45,886 research outputs found
-folds from Yang-Baxter deformations
Yang-Baxter (YB) deformations of type IIB string theory have been well
studied from the viewpoint of classical integrability. Most of the works,
however, are focused upon the local structure of the deformed geometries and
the global structure still remains unclear. In this work, we reveal a
non-geometric aspect of YB-deformed backgrounds as -fold by explicitly
showing the associated -duality monodromy. In
particular, the appearance of an extra vector field in the generalized
supergravity equations (GSE) leads to the non-geometric -flux. In addition,
we study a particular solution of GSE that is obtained by a non-Abelian
-duality but cannot be expressed as a homogeneous YB deformation, and show
that it can also be regarded as a -fold. This result indicates that
solutions of GSE should be non-geometric quite in general beyond the YB
deformation.Comment: 47 page
Truncations of the D9-brane action and type-I strings
The low-energy effective action of type-I superstring theory in ten
dimensions is obtained performing a truncation of type-IIB supergravity in a
background where D9-branes are present. The open sector corresponds to the
first order in the low-energy expansion of the D9-brane action in a type-I
background. In hep-th/9901055 it was shown that there are two ways of
performing a type-I truncation of the D9-brane action, and the resulting
truncated action was obtained in a flat background. We extend this result to a
generic type-I background, and argue that the two different truncations are in
correspondence with the open sector of the low-energy effective action of the
two different consistent ten-dimensional type-I string theories, namely the
SO(32) superstring and the non-supersymmetric string.Comment: 15 pages, LaTeX file. Refs. adde
The physical significance of the Babak-Grishchuk gravitational energy-momentum tensor
We examine the claim of Babak and Grishchuk [1] to have solved the problem of
localising the energy and momentum of the gravitational field. After
summarising Grishchuk's flat-space formulation of gravity, we demonstrate its
equivalence to General Relativity at the level of the action. Two important
transformations are described (diffeomorphisms applied to all fields, and
diffeomorphisms applied to the flat-space metric alone) and we argue that both
should be considered gauge transformations: they alter the mathematical
representation of a physical system, but not the system itself. By examining
the transformation properties of the Babak-Grishchuk gravitational
energy-momentum tensor under these gauge transformations (infinitesimal and
finite) we conclude that this object has no physical significance.Comment: 10 pages. Submitted to Phys. Rev. D; acknowledgements adjuste
Convolutional neural network architecture for geometric matching
We address the problem of determining correspondences between two images in
agreement with a geometric model such as an affine or thin-plate spline
transformation, and estimating its parameters. The contributions of this work
are three-fold. First, we propose a convolutional neural network architecture
for geometric matching. The architecture is based on three main components that
mimic the standard steps of feature extraction, matching and simultaneous
inlier detection and model parameter estimation, while being trainable
end-to-end. Second, we demonstrate that the network parameters can be trained
from synthetically generated imagery without the need for manual annotation and
that our matching layer significantly increases generalization capabilities to
never seen before images. Finally, we show that the same model can perform both
instance-level and category-level matching giving state-of-the-art results on
the challenging Proposal Flow dataset.Comment: In 2017 IEEE Conference on Computer Vision and Pattern Recognition
(CVPR 2017
An emergent geometric description for a topological phase transition in the Kitaev superconductor model
Resorting to Wilsonian renormalization group (RG) transformations, we propose
an emergent geometric description for a topological phase transition in the
Kitaev superconductor model. An effective field theory consists of an emergent
bulk action with an extra dimension, an ultraviolet (UV) boundary condition for
an initial value of a coupling function, and an infrared (IR) effective action
with a fully renormalized coupling function. The bulk action describes the
evolution of the coupling function along the direction of the extra dimension,
where the extra dimension is identified with an RG scale and the resulting
equation of motion is nothing but a function. In particular, the IR
effective field theory turns out to be consistent with a Callan-Symanzik
equation which takes into account both the bulk and IR boundary contributions.
This derived Callan-Symanzik equation gives rise to a metric structure. Based
on this emergent metric tensor, we uncover the equivalence of the entanglement
entropy between the emergent geometric description and the quantum field theory
in the vicinity of the quantum critical point.Comment: Two figures adde
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