172 research outputs found
Dark Energy in Modified Supergravity
We propose a supersymmetric extension of the dynamical dark energy function
and the corresponding scalar (super)potential in F(R) supergravity. Our model
is viable in the Einstein approximation, and also has an analytic (regular)
Wess-Zumino-type scalar superpotential. The hidden sector responsible for
spontaneous supersymmetry breaking is given.Comment: LaTeX, 9 pages, 1 figure; secs. 2 and 3 extended, references updated,
title and abstract revise
Slow-roll inflation in (R+R*4) gravity
We reconsider the toy-model of topological inflation, based on the
R*4-modified gravity. By using its equivalence to the certain scalar-tensor
gravity model in four space-time dimensions, we compute the inflaton scalar
potential and investigate a possibility of inflation. We confirm the existence
of the slow-roll inflation with an exit. However, the model suffers from the
eta-problem that gives rise to the unacceptable value of the spectral index n_s
of scalar perturbations.Comment: 12 pages, 3 figures, LaTeX, misprints corrected and references
update
More anomaly-free models of six-dimensional gauged supergravity
We construct a huge number of anomaly-free models of six-dimensional N =
(1,0) gauged supergravity. The gauge groups are products of U(1) and SU(2), and
every hyperino is charged under some of the gauge groups. It is also found that
the potential may have flat directions when the R-symmetry is diagonally gauged
together with another gauge group. In an appendix, we determine the
contribution to the global SU(2) anomaly from symplectic Majorana Weyl fermions
in six dimensions.Comment: 20 pages, v3: published versio
(4,4) superfield supergravity
We present the N=4 superspace constraints for the two-dimensional (2d)
off-shell (4,4) supergravity with the superfield strengths expressed in terms
of a (4,4) twisted (scalar) multiplet TM-I, as well as the corresponding
component results, in a form suitable for applications. The constraints are
shown to be invariant under the N=4 super-Weyl transformations, whose N=4
superfield parameters form another twisted (scalar) multiplet TM-II. To solve
the constraints, we propose the Ansatz which makes the N=4 superconformal
flatness of the N=4 supergravity curved superspace manifest. The locally (4,4)
supersymmetric TM-I matter couplings, with the potential terms resulting from
spontaneous supersymmetry breaking, are constructed. We also find the full
(4,4) superconformally invariant (improved) TM-II matter action. The latter can
be extended to the (4,4) locally supersymmetric Liouville action which is
suitable for describing (4,4) supersymmetric non-critical strings.Comment: 32 pages, LaTeX, revised version (one reference added, and one
Appendix is reduced
Remarks about massive and massless particles in supersymmetry
The internal space-time symmetry and simple supersymmetry of relativistic particles are briefly discussed in terms of the little group of the Poincare group. The little group generators in a finite-dimensional matrix representation of the N = 1 super-Poincare algebra are explicitly constructed. The supergeometry of a massive case continuously becomes that of a massless case in the infinite-momentum limit. The origin of the gage transformations associated with the massless supermultiplets becomes transparent in that limit
D-instantons and matter hypermultiplet
We calculate the D-instanton corrections (with all D-instanton numbers) to the quantum moduli space metric of a single matter hypermultiplet with toric isometry, in the effective N=2 supergravity arising in type-IIA superstrings compactified on a Calabi-Yau (CY) threefold of Hodge number h_{2,1}=1. The non-perturbative quaternionic hypermultiplet metric is derived by resolution of a complex orbifold singularity, thus generalizing the known (Ooguri-Vafa) solution in flat spacetime to N=2 supergravity
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