Old and New Fields on Super Riemann Surfaces

The ``new fields" or ``superconformal functions" on $N=1$ super Riemann surfaces introduced recently by Rogers and Langer are shown to coincide with the Abelian differentials (plus constants), viewed as a subset of the functions on the associated $N=2$ super Riemann surface. We confirm that, as originally defined, they do not form a super vector space.Comment: 9 pages, LaTex. Published version: minor changes for clarity, two new reference

Analysis of airborne Doppler lidar, Doppler radar and tall tower measurements of atmospheric flows in quiescent and stormy weather

The first experiment to combine airborne Doppler Lidar and ground-based dual Doppler Radar measurements of wind to detail the lower tropospheric flows in quiescent and stormy weather was conducted in central Oklahoma during four days in June-July 1981. Data from these unique remote sensing instruments, coupled with data from conventional in-situ facilities, i.e., 500-m meteorological tower, rawinsonde, and surface based sensors, were analyzed to enhance understanding of wind, waves and turbulence. The purposes of the study were to: (1) compare winds mapped by ground-based dual Doppler radars, airborne Doppler lidar, and anemometers on a tower; (2) compare measured atmospheric boundary layer flow with flows predicted by theoretical models; (3) investigate the kinematic structure of air mass boundaries that precede the development of severe storms; and (4) study the kinematic structure of thunderstorm phenomena (downdrafts, gust fronts, etc.) that produce wind shear and turbulence hazardous to aircraft operations. The report consists of three parts: Part 1, Intercomparison of Wind Data from Airborne Lidar, Ground-Based Radars and Instrumented 444 m Tower; Part 2, The Structure of the Convective Atmospheric Boundary Layer as Revealed by Lidar and Doppler Radars; and Part 3, Doppler Lidar Observations in Thunderstorm Environments

On the Monadic Second-Order Transduction Hierarchy

We compare classes of finite relational structures via monadic second-order transductions. More precisely, we study the preorder where we set C \subseteq K if, and only if, there exists a transduction {\tau} such that C\subseteq{\tau}(K). If we only consider classes of incidence structures we can completely describe the resulting hierarchy. It is linear of order type {\omega}+3. Each level can be characterised in terms of a suitable variant of tree-width. Canonical representatives of the various levels are: the class of all trees of height n, for each n \in N, of all paths, of all trees, and of all grids

Thermal Fluctuations of Elastic Filaments with Spontaneous Curvature and Torsion

We study the effects of thermal flucutations on thin elastic filaments with spontaneous curvature and torsion. We derive analytical expressions for the orientational correlation functions and for the persistence length of helices, and find that this length varies non-monotonically with the strength of thermal fluctuations. In the weak fluctuation regime, the persistence length of a spontaneously twisted helix has three resonance peaks as a function of the twist rate. In the limit of strong fluctuations, all memory of the helical shape is lost.Comment: 1 figur

Quantum Tunneling, Blackbody Spectrum and Non-Logarithmic Entropy Correction for Lovelock Black Holes

We show, using the tunneling method, that Lovelock black holes Hawking radiate with a perfect blackbody spectrum. This is a new result. Within the semiclassical (WKB) approximation the temperature of the spectrum is given by the semiclassical Hawking temperature. Beyond the semiclassical approximation the thermal nature of the spectrum does not change but the temperature undergoes some higher order corrections. This is true for both black hole (event) and cosmological horizons. Using the first law of thermodynamics the black hole entropy is calculated. Specifically the $D$-dimensional static, chargeless black hole solutions which are spherically symmetric and asymptotically flat, AdS or dS are considered. The interesting property of these black holes is that their semiclassical entropy does not obey the Bekenstein-Hawking area law. It is found that the leading correction to the semiclassical entropy for these black holes is not logarithmic and next to leading correction is also not inverse of horizon area. This is in contrast to the black holes in Einstein gravity. The modified result is due to the presence of Gauss-Bonnet term in the Lovelock Lagrangian. For the limit where the coupling constant of the Gauss-Bonnet term vanishes one recovers the known correctional terms as expected in Einstein gravity. Finally we relate the coefficient of the leading (non-logarithmic) correction with the trace anomaly of the stress tensor.Comment: minor modifications, two new references added, LaTeX, JHEP style, 34 pages, no figures, to appear in JHE

An Algorithmic Approach to Quantum Field Theory

The lattice formulation provides a way to regularize, define and compute the Path Integral in a Quantum Field Theory. In this paper we review the theoretical foundations and the most basic algorithms required to implement a typical lattice computation, including the Metropolis, the Gibbs sampling, the Minimal Residual, and the Stabilized Biconjugate inverters. The main emphasis is on gauge theories with fermions such as QCD. We also provide examples of typical results from lattice QCD computations for quantities of phenomenological interest.Comment: 44 pages, to be published in IJMP

Self dual models and mass generation in planar field theory

We analyse in three space-time dimensions, the connection between abelian self dual vector doublets and their counterparts containing both an explicit mass and a topological mass. Their correspondence is established in the lagrangian formalism using an operator approach as well as a path integral approach. A canonical hamiltonian analysis is presented, which also shows the equivalence with the lagrangian formalism. The implications of our results for bosonisation in three dimensions are discussed.Comment: 15 pages,Revtex, No figures; several changes; revised version to appear in Physical Review

Fast Optimal Transport Averaging of Neuroimaging Data

Knowing how the Human brain is anatomically and functionally organized at the level of a group of healthy individuals or patients is the primary goal of neuroimaging research. Yet computing an average of brain imaging data defined over a voxel grid or a triangulation remains a challenge. Data are large, the geometry of the brain is complex and the between subjects variability leads to spatially or temporally non-overlapping effects of interest. To address the problem of variability, data are commonly smoothed before group linear averaging. In this work we build on ideas originally introduced by Kantorovich to propose a new algorithm that can average efficiently non-normalized data defined over arbitrary discrete domains using transportation metrics. We show how Kantorovich means can be linked to Wasserstein barycenters in order to take advantage of an entropic smoothing approach. It leads to a smooth convex optimization problem and an algorithm with strong convergence guarantees. We illustrate the versatility of this tool and its empirical behavior on functional neuroimaging data, functional MRI and magnetoencephalography (MEG) source estimates, defined on voxel grids and triangulations of the folded cortical surface.Comment: Information Processing in Medical Imaging (IPMI), Jun 2015, Isle of Skye, United Kingdom. Springer, 201

Imaging Spectropolarimetry with IBIS II: on the fine structure of G-band bright features

We present new results from first observations of the quiet solar photosphere performed through the Interferometric BIdimensional Spectrometer (IBIS) in spectropolarimetric mode. IBIS allowed us to measure the four Stokes parameters in the FeI 630.15 nm and FeI 630.25 nm lines with high spatial and spectral resolutions for 53 minutes; the polarimetric sensitivity achieved by the instrument is 0.003 the continuum intensity level. We focus on the correlation which emerges between G-band bright feature brightness and magnetic filling factor of ~ 1000 G (kG) fields derived by inverting Stokes I and V profiles. More in detail, we present the correlation first in a pixel-by-pixel study of an approximatively 3 arcsec wide bright feature (a small network patch) and then we show that such a result can be extended to all the bright features found in the dataset at any instant of the time sequence. The higher the kG filling factor associated to a feature the higher the brightness of the feature itself. Filling factors up to about 35 % are obtained for the brightest features. Considering the values of the filling factors derived from the inversion analysis of spectropolarimetric data and the brightness variation observed in G-band data we put forward an upper limit for the smallest scale over which magnetic flux concentrations in intergranular lanes produce a G-band brightness enhancement (~ 0.1''). Moreover, the brightness saturation observed for feature sizes comparable to the resolution of the observations is compatible with large G-band bright features being clusters of sub-arcsecond bright points. This conclusion deserves to be confirmed by forthcoming spectropolarimetric observations at higher spatial resolution.Comment: 10 pages, 7 figures, 1 table - Accepted for publication on Ap