4,980 research outputs found
Strength distribution of repeatedly broken chains
We determine the probability distribution of the breaking strength for chains
of N links, which have been produced by repeatedly breaking a very long chain.Comment: 4 pages, 1 figur
Vortex signatures in annular Bose-Einstein condensates
We consider a Bose-Einstein condensate confined in a ``Mexican hat''
potential, with a quartic minus quadratic radial dependence. We find conditions
under which the ground state is annular in shape, with a hole in the center of
the condensate. Rotation leads to the appearance of stable multiply-quantized
vortices, giving rise to a superfluid flow around the ring. The collective
modes of the system are explored both numerically and analytically using the
Gross-Pitaevskii and hydrodynamic equations. Potential experimental schemes to
detect vorticity are proposed and evaluated, which include measuring the
splitting of collective mode frequencies, observing expansion following release
from the trap, and probing the momentum distribution of the condensate.Comment: 11 pages, 7 figure
Inelastic electron-nucleus scattering and scaling at high inelasticity
Highly inelastic electron scattering is analyzed within the context of the
unified relativistic approach previously considered in the case of quasielastic
kinematics. Inelastic relativistic Fermi gas modeling that includes the
complete inelastic spectrum - resonant, non-resonant and Deep Inelastic
Scattering - is elaborated and compared with experimental data. A
phenomenological extension of the model based on direct fits to data is also
introduced. Within both models, cross sections and response functions are
evaluated and binding energy effects are analyzed. Finally, an investigation of
the second-kind scaling behavior is also presented.Comment: 39 pages, 13 figures; formalism extended and slightly reorganized,
conclusions extended; to appear in Phys. Rev.
Semantic categories underlying the meaning of ‘place’
This paper analyses the semantics of natural language expressions that are associated with the intuitive notion of ‘place’. We note that the nature of such terms is highly contested, and suggest that this arises from two main considerations: 1) there are a number of logically
distinct categories of place expression, which are not always clearly distinguished in discourse about ‘place’; 2) the many non-substantive place count nouns (such as ‘place’, ‘region’, ‘area’, etc.) employed in natural
language are highly ambiguous. With respect to consideration 1), we propose that place-related expressions
should be classified into the following distinct logical types: a) ‘place-like’ count nouns (further subdivided into abstract, spatial and substantive varieties), b) proper names of ‘place-like’ objects, c) locative property phrases, and d) definite descriptions of ‘place-like’ objects. We outline possible formal representations for each of these. To address consideration 2), we examine meanings, connotations and ambiguities of the English vocabulary of abstract and generic place count nouns, and identify underlying elements of meaning, which explain both
similarities and differences in the sense and usage of the various terms
The Heat Kernel Expansion on a Cone and Quantum Fields Near Cosmic Strings
An asymptotic expansion of the trace of the heat kernel on a cone where the
heat coefficients have a delta function behavior at the apex is obtained. It is
used to derive the renormalized effective action and total energy of a
self-interacting quantum scalar field on the cosmic string space-time. Analogy
is pointed out with quantum theory with boundaries. The surface infinities in
the effective action are shown to appear and are removed by renormalization of
the string tension. Besides, the total renormalized energy turns out to be
finite due to cancelation of the known non-integrable divergence in the energy
density of the field with a counterterm in the bare string tension.Comment: 20 pages, JINR preprint August, 1993, E2-93-291, LATEX fil
The trace of the heat kernel on a compact hyperbolic 3-orbifold
The heat coefficients related to the Laplace-Beltrami operator defined on the
hyperbolic compact manifold H^3/\Ga are evaluated in the case in which the
discrete group \Ga contains elliptic and hyperbolic elements. It is shown
that while hyperbolic elements give only exponentially vanishing corrections to
the trace of the heat kernel, elliptic elements modify all coefficients of the
asymptotic expansion, but the Weyl term, which remains unchanged. Some physical
consequences are briefly discussed in the examples.Comment: 11 page
Quench Induced Vortices in the Symmetry Broken Phase of Liquid He
Motivated by the study of cosmological phase transitions, our understanding
of the formation of topological defects during spontaneous symmetry-breaking
and the associated non-equilibrium field theory has recently changed.
Experiments have been performed in superfluid He to test the new ideas
involved. In particular, it has been observed that a vortex density is seen
immediately after pressure quenches from just below the transition.
We discuss possible interpretations of these vortices, conclude they are
consistent with our ideas of vortex formation and propose a modification of the
original experiments.Comment: 29 pages, RevTeX with one EPS figur
Comments on Microcausality, Chaos, and Gravitational Observables
Observables in gravitational systems must be non-local so as to be invariant
under diffeomorphism gauge transformations. But at the classical level some
such observables can nevertheless satisfy an exact form of microcausality. This
property is conjectured to remain true at all orders in the semiclassical
expansion, though with limitations at finite or . We
also discuss related issues concerning observables in black hole spacetimes and
comment on the senses in which they do and do not experience the form of chaos
identified by Shenker and Stanford. In particular, in contrast to the situation
in a reflecting cavity, this chaos does not afflict observables naturally
associated with Hawking radiation for evaporating black holes.Comment: 16 pages, 1 figure; references adde
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