519 research outputs found
Non-Locality and Ellipticity in a Gauge-Invariant Quantization
The quantum theory of a free particle in two dimensions with non-local
boundary conditions on a circle is known to lead to surface and bulk states.
Such a scheme is here generalized to the quantized Maxwell field, subject to
mixed boundary conditions. If the Robin sector is modified by the addition of a
pseudo-differential boundary operator, gauge-invariant boundary conditions are
obtained at the price of dealing with gauge-field and ghost operators which
become pseudo-differential. A good elliptic theory is then obtained if the
kernel occurring in the boundary operator obeys certain summability conditions,
and it leads to a peculiar form of the asymptotic expansion of the symbol. The
cases of ghost operator of negative and positive order are studied within this
framework.Comment: 17 pages, plain Te
Workmen\u27s Compensation at Sea
At the present time there are three possible remedies available to seamen who are injured in the course of their employment. In order to maintain any of these actions, the injured party must of course qualify as a seaman. The traditional tests used to determine whether a maritime worker is a seaman are as follows: 1) the vessel must be in navigation, 2) the worker must have a more or less permanent connection with the vessel, and 3) the worker must be aboard the vessel primarily to aid in navigation. These standards have been somewhat modified by Offshore Company v. Robinson. In that case, the court stated that there is an evidentiary basis for holding a person to be a seaman if: 1) there is evidence that the worker was assigned permanently to a vessel, or performed a substantial part of his work aboard a vessel, and 2) his duties contributed to the function of the vessel or to the accomplishment of its mission. Therefore, it seems that it does not matter whether the vessel is actually in navigation or if the maritime worker is aboard primarily in aid of navigation so long as he performs a substantial part of his work on the vessel. Furthermore, the definition of vessel has been extended to cover almost any floating object that is capable of being moved from one place to another
Relativistically Covariant Symmetry in QED
We construct a relativistically covariant symmetry of QED. Previous local and
nonlocal symmetries are special cases. This generalized symmetry need not be
nilpotent, but nilpotency can be arranged with an auxiliary field and a certain
condition. The Noether charge generating the symmetry transformation is
obtained, and it imposes a constraint on the physical states.Comment: Latex file, 9 page
Boundary Operators in Quantum Field Theory
The fundamental laws of physics can be derived from the requirement of
invariance under suitable classes of transformations on the one hand, and from
the need for a well-posed mathematical theory on the other hand. As a part of
this programme, the present paper shows under which conditions the introduction
of pseudo-differential boundary operators in one-loop Euclidean quantum gravity
is compatible both with their invariance under infinitesimal diffeomorphisms
and with the requirement of a strongly elliptic theory. Suitable assumptions on
the kernel of the boundary operator make it therefore possible to overcome
problems resulting from the choice of purely local boundary conditions.Comment: 23 pages, plain Tex. The revised version contains a new section, and
the presentation has been improve
UV-finite scalar field theory with unitarity
In this paper we show how to define the UV completion of a scalar field
theory such that it is both UV-finite and perturbatively unitary. In the UV
completed theory, the propagator is an infinite sum of ordinary propagators. To
eliminate the UV divergences, we choose the coefficients and masses in the
propagator to satisfy certain algebraic relations, and define the infinite sums
involved in Feynman diagram calculation by analytic continuation. Unitarity can
be proved relatively easily by Cutkosky's rules. The theory is equivalent to
infinitely many particles with specific masses and interactions. We take the
theory as an example and demonstrate our idea through explicit Feynman
diagram computation.Comment: 14 pages, references adde
Nonlocal regularization of abelian models with spontaneous symmetry breaking
We demonstrate how nonlocal regularization is applied to gauge invariant
models with spontaneous symmetry breaking. Motivated by the ability to find a
nonlocal BRST invariance that leads to the decoupling of longitudinal gauge
bosons from physical amplitudes, we show that the original formulation of the
method leads to a nontrivial relationship between the nonlocal form factors
that can appear in the model.Comment: 11 pages, uses amsart. To appear in Mod. Phys. Lett
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An Analysis of How Students Take the Initiative in Keyboard-to-Keyboard Tutorial Dialogues in a Fixed Domain
By student initiatives we mean productions which the student could reasonably expect to modify the course of the tutorial dialog;ue. Asking a question is one kind of student initiative. This paper describes a system called CircSim-Tutor which we are building, the background of the project, the 28 hour-long tutoring sessions jmalyzed in this paper, and the analysis done. It compares our work to previous work, gives a classification of the student initiatives found and of the tutor's responses to them, and discusses some examples
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The Next Big Match: Convergence, Competition and Sports Media Rights
Using examples from a number of different European countries, this article analyses the increasingly prominent position of traditional telecommunications companies, such as British Telecom (UK), Deutsche Telekom (Germany), France Telecom/Orange (France) and Telefonica (Spain), in the contemporary sports media rights market. The first part of the article examines the commercial strategies of telecommunications operators and highlights how their acquisition of sports rights has been driven by the need to ensure a competitive position within an increasingly converged communications market. The second part of the article then moves on to consider the regulation of the sports media rights market. Most significantly, this section emphasises the need for further regulatory intervention to ensure that increased competition for sports rights leads to improved services and lower prices for consumers, rather than merely endlessly spiralling fees for the exclusive ownership of premium rights that are then passed on to sports channel and/or broadband subscribers
Hamilton-Jacobi formalism for Linearized Gravity
In this work we study the theory of linearized gravity via the
Hamilton-Jacobi formalism. We make a brief review of this theory and its
Lagrangian description, as well as a review of the Hamilton-Jacobi approach for
singular systems. Then we apply this formalism to analyze the constraint
structure of the linearized gravity in instant and front-form dynamics.Comment: To be published in Classical and Quantum Gravit
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