64,605 research outputs found
On effects of regular S=1 dilution of S=1/2 antiferromagnetic Heisenberg chains by a quantum Monte Carlo simulation
The effects of regular S=1 dilution of S=1/2 isotropic antiferromagnetic
chain are investigated by the quantum Monte Carlo loop/cluster algorithm. Our
numerical results show that there are two kinds of ground-state phases which
alternate with the variation of concentration. When the effective spin
of a unit cell is half-integer, the ground state is ferrimagnetic with gapless
energy spectrum and the magnetism becomes weaker with decreasing of the
concentration . While it is integer, a non-magnetic ground state
with gaped spectrum emerges and the gap gradually becomes narrowed as fitted by
a relation of .Comment: 6 pages, 9 figure
Hyperbolic metamaterial as a tunable near-field spatial filter for the implementation of the active plasmon injection loss compensation scheme
We present how to physically realize the auxiliary source described in the
recently introduced active plasmon injection loss compensation scheme for
enhanced near-field superlensing. Particularly, we show that the
characteristics of the auxiliary source described in the active plasmon
injection scheme including tunable narrow-band and selective amplification via
convolution can be realized by using a hyperbolic metamaterial functioning as a
near-field spatial filter. Besides loss compensation, the proposed near-field
spatial filter can be useful for real-time high resolution edge detection.Comment: 8 pages, 8 figure
Active plasmon injection scheme for subdiffraction imaging with imperfect negative index flat lens
We present an active physical implementation of the recently introduced
plasmon injection loss compensation scheme for Pendry's non-ideal negative
index flat lens in the presence of realistic material losses and
signal-dependent noise. In this active implementation, we propose to use a
physically convolved external auxiliary source for signal amplification and
suppression of the noise in the imaging system. In comparison with the previous
passive implementations of the plasmon injection scheme for sub-diffraction
limited imaging, where an inverse filter post-processing is used, the active
implementation proposed here allows for deeper subwavelength imaging far beyond
the passive post-processing scheme by extending the loss compensation to even
higher spatial frequencies.Comment: 13 pages, 15 figure
Investigation of jet quenching and elliptic flow within a pQCD-based partonic transport model
The partonic transport model BAMPS (a Boltzmann approach to multiparton
scatterings) is employed to investigate different aspects of heavy ion
collisions within a common framework based on perturbative QCD. This report
focuses on the joint investigation of the collective behavior of the created
medium and the energy loss of high-pT gluons traversing this medium. To this
end the elliptic flow and the nuclear modification factor of gluons in heavy
ion collisions at 200 AGeV are simulated with BAMPS. The mechanism for the
energy loss of high energy gluons within BAMPS is studied in detail. For this,
purely elastic interactions are compared to radiative processes, gg -> ggg,
that are implemented based on the matrix element by Gunion and Bertsch. The
latter are found to be the dominant source of energy loss within the framework
employed in this work.Comment: To appear in the proceedings of the 26th Winter Workshop on Nuclear
Dynamics (2010)
The Microscopic Structure of Adsorbed Water on Hydrophobic Surfaces under Ambient Conditions
The interaction of water vapor with hydrophobic surfaces is poorly understood. We utilize graphene templating to preserve and visualize the microscopic structures of adsorbed water on hydrophobic surfaces. Three well-defined surfaces [H–Si(111), graphite, and functionalized mica] were investigated, and water was found to adsorb as nanodroplets (~10–100 nm in size) on all three surfaces under ambient conditions. The adsorbed nanodroplets were closely associated with atomic-scale surface defects and step-edges and wetted all the hydrophobic substrates with contact angles < ~10°, resulting in total water adsorption that was similar to what is found for hydrophilic surfaces. These results point to the significant differences between surface processes at the atomic/nanometer scales and in the macroscopic world
Jet quenching and elliptic flow at RHIC and LHC within a pQCD-based partonic transport model
Fully dynamic simulations of heavy ion collisions at RHIC and at LHC energies
within the perturbative QCD-based partonic transport model BAMPS (Boltzmann
Approach to Multi-Parton Scatterings) are presented, focusing on the
simultaneous investigation of jet quenching and elliptic flow. The model
features inelastic 2 3 processes based on the Gunion-Bertsch matrix element
and has recently been extended to include light quark degrees of freedom,
allowing for direct comparison to hadronic data on the nuclear modification
factor via a fragmentation scheme for high-pT partons. The nuclear modification
factor of neutral pions in central Au+Au collisions at RHIC energy is compared
to experimental data. Furthermore first results on the nuclear modification
factor and the integrated elliptic flow of charged hadrons in Pb+Pb collisions
at LHC are presented and compared to recent ALICE data. These investigations
are complemented by a study on the suppression of D-mesons at LHC based on
elastic interactions with the medium.Comment: To appear in the proceedings of Quark Matter 201
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