65 research outputs found
A Two-Form Formulation of the Vector-Tensor Multiplet in Central Charge Superspace
A two-form formulation for the N=2 vector-tensor multiplet is constructed
using superfield methods in central charge superspace. The N=2 non-Abelian
standard supergauge multiplet in central charge superspace is also discussed,
as is with the associated Chern-Simons form. We give the constraints, solve the
Bianchi identities and present the action for a theory of the vector-tensor
multiplet coupled to the non-Abelian supergauge multiplet via the Chern-Simons
form.Comment: 16 pages, LaTeX2e with AMS-LaTe
Spherically Symmetric Solutions in M\o ller's Tetrad Theory of Gravitation
The general solution of M\o ller's field equations in case of spherical
symmetry is derived. The previously obtained solutions are verified as special
cases of the general solution.Comment: LaTeX2e with AMS-LaTeX 1.2, 8 page
Hamiltonian analysis of Poincar\'e gauge theory scalar modes
The Hamiltonian constraint formalism is used to obtain the first explicit
complete analysis of non-trivial viable dynamic modes for the Poincar\'e gauge
theory of gravity. Two modes with propagating spin-zero torsion are analyzed.
The explicit form of the Hamiltonian is presented. All constraints are obtained
and classified. The Lagrange multipliers are derived. It is shown that a
massive spin- mode has normal dynamical propagation but the associated
massless is pure gauge. The spin- mode investigated here is also
viable in general. Both modes exhibit a simple type of ``constraint
bifurcation'' for certain special field/parameter values.Comment: 28 pages, LaTex, submitted to International Journal of Modern Physics
Energy-Momentum Complex in M\o ller's Tetrad Theory of Gravitation
M\o ller's Tetrad Theory of Gravitation is examined with regard to the
energy-momentum complex. The energy-momentum complex as well as the
superpotential associated with M\o ller's theory are derived. M\o ller's field
equations are solved in the case of spherical symmetry. Two different
solutions, giving rise to the same metric, are obtained. The energy associated
with one solution is found to be twice the energy associated with the other.
Some suggestions to get out of this inconsistency are discussed at the end of
the paper.Comment: LaTeX2e with AMS-LaTeX 1.2, 13 page
Superform formulation for vector-tensor multiplets in conformal supergravity
The recent papers arXiv:1110.0971 and arXiv:1201.5431 have provided a
superfield description for vector-tensor multiplets and their Chern-Simons
couplings in 4D N = 2 conformal supergravity. Here we develop a superform
formulation for these theories. Furthermore an alternative means of gauging the
central charge is given, making use of a deformed vector multiplet, which may
be thought of as a variant vector-tensor multiplet. Its Chern-Simons couplings
to additional vector multiplets are also constructed. This multiplet together
with its Chern-Simons couplings are new results not considered by de Wit et al.
in hep-th/9710212.Comment: 28 pages. V2: Typos corrected and references updated; V3: References
updated and typo correcte
Selfdual Spin 2 Theory in a 2+1 Dimensional Constant Curvature Space-Time
The Lagrangian constraint analysis of the selfdual massive spin 2 theory in a
2+1 dimensional flat space-time and its extension to a curved one, are
performed. Demanding consistence of degrees of freedom in the model with
gravitational interaction, gives rise to physical restrictions on non minimal
coupling terms and background. Finally, a constant curvature scenario is
explored, showing the existence of forbidden mass values. Causality in these
spaces is discussed. Aspects related with the construction of the reduced
action and the one-particle exchange amplitude, are noted.Comment: 20 pages, references added, little modifications performe
Ghost-free braneworld bigravity
We consider a generalisation of the DGP model, by adding a second brane with
localised curvature, and allowing for a bulk cosmological constant and brane
tensions. We study radion and graviton fluctuations in detail, enabling us to
check for ghosts and tachyons. By tuning our parameters accordingly, we find
bigravity models that are free from ghosts and tachyons. These models will lead
to large distance modifications of gravity that could be observable in the near
future.Comment: Dedicated to the memory of Ian Kogan. Version to appear in Classical
and Quantum Gravit
The linear multiplet and ectoplasm
In the framework of the superconformal tensor calculus for 4D N=2
supergravity, locally supersymmetric actions are often constructed using the
linear multiplet. We provide a superform formulation for the linear multiplet
and derive the corresponding action functional using the ectoplasm method (also
known as the superform approach to the construction of supersymmetric
invariants). We propose a new locally supersymmetric action which makes use of
a deformed linear multiplet. The novel feature of this multiplet is that it
corresponds to the case of a gauged central charge using a one-form potential
not annihilated by the central charge (unlike the standard N=2 vector
multiplet). Such a gauge one-form can be chosen to describe a variant nonlinear
vector-tensor multiplet. As a byproduct of our construction, we also find a
variant realization of the tensor multiplet in supergravity where one of the
auxiliaries is replaced by the field strength of a gauge three-form.Comment: 31 pages; v3: minor corrections and typos fixed, version to appear in
JHE
Nonlinear multidimensional cosmological models with form fields: stabilization of extra dimensions and the cosmological constant problem
We consider multidimensional gravitational models with a nonlinear scalar
curvature term and form fields in the action functional. In our scenario it is
assumed that the higher dimensional spacetime undergoes a spontaneous
compactification to a warped product manifold. Particular attention is paid to
models with quadratic scalar curvature terms and a Freund-Rubin-like ansatz for
solitonic form fields. It is shown that for certain parameter ranges the extra
dimensions are stabilized. In particular, stabilization is possible for any
sign of the internal space curvature, the bulk cosmological constant and of the
effective four-dimensional cosmological constant. Moreover, the effective
cosmological constant can satisfy the observable limit on the dark energy
density. Finally, we discuss the restrictions on the parameters of the
considered nonlinear models and how they follow from the connection between the
D-dimensional and the four-dimensional fundamental mass scales.Comment: 21 pages, LaTeX2e, minor changes, improved references, fonts include
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