841 research outputs found
Pattern formation in oscillatory complex networks consisting of excitable nodes
Oscillatory dynamics of complex networks has recently attracted great
attention. In this paper we study pattern formation in oscillatory complex
networks consisting of excitable nodes. We find that there exist a few center
nodes and small skeletons for most oscillations. Complicated and seemingly
random oscillatory patterns can be viewed as well-organized target waves
propagating from center nodes along the shortest paths, and the shortest loops
passing through both the center nodes and their driver nodes play the role of
oscillation sources. Analyzing simple skeletons we are able to understand and
predict various essential properties of the oscillations and effectively
modulate the oscillations. These methods and results will give insights into
pattern formation in complex networks, and provide suggestive ideas for
studying and controlling oscillations in neural networks.Comment: 15 pages, 7 figures, to appear in Phys. Rev.
Transitions To the Long-Resident State in coupled chaotic oscillators
The behaviors of coupled chaotic oscillators before complete synchronization
were investigated. We report three phenomena: (1) The emergence of long-time
residence of trajectories besides one of the saddle foci; (2) The tendency that
orbits of the two oscillators get close becomes faster with increasing the
coupling strength; (3) The diffusion of two oscillator's phase difference is
first enhanced and then suppressed. There are exact correspondences among these
phenomena. The mechanism of these correspondences is explored. These phenomena
uncover the route to synchronization of coupled chaotic oscillators.Comment: 3 pages, 5 figure
Precise Measurement of Gravity Variations During a Total Solar Eclipse
The variations of gravity were measured with a high precision LaCoste-Romberg
D gravimeter during a total solar eclipse to investigate the effect of solar
eclipse on the gravitational field. The observed anomaly m/s during the eclipse implies that there may be a shielding
property of gravitation
N N bar,Delta bar N, Delta N bar excitation for the pion propagator in nuclear matter
The particle-hole and Delta -hole excitations are well-known elementary
excitation modes for the pion propagator in nuclear matter. But, the excitation
also involves antiparticles, namely, nucleon-antinucleon, anti-Delta-nucleon
and Delta-antinucleon excitations. These are important for high-energy momentum
as well, and have not been studied before, to our knowledge. In this paper, we
give both the formulas and the numerical calculations for the real and the
imaginary parts of these excitations.Comment: Latex, 3 eps file
Adapting to dynamic stimulus-response values: differential contributions of inferior frontal, dorsomedial, and dorsolateral regions of prefrontal cortex to decision making.
Dorsomedial prefrontal cortex (dmPFC), dorsolateral prefrontal cortex (dlPFC), and inferior frontal gyrus (IFG) have all been implicated in resolving decision conflict whether this conflict is generated by having to select between responses of similar value or by making selections following a reversal in reinforcement contingencies. However, work distinguishing their individual functional contributions remains preliminary. We used functional magnetic resonance imaging to delineate the functional role of these systems with regard to both forms of decision conflict. Within dmPFC and dlPFC, blood oxygen level-dependent responses increased in response to decision conflict regardless of whether the conflict occurred in the context of a reduction in the difference in relative value between objects, or an error following a reversal of reinforcement contingencies. Conjunction analysis confirmed that overlapping regions of dmPFC and dlPFC were activated by both forms of decision conflict. Unlike these regions, however, activity in IFG was not modulated by reductions in the relative value of available options. Moreover, although all three regions of prefrontal cortex showed enhanced activity to reversal errors, only dmPFC and dlPFC were also modulated by the magnitude of value change during the reversal. These data are interpreted with reference to models of dmPFC, dlPFC, and IFG functioning
Determining Heavy Hybrid Masses via QCD Sum Rules
The masses of charmonium and bottomonium hybrids are evaluated in
terms of QCD sum rules. We find that the ground state hybrid in charm sector
lies in GeV, while in bottom sector the hybrid may
situated in GeV. Since the numerical result on
charmonium hybrid mass is not compatible with the charmonium spectra, including
structures newly observed in experiment, we tempt to conclude that such a
hybrid does not purely exist, but rather as an admixture with other states,
like glueball and regular quarkonium, in experimental observation. However, our
result on bottomonium hybrid coincide with the "exotic structure" recently
observed at BELLE.Comment: 15 pages, 5 figures, version to appear in J.Phys.
Constraints on Scalar Dark Matter from Direct Experimental Searches
The standard model (SM) plus a real gauge-singlet scalar field dubbed darkon
(SM+D) is the simplest model possessing a weakly interacting massive particle
(WIMP) dark-matter candidate. The upper limits for the WIMP-nucleon elastic
cross-section as a function of WIMP mass from the recent XENON10 and CDMS-II
experiments rule out darkon mass ranges from 10 to (50,70,75) GeV for
Higgs-boson masses of (120,200,350) GeV, respectively. This may exclude the
possibility of the darkon providing an explanation for the gamma-ray excess
observed in the EGRET data. We show that by extending the SM+D to a
two-Higgs-doublet model plus a darkon the experimental constraints on the
WIMP-nucleon interactions can be circumvented due to suppression occurring at
some values of the product tan(alpha)tan(beta), with alpha being the
neutral-Higgs mixing angle and tan(beta) the ratio of vacuum expectation values
of the Higgs doublets. We also comment on the implication of the darkon model
for Higgs searches at the LHC.Comment: 15 pages, 8 figures, minor changes to match published versio
Some properties of the newly observed X(1835) state at BES
Recently the BES collaboration has announced observation of a resonant state
in the spectrum in
decay. Fitting the data with a state, the mass is determined to be
1833.7 MeV with statistic significance. This state is consistent
with the one extracted from previously reported threshold
enhancement data in . We study the properties of
this state using QCD anomaly and QCD sum rules assuming X(1835) to be a
pseudoscalar and show that it is consistent with data. We find that this state
has a sizeable matrix element leading to branching ratios
of and for
and for , respectively.
Combining the calculated branching ratio of and data on
threshold enhancement in , we determine the
coupling for interaction. We finally study branching ratios of
other decay modes. We find that can provide useful
tests for the mechanism proposed.Comment: 13 pages, 3 figures. The final version to appear at EPJ
A new approach to the exact solutions of the effective mass Schrodinger equation
Effective mass Schrodinger equation is solved exactly for a given potential.
Nikiforov-Uvarov method is used to obtain energy eigenvalues and the
corresponding wave functions. A free parameter is used in the transformation of
the wave function. The effective mass Schrodinger equation is also solved for
the Morse potential transforming to the constant mass Schr\"{o}dinger equation
for a potential. One can also get solution of the effective mass Schrodinger
equation starting from the constant mass Schrodinger equation.Comment: 14 page
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