808 research outputs found
Exotic smooth structures and symplectic forms on closed manifolds
We give a short proof of the (known) result that there are no Kaehler
structures on exotic tori. This yields a negative solution to a problem posed
by Benson and Gordon. W discuss the symplectic version of the problem and
analyze results which yield an evidence for the conjecture that there are no
symplectic structures on exotic tori.Comment: AMSLaTeX, 16 pages, a new version. A survey of the symplectic version
of the problem is adde
The Social Climbing Game
The structure of a society depends, to some extent, on the incentives of the
individuals they are composed of. We study a stylized model of this interplay,
that suggests that the more individuals aim at climbing the social hierarchy,
the more society's hierarchy gets strong. Such a dependence is sharp, in the
sense that a persistent hierarchical order emerges abruptly when the preference
for social status gets larger than a threshold. This phase transition has its
origin in the fact that the presence of a well defined hierarchy allows agents
to climb it, thus reinforcing it, whereas in a "disordered" society it is
harder for agents to find out whom they should connect to in order to become
more central. Interestingly, a social order emerges when agents strive harder
to climb society and it results in a state of reduced social mobility, as a
consequence of ergodicity breaking, where climbing is more difficult.Comment: 14 pages, 9 figure
Measurement of the Intrinsic Radiopurity of Cs-137/U-235/U-238/Th-232 in CsI(Tl) Crystal Scintillators
The inorganic crystal scintillator CsI(Tl) has been used for low energy
neutrino and Dark Matter experiments, where the intrinsic radiopurity is an
issue of major importance. Low-background data were taken with a CsI(Tl)
crystal array at the Kuo-Sheng Reactor Neutrino Laboratory. The pulse shape
discrimination capabilities of the crystal, as well as the temporal and spatial
correlations of the events, provide powerful means of measuring the intrinsic
radiopurity of Cs-137 as well as the U-235, U-238 and Th-232 series. The event
selection algorithms are described, with which the decay half-lives of Po-218,
Po-214, Rn-220, Po-216 and Po-212 were derived. The measurements of the
contamination levels, their concentration gradients with the crystal growth
axis, and the uniformity among different crystal samples, are reported. The
radiopurity in the U-238 and Th-232 series are comparable to those of the best
reported in other crystal scintillators. Significant improvements in
measurement sensitivities were achieved, similar to those from dedicated
massive liquid scintillator detector. This analysis also provides in situ
measurements of the detector performance parameters, such as spatial
resolution, quenching factors, and data acquisition dead time.Comment: 28 pages, 12 figure
Solar Hydrogen Burning and Neutrinos
We summarize the current status of laboratory measurements of nuclear cross
sections of the pp chain and CN cycle. We discuss the connections between such
measurements, predictions of solar neutrino fluxes, and the conclusion that
solar neutrinos oscillate before reaching earth.Comment: 34 pages, 6 figure
PNES around the world: Where we are now and how we can close the diagnosis and treatment gaps-an ILAE PNES Task Force report
An international consensus clinical practice statement issued in 2011 ranked psychogenic nonepileptic seizures (PNES) among the top three neuropsychiatric problems. An ILAE PNES Task Force was founded and initially charged with summarizing the current state of the art in terms of diagnosis and treatment, resulting in two publications. The first described different levels of diagnostic certainty. The second summarized current knowledge of management approaches. The present paper summarizes an international workshop of the ILAE PNES Task Force that focused on the current understanding and management of PNES around the world. We initially provide a knowledge update about the etiology, epidemiology, and prognosis of PNES-in adults and in special patient groups, such as children, older adults, and those with intellectual disability. We then explore clinical management pathways and obstacles to optimal care for this disorder around the world by focusing on a number of countries with different cultural backgrounds and at very different stages of social and economic development (United Kingdom, U.S.A., Zambia, Georgia, China, and Japan). Although evidence-based methods for the diagnosis and treatment of PNES have now been described, and much is known about the biopsychosocial underpinnings of this disorder, this paper describes gaps in care (not only in less developed countries) that result in patients with PNES not having adequate access to healthcare provisions. A range of challenges requiring solutions tailored to different healthcare systems emerges. Continued attention to PNES by the ILAE and other national and international neurologic, psychiatric, and health organizations, along with ongoing international collaboration, should ensure that patients with PNES do not lose out as healthcare services evolve around the world
System Size and Energy Dependence of Jet-Induced Hadron Pair Correlation Shapes in Cu+Cu and Au+Au Collisions at sqrt(s_NN) = 200 and 62.4 GeV
We present azimuthal angle correlations of intermediate transverse momentum
(1-4 GeV/c) hadrons from {dijets} in Cu+Cu and Au+Au collisions at sqrt(s_NN) =
62.4 and 200 GeV. The away-side dijet induced azimuthal correlation is
broadened, non-Gaussian, and peaked away from \Delta\phi=\pi in central and
semi-central collisions in all the systems. The broadening and peak location
are found to depend upon the number of participants in the collision, but not
on the collision energy or beam nuclei. These results are consistent with sound
or shock wave models, but pose challenges to Cherenkov gluon radiation models.Comment: 464 authors from 60 institutions, 6 pages, 3 figures, 2 tables.
Submitted to Physical Review Letters. Plain text data tables for the points
plotted in figures for this and previous PHENIX publications are (or will be)
publicly available at http://www.phenix.bnl.gov/papers.htm
Improved Measurement of Double Helicity Asymmetry in Inclusive Midrapidity pi^0 Production for Polarized p+p Collisions at sqrt(s)=200 GeV
We present an improved measurement of the double helicity asymmetry for pi^0
production in polarized proton-proton scattering at sqrt(s) = 200 GeV employing
the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The
improvements to our previous measurement come from two main factors: Inclusion
of a new data set from the 2004 RHIC run with higher beam polarizations than
the earlier run and a recalibration of the beam polarization measurements,
which resulted in reduced uncertainties and increased beam polarizations. The
results are compared to a Next to Leading Order (NLO) perturbative Quantum
Chromodynamics (pQCD) calculation with a range of polarized gluon
distributions.Comment: 389 authors, 4 pages, 2 tables, 1 figure. Submitted to Phys. Rev. D,
Rapid Communications. Plain text data tables for the points plotted in
figures for this and previous PHENIX publications are (or will be) publicly
available at http://www.phenix.bnl.gov/papers.htm
Simulation of the thermally induced austenitic phase transition in NiTi nanoparticles
The reverse martensitic ("austenitic") transformation upon heating of
equiatomic nickel-titanium nanoparticles with diameters between 4 and 17 nm is
analyzed by means of molecular-dynamics simulations with a semi-empirical model
potential. After constructing an appropriate order parameter to distinguish
locally between the monoclinic B19' at low and the cubic B2 structure at high
temperatures, the process of the phase transition is visualized. This shows a
heterogeneous nucleation of austenite at the surface of the particles, which
propagates to the interior by plane sliding, explaining a difference in
austenite start and end temperatures. Their absolute values and dependence on
particle diameter are obtained and related to calculations of the surface
induced size dependence of the difference in free energy between austenite and
martensite.Comment: 6 pages, 4 figures, accepted for publication in "The European
Physical Journal B
Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
Extensive experimental data from high-energy nucleus-nucleus collisions were
recorded using the PHENIX detector at the Relativistic Heavy Ion Collider
(RHIC). The comprehensive set of measurements from the first three years of
RHIC operation includes charged particle multiplicities, transverse energy,
yield ratios and spectra of identified hadrons in a wide range of transverse
momenta (p_T), elliptic flow, two-particle correlations, non-statistical
fluctuations, and suppression of particle production at high p_T. The results
are examined with an emphasis on implications for the formation of a new state
of dense matter. We find that the state of matter created at RHIC cannot be
described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted
to Nuclear Physics A as a regular article; v3 has minor changes in response
to referee comments. Plain text data tables for the points plotted in figures
for this and previous PHENIX publications are (or will be) publicly available
at http://www.phenix.bnl.gov/papers.htm
Heavy Quarks and Heavy Quarkonia as Tests of Thermalization
We present here a brief summary of new results on heavy quarks and heavy
quarkonia from the PHENIX experiment as presented at the "Quark Gluon Plasma
Thermalization" Workshop in Vienna, Austria in August 2005, directly following
the International Quark Matter Conference in Hungary.Comment: 8 pages, 5 figures, Quark Gluon Plasma Thermalization Workshop
(Vienna August 2005) Proceeding
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