11,686 research outputs found
Extremal Correlators in the AdS/CFT Correspondence
The non-renormalization of the 3-point functions of chiral primary operators in N=4 super-Yang-Mills theory is one of
the most striking facts to emerge from the AdS/CFT correspondence. A two-fold
puzzle appears in the extremal case, e.g. k_1 = k_2 + k_3. First, the
supergravity calculation involves analytic continuation in the k_i variables to
define the product of a vanishing bulk coupling and an infinite integral over
AdS. Second, extremal correlators are uniquely sensitive to mixing of the
single-trace operators with protected multi-trace operators in the
same representation of SU(4). We show that the calculation of extremal
correlators from supergravity is subject to the same subtlety of regularization
known for the 2-point functions, and we present a careful method which
justifies the analytic continuation and shows that supergravity fields couple
to single traces without admixture. We also study extremal n-point functions of
chiral primary operators, and argue that Type IIB supergravity requires that
their space-time form is a product of n-1 two-point functions (as in the free
field approximation) multiplied by a non-renormalized coefficient. This
non-renormalization property of extremal n-point functions is a new prediction
of the AdS/CFT correspondence. As a byproduct of this work we obtain the cubic
couplings and of fields in the dilaton and 5-sphere
graviton towers of Type IIB supergravity on .Comment: 26 pages, LateX, no figure
THE PARAPAPIO SPECIES OF STERKFONTEIN, TRANSVAAL, SOUTH AFRICA
The premolar and molar dimensions of the Parapapio specimens hitherto described
from the South African lower Pleistocene deposits at Sterkfontein have been
re-examined. The relatively minor sexual dimorphism in these teeth (except P3 length)
was confirmed. 103 new cercopithecoid specimens from Sterkfontein were tentatively
assigned to the 3 previously described Parapapio spp. from that site. The new and old
samples of each species were compared and then pooled. Analysis of this new enlarged
sample, and also the newly available distribution data of Parapapio from other South
African deposits, both tend to support the validity of 3 Parapapio spp., P. jonesi, P.
broomi and P. whitei, at Sterkfontein.Wenner-Gren Foundation for
Anthropological Researc
COBE ground segment attitude determination
The Cosmic Background Explorer (COBE) spacecraft was launched in November 1989 by NASA to survey the sky for primordial radiation left from the Big Bang explosion. The success of the mission requires an accurate determination of the spacecraft attitude. While the accuracy of the attitude obtained from the attitude sensors is adequate for two of the experiments, the higher accuracy required by the Diffuse Infrared Background Experiment (DIRBE) is obtained by using the DIRBE instrument as a special type of star sensor. Presented here is an overview of the attitude processing algorithms used at the Cosmology Data Analysis Center (CDAC) and the results obtained from the flight data
Involvement of carbon dioxide in the aerobic biodegradation of ethylene oxide, ethene, and vinyl chloride
The involvement of a carboxylase in metabolism of C-2 alkenes by Ochrobactrum sp. strain TD and Pseudomonas putida strain AJ was examined. With resting cells of strain TD grown on vinyl chloride, ethene, and ethylene oxide, the maximum specific rate of ethylene oxide consumption decreased significantly in the absence of external CO2 in comparison to cells provided with room air or added CO2. The amount of 14CO2 incorporated into biomass by resting cells of strain TD grown on ethylene oxide increased more than 13-fold when the assay substrate was ethylene oxide versus acetate. These results indicate that strain TD uses a carboxylase. Similar experiments were performed with strain AJ with the results suggesting that a carboxylase is not involved. In this regard, strain AJ is more similar to various Mycobacterium isolates that also do not appear to use a carboxylase during metabolism of vinyl chloride and ethene.Department of Biomedical and Biomolecular
Sciences, Sheffield Hallam University
Symmetry Breaking for Matter Coupled to Linearized Supergravity From the Perspective of the Current Supermultiplet
We consider a generic supersymmetric matter theory coupled to linearized
supergravity, and analyze scenarios for spontaneous symmetry breaking in terms
of vacuum expectation values of components of the current supermultiplet. When
the vacuum expectation of the energy momentum tensor is zero, but the scalar
current or pseudoscalar current gets an expectation, evaluation of the
gravitino self energy using the supersymmetry current algebra shows that there
is an induced gravitino mass term. The structure of this term generalizes the
supergravity action with cosmological constant to theories with CP violation.
When the vacuum expectation of the energy momentum tensor is nonzero,
supersymmetry is broken; requiring cancellation of the cosmological constant
gives the corresponding generalized gravitino mass formula.Comment: 11 page
The Hubble Constant
Considerable progress has been made in determining the Hubble constant over
the past two decades. We discuss the cosmological context and importance of an
accurate measurement of the Hubble constant, and focus on six high-precision
distance-determination methods: Cepheids, tip of the red giant branch, maser
galaxies, surface brightness fluctuations, the Tully-Fisher relation and Type
Ia supernovae. We discuss in detail known systematic errors in the measurement
of galaxy distances and how to minimize them. Our best current estimate of the
Hubble constant is 73 +/-2 (random) +/-4 (systematic) km/s/Mpc. The importance
of improved accuracy in the Hubble constant will increase over the next decade
with new missions and experiments designed to increase the precision in other
cosmological parameters. We outline the steps that will be required to deliver
a value of the Hubble constant to 2% systematic uncertainty and discuss the
constraints on other cosmological parameters that will then be possible with
such accuracy.Comment: To be published in Annual Reviews of Astronomy and Astrophysics, Vol.
48, 2010, consisting of 79 pages, 13 figures, 2 table
- …