180 research outputs found
Twisted String Theory in Anti-de Sitter Space
We construct a string theory in three-dimensional anti-de Sitter space-time
that is independent of the boundary metric. It is a topologically twisted
theory of quantum gravity. We study string theories with an asymptotic N=2
superconformal symmetry and demonstrate that, when the world sheet coupling to
the space-time boundary metric undergoes a U(1) R-symmetry twist, the
space-time boundary energy-momentum tensor becomes topological. As a by-product
of our analysis, we obtain the world sheet vertex operator that codes the
space-time energy-momentum for conformally flat boundary metrics.Comment: 23 page
Topological Gravity with Non-Compact Matter
We couple twisted non-compact N=(2,2) supersymmetric models to topological
gravity in two dimensions. We propose expressions for the genus zero
correlation functions based on a Kadomtsev-Petviashvili integrable hierarchy.
Moreover, we prove recursion relations satisfied by the topological gravity
amplitudes at all genera and compute characteristic critical exponents. We
discuss the extent to which moving beyond the N=2 central charge barrier opens
a window on two-dimensional gravity with central charge larger than one.Comment: 25 page
The Topological Symmetric Orbifold
We analyse topological orbifold conformal field theories on the symmetric
product of a complex surface M. By exploiting the mathematics literature we
show that a canonical quotient of the operator ring has structure constants
given by Hurwitz numbers. This proves a conjecture in the physics literature on
extremal correlators. Moreover, it allows to leverage results on the
combinatorics of the symmetric group to compute more structure constants
explicitly. We recall that the full orbifold chiral ring is given by a
symmetric orbifold Frobenius algebra. This construction enables the computation
of topological genus zero and genus one correlators, and to prove the vanishing
of higher genus contributions. The efficient description of all topological
correlators sets the stage for a proof of a topological AdS/CFT correspondence.
Indeed, we propose a concrete mathematical incarnation of the proof, relating
Gromow-Witten theory in the bulk to the quantum cohomology of the Hilbert
scheme on the boundary.Comment: 33 pages. v2: Remarks on proof adde
How to Train Your Dragon: Tamed Warping Network for Semantic Video Segmentation
Real-time semantic segmentation on high-resolution videos is challenging due
to the strict requirements of speed. Recent approaches have utilized the
inter-frame continuity to reduce redundant computation by warping the feature
maps across adjacent frames, greatly speeding up the inference phase. However,
their accuracy drops significantly owing to the imprecise motion estimation and
error accumulation. In this paper, we propose to introduce a simple and
effective correction stage right after the warping stage to form a framework
named Tamed Warping Network (TWNet), aiming to improve the accuracy and
robustness of warping-based models. The experimental results on the Cityscapes
dataset show that with the correction, the accuracy (mIoU) significantly
increases from 67.3% to 71.6%, and the speed edges down from 65.5 FPS to 61.8
FPS. For non-rigid categories such as "human" and "object", the improvements of
IoU are even higher than 18 percentage points
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