1,841 research outputs found
Scalar induced gravitational waves in symmetric teleparallel gravity with a parity-violating term
Gravitational waves (GWs) are useful to test gravitational theories and to
probe the physics in the early universe. In this paper, we investigate the
scalar induced gravitational waves (SIGWs) in symmetric teleparallel gravity
with a parity-violating term. The presence of the parity-violating term leads
to the velocity birefringence effect of the SIGWs. However, after taking into
account the observational constraints on the speed of GWs, the contribution
from the parity-violating term to SIGWs is negligible. Nevertheless, the
contribution to SIGWs from the perturbations of the connection can be
significant, and results in a multipeak structure in the energy density of
SIGWs. This feature makes the symmetric teleparallel gravity distinguishable
from the general relativity.Comment: 32 pages,2 figure
Scalar induced gravitational waves from Chern-Simons gravity during inflation era
We investigate the scalar induced gravitational waves (SIGWs) in the
Chern-Simons (CS) gravity with a dynamical scalar field during slow roll
inflation. Due to the parity violation in the CS term, the SIGWs are generally
polarized, which are effectively characterized by the degree of circular
polarization. We derive the semianalytic expression to evaluate the power
spectra and the degree of circular polarization of the SIGWs, which receive
contributions from the general relativity and the parity-violating term,
respectively. We find that the correction from the parity-violating CS term is
negligible on large scales, which means that the degree of circular
polarization of SIGWs is very small.Comment: 23 pages, references added, and a new discussion about a linear
coupling function added. Version to be published in JCA
Detection-driven exposure-correction network for nighttime drone-view object detection.
Drone-view object detection (DroneDet) models typically suffer a significant performance drop when applied to nighttime scenes. Existing solutions attempt to employ an exposure-adjustment module to reveal objects hidden in dark regions before detection. However, most exposure-adjustment models are only optimized for human perception, where the exposure-adjusted images may not necessarily enhance recognition. To tackle this issue, we propose a novel Detection-driven Exposure-Correction network for nighttime DroneDet, called DEDet. The DEDet conducts adaptive, non-linear adjustment of pixel values in a spatially fine-grained manner to generate DroneDet-friendly images. Specifically, we develop a Fine-grained Parameter Predictor (FPP) to estimate pixel-wise parameter maps of the image filters. These filters, along with the estimated parameters, are used to adjust pixel values of the low-light image based on non-uniform illuminations in drone-captured images. In order to learn the non-linear transformation from the original nighttime images to their DroneDet-friendly counterparts, we propose a Progressive Filtering module that applies recursive filters to iteratively refine the exposed image. Furthermore, to evaluate the performance of the proposed DEDet, we have built a dataset NightDrone to address the scarcity of the datasets specifically tailored for this purpose. Extensive experiments conducted on four nighttime datasets show that DEDet achieves a superior accuracy compared with the state-of-the-art methods. Furthermore, ablation studies and visualizations demonstrate the validity and interpretability of our approach. Our NightDrone dataset can be downloaded from https://github.com/yuexiemail/NightDrone-Dataset
The NN phase shifts in the extended quark-delocalization, color-screening model
An alternative method is applied to the study of nucleon-nucleon(NN)
scattering phase shifts in the framework of extended quark delocalization,
color-screening model(QDCSM), where the one-pion-exchange(OPE) with short-range
cutoff is included.Comment: 5 pages, 3 figures, two-colum
Cold hybrid electrical-optical ion trap
Advances in research such as quantum information and quantum chemistry
require subtle methods for trapping particles (including ions, neutral atoms,
molecules, etc.). Here we propose a hybrid ion trapping method by combining a
Paul trap with optical tweezers. The trap combines the advances of the
deep-potential feature for the Paul trap and the micromotion-free feature for
the optical dipole trap. By modulating the optical-dipole trap synchronously
with the radio frequency voltage of the Paul trap, the alternating electrical
force in the trap center is fully counteracted, and the micromotion temperature
of a cold trapped ion can reach the order of nK while the trap depth is beyond
300K. These features will enable cold collisions between an ion and an atom in
the -wave regime and stably trap the produced molecular ion in the cold
hybrid system. This will provide a unique platform for probing the interactions
between the ions and the surrounding neutral particles and enable the
investigation of new reaction pathways and reaction products in the cold
regime
Optimized detector tomography for photon-number resolving detectors with hundreds of pixels
Photon-number resolving detectors with hundreds of pixels are now readily
available, while the characterization of these detectors using detector
tomography is computationally intensive. Here, we present a modified detector
tomography model that reduces the number of variables that need optimization.
To evaluate the effectiveness and accuracy of our model, we reconstruct the
photon number distribution of optical coherent and thermal states using the
expectation-maximization-entropy algorithm. Our results indicate that the
fidelity of the reconstructed states remains above 99%, and the second and
third-order correlations agree well with the theoretical values for a mean
number of photons up to 100. We also investigate the computational resources
required for detector tomography and find out that our approach reduces the
solving time by around a half compared to the standard detector tomography
approach, and the required memory resources are the main obstacle for detector
tomography of a large number of pixels. Our results suggest that detector
tomography is viable on a supercomputer with 1~TB RAM for detectors with up to
340 pixels
Isolation, Identification and Determination of Six Nucleosides and Two Amino Acids from Bamboo Shoots of Gramineae Phyllostachys prominens (W Y Xiong)
Purpose: To develop a method to identify and quantify the compounds in the shoots of four Phyllostachys bamboo species (Gramineae Phyllostachys prominens W. Y. Xiong, Gramineae Phyllostachys iridescins C. Y. Yao Gramineae Phyllostachys pubescens (Carr.) Mitford, Gramineae Phyllostachys praecox C. D. Chu et C. S. Chao. ).Methods: The compounds in bamboo shoots were isolated and identified by ultraviolet (UV) spectroscopy, mass spectrometry (MS), and nuclear magnetic resonance (NMR). Quantitative analysis was performed by reversed-phase high performance liquid chromatography (RP-HPLC) using a C18 column and a mixture (1:1ratio) of acetonitrile and 15 mM ammonium acetate (pH 6.0) as mobile phase. This method was validated for its reproducibility, chemical stability, and recovery.Results: Six nucleosides and two amino acids were isolated from bamboo shoots, including guanosine, 2’-deoxyguanosine, adenosine, thymidine, uridine, cytidine, tryptophan, and phenylalanine. The HPLC method was rapid and reproducible. The intraday and interday concentrations of the eight identified compounds showed good linearity in the range of 0.22 - 60.00 μg/mL. The relative standard deviation (RSD) for intraday and interday precision for reproducibility and stability was < 3 %. The validated method was successfully applied to determine the content of the eight compounds in four different Phyllostachys species.Conclusion: Adenosine was isolated from bamboo shoots previously, but the isolation of the other seven compounds are reported here for the first time. The method proposed is sensitive and reproducible, and would facilitate studies of nutritional/medicinal compounds in bamboo shoot.Keywords: Bamboo shoots, Phyllostachys prominens, Guanosine, 2’ Deoxyguanosine, Adenosine, Thymidine, Uridine, Cytidine, Tryptophan, Phenylalanin
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