13 research outputs found
Gravity and antigravity in a brane world with metastable gravitons : Comment on hep-th/0002190 and hep-th/0003020
In the framework of a five-dimensional three-brane model with quasi-localized
gravitons we evaluate metric perturbations induced on the positive tension
brane by matter residing thereon. We find that at intermediate distances, the
effective four-dimensional theory coincides, up to small corrections, with
General Relativity. This is in accord with Csaki, Erlich and Hollowood and in
contrast to Dvali, Gabadadze and Porrati. We show, however, that at ultra-large
distances this effective four-dimensional theory becomes dramatically
different: conventional tensor gravity changes into scalar anti-gravity.Comment: 6 pages revtex, tex corrected, this paper should be read in tandem
with hep-th/000207
Towards a Unified Theory of Massless Superfields of All Superspins
We describe the ``universal'' action for massless superfields of all
superspins in N = 1, D = 4 anti-de Sitter superspace as a gauge theory of
unconstrained superfields taking their values in the commutative algebra of
analytic functions over a one-sheeted hyperboloid in . The action is
invariant under N = 2 supersymmetry transformations which form a closed algebra
off the mass-shell.Comment: 12 pages, LaTe
Quasi-localized states on noncommutative solitons
We consider noncommutative gauge theories which have zero mass states
propagating along both commutative and noncommutative dimensions. Solitons in
these theories generically carry U(m) gauge group on their world-volume. From
the point of view of string theory, these solitons correspond to
``branes within branes''. We show that once the world-volume U(m) gauge
theory is in the Higgs phase, light states become quasi-localized, rather than
strictly localized on the soliton, i.e. they mix with light bulk modes and have
finite widths to escape into the noncommutative dimensions. At small values of
U(m) symmetry breaking parameters, these widths are small compared to the
corresponding masses. Explicit examples considered are adjoint scalar field in
the background of a noncommutative vortex in U(1)-Higgs theory, and gauge
fields in instanton backgrounds in pure gauge noncommutative theories.Comment: 27 pages, references and comments added, final version to appear in
JHE
Ultra-large distance modification of gravity from Lorentz symmetry breaking at the Planck scale
We present an extension of the Randall--Sundrum model in which, due to
spontaneous Lorentz symmetry breaking, graviton mixes with bulk vector fields
and becomes quasilocalized. The masses of KK modes comprising the
four-dimensional graviton are naturally exponentially small. This allows to
push the Lorentz breaking scale to as high as a few tenth of the Planck mass.
The model does not contain ghosts or tachyons and does not exhibit the van
Dam--Veltman--Zakharov discontinuity. The gravitational attraction between
static point masses becomes gradually weaker with increasing of separation and
gets replaced by repulsion (antigravity) at exponentially large distances.Comment: 28 page