11 research outputs found
A Compact Codimension Two Braneworld with Precisely One Brane
Building on earlier work on football shaped extra dimensions, we construct a
compact codimension two braneworld with precisely one brane. The two extra
dimensions topologically represent a 2-torus which is stabilized by a bulk
cosmological constant and magnetic flux. The torus has positive constant
curvature almost everywhere, except for a single conical singularity at the
location of the brane. In contradistinction to the football shaped case, there
is no fine-tuning required for the brane tension. We also present some
plausibility arguments why the model should not suffer from serious stability
issues.Comment: 13 pages, 2 figures; references added, typos fixes; essentially the
version published in PR
Instantons and Holomorphic Couplings in Intersecting D-brane Models
We clarify certain aspects and discuss extensions of the recently introduced
string D-instanton calculus (hep-th/0609191). The one-loop determinants are
related to one-loop open string threshold corrections in intersecting D6-brane
models. Utilising a non-renormalisation theorem for the holomorphic Wilsonian
gauge kinetic functions, we derive a number of constraints for the moduli
dependence of the matter field Kaehler potentials of intersecting D6-brane
models on the torus. Moreover, we compute string one-loop corrections to the
Fayet-Iliopoulos terms on the D6-branes finding that they are proportional to
the gauge threshold corrections. Employing these results, we discuss the issue
of holomorphy for E2-instanton corrections to the superpotential. Eventually,
we discuss E2-instanton corrections to the gauge kinetic functions and the
FI-terms.Comment: 28 pages, 5 figure
Thresholds for Intersecting D-branes Revisited
Gauge threshold corrections for intersecting D6-brane string models on
toroidal orbifold backgrounds are reconsidered. Both by dimensionally
regularising the appearing open string one-loop diagrams in tree-channel as
well as by zeta-function regularisation of the corresponding loop-channel
one-loop diagrams, we arrive at a result which takes into account the infrared
divergence from the contribution of the massless states in the running of the
gauge coupling constant as well as the contribution of states, which become
light in certain regions of the moduli space.Comment: 14 page
Relative entropy as a measure of inhomogeneity in general relativity
We introduce the notion of relative volume entropy for two spacetimes with
preferred compact spacelike foliations. This is accomplished by applying the
notion of Kullback-Leibler divergence to the volume elements induced on
spacelike slices. The resulting quantity gives a lower bound on the number of
bits which are necessary to describe one metric given the other. For
illustration, we study some examples, in particular gravitational waves, and
conclude that the relative volume entropy is a suitable device for quantitative
comparison of the inhomogeneity of two spacetimes.Comment: 15 pages, 7 figure
Marginal deformations and 3-algebra structures
We study marginal deformations of superconformal Chern-Simons matter theories
that are based on 3-algebras. For this, we introduce the notion of an
associated 3-product, which captures very general gauge invariant deformations
of the superpotentials of the BLG and ABJM models. We also consider conformal
multi-trace deformations preserving N=2 supersymmetry. We then use N=2
supergraph techniques to compute the two-loop beta functions of these
deformations. Besides confirming conformal invariance of both the BLG and ABJM
models, we also verify that the recently proposed beta-deformations of the ABJM
model are indeed marginal to the order we are considering.Comment: v3: 34 pages, typos fixed and minor clarifications adde