3,893 research outputs found
Loop space and evolution of the light-like Wilson polygons
We address a connection between the energy evolution of the polygonal
light-like Wilson exponentials and the geometry of the loop space with the
gauge invariant Wilson loops of a variety of shapes being the fundamental
degrees of freedom. The renormalization properties and the differential area
evolution of these Wilson polygons are studied by making use of the universal
Schwinger quantum dynamical approach. We discuss the appropriateness of the
dynamical differential equations in the loop space to the study of the energy
evolution of the collinear and transverse-momentum dependent parton
distribution functions.Comment: 8 pages, 2 eps figures; needs ws-ijmpcs.cls (supplied). Invited talk
presented at the QCD Evolution Workshop, May 14 - 17 (2012), Thomas Jefferson
National Accelerator Facility, Newport News (VA), US
Atomic-scale visualization of quasiparticle interference on a type-II Weyl semimetal surface
We combine quasiparticle interference simulation (theory) and atomic
resolution scanning tunneling spectro-microscopy (experiment) to visualize the
interference patterns on a type-II Weyl semimetal MoWTe for
the first time. Our simulation based on first-principles band topology
theoretically reveals the surface electron scattering behavior. We identify the
topological Fermi arc states and reveal the scattering properties of the
surface states in MoWTe. In addition, our result reveals
an experimental signature of the topology via the interconnectivity of bulk and
surface states, which is essential for understanding the unusual nature of this
material.Comment: To appear in Phys. Rev. Let
On the probability of staying above a wall for the (2+1)-dimensional SOS model at low temperature
We obtain sharp asymptotics for the probability that the (2+1)-dimensional
discrete SOS interface at low temperature is positive in a large region. For a
square region , both under the infinite volume measure and under the
measure with zero boundary conditions around , this probability turns
out to behave like , with the
surface tension at zero tilt, also called step free energy, and the box
side. This behavior is qualitatively different from the one found for
continuous height massless gradient interface models.Comment: 21 pages, 6 figure
Local and global gestalt laws: A neurally based spectral approach
A mathematical model of figure-ground articulation is presented, taking into
account both local and global gestalt laws. The model is compatible with the
functional architecture of the primary visual cortex (V1). Particularly the
local gestalt law of good continuity is described by means of suitable
connectivity kernels, that are derived from Lie group theory and are neurally
implemented in long range connectivity in V1. Different kernels are compatible
with the geometric structure of cortical connectivity and they are derived as
the fundamental solutions of the Fokker Planck, the Sub-Riemannian Laplacian
and the isotropic Laplacian equations. The kernels are used to construct
matrices of connectivity among the features present in a visual stimulus.
Global gestalt constraints are then introduced in terms of spectral analysis of
the connectivity matrix, showing that this processing can be cortically
implemented in V1 by mean field neural equations. This analysis performs
grouping of local features and individuates perceptual units with the highest
saliency. Numerical simulations are performed and results are obtained applying
the technique to a number of stimuli.Comment: submitted to Neural Computatio
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