Determination of the propagator in QED3 by spectral function

To study the infrared behaviour of the propagator, exponentiation of the lowest order spectral function has been known.We show this method is helpful in super renormalizable theory with dimension-full coupling constant.In the 1/N approximation anomalous dimension is independent of $N$,which plays an important role for confinement and pair condensation.Comment: 6 pages Latex,2 figures.introduction is modified.mistakes in equations are corrected.figure captions are correcte

Estimating stellar rotation from starspot detection during planetary transits

A new method for determining the stellar rotation period is proposed here, based on the detection of starspots during transits of an extra-solar planet orbiting its host star. As the planet eclipses the star, it may pass in front of a starspot which will then make itself known through small flux variations in the transit light curve. If we are lucky enough to catch the same spot on two consecutive transits, it is possible to estimate the stellar rotational period. This method is successfully tested on transit simulations on the Sun yielding the correct value for the solar period. By detecting two starspots on more than one transit of HD 209458 observed by the Hubble Space Telescope, it was possible to estimate a period of either 9.9 or 11.4 days for the star, depending on which spot is responsible for the signature in the light curve a few transits later. Comparison with period estimates of HD209458 reported in the literature indicates that 11.4 days is the most likely stellar rotation period.Comment: 13 pages, 5 figure

#cutting: non-suicidal self-injury (NSSI) on Instagram

Social media presents an important means for social interaction, especially among adolescents, with Instagram being the most popular platform in this age-group. Pictures and communication about non-suicidal self-injury (NSSI) can frequently be found on the internet. During 4 weeks in April 2016, n = 2826 (from n = 1154 accounts) pictures which directly depicted wounds on Instagram were investigated. Those pictures, associated comments, and user accounts were independently rated for content. Associations between characteristics of pictures and comments as well as weekly and daily trends of posting behavior were analyzed. Most commonly, pictures depicted wounds caused by cutting on arms or legs and were rated as mild or moderate injuries. Pictures with increasing wound grades and those depicting multiple methods of NSSI generated elevated amounts of comments. While most comments were neutral or empathic with some offering help, few comments were hostile. Pictures were mainly posted in the evening hours, with a small peak in the early morning. While there was a slight peak of pictures being posted on Sundays, postings were rather evenly spread across the week. Pictures of NSSI are frequently posted on Instagram. Social reinforcement might play a role in the posting of more severe NSSI pictures. Social media platforms need to take appropriate measures for preventing online social contagion

Higher-dimensional Algebra and Topological Quantum Field Theory

The study of topological quantum field theories increasingly relies upon concepts from higher-dimensional algebra such as n-categories and n-vector spaces. We review progress towards a definition of n-category suited for this purpose, and outline a program in which n-dimensional TQFTs are to be described as n-category representations. First we describe a "suspension" operation on n-categories, and hypothesize that the k-fold suspension of a weak n-category stabilizes for k >= n+2. We give evidence for this hypothesis and describe its relation to stable homotopy theory. We then propose a description of n-dimensional unitary extended TQFTs as weak n-functors from the "free stable weak n-category with duals on one object" to the n-category of "n-Hilbert spaces". We conclude by describing n-categorical generalizations of deformation quantization and the quantum double construction.Comment: 36 pages, LaTeX; this version includes all 36 figure

Infrared Exponents and Running Coupling of SU(N) Yang-Mills Theories

We present approximate solutions for the gluon and ghost propagators as well as the running coupling in Landau gauge Yang-Mills theories. We solve the corresponding Dyson-Schwinger equations in flat Euclidean space-time without any angular approximation. This supplements recently obtained results employing a four-torus, i.e. a compact space-time manifold, as infrared regulator. We confirm previous findings deduced from an extrapolation with tori of different volumes: the gluon propagator is weakly vanishing in the infrared and the ghost propagator is highly singular. For non-vanishing momenta our propagators are in remarkable agreement with recent lattice calculations.Comment: 11 pages, 4 figure

Neural Network Ensembles and Their Application to Traffic Flow Prediction in Telecommunications Networks

This series is dedicated to reporting our recent research in spatial science in general and economic geography & geoinformatics in particular. It contains scientific studies focusing on spatial phenomena, utilizing theoretical frameworks, analytical methods and empirical procedures specifically designed for spatial analysis. The aim is to present the research at the Department to an informed readership in universities, research organizations and policy-making institutions throughout the world. The type of materials considered for publication in the series includes interim reports presenting work in progress and papers which have been submitted for publication elsewhere.Series: Discussion Papers of the Institute for Economic Geography and GIScienc

Hydraulic and mechanical properties of glacial sediments beneath Unteraargletscher, Switzerland: implications for glacier basal motion

The force on a ‘ploughmeter’ and subglacial water pressure have been measured in the same borehole at Unteraargletscher, Switzerland, in order to investigate ice–sediment coupling and the motion at the base of a soft-bedded glacier. A strong inverse correlation of the recorded pressure and force fluctuations, in conjunction with a significant time lag between the two signals, suggests that pore-water pressures directly affect the strength of the subglacial sediment. The lag is interpreted to reflect the time required for the water-pressure wave to propagate through the pores of the sediment to the depth of the ploughmeter. Analysis of the propagation velocity of this pressure wave yielded an estimate of the hydraulic diffusivity, a key parameter necessary to characterize transient pore-water flow. Furthermore, the inferred inverse relationship between pore-water pressure and sediment strength implies that Coulomb-plastic deformation is an appropriate rheological model for the sediment underlying Unteraargletscher. However, the sediment strength as derived from the ploughmeter data was found to be one order of magnitude smaller than that calculated for a Coulomb-frictional material using the water-pressure measurements. This significant discrepancy might result from pore-water pressures in excess of hydrostatic down-glacier from the ploughmeter. As the ploughmeter is dragged through the sediment, sediment is compressed. If the rate of this compression is large relative to the rate at which pore water can drain away, excess pore-water pressures will develop that have the potential to weaken the sediment. The same process could lead to highly fluid sediment down-glacier from clasts that protrude into the glacier sole and thus would otherwise provide the roughness to couple the glacier to its bed (Iverson, 1999). Rapidly sliding glaciers overlying sediments might therefore move predominantly by ‘ploughing’, which tends to focus basal motion near the glacier sole rather than at depth in the bed

Leading-order calculation of hadronic contributions to the muon g−2g-2 using the Dyson-Schwinger approach

We present a calculation of the hadronic vacuum polarization (HVP) tensor within the framework of Dyson--Schwinger equations. To this end we use a well-established phenomenological model for the quark-gluon interaction with parameters fixed to reproduce hadronic observables. From the HVP tensor we compute both the Adler function and the HVP contribution to the anomalous magnetic moment of the muon, $a_\mu$. We find $a_\mu^{HVP}= 6760\times 10^{-11}$ which deviates about two percent from the value extracted from experiment. Additionally, we make comparison with a recent lattice determination of $a_\mu^{HVP}$ and find good agreement within our approach. We also discuss the implications of our result for a corresponding calculation of the hadronic light-by-light scattering contribution to $a_\mu$.Comment: 9 pages, 8 figure

Temperature Dependence of Gluon and Ghost Propagators in Landau-Gauge Yang-Mills Theory below the Phase Transition

The Dyson-Schwinger equations of Landau-gauge Yang-Mills theory for the gluon and ghost propagators are investigated. Numerical results are obtained within a truncation scheme which has proven to be successful at vanishing temperature. For temperatures up to 250 MeV we find only minor quantitative changes in the infrared behaviour of the gluon and ghost propagators. The effective action calculated from these propagators is temperature-independent within the numerical uncertainty.Comment: 9 pages, 14 figures, submitted to EPJ C, typos corrected, reference and 2 minor clarifications added, in v3: one paragraph extended, some references added, version to appear in EPJ

Using Option Theory to Determine Optimal IRA Investment

Given the current uncertain economic trends, the decision to contribute to a personal retirement account can be a financial challenge taking a great deal of courage. Using the option theory, this paper presents arguments to justify the optimal contribution to maximize an IRA investment return