose morphological classes have been uniformly determined. Ionic abundances and plasma diagnostics were derived from selected optical line strengths in the literature, and elemental abundances were estimated with the Ionization Correction Factor developed by Kingsbourgh & Barlow (1994). We compare the elemental abundances to the final yields obtained from stellar evolution models of low-and intermediate-mass stars, and we confirm that most Bipolar planetary nebulae have high nitrogen and helium abundance, and are the likely progeny of stars with main-sequence mass larger than 3 solar masses. We derive =0.27, and discuss the implication of such a high ratio in connection with the solar neon abundance. We determine the galactic gradients of oxygen and neon, and found Delta log (O/H)/Delta R=-0.01 dex/kpc$ and Delta log (Ne/H)/Delta R=-0.01 dex/kpc. These flat PN gradients do not reconcile with galactic metallicity gradients flattening with time.Comment: The Astrophysical Journal, in pres

Topological phases from higher gauge symmetry in 3+1 dimensions

We propose an exactly solvable Hamiltonian for topological phases in 3 + 1 dimensions utilizing ideas from higher lattice gauge theory, where the gauge symmetry is given by a finite 2-group. We explicitly show that the model is a Hamiltonian realization of Yetter's homotopy 2-type topological quantum field theory whereby the ground-state projector of the model defined on the manifold M 3 is given by the partition function of the underlying topological quantum field theory for M 3 × [ 0 , 1 ] . We show that this result holds in any dimension and illustrate it by computing the ground state degeneracy for a selection of spatial manifolds and 2-groups. As an application we show that a subset of our model is dual to a class of Abelian Walker-Wang models describing 3 + 1 dimensional topological insulators

Representations of the loop braid group and Aharonov–Bohm like effects in discrete (3+1)-dimensional higher gauge theory

We show that representations of the loop braid group arise from Aharonov–Bohm like effects in finite 2‑group (3+1) -dimensional topological higher gauge theory. For this we introduce a minimal categorification of biracks, which we call W‑bikoids (welded bikoids). Our main example of W‑bikoids arises from finite 2‑groups, realised as crossed modules of groups. Given a W‑bikoid, and hence a groupoid of symmetries, we construct a family of unitary representations of the loop braid group derived from representations of the groupoid algebra. We thus give a candidate for higher Bais’ flux metamorphosis, and hence also a version of a ‘higher quantum group’