247 research outputs found
Time Delay Effects on Coupled Limit Cycle Oscillators at Hopf Bifurcation
We present a detailed study of the effect of time delay on the collective
dynamics of coupled limit cycle oscillators at Hopf bifurcation. For a simple
model consisting of just two oscillators with a time delayed coupling, the
bifurcation diagram obtained by numerical and analytical solutions shows
significant changes in the stability boundaries of the amplitude death, phase
locked and incoherent regions. A novel result is the occurrence of amplitude
death even in the absence of a frequency mismatch between the two oscillators.
Similar results are obtained for an array of N oscillators with a delayed mean
field coupling and the regions of such amplitude death in the parameter space
of the coupling strength and time delay are quantified. Some general analytic
results for the N tending to infinity (thermodynamic) limit are also obtained
and the implications of the time delay effects for physical applications are
discussed.Comment: 20 aps formatted revtex pages (including 13 PS figures); Minor
changes over the previous version; To be published in Physica
Dynamics of a Limit Cycle Oscillator under Time Delayed Linear and Nonlinear Feedbacks
We study the effects of time delayed linear and nonlinear feedbacks on the
dynamics of a single Hopf bifurcation oscillator. Our numerical and analytic
investigations reveal a host of complex temporal phenomena such as phase slips,
frequency suppression, multiple periodic states and chaos. Such phenomena are
frequently observed in the collective behavior of a large number of coupled
limit cycle oscillators. Our time delayed feedback model offers a simple
paradigm for obtaining and investigating these temporal states in a single
oscillator.We construct a detailed bifurcation diagram of the oscillator as a
function of the time delay parameter and the driving strengths of the feedback
terms. We find some new states in the presence of the quadratic nonlinear
feedback term with interesting characteristics like birhythmicity, phase
reversals, radial trapping, phase jumps and spiraling patterns in the amplitude
space. Our results may find useful applications in physical, chemical or
biological systems.Comment: VERSION 4: Fig. 10(d) added, an uncited reference removed; (To appear
in Physica D) (17 pages, 21 figures, two column, aps RevTeX); VERSION 3:
Revised. In Section 2, small tau approximation added; Section 3 is divided
into subsections; periodic solution discussed in detail; Figs. 7 and 11
discarded; Figs. 12 and 14 altered; three new figures (now Figs. 10, 11 and
21) added. VERSION 2: Figs. 1 and 2 replace
Antideuteron and deuteron production in mid-central Pb+Pb collisions at 158 GeV
Production of deuterons and antideuterons was studied by the NA49 experiment
in the 23.5% most central Pb+Pb collisions at the top SPS energy of
=17.3 GeV. Invariant yields for and were measured
as a function of centrality in the center-of-mass rapidity range .
Results for together with previously published
measurements are discussed in the context of the coalescence model. The
coalescence parameters were deduced as a function of transverse momentum
and collision centrality.Comment: 9 figure
Biological aspects of the leafminer Liriomyza sativae (Diptera: Agromyzidae) on melon (Cucumis melo L.)
High p_T Spectra of Identified Particles Produced in Pb+Pb Collisions at 158GeV/nucleon Beam Energy
Transverse momentum spectra of pi^{+/-}, p, pbar, K^{+/-}, K^0_s and Lambda
at midrapidity were measured at high p_T in Pb+Pb collisions at 158GeV/nucleon
beam energy by the NA49 experiment. Particle yield ratios (p/pi, K/pi and
Lambda/K^0_s) show an enhancement of the baryon/meson ratio for p_T>2GeV/c. The
nuclear modification factor R_{CP} is extracted and compared to RHIC
measurements and pQCD calculations.Comment: Quark Matter 2005 parallel section proceeding
High p_T Spectra of Identified Particles Produced in Pb+Pb Collisions at 158A GeV Beam Energy
Results of the NA49 collaboration on the production of hadrons with large
transverse momentum in Pb+Pb collisions at 158A GeV beam energy are presented.
A range up to p_T = 4 GeV/c is covered. The nuclear modification factor R_CP is
extracted for pions, kaons and protons, and the baryon to meson ratios p/pi+,
pbar/pi- and Lambda/K^0_s are studied. All results are compared to other
measurements at SPS and RHIC and to theoretical calculations.Comment: Submitted to J. Phys. G (Proceedings of the 9th International
Conference on Strangeness in Quark Matter, Los Angeles, USA, March 26-31,
2006). 5 pages, 3 figure
Strangeness production at SPS energies
We present a summary of measurements of strange particles performed by the
experiment NA49 in central and minimum bias Pb+Pb collisions in the beam energy
range 20A - 158A GeV. New results on Xi production in central Pb+Pb collisions
and on Lambda, Xi production in minimum bias collisions are shown. Transverse
mass spectra and rapidity distributions of strange particles at different
energies are compared. The energy dependence of the particle yields and ratios
is discussed. NA49 measurements of the Lambda and Xi enhancement factors are
shown for the first time.Comment: Submitted to J. Phys. G (Proceedings of the 9th International
Conference on Strangeness in Quark Matter, Los Angeles, USA, March 26-31,
2006). 9 pages, 9 figure
Single Spin Asymmetry in Polarized Proton-Proton Elastic Scattering at GeV
We report a high precision measurement of the transverse single spin
asymmetry at the center of mass energy GeV in elastic
proton-proton scattering by the STAR experiment at RHIC. The was measured
in the four-momentum transfer squared range \GeVcSq, the region of a significant interference between the
electromagnetic and hadronic scattering amplitudes. The measured values of
and its -dependence are consistent with a vanishing hadronic spin-flip
amplitude, thus providing strong constraints on the ratio of the single
spin-flip to the non-flip amplitudes. Since the hadronic amplitude is dominated
by the Pomeron amplitude at this , we conclude that this measurement
addresses the question about the presence of a hadronic spin flip due to the
Pomeron exchange in polarized proton-proton elastic scattering.Comment: 12 pages, 6 figure
Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV
We report a measurement of the longitudinal double-spin asymmetry A_LL and
the differential cross section for inclusive Pi0 production at midrapidity in
polarized proton collisions at sqrt(s) = 200 GeV. The cross section was
measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be
in good agreement with a next-to-leading order perturbative QCD calculation.
The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T <
11 GeV/c and excludes a maximal positive gluon polarization in the proton. The
mean transverse momentum fraction of Pi0's in their parent jets was found to be
around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC
High non-photonic electron production in + collisions at = 200 GeV
We present the measurement of non-photonic electron production at high
transverse momentum ( 2.5 GeV/) in + collisions at
= 200 GeV using data recorded during 2005 and 2008 by the STAR
experiment at the Relativistic Heavy Ion Collider (RHIC). The measured
cross-sections from the two runs are consistent with each other despite a large
difference in photonic background levels due to different detector
configurations. We compare the measured non-photonic electron cross-sections
with previously published RHIC data and pQCD calculations. Using the relative
contributions of B and D mesons to non-photonic electrons, we determine the
integrated cross sections of electrons () at 3 GeV/10 GeV/ from bottom and charm meson decays to be = 4.0({\rm
stat.})({\rm syst.}) nb and =
6.2({\rm stat.})({\rm syst.}) nb, respectively.Comment: 17 pages, 17 figure
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