2,209 research outputs found
Superconducting cosmic strings as sources of cosmological fast radio bursts
In this paper we calculate the radio burst signals from three kinds of
structures of superconducting cosmic strings. By taking into account the
observational factors including scattering and relativistic effects, we derive
the event rate of radio bursts as a function of redshift with the theoretical
parameters and of superconducting strings. Our analyses
show that cusps and kinks may have noticeable contributions to the event rate
and in most cases cusps would dominate the contribution, while the kink-kink
collisions tend to have secondary effects. By fitting theoretical predictions
with the normalized data of fast radio bursts, we for the first time constrain
the parameter space of superconducting strings and report that the parameter
space of and fit the observation well although the statistic
significance is low due to the lack of observational data. Moreover, we derive
two types of best fittings, with one being dominated by cusps with a redshift
, and the other dominated by kinks at the range of the maximal event
rate.Comment: 13 pages, 2 figures, 1 table; references update
Na4Ir3O8 as a 3D spin liquid with fermionic spinons
Spin liquid states for spin-1/2 antiferromagnetic Heisenberg model on a
hyperkagome lattice are studied. We classify and study flux states according to
symmetries. Applying this model to Na4Ir3O8, we propose that the high
temperature state may be described by a spinon Fermi surface, which forms a
paired state with line nodes below 20 K. The possible mixed spin singlet and
spin triplet pairing states are discussed according to the lattice symmetry
which breaks inversion.Comment: final versio
Interference of Two-Dimensional Bose-Einstein Condensates in Micro-Gravity
We investigate the interference of two-dimensional Bose-Einstein condensates
in micro-gravity, which influenced by the interaction strength, initial
momentum, gravitational potential and phase difference. We demonstrate that the
gravitational potential from the Earth can change the density distribution and
phase distribution of the condensate's wave function. As time evolves, a
portion of the gravitational potential energy of the microscopic particles can
be converted into kinetic energy, which changes the motion of the microscopic
particles, and leads to the varying of the density and phase distribution of
the wave function. Nevertheless, the influences of the Earth's gravity on the
wave function can be eliminated by the micro-gravity environment, which
confirmed by many micro-gravity cold atom experiments. Our results present the
influences of gravity and other parameters on interference of Bose-Einstein
condensates, which help us to reveal the intrinsic natures of the related
theoretical predictions and experimental phenomena. Furthermore, our work
builds a bridge between the related physical phenomena and our physical
intuition about the Bose-Einstein condensates in micro-gravity environment
The contribution of T2 relaxation time to diffusion MRI quantification and its clinical implications: a hypothesis
Considering liver as the reference, that both fast diffusion (PF) and slow
diffusion (Dslow) of the spleen are much underestimated is likely due to the
MRI properties of the spleen such as the much longer T2 relaxation time. It is
possible that longer T2 relaxation time partially mitigates the signal decay
effect of various gradients on diffusion weighted image. This phenomenon will
not be limited to the spleen. Most liver tumors have a longer T2 relaxation
time than their native normal tissue and this is considered to be associated
with oedema. On the other hand, most tumors are measured with lower MRI
diffusion (despite being oedematous). The reason why malignant tumors have
lower diffusion value [apparent diffusion coefficient (ADC) and Dslow] are
poorly understood but has been proposed to be related to a combination of
higher cellularity, tissue disorganization, and increased extracellular space
tortuosity. These explanations may be true, but it is also possible to that
many tumors have MRI properties similar to the spleen such as longer T2
(relative to the liver) and these MRI properties may also contribute to the
lower MRI measured ADC and Dslow . In other words, if we could hypothetically
plant a piece of spleen tissue in the liver, MRI would recognize this planted
spleen tissue as being similar to a tumor and measure it to have lower
diffusion than the liver
A Note on Scalar-Valued Gap Functions for Generalized Vector Variational Inequalities
This paper is concerned with gap functions of generalized vector variational inequalities (GVVI). By using scalarization approach, scalar-valued variational inequalities of (GVVI) are introduced. Some relationships between the solutions of (GVVI) and its scalarized versions are established. Then, by using these relationships and some mild conditions, scalar-valued gap functions for (GVVI) are established
Nighttime Thermal Infrared Image Colorization with Feedback-based Object Appearance Learning
Stable imaging in adverse environments (e.g., total darkness) makes thermal
infrared (TIR) cameras a prevalent option for night scene perception. However,
the low contrast and lack of chromaticity of TIR images are detrimental to
human interpretation and subsequent deployment of RGB-based vision algorithms.
Therefore, it makes sense to colorize the nighttime TIR images by translating
them into the corresponding daytime color images (NTIR2DC). Despite the
impressive progress made in the NTIR2DC task, how to improve the translation
performance of small object classes is under-explored. To address this problem,
we propose a generative adversarial network incorporating feedback-based object
appearance learning (FoalGAN). Specifically, an occlusion-aware mixup module
and corresponding appearance consistency loss are proposed to reduce the
context dependence of object translation. As a representative example of small
objects in nighttime street scenes, we illustrate how to enhance the realism of
traffic light by designing a traffic light appearance loss. To further improve
the appearance learning of small objects, we devise a dual feedback learning
strategy to selectively adjust the learning frequency of different samples. In
addition, we provide pixel-level annotation for a subset of the Brno dataset,
which can facilitate the research of NTIR image understanding under multiple
weather conditions. Extensive experiments illustrate that the proposed FoalGAN
is not only effective for appearance learning of small objects, but also
outperforms other image translation methods in terms of semantic preservation
and edge consistency for the NTIR2DC task.Comment: 14 pages, 14 figures. arXiv admin note: text overlap with
arXiv:2208.0296
W boson mass in the NP models with extra gauge group
The precise measurement of the W boson mass is closely related to the
contributions of new physics (NP), which can significantly constrain the
parameter space of NP models, particularly those with an additional
local gauge group. The inclusion of a new gauge boson and gauge couplings
in these models can contribute to the oblique parameters , , and W
boson mass at tree level. Taking into account the effects of kinetic mixing, we
calculate and analyze the oblique parameters , , and W boson mass in
such NP models in this study. It is found that the kinetic mixing effects can
make significant contributions to the W boson mass, which can satisfy the
recently measured W boson mass at CDF II or ATLAS by choosing appropriate
values of gauge coupling constants and extra group charges of leptons or
scalar doublets. In addition, if the leptonic Yukawa couplings are invariant
under the extra local gauge group, these contributions can be eliminated
by redefining the gauge boson fields through eliminating the neutral currents
involving charged leptons, even with nonzero kinetic mixing effects.Comment: 11 pages, 2 figure
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