12,101 research outputs found
QCD near the Light Cone
Starting from the QCD Lagrangian, we present the QCD Hamiltonian for near
light cone coordinates. We study the dynamics of the gluonic zero modes of this
Hamiltonian. The strong coupling solutions serve as a basis for the complete
problem. We discuss the importance of zero modes for the confinement mechanism.Comment: 32 pages, ReVTeX, 2 Encapsulated PostScript figure
Uniform existence of the integrated density of states for random Schr\"odinger operators on metric graphs over
We consider ergodic random magnetic Schr\"odinger operators on the metric
graph with random potentials and random boundary conditions
taking values in a finite set. We show that normalized finite volume eigenvalue
counting functions converge to a limit uniformly in the energy variable. This
limit, the integrated density of states, can be expressed by a closed
Shubin-Pastur type trace formula. It supports the spectrum and its points of
discontinuity are characterized by existence of compactly supported
eigenfunctions. Among other examples we discuss percolation models.Comment: 17 pages; typos removed, references updated, definition of subgraph
densities explaine
-approximation of the integrated density of states for Schr\"odinger operators with finite local complexity
We study spectral properties of Schr\"odinger operators on \RR^d. The
electromagnetic potential is assumed to be determined locally by a colouring of
the lattice points in \ZZ^d, with the property that frequencies of finite
patterns are well defined. We prove that the integrated density of states
(spectral distribution function) is approximated by its finite volume
analogues, i.e.the normalised eigenvalue counting functions. The convergence
holds in the space where is any finite energy interval and is arbitrary.Comment: 15 pages; v2 has minor fixe
Transverse QCD Dynamics Near the Light Cone
Starting from the QCD Hamiltonian in near-light cone coordinates, we study
the dynamics of the gluonic zero modes. Euclidean 2+1 dimensional lattice
simulations show that the gap at strong coupling vanishes at intermediate
coupling. This result opens the possibility to synchronize the continuum limit
with the approach to the light cone.Comment: 15 pages, LaTeX, 3 figures (7 PS files
Looking the Part: Television Leads Less Informed Citizens to Vote Based on Candidates’ Appearance
As long as there has been democratic government, skeptics have worried that citizens would base their choices and their votes on superficial considerations. A series of recent studies seems to validate these fears, suggesting that candidates who merely look more capable or attractive perform better in elections. In this article, we examine the underlying process behind the appearance effect. Specifically, we test whether the effect of appearance is more pronounced among those who know little about politics but are exposed to visual images of candidates. To do so, we combine appearance-based assessments of U.S. Senate and gubernatorial candidates with individual-level survey data measuring vote intent, political knowledge, and television exposure. Confirming long-standing concerns about image and television, we find that appealing-looking politicians benefit disproportionately from television exposure, primarily among less knowledgeable individuals
Anti-ferromagnetic ordering in arrays of superconducting pi-rings
We report experiments in which one dimensional (1D) and two dimensional (2D)
arrays of YBa2Cu3O7-x-Nb pi-rings are cooled through the superconducting
transition temperature of the Nb in various magnetic fields. These pi-rings
have degenerate ground states with either clockwise or counter-clockwise
spontaneous circulating supercurrents. The final flux state of each ring in the
arrays was determined using scanning SQUID microscopy. In the 1D arrays,
fabricated as a single junction with facets alternating between alignment
parallel to a [100] axis of the YBCO and rotated 90 degrees to that axis,
half-fluxon Josephson vortices order strongly into an arrangement with
alternating signs of their magnetic flux. We demonstrate that this ordering is
driven by phase coupling and model the cooling process with a numerical
solution of the Sine-Gordon equation. The 2D ring arrays couple to each other
through the magnetic flux generated by the spontaneous supercurrents. Using
pi-rings for the 2D flux coupling experiments eliminates one source of disorder
seen in similar experiments using conventional superconducting rings, since
pi-rings have doubly degenerate ground states in the absence of an applied
field. Although anti-ferromagnetic ordering occurs, with larger negative bond
orders than previously reported for arrays of conventional rings, long-range
order is never observed, even in geometries without geometric frustration. This
may be due to dynamical effects. Monte-Carlo simulations of the 2D array
cooling process are presented and compared with experiment.Comment: 10 pages, 15 figure
Quantum Electrodynamics in the Light-Front Weyl Gauge
We examine QED(3+1) quantised in the `front form' with finite `volume'
regularisation, namely in Discretised Light-Cone Quantisation. Instead of the
light-cone or Coulomb gauges, we impose the light-front Weyl gauge . The
Dirac method is used to arrive at the quantum commutation relations for the
independent variables. We apply `quantum mechanical gauge fixing' to implement
Gau{\ss}' law, and derive the physical Hamiltonian in terms of unconstrained
variables. As in the instant form, this Hamiltonian is invariant under global
residual gauge transformations, namely displacements. On the light-cone the
symmetry manifests itself quite differently.Comment: LaTeX file, 30 pages (A4 size), no figures. Submitted to Physical
review D. January 18, 1996. Originally posted, erroneously, with missing
`Weyl' in title. Otherwise, paper is identica
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