3,040 research outputs found
Zero Modes for the D=11 Membrane and Five-Brane
There exist extremal p-brane solutions of supergravity for
p=2~and~5. In this paper we investigate the zero modes of the membrane and the
five-brane solutions as a first step toward understanding the full quantum
theory of these objects. It is found that both solutions possess the correct
number of normalizable zero modes dictated by supersymmetry.Comment: Minor typos corrected, one reference added, agrees with published
version. 9 RevTeX pages, 1 figure include
Vacuum interpolation in supergravity via super p-branes
We show that many of the recently proposed supersymmetric p-brane solutions
of d=10 and d=11 supergravity have the property that they interpolate between
Minkowski spacetime and a compactified spacetime, both being supersymmetric
supergravity vacua. Our results imply that the effective worldvolume action for
small fluctuations of the super p-brane is a supersingleton field theory for
, as has been often conjectured in the past.Comment: 8p
Intersecting D-Branes in ten and six dimensions
We show how, via -duality, intersecting -Brane configurations in ten
(six) dimensions can be obtained from the elementary -Brane configurations
by embedding a Type IIB -Brane into a Type IIB Nine-Brane (Five-Brane) and
give a classification of such configurations. We show that only a very specific
subclass of these configurations can be realized as (supersymmetric) solutions
to the equations of motion of IIA/IIB supergravity. Whereas the elementary
-brane solutions in are characterized by a single harmonic function,
those in contain two independent harmonic functions and may be viewed as
the intersection of two elementary -branes. Using
string/string/string triality in six dimensions we show that the heterotic
version of the elementary -Brane solutions correspond in ten
dimensions to intersecting Neveu-Schwarz/Neveu-Schwarz (NS/NS) strings or
five-branes and their -duals. We comment on the implications of our results
in other than ten and six dimensions.Comment: 18 pages, Latex, (substantial changes in section 2
Antimicrobial susceptibility of Gram-negative uropathogens isolated from obstetric patients.
OBJECTIVE: To evaluate the antimicrobial susceptibility of Gram-negative uropathogens isolated from pregnant women. METHODS: We performed a snapshot cohort study of women receiving care in the University of Florida prenatal clinics during March 2000. Subjects with asymptomatic bacteriuria or cystitis were identified and the antimicrobial susceptibility of each pathogen was recorded. Data were analyzed using chi-square, Fisher's exact test and ninety-five percent confidence intervals, as appropriate. RESULTS: Ninety-five positive cultures were identified. Isolates were more often susceptible to trimethoprim-sulfamethoxazole (TMP-SMX) (87%) and nitrofurantoin (89%) than to ampicillin (72%) (p < 0.03). Escherichia coli accounted for 71 (75%) cases and was more often susceptible to nitrofurantoin (100%) than to TMP-SMX (87%) (p < 0.01). Proteus isolates were all susceptible to TMP-SMX and resistant to nitrofurantoin (p < 0.01). CONCLUSIONS: Both TMP-SMX and nitrofurantoin are superior to ampicillin for empiric treatment of lower urinary tract infection in pregnant women. Nitrofurantoin is superior to TMP-SMX for treatment of infections caused by E. coli. For suspected or confirmed cases caused by Proteus organisms, TMP-SMX is the preferred agent
Effective potential and stability of the rigid membrane
The calculation of the effective potential for fixed-end and toroidal rigid
-branes is performed in the one-loop as well as in the approximations.
The analysis of the involved zeta-functions (of inhomogeneous Epstein type)
which appear in the process of regularization is done in full detail.
Assymptotic formulas (allowing only for exponentially decreasing errors of
order ) are found which carry all the dependences on the basic
parameters of the theory explicitly. The behaviour of the effective potential
(specified to the membrane case ) is investigated, and the extrema of this
effective potential are obtained.Comment: 15 PAGE
E(7) Symmetric Area of the Black Hole Horizon
Extreme black holes with 1/8 of unbroken N=8 supersymmetry are characterized
by the non-vanishing area of the horizon. The central charge matrix has four
generic eigenvalues. The area is proportional to the square root of the
invariant quartic form of . It vanishes in all cases when 1/4 or 1/2
of supersymmetry is unbroken. The supergravity non-renormalization theorem for
the area of the horizon in N=8 case protects the unique U-duality invariant.Comment: a reference added, misprints remove
Dimensional reduction of 4d heterotic string black holes
We perform the spherical symmetric dimensional reduction of
heterotic string theory. We find a class of two-dimensional (2d) dilaton
gravity models that gives a general description of the near-horizon,
near-extremal behavior of four-dimensional (4d) heterotic string black holes.
We show that the duality group of the 4d theory is realized in two dimensions
in terms of Weyl transformations of the metric. We use the 2d dilaton gravity
theory to compute the statistical entropy of the near-extremal 4d,
, black hole.Comment: 12 pages, LaTex fil
Partition Functions for the Rigid String and Membrane at Any Temperature
Exact expressions for the partition functions of the rigid string and
membrane at any temperature are obtained in terms of hypergeometric functions.
By using zeta function regularization methods, the results are analytically
continued and written as asymptotic sums of Riemann-Hurwitz zeta functions,
which provide very good numerical approximations with just a few first terms.
This allows to obtain systematic corrections to the results of Polchinski et
al., corresponding to the limits and of
the rigid string, and to analyze the intermediate range of temperatures. In
particular, a way to obtain the Hagedorn temperature for the rigid membrane is
thus found.Comment: 20 pages, LaTeX file, UB-ECM-PF 93/
Invest to Save: Report and Recommendations of the NSF-DELOS Working Group on Digital Archiving and Preservation
Digital archiving and preservation are important areas for research and development, but there is no agreed upon set of priorities or coherent plan for research in this area. Research projects in this area tend to be small and driven by particular institutional problems or concerns. As a consequence, proposed solutions from experimental projects and prototypes tend not to scale to millions of digital objects, nor do the results from disparate projects readily build on each other. It is also unclear whether it is worthwhile to seek general solutions or whether different strategies are needed for different types of digital objects and collections. The lack of coordination in both research and development means that there are some areas where researchers are reinventing the wheel while other areas are neglected.
Digital archiving and preservation is an area that will benefit from an exercise in analysis, priority setting, and planning for future research. The WG aims to survey current research activities, identify gaps, and develop a white paper proposing future research directions in the area of digital preservation. Some of the potential areas for research include repository architectures and inter-operability among digital archives; automated tools for capture, ingest, and normalization of digital objects; and harmonization of preservation formats and metadata. There can also be opportunities for development of commercial products in the areas of mass storage systems, repositories and repository management systems, and data management software and tools.
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