49 research outputs found
The -string spectrum
We study the spectrum of strings. In particular, we show that for
appropriately chosen space-time signature, one of the scalar fields is singled
out by the spin-3 constraint and is ``frozen'': no creation operators from it
can appear in physical states and the corresponding momentum must assume a
specific fixed value. The remaining theory is unitary and resembles an ordinary
string theory in with anomalies cancelled by appropriate background
charges. In the case of the string, however, the spin-two ``graviton'' is
massive.Comment: 14 Page
Four Dimensional String/String/String Triality
In six spacetime dimensions, the heterotic string is dual to a Type
string. On further toroidal compactification to four spacetime dimensions, the
heterotic string acquires an SL(2,\BbbZ)_S strong/weak coupling duality and
an SL(2,\BbbZ)_T \times SL(2,\BbbZ)_U target space duality acting on the
dilaton/axion, complex Kahler form and the complex structure fields
respectively. Strong/weak duality in interchanges the roles of and
in yielding a Type string with fields . This suggests
the existence of a third string (whose six-dimensional interpretation is more
obscure) that interchanges the roles of and . It corresponds in fact to
a Type string with fields leading to a four-dimensional
string/string/string triality. Since SL(2,\BbbZ)_S is perturbative for the
Type string, this triality implies -duality for the heterotic
string and thus fills a gap left by duality. For all three strings the
total symmetry is SL(2,\BbbZ)_S \times O(6,22;\BbbZ)_{TU}. The
O(6,22;\BbbZ) is {\it perturbative} for the heterotic string but contains the
conjectured {\it non-perturbative} SL(2,\BbbZ)_X, where is the complex
scalar of the Type string. Thus four-dimensional triality also
provides a (post-compactification) justification for this conjecture. We
interpret the Bogomol'nyi spectrum from all three points of view. In
particular we generalize the Sen-Schwarz formula for short multiplets to
include intermediate multiplets also and discuss the corresponding black hole
spectrum both for the theory and for a truncated ---- symmetric
theory. Just as the first two strings are described by the
four-dimensional {\it elementary} and {\it dual solitonic} solutions, so theComment: 36 pages, Latex, 2 figures, some references changed, minor changes in
formulas and tables; to appear in Nucl. Phys.
Regularisation, the BV method, and the antibracket cohomology
We review the Lagrangian Batalin--Vilkovisky method for gauge theories. This
includes gauge fixing, quantisation and regularisation. We emphasize the role
of cohomology of the antibracket operation. Our main example is gravity,
for which we also discuss the solutions for the cohomology in the space of
local integrals. This leads to the most general form for the action, for
anomalies and for background charges.Comment: 12 pages, LaTeX, Preprint-KUL-TF-94/2
Type 0 T-Duality and the Tachyon Coupling
We consider the T-duality relations between Type 0A and 0B theories, and show
that this constraints the possible couplings of the tachyon to the RR-fields.
Due to the `doubling' of the RR sector in Type 0 theories, we are able to
introduce a democratic formulation for the Type 0 effective actions, in which
there is no Chern-Simons term in the effective action. Finally we discuss how
to embed Type II solutions into Type 0 theories.Comment: some misprints corrected and a reference adde
General Brane Geometries from Scalar Potentials: Gauged Supergravities and Accelerating Universes
We find broad classes of solutions to the field equations for d-dimensional
gravity coupled to an antisymmetric tensor of arbitrary rank and a scalar field
with non-vanishing potential. Our construction generates these configurations
from the solution of a single nonlinear ordinary differential equation, whose
form depends on the scalar potential. For an exponential potential we find
solutions corresponding to brane geometries, generalizing the black p-branes
and S-branes known for the case of vanishing potential. These geometries are
singular at the origin with up to two (regular) horizons. Their asymptotic
behaviour depends on the parameters of the model. When the singularity has
negative tension or the cosmological constant is positive we find
time-dependent configurations describing accelerating universes. Special cases
give explicit brane geometries for (compact and non-compact) gauged
supergravities in various dimensions, as well as for massive 10D supergravity,
and we discuss their interrelation. Some examples lift to give new solutions to
10D supergravity. Limiting cases with a domain wall structure preserve part of
the supersymmetries of the vacuum. We also consider more general potentials,
including sums of exponentials. Exact solutions are found for these with up to
three horizons, having potentially interesting cosmological interpretation. We
give several additional examples which illustrate the power of our techniques.Comment: 54 pages, 6 figures. Uses JHEP3. Published versio
Supersymmetric, cold and lukewarm black holes in cosmological Einstein-Maxwell theory
In flat space, the extreme Reissner-Nordstr\o m (RN) black hole is
distinguished by its coldness (vanishing Hawking temperature) and its
supersymmetry. We examine RN solutions to Einstein-Maxwell theory with a
cosmological constant , classifying the cold black holes and, for
positive , the ``lukewarm" black holes at the same temperature as the
de Sitter thermal background. For negative , we classify the
supersymmetric solutions within the context of gauged supergravity. One
finds supersymmetric analogues of flat-space extreme RN black holes, which for
nonzero differ from the cold black holes. In addition, there is an
exotic class of supersymmetric solutions which cannot be continued to flat
space, since the magnetic charge becomes infinite in that limit.Comment: (18 pp., plain tex
Brane-world Kaluza-Klein reductions and Branes on the Brane
We present a systematic study of a new type of consistent ``Brane-world
Kaluza-Klein Reduction,'' which describe fully non-linear deformations of
co-dimension one objects that arise as solutions of a large class of gauged
supergravity theories in diverse dimensions, and whose world-volume theories
are described by ungauged supergravities with one half of the original
supersymmetry. In addition, we provide oxidations of these Ansatze which are in
general related to sphere compactified higher dimensional string theory or
M-theory. Within each class we also provide explicit solutions of brane
configurations localised on the world-brane. We show that at the Cauchy horizon
(in the transverse dimension of the consistently Kaluza-Klein reduced
world-brane) there is a curvature singularity for any configuration with a
non-null Riemann curvature or a non-vanishing Ricci scalar that lives in the
world-brane. Since the massive Kaluza-Klein modes can be consistently
decoupled, they cannot participate in regulating these singularities.Comment: latex, 30 page
Supersymmetry of the 2+1 black holes
The supersymmetry properties of the asymptotically anti-de Sitter black holes
of Einstein theory in 2+1 dimensions are investigated. It is shown that (i) the
zero mass black hole has two exact super- symmetries; (ii) extreme
black holes with have only one; and (iii) generic black holes do
not have any. It is also argued that the zero mass hole is the ground state of
(1,1)-adS supergravity with periodic (``Ramond") boundary conditions on the
spinor fields.Comment: 9 pages LaTeX file, ULB-PMIF-93/0
Supersymmetry and Stationary Solutions in Dilaton-Axion Gravity
New stationary solutions of -dimensional dilaton-axion gravity are
presented, which correspond to the charged Taub-NUT and Israel-Wilson-Perjes
(IWP) solutions of Einstein-Maxwell theory. The charged axion-dilaton Taub-NUT
solutions are shown to have a number of interesting properties: i) manifest
symmetry, ii) an infinite throat in an extremal limit, iii) the
throat limit coincides with an exact CFT construction.
The IWP solutions are shown to admit supersymmetric Killing spinors, when
embedded in supergravity. This poses a problem for the interpretation
of supersymmetric rotating solutions as physical ground states. In the context
of -dimensional geometry, we show that dimensionally lifted versions of the
IWP solutions are dual to certain gravitational waves in string theory.Comment: 23 pages (latex), SU-ITP-94-12, UMHEP-407, QMW-PH-94-1
Sugawara-type constraints in hyperbolic coset models
In the conjectured correspondence between supergravity and geodesic models on
infinite-dimensional hyperbolic coset spaces, and E10/K(E10) in particular, the
constraints play a central role. We present a Sugawara-type construction in
terms of the E10 Noether charges that extends these constraints infinitely into
the hyperbolic algebra, in contrast to the truncated expressions obtained in
arXiv:0709.2691 that involved only finitely many generators. Our extended
constraints are associated to an infinite set of roots which are all imaginary,
and in fact fill the closed past light-cone of the Lorentzian root lattice. The
construction makes crucial use of the E10 Weyl group and of the fact that the
E10 model contains both D=11 supergravity and D=10 IIB supergravity. Our
extended constraints appear to unite in a remarkable manner the different
canonical constraints of these two theories. This construction may also shed
new light on the issue of `open constraint algebras' in traditional canonical
approaches to gravity.Comment: 49 page