12,708 research outputs found
Special geometry and symplectic transformations
Special Kahler manifolds are defined by coupling of vector multiplets to
supergravity. The coupling in rigid supersymmetry exhibits similar
features. These models contain vectors in rigid supersymmetry and in
supergravity, and complex scalars. Apart from exceptional cases they are
defined by a holomorphic function of the scalars. For supergravity this
function is homogeneous of second degree in an -dimensional projective
space. Another formulation exists which does not start from this function, but
from a symplectic - or -dimensional complex space. Symplectic
transformations lead either to isometries on the manifold or to symplectic
reparametrizations. Finally we touch on the connection with special
quaternionic and very special real manifolds, and the classification of
homogeneous special manifolds.Comment: 11 pages, latex using espcrc2, no figures. Some factors and minor
corrections. Version to be published in the proceedings of the Spring
workshop on String theory, Trieste, April 199
The N=2 Super Yang-Mills Low-Energy Effective Action at Two Loops
We have carried out a two loop computation of the low-energy effective action
for the four-dimensional N=2 supersymmetric Yang-Mills system coupled to
hypermultiplets, with the chiral superfields of the vector multiplet lying in
an abelian subalgebra. We have found a complete cancellation at the level of
the integrands of Feynman amplitudes, and therefore the two loop contribution
to the action, effective or Wilson, is identically zero.Comment: 8 pages, Latex, 2 .eps figure
Consistent truncation of d = 11 supergravity on AdS_4 x S^7
We study the system of equations derived twenty five years ago by B. de Wit
and the first author [Nucl. Phys. B281 (1987) 211] as conditions for the
consistent truncation of eleven-dimensional supergravity on AdS_4 x S^7 to
gauged N = 8 supergravity in four dimensions. By exploiting the E_7(7)
symmetry, we determine the most general solution to this system at each point
on the coset space E_7(7)/SU(8). We show that invariants of the general
solution are given by the fluxes in eleven-dimensional supergravity. This
allows us to both clarify the explicit non-linear ansatze for the fluxes given
previously and to fill a gap in the original proof of the consistent
truncation. These results are illustrated with several examples.Comment: 41 pages, typos corrected, published versio
AMBER and CRIRES observations of the binary sgB[e] star HD 327083: evidence of a gaseous disc traced by CO bandhead emission
HD 327083 is a sgB[e] star that forms a binary system with an orbital
semi-major axis of ~1.7 AU. Our previous observations using the VLTI and AMBER
in the medium resolution K-band mode spatially resolved the environment of HD
327083. The continuum visibilities obtained indicate the presence of a
circumbinary disc. CO bandhead emission was also observed. However, due to the
limited spectral resolution of the previous observations, the kinematic
structure of the emitting material was not constrained. In this paper, we
address this and probe the source of the CO emission with high spectral
resolution and spatial precision. We have observed HD 327083 with high spectral
resolution (25 & 6 km/s) using AMBER and CRIRES. The observations are compared
to kinematical models to constrain the source of the emission. It is shown that
the CO bandhead emission can be reproduced using a model of a Keplerian disc
with an inclination and size consistent with our previous VLTI observations.
The model is compared to AMBER differential phase measurements, which have a
precision as high as 30-micro-arcseconds. A differential phase signal
corresponding to 0.15 milli-arcseconds (~5 sigma) is seen over the bandhead
emission, which is in excellent agreement with the model that fits the CRIRES
observations. In comparison, a model of an equatorial outflow, as envisaged in
the standard sgB[e] scenario, does not reproduce the observations well. The
excellent agreement between the disc model and observations in the spatial and
spectral domains is compelling evidence that the CO bandhead emission of HD
327083 originates in a circumbinary Keplerian disc. In contrast, the model of
an equatorial outflow cannot reproduce the observations well. This suggests
that the standard sgB[e] scenario is not applicable to HD 327083, which
supports the hypothesis that the B[e] behaviour of HD 327083 is due to binarity
(ABRIDGED).Comment: Accepted for publication in A&
M Theory As A Matrix Model: A Conjecture
We suggest and motivate a precise equivalence between uncompactified eleven
dimensional M-theory and the N = infinity limit of the supersymmetric matrix
quantum mechanics describing D0-branes. The evidence for the conjecture
consists of several correspondences between the two theories. As a consequence
of supersymmetry the simple matrix model is rich enough to describe the
properties of the entire Fock space of massless well separated particles of the
supergravity theory. In one particular kinematic situation the leading large
distance interaction of these particles is exactly described by supergravity .
The model appears to be a nonperturbative realization of the holographic
principle. The membrane states required by M-theory are contained as
excitations of the matrix model. The membrane world volume is a noncommutative
geometry embedded in a noncommutative spacetime.Comment: Typo and tex error corrected. 41 pages, harvma
Off-shell N=2 tensor supermultiplets
A multiplet calculus is presented for an arbitrary number n of N=2 tensor
supermultiplets. For rigid supersymmetry the known couplings are reproduced. In
the superconformal case the target spaces parametrized by the scalar fields are
cones over (3n-1)-dimensional spaces encoded in homogeneous SU(2) invariant
potentials, subject to certain constraints. The coupling to conformal
supergravity enables the derivation of a large class of supergravity
Lagrangians with vector and tensor multiplets and hypermultiplets. Dualizing
the tensor fields into scalars leads to hypermultiplets with hyperkahler or
quaternion-Kahler target spaces with at least n abelian isometries. It is
demonstrated how to use the calculus for the construction of Lagrangians
containing higher-derivative couplings of tensor multiplets. For the
application of the c-map between vector and tensor supermultiplets to
Lagrangians with higher-order derivatives, an off-shell version of this map is
proposed. Various other implications of the results are discussed. As an
example an elegant derivation of the classification of 4-dimensional
quaternion-Kahler manifolds with two commuting isometries is given.Comment: 36 page
N=2 Conformal Superspace in Four Dimensions
We develop the geometry of four dimensional N=2 superspace where the entire
conformal algebra of SU(2,2|2) is realized linearly in the structure group
rather than just the SL(2,C) x U(2)_R subgroup of Lorentz and R-symmetries,
extending to N=2 our prior result for N=1 superspace. This formulation
explicitly lifts to superspace the existing methods of the N=2 superconformal
tensor calculus; at the same time the geometry, when degauged to SL(2,C) x
U(2)_R, reproduces the existing formulation of N=2 conformal supergravity
constructed by Howe.Comment: 43 pages; v2 references added, acknowledgments update
Completeness in supergravity constructions
We prove that the supergravity r- and c-maps preserve completeness. As a
consequence, any component H of a hypersurface {h=1} defined by a homogeneous
cubic polynomial such that -d^2 h is a complete Riemannian metric on H defines
a complete projective special Kahler manifold and any complete projective
special Kahler manifold defines a complete quaternionic Kahler manifold of
negative scalar curvature. We classify all complete quaternionic Kahler
manifolds of dimension less or equal to 12 which are obtained in this way and
describe some complete examples in 16 dimensions.Comment: 29 page
Wild ruminants as reservoirs of domestic livestock gastrointestinal T nematodes
Gastrointestinal nematode (GIN) infections in cattle cause appetite suppression which leads to poor feed conversion, reduced weight gain and reduced milk production. Overuse and exclusive reliance on anthelmintic drugs has resulted in widespread resistance in many parasitic nematode species infecting livestock making control increasingly difficult. Wild ruminants are competent hosts of a number of nematode species that typically infect and are best adapted for cattle, sheep, and goats. Thus, the potential exists for wild ruminants to act as reservoirs in the translocation of domestic GIN, including those carrying anthelmintic resistance mutations as well as susceptible genotypes. The potential for parasite exchange is heightened by interfaces or ecotones between managed and wild rangelands, and by perturbations linked to climate warming that can increasingly alter the distributions of wild ungulates and their interactions with domestic and free-ranging ruminants. To investigate the extent to which wild ruminants harbour parasites capable of infecting domestic ruminants we first performed an epidemiological study of feces from wildlife hosts that spanned 16 states and included white-tailed deer (85 % of the samples), pronghorn, elk, mule deer, bighorn sheep, moose, cattle, and caribou across the United States. All samples were cultured to third stage larvae and nematode DNA was isolated and PCR amplified. Among the 548 wild ruminant samples received, 33 % (181 samples) were positive for nematode DNA, among which half (84 samples) contained DNA from GIN species commonly found in cattle. DNA from cattle GIN species was detected in 46 % of samples from the Northeast, 42 % from the Southeast, 10 % from the Midwest, 0 % from the Southwest and 11 % from the West. Deep amplicon sequencing of the ITS-2 rDNA indicated that Ostertagia and Trichostrongylus were present in 90 % and 69 % of the nematode DNA positive samples, respectively, whereas Haemonchus, Cooperia and Oesophagostomum were present in 26 %, 2 % and 10 % of the samples, respectively. These data clearly show that wild ruminants commonly harbour multiple parasite species whose primary hosts are domestic cattle, and suggest that further work is warranted to investigate their specific roles in the management of anthelmintic resistance
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