30,184 research outputs found
The Jackiw-Pi model and its symmetries
The non-Abelian gauge model proposed by Jackiw and Pi, which generates an
even-parity mass term in three space-time dimensions, is revisited in this
letter. All the symmetries of the model are collected and established by means
of BRS invariance and Slavnov-Taylor identity. The path for the perturbatively
quantization of the Jackiw-Pi model, through the algebraic method of
renormalization, is presented.Comment: 5 page
Flavor constraints on electroweak ALP couplings
We explore the signals of axion-like particles (ALPs) in flavor-changing
neutral current (FCNC) processes. The most general effective linear Lagrangian
for ALP couplings to the electroweak bosonic sector is considered, and its
contribution to FCNC decays is computed up to one-loop order. The interplay
between the different couplings opens new territory for experimental
exploration, as analyzed here in the ALP mass range GeV.
When kinematically allowed, decays provide the most
stringent constraints for channels with invisible final states, while -meson
decays are more constraining for visible decay channels, such as displaced
vertices in data. The complementarity with
collider constraints is discussed as well.Comment: 12 pages, 6 figure
Quantum Baker Maps for Spiraling Chaotic Motion
We define a coupling of two baker maps through a pi/2 rotation both in
position and in momentum. The classical trajectories thus exhibit spiraling, or
loxodromic motion, which is only possible for conservative maps of at least two
degrees of freedom. This loxodromic baker map is still hyperbolic, that is,
fully chaotic. Quantization of this map follows on similar lines to other
generalized baker maps. It is found that the eigenvalue spectrum for quantum
loxodromic baker map is far removed from those of the canonical random matrix
ensembles. An investigation of the symmetries of the loxodromic baker map
reveals the cause of this deviation from the Bohigas-Giannoni-Schmit
conjecture
Vintage Capital and the Dynamics of the AK Model
This paper analyzes the equilibrium dynamics of an AK-type endogenous growth model with vintage capital. The inclusion of vintage capital leads to oscillatory dynamics governed by replacement echoes, which additionally influence the intercept of the balanced growth path. These features, which are in sharp contrast to those from the standard AK model, can contribute to explaining the short-run deviations observed between investment and growth rates time series. To characterize the convergence properties and the dynamics of the model we develop analytical and numerical methods that should be of interest for the general resolution of endogenous growth models with vintage capital.
An Adaptive Sampling Scheme to Efficiently Train Fully Convolutional Networks for Semantic Segmentation
Deep convolutional neural networks (CNNs) have shown excellent performance in
object recognition tasks and dense classification problems such as semantic
segmentation. However, training deep neural networks on large and sparse
datasets is still challenging and can require large amounts of computation and
memory. In this work, we address the task of performing semantic segmentation
on large data sets, such as three-dimensional medical images. We propose an
adaptive sampling scheme that uses a-posterior error maps, generated throughout
training, to focus sampling on difficult regions, resulting in improved
learning. Our contribution is threefold: 1) We give a detailed description of
the proposed sampling algorithm to speed up and improve learning performance on
large images. We propose a deep dual path CNN that captures information at fine
and coarse scales, resulting in a network with a large field of view and high
resolution outputs. We show that our method is able to attain new
state-of-the-art results on the VISCERAL Anatomy benchmark
Optical frequency comb generation from a monolithic microresonator
Optical frequency combs provide equidistant frequency markers in the
infrared, visible and ultra-violet and can link an unknown optical frequency to
a radio or microwave frequency reference. Since their inception frequency combs
have triggered major advances in optical frequency metrology and precision
measurements and in applications such as broadband laser-based gas sensing8 and
molecular fingerprinting. Early work generated frequency combs by intra-cavity
phase modulation while to date frequency combs are generated utilizing the
comb-like mode structure of mode-locked lasers, whose repetition rate and
carrier envelope phase can be stabilized. Here, we report an entirely novel
approach in which equally spaced frequency markers are generated from a
continuous wave (CW) pump laser of a known frequency interacting with the modes
of a monolithic high-Q microresonator13 via the Kerr nonlinearity. The
intrinsically broadband nature of parametric gain enables the generation of
discrete comb modes over a 500 nm wide span (ca. 70 THz) around 1550 nm without
relying on any external spectral broadening. Optical-heterodyne-based
measurements reveal that cascaded parametric interactions give rise to an
optical frequency comb, overcoming passive cavity dispersion. The uniformity of
the mode spacing has been verified to within a relative experimental precision
of 7.3*10(-18).Comment: Manuscript and Supplementary Informatio
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