1,815 research outputs found
Pixelwise Instance Segmentation with a Dynamically Instantiated Network
Semantic segmentation and object detection research have recently achieved
rapid progress. However, the former task has no notion of different instances
of the same object, and the latter operates at a coarse, bounding-box level. We
propose an Instance Segmentation system that produces a segmentation map where
each pixel is assigned an object class and instance identity label. Most
approaches adapt object detectors to produce segments instead of boxes. In
contrast, our method is based on an initial semantic segmentation module, which
feeds into an instance subnetwork. This subnetwork uses the initial
category-level segmentation, along with cues from the output of an object
detector, within an end-to-end CRF to predict instances. This part of our model
is dynamically instantiated to produce a variable number of instances per
image. Our end-to-end approach requires no post-processing and considers the
image holistically, instead of processing independent proposals. Therefore,
unlike some related work, a pixel cannot belong to multiple instances.
Furthermore, far more precise segmentations are achieved, as shown by our
state-of-the-art results (particularly at high IoU thresholds) on the Pascal
VOC and Cityscapes datasets.Comment: CVPR 201
Money in Gas-Like Markets: Gibbs and Pareto Laws
We consider the ideal-gas models of trading markets, where each agent is
identified with a gas molecule and each trading as an elastic or
money-conserving (two-body) collision. Unlike in the ideal gas, we introduce
saving propensity of agents, such that each agent saves a fraction
of its money and trades with the rest. We show the steady-state money
or wealth distribution in a market is Gibbs-like for , has got a
non-vanishing most-probable value for and Pareto-like when
is widely distributed among the agents. We compare these results with
observations on wealth distributions of various countries.Comment: 4 pages, 2 eps figures, in Conference Procedings of International
Conference on "Unconventional Applications of Statistical Physics", Kolkata,
India, March 2003; paper published in Physica Scripta T106 (2003) 3
Productivity, Preferences and UIP deviations in an Open Economy Business Cycle Model
We show that a flex-price two-sector open economy DSGE model can explain the poor degree of international risk sharing and exchange rate disconnect. We use a suite of model evaluation measures and examine the role of (i) traded and non-traded sectors; (ii) financial market incompleteness; (iii)
preference shocks; (iv) deviations from UIP condition for the exchange rates;
and (v) creditor status in net foreign assets. We find that there is a good case for
both traded and non-traded productivity shocks as well as UIP deviations in
explaining the puzzles
Example of a first-order N\'eel to Valence-Bond-Solid transition in two-dimensions
We consider the Heisenberg model with nearest-neighbor interaction
and an additional multi-spin interaction on the square lattice. The
term consists of three bond-singlet projectors and is chosen to favor the
formation of a valence-bond solid (VBS) where the valence bonds (singlet pairs)
form a staggered pattern. The model exhibits a quantum phase transition from
the N\'eel state to the VBS as a function of . We study the model using
quantum Monte Carlo (stochastic series expansion) simulations. The N\'eel-VBS
transition in this case is strongly first-order in nature, in contrast to
similar previously studied models with continuous transitions into columnar VBS
states. The qualitatively different transitions illustrate the important role
of an emerging U(1) symmetry in the latter case, which is not possible in the
present model due to the staggered VBS pattern (which does not allow local
fluctuations necessary to rotate the local VBS order parameter).Comment: 8 pages, 7 figure
Superfluid Insulator Transitions of Hard-Core Bosons on the Checkerboard Lattice
We study hard-core bosons on the checkerboard lattice with nearest neighbour
unfrustrated hopping and `tetrahedral' plaquette charging energy .
Analytical arguments and Quantum Monte Carlo simulations lead us to the
conclusion that the system undergoes a zero temperature () quantum phase
transition from a superfluid phase at small to a large Mott
insulator phase with = 1/4 for a range of values of the chemical
potential . Further, the quarter-filled insulator breaks lattice
translation symmetry in a characteristic four-fold ordering pattern, and
occupies a lobe of finite extent in the - phase diagram. A Quantum
Monte-Carlo study slightly away from the tip of the lobe provides evidence for
a direct weakly first-order superfluid-insulator transition away from the tip
of the lobe. While analytical arguments leads us to conclude that the
transition {\em at} the tip of the lobe belongs to a different landau-forbidden
second-order universality class, an extrapolation of our numerical results
suggests that the size of the first-order jump does not go to zero even at the
tip of the lobe.Comment: published versio
Metrics with Galilean Conformal Isometry
The Galilean Conformal Algebra (GCA) arises in taking the non-relativistic
limit of the symmetries of a relativistic Conformal Field Theory in any
dimensions. It is known to be infinite-dimensional in all spacetime dimensions.
In particular, the 2d GCA emerges out of a scaling limit of linear combinations
of two copies of the Virasoro algebra. In this paper, we find metrics in
dimensions greater than two which realize the finite 2d GCA (the global part of
the infinite algebra) as their isometry by systematically looking at a
construction in terms of cosets of this finite algebra. We list all possible
sub-algebras consistent with some physical considerations motivated by earlier
work in this direction and construct all possible higher dimensional
non-degenerate metrics. We briefly study the properties of the metrics
obtained. In the standard one higher dimensional "holographic" setting, we find
that the only non-degenerate metric is Minkowskian. In four and five
dimensions, we find families of non-trivial metrics with a rather exotic
signature. A curious feature of these metrics is that all but one of them are
Ricci-scalar flat.Comment: 20 page
Holistic, Instance-Level Human Parsing
Object parsing -- the task of decomposing an object into its semantic parts
-- has traditionally been formulated as a category-level segmentation problem.
Consequently, when there are multiple objects in an image, current methods
cannot count the number of objects in the scene, nor can they determine which
part belongs to which object. We address this problem by segmenting the parts
of objects at an instance-level, such that each pixel in the image is assigned
a part label, as well as the identity of the object it belongs to. Moreover, we
show how this approach benefits us in obtaining segmentations at coarser
granularities as well. Our proposed network is trained end-to-end given
detections, and begins with a category-level segmentation module. Thereafter, a
differentiable Conditional Random Field, defined over a variable number of
instances for every input image, reasons about the identity of each part by
associating it with a human detection. In contrast to other approaches, our
method can handle the varying number of people in each image and our holistic
network produces state-of-the-art results in instance-level part and human
segmentation, together with competitive results in category-level part
segmentation, all achieved by a single forward-pass through our neural network.Comment: Poster at BMVC 201
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