5,068 research outputs found
Effective field theory from modified gravity with massive modes
Massive gravitational modes in effective field theories can be recovered by
extending General Relativity and taking into account generic functions of the
curvature invariants, not necessarily linear in the Ricci scalar R. In
particular, adopting the minimal extension of f(R) gravity, an effective field
theory with massive modes is straightforwardly recovered. This approach allows
to evade shortcomings like ghosts and discontinuities if a suitable choice of
expansion parameters is performed.Comment: 11 pages, no figures; title and text match published versio
Finding any Waldo: zero-shot invariant and efficient visual search
Searching for a target object in a cluttered scene constitutes a fundamental
challenge in daily vision. Visual search must be selective enough to
discriminate the target from distractors, invariant to changes in the
appearance of the target, efficient to avoid exhaustive exploration of the
image, and must generalize to locate novel target objects with zero-shot
training. Previous work has focused on searching for perfect matches of a
target after extensive category-specific training. Here we show for the first
time that humans can efficiently and invariantly search for natural objects in
complex scenes. To gain insight into the mechanisms that guide visual search,
we propose a biologically inspired computational model that can locate targets
without exhaustive sampling and generalize to novel objects. The model provides
an approximation to the mechanisms integrating bottom-up and top-down signals
during search in natural scenes.Comment: Number of figures: 6 Number of supplementary figures: 1
Constraints on Higher Spin CFT
We derive constraints on two-dimensional conformal field theories with higher
spin symmetry due to unitarity, modular invariance, and causality. We focus on
CFTs with symmetry in the "irrational" regime, where
and the theories have an infinite number of higher-spin primaries. The most
powerful constraints come from positivity of the Kac matrix, which (unlike the
Virasoro case) is non-trivial even when . This places a lower bound on
the dimension of any non-vacuum higher-spin primary state, which is linear in
the central charge. At large , this implies that the dual holographic
theories of gravity in AdS, if they exist, have no local, perturbative
degrees of freedom in the semi-classical limit.Comment: 31 pages+refs, 4 figure
Gravity and axions from a random UV QFT
It is postulated that the UV QFT is enormous and random. The coupling of the
Standard Model to such QFT is analyzed. It is argued that massless 4d gravity
and axions are general avatars of the postulate. The equivalence principle
emerges naturally as well as a concrete set of sources for its breaking. The
axion scale is related to the 4d Planck scale as , where is the
"number of colors" of the (almost) hidden UV CFT.Comment: Latex, 39 page
Closed-loop Reference Models for Output-Feedback Adaptive Systems
Closed-loop reference models have recently been proposed for states
accessible adaptive systems. They have been shown to have improved transient
response over their open loop counter parts. The results in the states
accessible case are extended to single input single output plants of arbitrary
relative degree.Comment: v1 Submitted to European Control Conference 2013, v2 Typos correcte
Harvesting Multiple Views for Marker-less 3D Human Pose Annotations
Recent advances with Convolutional Networks (ConvNets) have shifted the
bottleneck for many computer vision tasks to annotated data collection. In this
paper, we present a geometry-driven approach to automatically collect
annotations for human pose prediction tasks. Starting from a generic ConvNet
for 2D human pose, and assuming a multi-view setup, we describe an automatic
way to collect accurate 3D human pose annotations. We capitalize on constraints
offered by the 3D geometry of the camera setup and the 3D structure of the
human body to probabilistically combine per view 2D ConvNet predictions into a
globally optimal 3D pose. This 3D pose is used as the basis for harvesting
annotations. The benefit of the annotations produced automatically with our
approach is demonstrated in two challenging settings: (i) fine-tuning a generic
ConvNet-based 2D pose predictor to capture the discriminative aspects of a
subject's appearance (i.e.,"personalization"), and (ii) training a ConvNet from
scratch for single view 3D human pose prediction without leveraging 3D pose
groundtruth. The proposed multi-view pose estimator achieves state-of-the-art
results on standard benchmarks, demonstrating the effectiveness of our method
in exploiting the available multi-view information.Comment: CVPR 2017 Camera Read
Cohomology of algebraic groups, Lie algebras, and finite groups of Lie type
Let G be a reductive algebraic group over a field of prime characteristic.
One can associate to G (or subgroups thereof) its Lie algebra, its Frobenius
kernels, and the finite Chevalley group of points over a finite field. The
representation theories of these structures are highly interconnected. This
expository article will focus specifically on the cohomology theories of these
structures and the relationships between them with the aim of highlighting a
few key developments over the past 20 years and related open questions
Occlusion Coherence: Detecting and Localizing Occluded Faces
The presence of occluders significantly impacts object recognition accuracy.
However, occlusion is typically treated as an unstructured source of noise and
explicit models for occluders have lagged behind those for object appearance
and shape. In this paper we describe a hierarchical deformable part model for
face detection and landmark localization that explicitly models part occlusion.
The proposed model structure makes it possible to augment positive training
data with large numbers of synthetically occluded instances. This allows us to
easily incorporate the statistics of occlusion patterns in a discriminatively
trained model. We test the model on several benchmarks for landmark
localization and detection including challenging new data sets featuring
significant occlusion. We find that the addition of an explicit occlusion model
yields a detection system that outperforms existing approaches for occluded
instances while maintaining competitive accuracy in detection and landmark
localization for unoccluded instances
F-theorem, duality and SUSY breaking in one-adjoint Chern-Simons-Matter theories
We extend previous work on N=2 Chern-Simons theories coupled to a single
adjoint chiral superfield using localization techniques and the F-maximization
principle. We provide tests of a series of proposed 3D Seiberg dualities and a
new class of tests of the conjectured F-theorem. In addition, a proposal is
made for a modification of the F-maximization principle that takes into account
the effects of decoupling fields. Finally, we formulate and provide evidence
for a new general non-perturbative constraint on spontaneous supersymmetry
breaking in three dimensions based on Q-deformed S^3 partition functions. An
explicit illustration based on the known analytic solution of the Chern-Simons
matrix model is presented.Comment: 42 pages, 12 figures; v2 mostly cosmetic changes, references added;
v3 minor changes to match the published version in NP
- …