16,909 research outputs found
Sp(4,R)/GL(2,R) Matrix Structure of Geodesic Solutions for Einstein--Maxwell--Dilaton--Axion Theory
The constructed matrix operator defines the family of
isotropic geodesic containing vacuum point lines in the target space of the
stationary D=4 Einstein--Maxwell--dilaton--axion theory. This operator is used
to derive a class of solutions which describes a point center system with
nontrivial values of mass, parameter NUT, as well as electric, magnetic,
dilaton and axion charges. It is shown that this class contains both particular
solutions Majumdar--Papapetrou--like black holes and massless asymptotically
nonflat naked singularities.Comment: 20 pages, RevTex, no figures, Submitted to Phys.Rev.
Dynamics of Interacting Quintessence Models: Observational Constraints
Interacting quintessence models have been proposed to explain or, at least,
alleviate the coincidence problem of late cosmic acceleration. In this paper we
are concerned with two aspects of these kind of models: (i) the dynamical
evolution of the model of Chimento et al. [L.P. Chimento, A.S. Jakubi, D.
Pavon, and W. Zimdahl, Phys. Rev. D 67, 083513 (2003).], i.e., whether its
cosmological evolution gives rise to a right sequence of radiation, dark matter
and dark energy dominated eras, and (ii) whether the dark matter dark energy
ratio asymptotically evolves towards a non-zero constant. After showing that
the model correctly reproduces these eras, we correlate three data sets that
constrain the interaction at three redshift epochs: , ,
and . We discuss the model selection and argue that even if the model
under consideration fulfills both requirements, it is heavily constrained by
observation. The prospects that the coincidence problem can be explained by the
coupling of dark matter to dark energy are not clearly favored by the data.Comment: 16 pages, 7 figures and 3 tables. Modifications introduced to match
published versio
Antarctic meteorite newsletter. Volume 4: Number 1, February 1981: Antarctic meteorite descriptions, 1976, 1977, 1978, 1979
This issue of the Newsletter is essentially a catalog of all antarctic meteorites in the collections of the Johnson Space Center Curation Facility and the Smithsonian except for 288 pebbles now being classed. It includes listings of all previously distributed data sheets plus a number of new ones for 1979. Indexes of samples include meteorite name/number, classification, and weathering category. Separate indexes list type 3 and 4 chondrites, all irons, all achondrites, and all carbonaceous chondrites
Antarctic meteorite descriptions 1976-1977-1978-1979
All previously distributed meteorite data sheets, plus a number of new ones for 1979 chondrites are included. A comprehensive sample index listing meteorite name/number, classification, and weathering category is also included. Separate indexes listing all petrologic type 3 and type 4 chondrites, all irons, all achondrites, and all carbonaceous chondrites in the collection is provided
Fungal Respiratory Infections in Cystic Fibrosis (CF): Recent Progress and Future Research Agenda
International audienc
A Solution to the Galactic Foreground Problem for LISA
Low frequency gravitational wave detectors, such as the Laser Interferometer
Space Antenna (LISA), will have to contend with large foregrounds produced by
millions of compact galactic binaries in our galaxy. While these galactic
signals are interesting in their own right, the unresolved component can
obscure other sources. The science yield for the LISA mission can be improved
if the brighter and more isolated foreground sources can be identified and
regressed from the data. Since the signals overlap with one another we are
faced with a ``cocktail party'' problem of picking out individual conversations
in a crowded room. Here we present and implement an end-to-end solution to the
galactic foreground problem that is able to resolve tens of thousands of
sources from across the LISA band. Our algorithm employs a variant of the
Markov Chain Monte Carlo (MCMC) method, which we call the Blocked Annealed
Metropolis-Hastings (BAM) algorithm. Following a description of the algorithm
and its implementation, we give several examples ranging from searches for a
single source to searches for hundreds of overlapping sources. Our examples
include data sets from the first round of Mock LISA Data Challenges.Comment: 19 pages, 27 figure
A-Model Correlators from the Coulomb Branch
We compute the contribution of discrete Coulomb vacua to A-Model correlators
in toric Gauged Linear Sigma Models. For models corresponding to a compact
variety, this determines the correlators at arbitrary genus. For non-compact
examples, our results imply the surprising conclusion that the quantum
cohomology relations break down for a subset of the correlators.Comment: 27 pages, 1 xy-pic figur
The loss of anisotropy in MgB2 with Sc substitution and its relationship with the critical temperature
The electrical conductivity anisotropy of the sigma-bands is calculated for
the (Mg,Sc)B2 system using a virtual crystal model. Our results reveal that
anisotropy drops with relatively little scandium content (< 30%); this
behaviour coincides with the lowering of Tc and the reduction of the Kohn
anomaly. This anisotropy loss is also found in the Al and C doped systems. In
this work it is argued that the anisotropy, or 2D character, of the sigma-bands
is an important parameter for the understanding of the high Tc found in MgB2
M-Theory on (K3 X S^1)/Z_2
We analyze -theory compactified on where the
changes the sign of the three form gauge field, acts on as a parity
transformation and on K3 as an involution with eight fixed points preserving
SU(2) holonomy. At a generic point in the moduli space the resulting theory has
as its low energy limit N=1 supergravity theory in six dimensions with eight
vector, nine tensor and twenty hypermultiplets. The gauge symmetry can be
enhanced (e.g. to ) at special points in the moduli space. At other
special points in the moduli space tensionless strings appear in the theory.Comment: LaTeX file, 11 page
A super-analogue of Kontsevich's theorem on graph homology
In this paper we will prove a super-analogue of a well-known result by
Kontsevich which states that the homology of a certain complex which is
generated by isomorphism classes of oriented graphs can be calculated as the
Lie algebra homology of an infinite-dimensional Lie algebra of symplectic
vector fields.Comment: 15 page
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