2,860 research outputs found
Putting String/Fivebrane Duality to the Test
According to string/fivebrane duality, the Green-Schwarz factorization of the
spacetime anomaly polynomial into means that just
as is the anomaly polynomial of the string worldsheet so
should be the anomaly polynomial of the fivebrane worldvolume. To test
this idea we perform a fivebrane calculation of and find perfect
agreement with the string one--loop result.Comment: 14 pages, CERN TH-6614/92, CTP-TAMU 60/9
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
Abelian gauge theories on compact manifolds and the Gribov ambiguity
We study the quantization of abelian gauge theories of principal torus
bundles over compact manifolds with and without boundary. It is shown that
these gauge theories suffer from a Gribov ambiguity originating in the
non-triviality of the bundle of connections whose geometrical structure will be
analyzed in detail. Motivated by the stochastic quantization approach we
propose a modified functional integral measure on the space of connections that
takes the Gribov problem into account. This functional integral measure is used
to calculate the partition function, the Greens functions and the field
strength correlating functions in any dimension using the fact that the space
of inequivalent connections itself admits the structure of a bundle over a
finite dimensional torus. The Greens functions are shown to be affected by the
non-trivial topology, giving rise to non-vanishing vacuum expectation values
for the gauge fields.Comment: 33 page
Seasonal changes in photosynthesis of eight savanna tree species
Seasonal variations in carbon assimilation of eight tree species of a north Australian tropical savanna were examined over two wet seasons and one dry season (18 months). Assimilation rates (A) in the two evergreen species, Eucalyptus tetrodonta F. Muell. and E. miniata A. Cunn. ex Schauer, were high throughout the study although there was a 10-20% decline in the dry season compared with the wet season. The three semi-deciduous species (Erythrophleum chlorostachys (F. Muell.) Baillon, Eucalyptus clavigera A. Cunn. ex Schauer, and Xanthostemon paradoxus F. Muell.) showed a 25-75% decline in A in the dry season compared with the wet season, and the deciduous species (Terminalia ferdinandiana Excell, Planchonia careya (F. Muell.) Kunth, and Cochlospermum fraseri Planchon) were leafless for several months in the dry season. Generally, the ratio of intercellular CO2 concentration to ambient CO2 concentration (C(i):C(a)) was larger in the wet season than in the dry season, indicating a smaller stomatal limitation of photosynthesis in the wet season compared with the dry season. In all species, the C(i):C(a) ratio and A were essentially independent of leaf-to-air vapor pressure difference (LAVPD) during the wet season, but both parameters generally declined with increasing LAVPD in the dry season. The slope of the positive correlation between A and transpiration rate (E) was less in the wet season than in the dry season. There was no evidence that high E inhibited A. Instantaneous transpiration efficiency was lowest in the wet season and highest during the dry season. Nitrogen-use efficiency (NUE) was higher in the wet season than in the dry season because the decline in A in the dry season was proportionally larger than the decline in foliar nitrogen content. In the wet season, evergreen species exhibited higher NUE than semi-deciduous and deciduous species. In all species, A was linearly correlated with specific leaf area (SLA) and foliar N content. Foliar N content increased with increasing SLA. All species showed a decline in midday leaf water potential as the dry season progressed. Dry season midday water potentials were lowest in semi-deciduous species and highest in the deciduous species, with evergreen species exhibiting intermediate values
Resolution of Cosmological Singularities
We show that a class of 3+1 dimensional Friedmann-Robertson-Walker
cosmologies can be embedded within a variety of solutions of string theory. In
some realizations the apparent singularities associated with the big bang or
big crunch are resolved at non-singular horizons of higher-dimensional
quasi-black hole solutions (with compactified real time); in others plausibly
they are resolved at D-brane bound states having no conventional space-time
interpretation.Comment: 11 pages, latex. Two references added, one typo correcte
Fundamental constants in effective theory
There is a discussion between L. B. Okun, G. Veneziano and M. J. Duff,
concerning the number of fundamental dimensionful constants in physics
(physics/0110060). They advocated correspondingly 3, 2 and 0 fundamental
constants. Here we consider this problem on example of the effective
relativistic quantum field theory, which emerges in the low energy corner of
quantum liquids and which reproduces many features of our physics including
chiral fermions, gauge fields and dynamical gravity.Comment: LaTeX file, 9 pages, version submitted to JETP Letter
Trialogue on the number of fundamental constants
This paper consists of three separate articles on the number of fundamental
dimensionful constants in physics. We started our debate in summer 1992 on the
terrace of the famous CERN cafeteria. In the summer of 2001 we returned to the
subject to find that our views still diverged and decided to explain our
current positions. LBO develops the traditional approach with three constants,
GV argues in favor of at most two (within superstring theory), while MJD
advocates zero.Comment: Version appearing in JHEP; 31 pages late
Timelike Hopf Duality and Type IIA^* String Solutions
The usual T-duality that relates the type IIA and IIB theories compactified
on circles of inversely-related radii does not operate if the dimensional
reduction is performed on the time direction rather than a spatial one. This
observation led to the recent proposal that there might exist two further
ten-dimensional theories, namely type IIA^* and type IIB^*, related to type IIB
and type IIA respectively by a timelike dimensional reduction. In this paper we
explore such dimensional reductions in cases where time is the coordinate of a
non-trivial U(1) fibre bundle. We focus in particular on situations where there
is an odd-dimensional anti-de Sitter spacetime AdS_{2n+1}, which can be
described as a U(1) bundle over \widetilde{CP}^n, a non-compact version of CP^n
corresponding to the coset manifold SU(n,1)/U(n). In particular, we study the
AdS_5\times S^5 and AdS_7\times S^4 solutions of type IIB supergravity and
eleven-dimensional supergravity. Applying a timelike Hopf T-duality
transformation to the former provides a new solution of the type IIA^* theory,
of the form \widetilde{CP}^2\times S^1\times S^5. We show how the Hopf-reduced
solutions provide further examples of ``supersymmetry without supersymmetry.''
We also present a detailed discussion of the geometrical structure of the
Hopf-fibred metric on AdS_{2n+1}, and its relation to the horospherical metric
that arises in the AdS/CFT correspondence.Comment: Latex, 26 page
CCRS proposal for evaluating LANDSAT-4 MSS and TM data
The measurement of registration errors in LANDSAT MSS data is discussed as well as the development of a revised algorithm for the radiometric calibration of TM data and the production of a geocoded TM image
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