22,487 research outputs found
Abelian Duality
We show that on three-dimensional Riemannian manifolds without boundaries and
with trivial first real de Rham cohomology group (and in no other dimensions)
scalar field theory and Maxwell theory are equivalent: the ratio of the
partition functions is given by the Ray-Singer torsion of the manifold. On the
level of interaction with external currents, the equivalence persists provided
there is a fixed relation between the charges and the currents.Comment: 11 pages, LaTeX, no figures, a reference added, submitted to Phys.
Rev.
A Note on Marginally Stable Bound States in Type II String Theory
Spectrum of elementary string states in type II string theory contains
ultra-short multiplets that are marginally stable. -duality transformation
converts these states into bound states at threshold of -branes carrying
Ramond-Ramond charges, and wrapped around -cycles of a torus. We propose a
test for the existence of these marginally stable bound states. Using the
recent results of Polchinski and of Witten, we argue that the spectrum of bound
states of -branes is in agreement with the prediction of -duality.Comment: LaTeX file, 6 page
Effect of Poisson ratio on cellular structure formation
Mechanically active cells in soft media act as force dipoles. The resulting
elastic interactions are long-ranged and favor the formation of strings. We
show analytically that due to screening, the effective interaction between
strings decays exponentially, with a decay length determined only by geometry.
Both for disordered and ordered arrangements of cells, we predict novel phase
transitions from paraelastic to ferroelastic and anti-ferroelastic phases as a
function of Poisson ratio.Comment: 4 pages, Revtex, 4 Postscript figures include
Weak Scale Superstrings
Recent developments in string duality suggest that the string scale may not
be irrevocably tied to the Planck scale. Two explicit but unrealistic examples
are described where the ratio of the string scale to the Planck scale is
arbitrarily small. Solutions which are more realistic may exist in the
intermediate coupling or ``truly strong coupling'' region of the heterotic
string. Weak scale superstrings have dramatic experimental consequences for
both collider physics and cosmology.Comment: harvmac, 14 pages. References added, 3 typos fixed, Comments added at
beginning of section 4 emphasizing flaws of the toy example
Magnetic structure and orbital ordering in BaCoO3 from first-principles calculations
Ab initio calculations using the APW+lo method as implemented in the WIEN2k
code have been used to describe the electronic structure of the
quasi-one-dimensional system BaCoO3. Both, GGA and LDA+U approximations were
employed to study different orbital and magnetic orderings. GGA predicts a
metallic ground state whereas LDA+U calculations yield an insulating and
ferromagnetic ground state (in a low-spin state) with an alternating orbital
ordering along the Co-Co chains, consistent with the available experimental
data.Comment: 8 pages, 9 figure
Kaluza-Klein electrically charged black branes in M-theory
We present a class of Kaluza-Klein electrically charged black p-brane
solutions of ten-dimensional, type IIA superstring theory. Uplifting to eleven
dimensions these solutions are studied in the context of M-theory. They can be
interpreted either as a p+1 extended object trapped around the eleventh
dimension along which momentum is flowing or as a boost of the following
backgrounds: the Schwarzschild black (p+1)-brane or the product of the
(10-p)-dimensional Euclidean Schwarzschild manifold with the (p+1)-dimensional
Minkowski spacetime.Comment: 16 pages, uses latex and epsf macro, figures include
3-D Photoionization Structure and Distances of Planetary Nebulae II. Menzel 1
We present the results of a spatio-kinematic study of the planetary nebula
Menzel 1 using spectro-photometric mapping and a 3-D photoionization code. We
create several 2-D emission line images from our long-slit spectra, and use
these to derive the line fluxes for 15 lines, the Halpha/Hbeta extinction map,
and the [SII] line ratio density map of the nebula. We use our photoionization
code constrained by these data to derive the three-dimensional nebular
structure and ionizing star parameters of Menzel 1 by simultaneously fitting
the integrated line intensities, the density map, and the observed morphologies
in several lines, as well as the velocity structure. Using theoretical
evolutionary tracks of intermediate and low mass stars, we derive a mass for
the central star of 0.63+-0.05 Msolar. We also derive a distance of 1050+_150
pc to Menzel 1.Comment: To be published in ApJ of 10th February 2005. 12 figure
Type IIB instanton as a wave in twelve dimensions
0-brane of type IIA string theory can be interpreted as a dimensional
reduction of a gravitational wave in 11 dimensions. We observe that a similar
interpretation applies also to the D-instanton background of type IIB theory:
it can be viewed as a reduction (along one spatial and one time-like direction)
of a wave in a 12-dimensional theory. The instanton charge is thus related to a
linear momentum in 12 dimensions. This suggests that the instanton should play
as important role in type IIB theory as the 0-brane is supposed to play in type
IIA theory.Comment: 7 pages, harvmac (minor corrections and a reference added
Self-Duality in Nonlinear Electromagnetism
We discuss duality invariant interactions between electromagnetic fields and
matter. The case of scalar fields is treated in some detail.Comment: 10 pages, full postscript also available from
http://theor1.lbl.gov/www/theorygroup/papers/40770.p
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