Coulomb gluons and the ordering variable

We study in detail the exchange of a Coulomb (Glauber) gluon in the first few orders of QCD perturbation theory in order to shed light on their accounting to all orders. We find an elegant cancellation of graphs that imposes a precise ordering on the transverse momentum of the exchanged Coulomb gluon.Comment: 28 pages, 12 figure

Ordering multiple soft gluon emissions

We present an expression for the QCD amplitude for a general hard scattering process with any number of soft gluon emissions, to one-loop accuracy. The amplitude is written in two different but equivalent ways: as a product of operators ordered in dipole transverse momentum and as a product of loop-expanded currents. We hope that these results will help in the development of an all-orders algorithm for multiple emissions that includes the full colour structure and both the real and imaginary contributions to the amplitude.Comment: v4: 3 pages; 1 figure, 4 references and small clarifications added. Version accepted for publication in Physical Review Letter

Efficient transfer entropy analysis of non-stationary neural time series

Information theory allows us to investigate information processing in neural systems in terms of information transfer, storage and modification. Especially the measure of information transfer, transfer entropy, has seen a dramatic surge of interest in neuroscience. Estimating transfer entropy from two processes requires the observation of multiple realizations of these processes to estimate associated probability density functions. To obtain these observations, available estimators assume stationarity of processes to allow pooling of observations over time. This assumption however, is a major obstacle to the application of these estimators in neuroscience as observed processes are often non-stationary. As a solution, Gomez-Herrero and colleagues theoretically showed that the stationarity assumption may be avoided by estimating transfer entropy from an ensemble of realizations. Such an ensemble is often readily available in neuroscience experiments in the form of experimental trials. Thus, in this work we combine the ensemble method with a recently proposed transfer entropy estimator to make transfer entropy estimation applicable to non-stationary time series. We present an efficient implementation of the approach that deals with the increased computational demand of the ensemble method's practical application. In particular, we use a massively parallel implementation for a graphics processing unit to handle the computationally most heavy aspects of the ensemble method. We test the performance and robustness of our implementation on data from simulated stochastic processes and demonstrate the method's applicability to magnetoencephalographic data. While we mainly evaluate the proposed method for neuroscientific data, we expect it to be applicable in a variety of fields that are concerned with the analysis of information transfer in complex biological, social, and artificial systems.Comment: 27 pages, 7 figures, submitted to PLOS ON

Pointwise convergence of vector-valued Fourier series

We prove a vector-valued version of Carleson's theorem: Let Y=[X,H]_t be a complex interpolation space between a UMD space X and a Hilbert space H. For p\in(1,\infty) and f\in L^p(T;Y), the partial sums of the Fourier series of f converge to f pointwise almost everywhere. Apparently, all known examples of UMD spaces are of this intermediate form Y=[X,H]_t. In particular, we answer affirmatively a question of Rubio de Francia on the pointwise convergence of Fourier series of Schatten class valued functions.Comment: 26 page

Isolating causality between gender and corruption: An IV approach

We address the persistent reverse causality problem in estimating the causal effect of female labor force participation (FLFP) on corruption. Employing plow usage as an instrumental variable, an increase in FLFP by one standard deviation is suggested to improve the Corruption Perceptions Index (CPI, ranging from zero to ten) by 0.52 points. This effect is stronger than a one standard deviation change of education levels, government size, or ethnic fractionalization

Mandate M 376: new software accessibility requirements

Software needs to be accessible for persons with disabilities and there are several guidelines to assist developers in building more accessible software. Regulation activities are beginning to make the accessibility of software a mandatory requirement in some countries. One such activity is the European Mandate M 376, which will result in a European standard (EN 301 549) defining functional accessibility requirements for information and communication technology products and services. This paper provides an overview of Mandate M 376 and EN 301 549, and describes the requirements for software accessibility defined in EN 301 549, according to a feature-based approac

Spaces determined by selections

AbstractA function ψ:[X]2→X is a called a weak selection if ψ({x,y})∈{x,y} for every x,y∈X. To each weak selection ψ, one associates a topology τψ, generated by the sets (←,x)={y≠x:ψ(x,y)=y} and (x,→)={y≠x:ψ(x,y)=x}. Answering a question of S. García-Ferreira and A.H. Tomita [S. García-Ferreira, A.H. Tomita, A non-normal topology generated by a two-point selection, Topology Appl. 155 (10) (2008) 1105–1110], we show that (X,τψ) is completely regular for every weak selection ψ. We further investigate to what extent the existence of a continuous weak selection on a topological space determines the topology of X. In particular, we answer two questions of V. Gutev and T. Nogura [V. Gutev, T. Nogura, Selection problems for hyperspaces, in: E. Pearl (Ed.), Open Problems in Topology 2, Elsevier B.V., 2007, pp. 161–170]