278 research outputs found
Finite size effects in perturbed boundary conformal field theories
We discuss the finite-size properties of a simple integrable quantum field
theory in 1+1 dimensions with non-trivial boundary conditions. Novel
off-critical identities between cylinder partition functions of models with
differing boundary conditions are derived.Comment: 7 pages, 11 figures, JHEP proceedings style. Uses epsfig, amssymb.
Talk given at the conference `Nonperturbative Quantum Effects 2000', Pari
Dissipative Pairing Interactions: Quantum Instabilities, Topological Light, and Volume-Law Entanglement
We analyze an unusual class of bosonic dynamical instabilities that arise
from dissipative (or non-Hermitian) pairing interactions. We show that,
surprisingly, a completely stable dissipative pairing interaction can be
combined with simple hopping or beam-splitter interactions (also stable) to
generate instabilities. Further, we find that the dissipative steady state in
such a situation remains completely pure up until the instability threshold (in
clear distinction from standard parametric instabilities). These
pairing-induced instabilities also exhibit an extremely pronounced sensitivity
to wavefunction localization. This provides a simple yet powerful method for
selectively populating and entangling edge modes of photonic (or more general
bosonic) lattices having a topological bandstructure. The underlying
dissipative pairing interaction is experimentally resource-friendly, requiring
the addition of a single additional localized interaction to an existing
lattice, and is compatible with a number of existing platforms, including
superconducting circuits
Distribution, Abundance and Diversity of Benthic Macroinvertebrates on the Canadian Continental Shelf and Slope of Southern Davis Strait and Ungava Bay
Stations in a survey of benthic invertebrates on the Canadian continental shelf and slope of southeastern Baffin Island, in Ungava Bay, and on the northern Labrador Shelf, fell into definite groups as a result of an objective analysis of similarity in species composition. The groupings were shown to correspond to major water masses in the area. Groups corresponding to cold surface water masses, to the deep Irminger Atlantic water mass, and to mixtures of these with adjacent water masses were observed. The Irminger Atlantic group dominated on the Baffin Island continental shelf. Species diversity, also measured in the study, was high, with large numbers of species present in low abundance.Key words: marine, benthos, invertebrates, distribution, shelf, slope, Davis Strait, Ungava Bay, subarticMots clés: marin, benthos, invertébrés, distribution, plateau, versant, détroit de Davis, baie d'Ungava, subarctiqu
How an antenna launches its input power into radiation: the pattern of the Poynting vector at and near an antenna
In this paper I first address the question of whether the seat of the power
radiated by an antenna made of conducting members is distributed over the
``arms'' of the antenna according to -J . E, where J is the specified current
density and E is the electric field produced by that source. Poynting's theorem
permits only a global identification of the total input power, usually from a
localized generator, with the total power radiated to infinity, not a local
correspondence of -J . E dv with some specific radiated power, r^2 S . n dO. I
then describe a model antenna consisting of two perfectly conducting
hemispheres of radius a separated by a small equatorial gap across which occurs
the driving oscillatory electric field. The fields and surface current are
determined by solution of the boundary value problem. In contrast to the first
approach (not a boundary value problem), the tangential electric field vanishes
on the metallic surface. There is no radial Poynting vector normal to the
surface. Numerical examples are shown to illustrate how the energy flows from
the input region of the gap and is guided near the antenna by its ``arms''
until it is launched at larger r/a into the radiation pattern determined by the
value of ka.Comment: 24pages, 8 figures, submitted for publicatio
Navigation input to level C OFT navigation functional subsystem software requirements (rendezvous onorbit-2)
Navigation software design requirements are presented for the orbital flight test phase of space shuttle. Computer loads for the entire onorbit-2 operation are documented
Perturbed Defects and T-Systems in Conformal Field Theory
Defect lines in conformal field theory can be perturbed by chiral defect
fields. If the unperturbed defects satisfy su(2)-type fusion rules, the
operators associated to the perturbed defects are shown to obey functional
relations known from the study of integrable models as T-systems. The procedure
is illustrated for Virasoro minimal models and for Liouville theory.Comment: 24 pages, 13 figures; v2: typos corrected, in particular in (2.10)
and app. A.2, version to appear in J.Phys.
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