1,110,637 research outputs found
Focus Is All You Need: Loss Functions For Event-based Vision
Event cameras are novel vision sensors that output pixel-level brightness
changes ("events") instead of traditional video frames. These asynchronous
sensors offer several advantages over traditional cameras, such as, high
temporal resolution, very high dynamic range, and no motion blur. To unlock the
potential of such sensors, motion compensation methods have been recently
proposed. We present a collection and taxonomy of twenty two objective
functions to analyze event alignment in motion compensation approaches (Fig.
1). We call them Focus Loss Functions since they have strong connections with
functions used in traditional shape-from-focus applications. The proposed loss
functions allow bringing mature computer vision tools to the realm of event
cameras. We compare the accuracy and runtime performance of all loss functions
on a publicly available dataset, and conclude that the variance, the gradient
and the Laplacian magnitudes are among the best loss functions. The
applicability of the loss functions is shown on multiple tasks: rotational
motion, depth and optical flow estimation. The proposed focus loss functions
allow to unlock the outstanding properties of event cameras.Comment: 29 pages, 19 figures, 4 table
Overdamped dynamics of a Brownian particle levitated in a Paul trap
We study the dynamics of the center of mass of a Brownian particle levitated
in a Paul trap. We focus on the overdamped regime in the context of
levitodynamics, comparing theory with our numerical simulations and
experimental data from a nanoparticle in a Paul trap. We provide an exact
analytical solution to the stochastic equation of motion, expressions for the
standard deviation of the motion, and thermalization times by using the WKB
method under two different limits. Finally, we prove the power spectral density
of the motion can be approximated by that of an Ornstein-Uhlenbeck process and
use the found expression to calibrate the motion of a trapped particle
Constraints on Covariant Horava-Lifshitz Gravity from frame-dragging experiment
The effects of Horava-Lifshitz corrections to the gravito-magnetic field are
analyzed. Solutions in the weak field, slow motion limit, referring to the
motion of a satellite around the Earth are considered. The post-newtonian
paradigm is used to evaluate constraints on the Horava-Lifshitz parameter space
from current satellite and terrestrial experiments data. In particular, we
focus on GRAVITY PROBE B, LAGEOS and the more recent LARES mission, as well as
a forthcoming terrestrial project, GINGER.Comment: 14 pages, 1 figur
Continuous point symmetries in Group Field Theories
We discuss the notion of symmetries in non-local field theories characterized
by integro-differential equations of motion, from a geometric perspective. We
then focus on Group Field Theory (GFT) models of quantum gravity and provide a
general analysis of their continuous point symmetry transformations, including
the generalized conservation laws following from them
Non-Volkov solutions for a charge in a plane wave
We focus our attention, once again, on the Klein--Gordon and Dirac equations
with a plane-wave field. We recall that for the first time a set of solutions
of these equations was found by Volkov. The Volkov solutions are widely used in
calculations of quantum effects with electrons and other elementary particles
in laser beams. We demonstrate that one can construct sets of solutions which
differ from the Volkov solutions and which may be useful in physical
applications. For this purpose, we show that the transversal charge motion in a
plane wave can be mapped by a special transformation to transversal free
particle motion. This allows us to find new sets of solutions where the
transversal motion is characterized by quantum numbers different from Volkov's
(in the Volkov solutions this motion is characterized by the transversal
momentum). In particular, we construct solutions with semiclassical transversal
charge motion (transversal squeezed coherent states). In addition, we
demonstrate how the plane-wave field can be eliminated from the transversal
charge motion in a more complicated case of the so-called combined
electromagnetic field (a combination of a plane-wave field and constant
colinear electric and magnetic fields). Thus, we find new sets of solutions of
the Klein--Gordon and Dirac equations with the combined electromagnetic field.Comment: LaTex file, 14 page
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