18,981 research outputs found
Towards Distributed Convoy Pattern Mining
Mining movement data to reveal interesting behavioral patterns has gained
attention in recent years. One such pattern is the convoy pattern which
consists of at least m objects moving together for at least k consecutive time
instants where m and k are user-defined parameters. Existing algorithms for
detecting convoy patterns, however do not scale to real-life dataset sizes.
Therefore a distributed algorithm for convoy mining is inevitable. In this
paper, we discuss the problem of convoy mining and analyze different data
partitioning strategies to pave the way for a generic distributed convoy
pattern mining algorithm.Comment: SIGSPATIAL'15 November 03-06, 2015, Bellevue, WA, US
The I^G J^{PC}=1^- 1^{-+} Tetraquark States
We study the tetraquark states with I^G J^{PC}=1^- 1^{-+} in the QCD sum
rule. After exhausting all possible flavor structures, we analyses both the SVZ
and finite energy sum rules. Both approaches lead to a mass around 1.6 GeV for
the state with the quark contents q q q_bar q_bar, and around 2.0 GeV for the
state with the quark contents q s q_bar s_bar. The flavor structure 3_bar *
6_bar + 6 * 3 is preferred. Our analysis strongly indicates that both pi1(1600)
and pi1(2015) are also compatible with the exotic tetraquark interpretation,
which are sometimes labeled as candidates of the 1^{-+} hybrid mesons. Moreover
one of their dominant decay modes is a pair of axial-vector and pseudoscalar
mesons such as b1(1235) pi, which is sometimes considered as the characteristic
decay mode of the hybrid mesons.Comment: 18 pages, 14 figures, revised version to appear in Phys. Rev.
Revisiting f(R) gravity models that reproduce CDM expansion
We reconstruct an gravity model that gives rise to the particular
CDM background evolution of the universe. We find well-defined,
real-valued analytical forms for the model to describe the universe both
in the early epoch from the radiation to matter dominated eras and the late
time acceleration period. We further examine the viability of the derived
model and find that it is viable to describe the evolution of the
universe in the past and there does not exist the future singularity in the
Lagrangian.Comment: 7 pages, 2 figures, revised version, accepted for publication in PR
Exotic Tetraquark ud bar[s] bar[s] of J^P=0^+ in the QCD Sum Rule
We study a QCD sum rule analysis for an exotic tetraquark ud bar[s] bar[s] of
J^P=0^+ and I = 1. We construct q q bar[q] bar[q] currents in a local product
form and find that there are five independent currents for this channel. Due to
high dimensional nature of the current, it is not easy to form a good sum rule
when using a single current. This means that we do not find any sum rule window
to extract reliable results, due to the insufficient convergence of the OPE and
to the exceptional important role of QCD continuum. Then we examine sum rules
by using currents of linear combinations of two currents among the independent
ones. We find two reasonable cases that predict a mass of the tetraquark around
1.5 GeV.Comment: 15 pages, 8 figures, revised versio
Light Scalar Tetraquark Mesons in the QCD Sum Rule
We study the lowest-lying scalar mesons in the QCD sum rule by considering
them as tetraquark states. We find that there are five independent currents for
each state with a certain flavor structure. By forming linear combinations, we
find that some mixed currents give reliable QCD sum rules. Among various
tetraquark currents, we consider those which are constructed by the diquarks
having anti-symmetric and symmetric flavor structures. That the results of the
QCD sum rule derived from the two types of currents are similar suggests that
the tetraquark states can have a large mixing between different flavor
structures.Comment: 18 pages, 5 figures; reference added, minor corrections; version to
appear in Phys.Rev.
QCD Effects in High Energy Processes
In this talk, some important QCD effects in Higgs physics, supersymmetry and
top physics, as well as the factorization and resummation techniques in QCD are
reviewed.Comment: LaTeX, 13 pages, uses ws-ijmpa.cls. Based on an invited talk at the
International Conference on QCD and Hadronic Physics, Beijing, China, June
16--20, 2005. Minor change
Statistical study of the conductance and shot noise in open quantum-chaotic cavities: Contribution from whispering gallery modes
In the past, a maximum-entropy model was introduced and applied to the study
of statistical scattering by chaotic cavities, when short paths may play an
important role in the scattering process. In particular, the validity of the
model was investigated in relation with the statistical properties of the
conductance in open chaotic cavities. In this article we investigate further
the validity of the maximum-entropy model, by comparing the theoretical
predictions with the results of computer simulations, in which the Schroedinger
equation is solved numerically inside the cavity for one and two open channels
in the leads; we analyze, in addition to the conductance, the zero-frequency
limit of the shot-noise power spectrum. We also obtain theoretical results for
the ensemble average of this last quantity, for the orthogonal and unitary
cases of the circular ensemble and an arbitrary number of channels. Generally
speaking, the agreement between theory and numerics is good. In some of the
cavities that we study, short paths consist of whispering gallery modes, which
were excluded in previous studies. These cavities turn out to be all the more
interesting, as it is in relation with them that we found certain systematic
discrepancies in the comparison with theory. We give evidence that it is the
lack of stationarity inside the energy interval that is analyzed, and hence the
lack of ergodicity that gives rise to the discrepancies. Indeed, the agreement
between theory and numerical simulations is improved when the energy interval
is reduced to a point and the statistics is then collected over an ensemble. It
thus appears that the maximum-entropy model is valid beyond the domain where it
was originally derived. An understanding of this situation is still lacking at
the present moment.Comment: Revised version, minor modifications, 28 pages, 7 figure
- …