263 research outputs found
Gauss-Bonnet type identity in Weyl-Cartan space
The Gauss-Bonnet type identity is derived in a Weyl-Cartan space on the basis
of the variational method.Comment: 5 page
Euclidean-signature Supergravities, Dualities and Instantons
We study the Euclidean-signature supergravities that arise by compactifying
D=11 supergravity or type IIB supergravity on a torus that includes the time
direction. We show that the usual T-duality relation between type IIA and type
IIB supergravities compactified on a spatial circle no longer holds if the
reduction is performed on the time direction. Thus there are two inequivalent
Euclidean-signature nine-dimensional maximal supergravities. They become
equivalent upon further spatial compactification to D=8. We also show that
duality symmetries of Euclidean-signature supergravities allow the harmonic
functions of any single-charge or multi-charge instanton to be rescaled and
shifted by constant factors. Combined with the usual diagonal dimensional
reduction and oxidation procedures, this allows us to use the duality
symmetries to map any single-charge or multi-charge p-brane soliton, or any
intersection, into its near-horizon regime. Similar transformations can also be
made on non-extremal p-branes. We also study the structures of duality
multiplets of instanton and (D-3)-brane solutions.Comment: Latex, 50 pages, typos corrected and references adde
Representations of G+++ and the role of space-time
We consider the decomposition of the adjoint and fundamental representations
of very extended Kac-Moody algebras G+++ with respect to their regular A type
subalgebra which, in the corresponding non-linear realisation, is associated
with gravity. We find that for many very extended algebras almost all the A
type representations that occur in the decomposition of the fundamental
representations also occur in the adjoint representation of G+++. In
particular, for E8+++, this applies to all its fundamental representations.
However, there are some important examples, such as An+++, where this is not
true and indeed the adjoint representation contains no generator that can be
identified with a space-time translation. We comment on the significance of
these results for how space-time can occur in the non-linear realisation based
on G+++. Finally we show that there is a correspondence between the A
representations that occur in the fundamental representation associated with
the very extended node and the adjoint representation of G+++ which is
consistent with the interpretation of the former as charges associated with
brane solutions.Comment: 45 pages, 9 figures, 9 tables, te
Gravity in the dynamical approach to the cosmological constant
One of the most disturbing difficulties in thinking about the cosmological
constant is that it is not stable under radiative corrections. The feedback
mechanism proposed in [hep-th/0306108] is a dynamical way to protect a zero or
small cosmological constant against radiative corrections. Hence, while this by
itself does not solve the cosmological constant problem, it can help solving
the problem. In the present paper we investigate stability and gravity in this
approach and show that the feedback mechanism is both classically and quantum
mechanically stable and has self-consistent, stable dynamics.Comment: 40 pages; references added; 3 new sections added to explain
underlying idea, numerical results and quantum mechanical stability; version
to appear in PR
Special geometry of Euclidean supersymmetry II: hypermultiplets and the c-map
We construct two new versions of the c-map which allow us to obtain the
target manifolds of hypermultiplets in Euclidean theories with rigid N =2
supersymmetry. While the Minkowskian para-c-map is obtained by dimensional
reduction of the Minkowskian vector multiplet lagrangian over time, the
Euclidean para-c-map corresponds to the dimensional reduction of the Euclidean
vector multiplet lagrangian. In both cases the resulting hypermultiplet target
spaces are para-hyper-Kahler manifolds. We review and prove the relevant
results of para-complex and para-hypercomplex geometry. In particular, we give
a second, purely geometrical construction of both c-maps, by proving that the
cotangent bundle N=T^*M of any affine special (para-)Kahler manifold M is
para-hyper-Kahler.Comment: 36 pages, 1 figur
BPS Force Balances via Spin-Spin Interactions
We study two systems of BPS solitons in which spin-spin interactions are
important in establishing the force balances which allow static, multi-soliton
solutions to exist. Solitons in the Israel-Wilson-Perjes (IWP) spacetimes each
carry arbitrary, classical angular momenta. Solitons in the Aichelburg-Embacher
"superpartner" spacetimes carry quantum mechanical spin, which originates in
the zero-modes of the gravitino field of N=2 supergravity in an extreme
Reissner-Nordstrom background. In each case we find a cancellation between
gravitational spin-spin and magnetic dipole-dipole forces, in addition to the
usual one between Newtonian gravitational attraction and Coulombic
electrostatic repulsion. In both cases, we analyze the forces between two
solitons by treating one of the solitons as a probe or test particle, with the
appropriate properties, moving in the background of the other. In the IWP case,
the equation of motion for a spinning test particle, originally due to
Papapetrou, includes a coupling between the background curvature and the spin
of the test particle. In the superpartner case, the relevant equation of motion
follows from a kappa-symmetric superparticle action.Comment: 11 page
Anomaly candidates and invariants of D=4, N=1 supergravity theories
All anomaly candidates and the form of the most general invariant local
action are given for old and new minimal supergravity, including the cases
where additional Yang--Mills and chiral matter multiplets are present.
Furthermore nonminimal supergravity is discussed. In this case local
supersymmetry itself may be anomalous and some of the corresponding anomaly
candidates are given explicitly. The results are obtained by solving the
descent equations which contain the consistency equation satisfied by
integrands of anomalies and invariant actions.Comment: 19 pages, LaTex, NIKHEF-H 93-12, ITP-UH 07/9
Composite fluxbranes with general intersections
Generalized composite fluxbrane solutions for a wide class of intersection
rules are obtained. The solutions are defined on a manifold which contains a
product of n Ricci-flat spaces M_1 x ... x M_n with 1-dimensional M_1. They are
defined up to a set of functions H_s obeying non-linear differential equations
equivalent to Toda-type equations with certain boundary conditions imposed. A
conjecture on polynomial structure of governing functions H_s for intersections
related to semisimple Lie algebras is suggested. This conjecture is valid for
Lie algebras: A_m, C_{m+1}, m > 0. For simple Lie algebras the powers of
polynomials coincide with the components of the dual Weyl vector in the basis
of simple roots. Explicit formulas for A_1 + ... + A_1 (orthogonal),
"block-ortogonal" and A_2 solutions are obtained. Certain examples of solutions
in D = 11 and D =10 (II A) supergravities (e.g. with A_2 intersection rules)
and Kaluza-Klein dyonic A_2 flux tube, are considered.Comment: 19 pages, Latex, 1 reference (on a pioneering paper of Gibbons and
Wiltshire) and two missing relations are added Published: Class. Quantum
Grav. 19 (2002) 3033-304
Multiple M0-brane system in an arbitrary eleven dimensional supergravity background
The equations of motion of multiple M0{brane (multiple M-wave or mM0) system
in an arbitrary D = 11 supergravity superspace, which generalize the Matrix
model equations for the case of inter- action with a generic 11D supergravity
background, are obtained in the frame of superembedding approach. We also
derive the BPS equations for supersymmetric bosonic solutions of these mM0
equations and show that the set of 1/2 BPS solutions contain a fuzzy sphere
modeling M2 brane as well as that the Nahm equation appears as a particular
case of the 1/4 BPS equations.Comment: RevTeX4, 20 pages, no figures. V2: misprints corrected, minor
changes, published in Phys. Rev. D82, 105030 (2010)). V3. Dec. 2011 :
misprints in coeffs of Eqs.(5.10) correcte
Cosmological Models with Variable Gravitational and Cosmological constants in Gravity
We consider the evolution of a flat Friedmann-Roberstson-Walker Universe in a
higher derivative theories, including terms to the
Einstein-Hilbert action in the presence of a variable gravitational and
cosmological constants. We study here the evolution of the gravitational and
cosmological constants in the presence of radiation and matter domination era
of the universe. We present here new cosmological solutions which are
physically interesting for model building.Comment: 14 pages, no figure. to be published in Int. J. Mod. Phys.
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