1,301 research outputs found
Poincare Polynomials and Level Rank Dualities in the Coset Construction
We review the coset construction of conformal field theories; the emphasis is
on the construction of the Hilbert spaces for these models, especially if fixed
points occur. This is applied to the superconformal cosets constructed by
Kazama and Suzuki. To calculate heterotic string spectra we reformulate the
Gepner con- struction in terms of simple currents and introduce the so-called
extended Poincar\'e polynomial. We finally comment on the various equivalences
arising between models of this class, which can be expressed as level rank
dualities. (Invited talk given at the III. International Conference on
Mathematical Physics, String Theory and Quantum Gravity, Alushta, Ukraine, June
1993. To appear in Theor. Math. Phys.)Comment: 14 pages in LaTeX, HD-THEP-93-4
A Unified Approach to Solvable Models of Dilaton Gravity in Two-Dimensions Based on Symmetry
A large class of solvable models of dilaton gravity in two space-time
dimensions, capable of describing black hole geometry, are analyzed in a
unified way as non-linear sigma models possessing a special symmetry. This
symmetry, which can be neatly formulated in the target-space-covariant manner,
allows one to decompose the non-linearly interacting dilaton-gravity system
into a free field and a field satisfying the Liouville equation with in general
non-vanishing cosmological term. In this formulation, all the existent models
are shown to fall into the category with vanishing cosmological constant.
General analysis of the space-time structureinduced by a matter shock wave is
performed and new models, with and without the cosmological term, are
discussed.Comment: 29 pages, LaTe
The Large N 't Hooft Limit of Kazama-Suzuki Model
We consider N=2 Kazama-Suzuki model on CP^N=SU(N+1)/SU(N)xU(1). It is known
that the N=2 current algebra for the supersymmetric WZW model, at level k, is a
nonlinear algebra. The N=2 W_3 algebra corresponding to N=2 was recovered from
the generalized GKO coset construction previously. For N=4, we construct one of
the higher spin currents, in N=2 W_5 algebra, with spins (2, 5/2, 5/2, 3). The
self-coupling constant in the operator product expansion of this current and
itself depends on N as well as k explicitly. We also observe a new higher spin
primary current of spins (3, 7/2, 7/2, 4). From the behaviors of N=2, 4 cases,
we expect the operator product expansion of the lowest higher spin current and
itself in N=2 W_{N+1} algebra. By taking the large (N, k) limit on the various
operator product expansions in components, we reproduce, at the linear order,
the corresponding operator product expansions in N=2 classical
W_{\infty}^{cl}[\lambda] algebra which is the asymptotic symmetry of the higher
spin AdS_3 supergravity found recently.Comment: 44 pages; the two typos in the first paragraph of page 23 corrected
and to appear in JHE
Presence and mobility of arsenic in estuarine wetland soils of the Scheldt estuary (Belgium)
We aimed to assess the presence and availability of arsenic (As) in intertidal marshes of the Scheldt estuary. Arsenic content was determined in soils sampled at 4 sampling depths in 11 marshes, together with other physicochemical characteristics. Subsequently, a greenhouse experiment was set up in which pore water arsenic (As) concentrations were measured 4 times in a 298-day period in 4 marsh soils at different sampling depths (10, 30, 60 and 90 cm) upon adjusting the water table level to 0, 40 and 80 cm below the surface of these soils. The As content in the soil varied significantly with sampling depth and location. Clay and organic matter seem to promote As accumulation in the upper soil layer (0–20 cm below the surface), whereas sulfide precipitation plays a significant role at higher sampling depths (20– 100 cm below the surface). The As concentrations in the pore water of the greenhouse experiment often significantly exceeded the Flemish soil sanitation thresholds for groundwater. There were indications that As release is not only affected by the reductive dissolution of Fe/Mn oxides, but also by e.g. a direct reduction of As(V) to As(III). Below the water table, sulfide precipitation seems to lower As mobility when reducing conditions have been sufficiently established. Above the water table, sulfates and bicarbonates induce As release from the solid soil phase to the pore water
Extraction of Black Hole Geometry in Exactly Quantized Two Dimensional Dilaton Gravity
Based on our previous work, in which a model of two dimensional dilaton
gravity of the type proposed by Callan, Giddings, Harvey and Strominger was
rigorously quantized, we explicitly demonstrate how one can extract space-time
geometry in exactly solvable theory of quantum gravity. In particular, we have
been able to produce a prototypical configuration in which a ( smeared ) matter
shock wave generates a black hole without naked sigularity.Comment: LATEX file 10 pages. UT-Komaba 93-13. 1 figure in postscrip
The Operator Product Expansion of the Lowest Higher Spin Current at Finite N
For the N=2 Kazama-Suzuki(KS) model on CP^3, the lowest higher spin current
with spins (2, 5/2, 5/2,3) is obtained from the generalized GKO coset
construction. By computing the operator product expansion of this current and
itself, the next higher spin current with spins (3, 7/2, 7/2, 4) is also
derived. This is a realization of the N=2 W_{N+1} algebra with N=3 in the
supersymmetric WZW model. By incorporating the self-coupling constant of lowest
higher spin current which is known for the general (N,k), we present the
complete nonlinear operator product expansion of the lowest higher spin current
with spins (2, 5/2, 5/2, 3) in the N=2 KS model on CP^N space. This should
coincide with the asymptotic symmetry of the higher spin AdS_3 supergravity at
the quantum level. The large (N,k) 't Hooft limit and the corresponding
classical nonlinear algebra are also discussed.Comment: 62 pages; the footnotes added, some redundant appendices removed, the
presentations in the whole paper improved and to appear in JHE
No N=4 Strings on Wolf Spaces
We generalize the standard supersymmetric Kazama-Suzuki coset
construction to the case by requiring the {\it non-linear}
(Goddard-Schwimmer) quasi-superconformal algebra to be realized on
cosets. The constraints that we find allow very simple geometrical
interpretation and have the Wolf spaces as their natural solutions. Our results
obtained by using components-level superconformal field theory methods are
fully consistent with standard results about supersymmetric
two-dimensional non-linear sigma-models and WZNW models on Wolf spaces.
We construct the actions for the latter and express the quaternionic structure,
appearing in the coset solution, in terms of the symplectic structure
associated with the underlying Freudenthal triple system. Next, we gauge the
QSCA and build a quantum BRST charge for the string propagating on
a Wolf space. Surprisingly, the BRST charge nilpotency conditions rule out the
non-trivial Wolf spaces as consistent string backgrounds.Comment: 31 pages, LaTeX, special macros are include
Exact Models of Extremal Dyonic 4D Black Hole Solutions of Heterotic String Theory
Families of exact supersymmetric conformal field theories of
magnetically and electrically charged extremal 4D black hole solutions of
heterotic string theory are presented. They are constructed using a
supersymmetric WZW model where anomalously embedded
subgroups are gauged. Crucial cancelations of the
anomalies coming from the supersymmetric fermions, the current algebra fermions
and the gauging ensure that there is a consistency of these models at the
quantum level. Various 2D models, which may be considered as building blocks
for extremal 4D constructions, are presented. They generalise the class of 2D
models which might be obtained from gauging and coincide with known
heterotic string backgrounds. The exact conformal field theory presented by
Giddings, Polchinski and Strominger describing the angular sector of the
extremal magnetically charged black hole is a special case of this
construction. An example where the radial and angular theories are mixed
non--trivially is studied in detail, resulting in an extremal dilatonic
Taub--NUT--like dyon.Comment: 42 pages (Plain TEX), IASSNS-HEP-94/20 (Revised version has minor
corrections, references and a note added and is now identical to published
version in Phys Rev D.
Effect of recovery period of mixture pasture on cattle behaviour, pasture biomass production and pasture nutritional value
Soluble models in 2d dilaton gravity
A one-parameter class of simple models of two-dimensional dilaton gravity,
which can be exactly solved including back-reaction effects, is investigated at
both classical and quantum levels. This family contains the RST model as a
special case, and it continuously interpolates between models having a flat
(Rindler) geometry and a constant curvature metric with a non-trivial dilaton
field. The processes of formation of black hole singularities from collapsing
matter and Hawking evaporation are considered in detail. Various physical
aspects of these geometries are discussed, including the cosmological
interpretation.Comment: 15 pages, harvmac, 3 figure
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