3,467 research outputs found
Integral Reduction by Unitarity Method for Two-loop Amplitudes: A Case Study
In this paper, we generalize the unitarity method to two-loop diagrams and
use it to discuss the integral bases of reduction. To test out method, we focus
on the four-point double-box diagram as well as its related daughter diagrams,
i.e., the double-triangle diagram and the triangle-box diagram. For later two
kinds of diagrams, we have given complete analytical results in general
(4-2\eps)-dimension.Comment: 52 pages, 1 figur
Twist-3 contributions to processes in perturbative QCD approach
As one of the simplest hadronic processes, () could be a good testing ground for our understanding of
the perturbative and nonperturbative structure of QCD, and will be studied with
high precision at BELLE-\RNum{2} in the near future. In this paper, we revisit
these processes with twist-3 corrections in the perturbative QCD approach based
on the factorization theorem, in which transverse degrees of freedom as
well as resummation effects are taken into account. The influence of the
distribution amplitudes on the cross sections are discussed in detail. Our work
shows that not only the transverse momentum effects but also the twist-3
corrections play a significant role in the processes in the intermediate energy region. Especially in the few GeV
region, the twist-3 contributions become dominant in the cross sections. And it
is noteworthy that both the twist-3 result of the cross
section and that of the cross section agree well with the BELLE
and ALEPH measurements. For the pion and kaon angular distributions, there
still exist discrepancies between our results and the experimental
measurements. Possible reasons for these discrepancies are discussed briefly.Comment: 19 pages, 7 figures and 2 tables. Contents improved and more
discussions adde
AN ANALYSIS OF THE INFLUENCE OF THE INTERNET PLUS ON THE ANXIETY OF COLLEGE STUDENTS IN COLLEGE ENGLISH TEACHING
AN ANALYSIS OF THE INFLUENCE OF THE INTERNET PLUS ON THE ANXIETY OF COLLEGE STUDENTS IN COLLEGE ENGLISH TEACHING
Fluctuation and localization of acoustic waves in bubbly water
Here the fluctuation properties of acoustic localization in bubbly water is
explored. We show that the strong localization can occur in such a system for a
certain frequency range and sufficient filling fractions of air-bubbles. Two
fluctuating quantities are considered, that is, the fluctuation of transmission
and the fluctuation of the phase of acoustic wave fields. When localization
occurs, these fluctuations tend to vanish, a feature able to uniquely identify
the phenomenon of wave localization.Comment: 10 pages, 4 figure
Experimental analysis for the effect of dynamic capillarity on stress transformation in porous silicon
The evolution of real-time stress in porous silicon(PS) during drying is investigated using micro-Raman spectroscopy. The results show that the PS sample underwent non-negligible stress when immersed in liquid and suffered a stress impulsion during drying. Such nonlinear transformation and nonhomogeneneous distribution of stress are regarded as the coupling effects of several physical phenomena attributable to the intricate topological structure of PS. The effect of dynamic capillarity can induce microcracks and even collapse in PSstructures during manufacture and storage.This work is funded by the National Natural Science
Foundation of China Contract Nos. 10732080 and
10502014
StarGO: A New Method to Identify the Galactic Origins of Halo Stars
We develop a new method StarGO (Stars' Galactic Origin) to identify the
galactic origins of halo stars using their kinematics. Our method is based on
self-organizing map (SOM), which is one of the most popular unsupervised
learning algorithms. StarGO combines SOM with a novel adaptive group
identification algorithm with essentially no free parameters. In order to
evaluate our model, we build a synthetic stellar halo from mergers of nine
satellites in the Milky Way. We construct the mock catalogue by extracting a
heliocentric volume of 10 kpc from our simulations and assigning expected
observational uncertainties corresponding to bright stars from Gaia DR2 and
LAMOST DR5. We compare the results from StarGO against that from a
Friends-of-Friends (FoF) based method in the space of orbital energy and
angular momentum. We show that StarGO is able to systematically identify more
satellites and achieve higher number fraction of identified stars for most of
the satellites within the extracted volume. When applied to data from Gaia DR2,
StarGO will enable us to reveal the origins of the inner stellar halo in
unprecedented detail.Comment: 11 pages, 7 figures, Accepted for publication in Ap
Dynamic behavior of an eco-epidemic system with impulsive birth
AbstractIn the paper, we investigate an eco-epidemic system with impulsive birth. The conditions for the stability of infection-free periodic solution are given by applying Floquet theory of linear periodic impulsive equation. And we give the conditions of persistence by constructing a consequence of some abstract monotone iterative schemes. By using the method of coincidence degree, a set of sufficient conditions are derived for the existence of at least one strictly positive periodic solution. Finally, numerical simulation shows that there exists a stable positive periodic solution with a maximum value no larger than a given level. Thus, we can use the stability of the positive periodic solution and its period to control insect pests at acceptably low levels
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