Lightlike singularities in compactified supergravity

We discuss the (causal) structure of a recently found black hole solution of compatified d = 11 supergravity. It is shown that the singularity is in fact lightlike and coincides with the horizon. Consequences are that the Hawking temperature is undetermined and that there is no other universe connected to the singularity.     

Anyonic order parameters for discrete gauge theories on the lattice

We present a new family of gauge invariant non-local order parameters for (non-abelian) discrete gauge theories on a Euclidean lattice, which are in one-to-one correspondence with the excitation spectrum that follows from the representation theory of the quantum double D(H) of the finite group H. These combine magnetic flux-sector labeled by a conjugacy class with an electric representation of the centralizer subgroup that commutes with the flux. In particular, cases like the trivial class for magnetic flux, or the trivial irrep for electric charge, these order parameters reduce to the familiar Wilson and the ’t Hooft operators, respectively. It is pointed out that these novel operators are crucial for probing the phase structure of a class of discrete lattice models we define, using Monte Carlo simulations.     

Energy-loss mechanisms and the annihilation of confined monopoles

The annihilation process for a superheavy monopole-antimonopole pair connected by a relatively light magnetic flux tube (which is possibly relevant to the cosmological monopole problem) is studied. Three energy-loss mechanisms are considered in some detail. The first two are the radiation of photons and weak bosons due to the linear and Coulomb parts of the potential, respectively. Then the energy loss due to the frictional drag of monopoles moving through a relativistic plasma is analyzed. We argue that for the parameters relevant to standard theories this last mechanism dominates by many orders of magnitude and leads to an almost instantaneous annihilation at the time confinement takes place. The implications of this work for the dilution of the baryon to entropy ratio are described.     

The breaking of quantum double symmetries by defect condensation

In this paper, we study the phenomenon of Hopf or more specifically quantum double symmetry breaking. We devise a criterion for this type of symmetry breaking which is more general than the one originally proposed in F.A. Bais, B.J. Schroers, J.K. Slingerland [Broken quantum symmetry and confinement phases in planar physics, Phys. Rev. Lett. 89 (2002) 181601]; Hopf symmetry breaking and confinement in (2+1)-dimensional gauge theory, JHEP 05 (2003) 068], and therefore extends the number of possible breaking patterns that can be described consistently. We start by recalling why the extended symmetry notion of quantum double algebras is an optimal tool when analyzing a wide variety of two-dimensional physical systems including quantum fluids, crystals and liquid crystals. The power of this approach stems from the fact that one may characterize both ordinary and topological modes as representations of a single (generally nonabelian) Hopf symmetry. In principle a full classification of defect mediated as well as ordinary symmetry breaking patterns and subsequent confinement phenomena can be given. The formalism applies equally well to systems exhibiting global, local, internal and/or external (i.e. spatial) symmetries. The subtle differences in interpretation for the various situations are pointed out. We show that the Hopf symmetry breaking formalism reproduces the known results for ordinary (electric) condensates, and we derive formulae for defect (magnetic) condensates which also involve the phenomenon of symmetry restoration. These results are applied in two papers which will be published in parallel [C.J.M. Mathy, F.A. Bais, Nematic phases and the breaking of double symmetries, arXiv:cond-mat/0602109, 2006; F.A. Bais, C.J.M. Mathy, Defect mediated melting and the breaking of quantum double symmetries, arXiv:cond-mat/0602101, 2006].     

Variability of Cloud-free Ultraviolet Dose Rates on Global Scale Due to Modeled Scenarios of Future Ozone Recovery

Simulations of the total ozone content and vertical ozone and temperature profiles during the period 1980–2080 from three chemistry climate models (CCMs) were used and the future variability of five UV dose rate types in global scale was simulated. For each CCM, radiative transfer calculations for cloud-free skies and constant values of aerosol optical properties and surface reflectivity were performed and the percentage difference, relative to the mean over the period 1996–2005, was calculated. The potential biological consequences of ozone recovery are quantified due to the different influence of ozone-absorbing wavelengths on the selected UV action spectra: average percentage differences between a few and 60% are revealed during the 2070s, depending on the latitude zone and the season. Although the research into the prediction of UV radiation levels is ongoing, due to the possible future changes in cloudiness, aerosols or surface reflectivity, the long-term changes in ozone, as projected by the CCMs in a similar way, will affect strongly some of the selected UV dose rates in the future.     

On the complete integrability of the static axially symmetric self-dual gauge field equations for an arbitrary group

We present an analysis of static axially symmetric gauge fields for an arbitrary gauge group G. Two ansätze are considered. The full ansatz involves a total of 4d(d = dim G), the reduced ansatz only 2d functions of (?, z). Imposing self-duality is shown to reduce the problem to a sigma model in the curved two-dimensional (?, z) space over the coset spaces G?/G for the full, and G¹/K for the reduced ansatz. G? is the complexification of G. ¹ is a particular non-compact form of G, and K the local form-preserving symmetry group of the reduced ansatz. We give explicitly the Lax-pair type representations (linear scattering problem) of the sigma model, indicating that the standard methods available for certain non-linear two-dimensional problems can be used to generate solutions. Our procedure has the advantage that only real fields over a real manifold enter the analysis.     

On a core instability of ''t Hooft–Polyakov type monopoles

We discuss a core instability of 't Hooft–Polyakov monopoles in Alice electrodynamics type of models in which charge conjugation symmetry is gauged. The monopole may deform into a toroidal defect which carries an Alice flux and a (non-localizable) magnetic Cheshire charge.