5,667 research outputs found
Self-Similar Random Processes and Infinite-Dimensional Configuration Spaces
We discuss various infinite-dimensional configuration spaces that carry
measures quasiinvariant under compactly-supported diffeomorphisms of a manifold
M corresponding to a physical space. Such measures allow the construction of
unitary representations of the diffeomorphism group, which are important to
nonrelativistic quantum statistical physics and to the quantum theory of
extended objects in d-dimensional Euclidean space. Special attention is given
to measurable structure and topology underlying measures on generalized
configuration spaces obtained from self-similar random processes (both for d =
1 and d > 1), which describe infinite point configurations having accumulation
points
On the Fock space for nonrelativistic anyon fields and braided tensor products
We realize the physical N-anyon Hilbert spaces, introduced previously via
unitary representations of the group of diffeomorphisms of the plane, as N-fold
braided-symmetric tensor products of the 1-particle Hilbert space. This
perspective provides a convenient Fock space construction for nonrelativistic
anyon quantum fields along the more usual lines of boson and fermion fields,
but in a braided category. We see how essential physical information is thus
encoded. In particular we show how the algebraic structure of our anyonic Fock
space leads to a natural anyonic exclusion principle related to intermediate
occupation number statistics, and obtain the partition function for an
idealised gas of fixed anyonic vortices.Comment: Added some references, more explicit formulae for the discrete case
and remark on partition function. 25 pages latex, no figure
Local Currents for a Deformed Algebra of Quantum Mechanics with a Fundamental Length Scale
We explore some explicit representations of a certain stable deformed algebra
of quantum mechanics, considered by R. Vilela Mendes, having a fundamental
length scale. The relation of the irreducible representations of the deformed
algebra to those of the (limiting) Heisenberg algebra is discussed, and we
construct the generalized harmonic oscillator Hamiltonian in this framework. To
obtain local currents for this algebra, we extend the usual nonrelativistic
local current algebra of vector fields and the corresponding group of
diffeomorphisms, modeling the quantum configuration space as a commutative
spatial manifold with one additional dimension.Comment: 10 pages REVTex, no figure
Strategic Factors in Nineteenth Century American Economic History: A Volume to Honor Robert W. Fogel
Conformal inversion and Maxwell field invariants in four- and six-dimensional spacetimes
Conformally compactified (3+1)-dimensional Minkowski spacetime may be
identified with the projective light cone in (4+2)-dimensional spacetime. In
the latter spacetime the special conformal group acts via rotations and boosts,
and conformal inversion acts via reflection in a single coordinate.
Hexaspherical coordinates facilitate dimensional reduction of Maxwell
electromagnetic field strength tensors to (3+1) from (4 + 2) dimensions. Here
we focus on the operation of conformal inversion in different
coordinatizations, and write some useful equations. We then write a conformal
invariant and a pseudo-invariant in terms of field strengths; the
pseudo-invariant in (4+2) dimensions takes a new form. Our results advance the
study of general nonlinear conformal-invariant electrodynamics based on
nonlinear constitutive equations.Comment: 10 pages, birkjour.cls, submitted for the Proceedings of the XXXIInd
Workshop on Geometric Methods in Physics, (Bialowieza, Poland, July 2013),
v2: minor improvement
The Poor at Birth: Infant Auxology and Mortality at Philadelphia's Almshouse Hospital, 1848-1873
This paper presents an analysis of birth weights and infant mortality in mid-nineteenth century Philadelphia using obstetrics records of Philadelphia's Almshouse hospital, an institution for the poor and their offspring. Children of the poor weighed between 2,900 and 3,200 grams on average at birth, or about the 10th to 25th percentile of modern birth weight standards. 3rthweights declined during the Civil War decade, consistent with the poor state of the economy in the l80s, because birth weights were lower than modern standards the urban poor suffered from higher rates of infant mortality than today. But infant mortality was far worse than that expected from a modern schedule of mortality by birth weight, and a major determinant of excess mortality appears to be the poor quality of nineteenth century obstetrics.
Unconstrained Astrometric Orbits for Hipparcos Stars with Stochastic Solutions
A considerable number of astrometric binaries whose positions on the sky do
not obey the standard model of mean position, parallax and linear proper
motion, were observed by the Hipparcos satellite. Some of them remain
non-discovered, and their observational data have not been properly processed
with the more adequate astrometric model that includes nonlinear orbital
motion. We develop an automated algorithm based on "genetic optimization", to
solve the orbital fitting problem with no prior information about the orbital
elements is available (from, e.g., spectroscopic data or radial velocity
monitoring). We test this method on Hipparcos stars with known orbital
solutions in the catalog, and further apply it to stars with stochastic
solutions, which may be unresolved binaries. At a confidence level of 99%,
orbital fits are obtained for 65 stars, most of which have not been known as
binary. A few of the new probable binaries with A-type primaries with periods
444-2015 d are chemically peculiar stars, including Ap and \lambda Boo type.
The anomalous spectra of these stars are explained as admixture of the light
from the unresolved, sufficiently bright and massive companions. We estimate
the apparent orbits of four stars which have been identified as members of the
300 Myr-old UMa kinematic group. Another four new nearby binaries may include
low-mass M-type or brown dwarf companions. Similar astrometric models and
algorithms can be used for binary stars and planet hosts observed by SIM
PlanetQuest and Gaia
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