2,176 research outputs found
Epitaxial growth of Cu on Cu(001): experiments and simulations
A quantitative comparison between experimental and Monte Carlo simulation
results for the epitaxial growth of Cu/Cu(001) in the submonolayer regime is
presented. The simulations take into account a complete set of hopping
processes whose activation energies are derived from semi-empirical
calculations using the embedded-atom method. The island separation is measured
as a function of the incoming flux and the temperature. A good quantitative
agreement between the experiment and simulation is found for the island
separation, the activation energies for the dominant processes, and the
exponents that characterize the growth. The simulation results are then
analyzed at lower coverages, which are not accessible experimentally, providing
good agreement with theoretical predictions as well.Comment: Latex document. 7 pages. 3 embedded figures in separate PS files. One
bbl fil
Observations and predictions at CesrTA, and outlook for ILC
In this paper, we will describe some of the recent experimental measurements
[1, 2, 3] performed at CESRTA [4], and the supporting simulations, which probe
the interaction of the electron cloud with the stored beam. These experiments
have been done over a wide range of beam energies, emittances, bunch currents,
and fill patterns, to gather sufficient information to be able to fully
characterize the beam-electron-cloud interaction and validate the simulation
programs. The range of beam conditions is chosen to be as close as possible to
those of the ILC damping ring, so that the validated simulation programs can be
used to predict the performance of these rings with regard to electroncloud-
related phenomena. Using the new simulation code Synrad3D to simulate the
synchrotron radiation environment, a vacuum chamber design has been developed
for the ILC damping ring which achieves the required level of photoelectron
suppression. To determine the expected electron cloud density in the ring, EC
buildup simulations have been done based on the simulated radiation environment
and on the expected performance of the ILC damping ring chamber mitigation
prescriptions. The expected density has been compared with analytical estimates
of the instability threshold, to verify that the ILC damping ring vacuum
chamber design is adequate to suppress the electron cloud single-bunch
head-tail instability.Comment: 11 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop
on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba,
Ital
Vortex State of TlBaCuO via Tl NMR at 2 Tesla
We report a Tl NMR study of vortex state for an aligned
polycrystalline sample of an overdoped high- superconductor
TlBaCuO (85 K) with magnetic field 2 T along
the c axis. We observed an imperfect vortex lattice, so-called Bragg glass at
=5 K, coexistence of vortex solid with liquid between 10 and 60 K, and
vortex melting between 65 and 85 K. No evidence for local antiferromagnetic
ordering at vortex cores was found for our sample.Comment: 4 pages with 5 figure
Effective Lagrangian for strongly coupled domain wall fermions
We derive the effective Lagrangian for mesons in lattice gauge theory with
domain-wall fermions in the strong-coupling and large-N_c limits. We use the
formalism of supergroups to deal with the Pauli-Villars fields, needed to
regulate the contributions of the heavy fermions. We calculate the spectrum of
pseudo-Goldstone bosons and show that domain wall fermions are doubled and
massive in this regime. Since we take the extent and lattice spacing of the
fifth dimension to infinity and zero respectively, our conclusions apply also
to overlap fermions.Comment: 26 pp. RevTeX and 3 figures; corrected error in symmetry breaking
scheme and added comments to discussio
Dynamic nuclear polarization and spin-diffusion in non-conducting solids
There has been much renewed interest in dynamic nuclear polarization (DNP),
particularly in the context of solid state biomolecular NMR and more recently
dissolution DNP techniques for liquids. This paper reviews the role of spin
diffusion in polarizing nuclear spins and discusses the role of the spin
diffusion barrier, before going on to discuss some recent results.Comment: submitted to Applied Magnetic Resonance. The article should appear in
a special issue that is being published in connection with the DNP Symposium
help in Nottingham in August 200
Cereals
The tropical cereal crops such as maize, rice, sorghum, and millets, are the staple foods of billions of people in developing countries. Their sustainable improvement is crucial to achieving food security in the face of climate change in the growing demand for food. The need to conserve the diversity of these crops and their wild relatives is therefore particularly important. This chapter outlines the diversity within each crop pool and summarizes their state of conservation ex situ. Many of the 1,750+ genebanks around the world contain accessions of at least one of these crops and their wild relatives, and altogether there are thousands of accessions of each of them. A significant proportion of this germplasm is freely distributed to scientists and breeders around the world with the Standard Material Transfer Agreement of the International Treaty on Plant Genetic Resources for Food and Agriculture. However, this use can be effective only if the germplasm and associated passport, characterization, and evaluation data are readily available. As additional insurance against loss of diversity, many accessions are now also conserved in the Svalbard Global Seed Vault in Norwa
The phase diagram of Yang-Mills theory with a compact extra dimension
We present a non-perturbative study of the phase diagram of SU(2) Yang-Mills
theory in a five-dimensional spacetime with a compact extra dimension. The
non-renormalizable theory is regularized on an anisotropic lattice and
investigated through numerical simulations in a regime characterized by a
hierarchy between the scale of low-energy physics, the inverse compactification
radius, and the cutoff scale. We map out the structure of the phase diagram and
the pattern of lines corresponding to fixed values of the ratio between the
mass of the fifth component of the gauge field and the non-perturbative mass
gap of the four-dimensional modes. We discuss different limits of the model,
and comment on the implications of our findings.Comment: 17 pages, 9 figure
Property (T) and rigidity for actions on Banach spaces
We study property (T) and the fixed point property for actions on and
other Banach spaces. We show that property (T) holds when is replaced by
(and even a subspace/quotient of ), and that in fact it is
independent of . We show that the fixed point property for
follows from property (T) when 1
. For simple Lie groups and their lattices, we prove that the fixed point property for holds for any if and only if the rank is at least two. Finally, we obtain a superrigidity result for actions of irreducible lattices in products of general groups on superreflexive Banach spaces.Comment: Many minor improvement
Televised Executions and the Constitution: Recognizing a First Amendment Right of Access to State Executions
This article examines the history of public and private executions and the passage of private execution laws. It concludes that existing laws restricting media access to executions – and requiring private executions that exclude television cameras – are unconstitutional. The author examines existing statutory schemes which curtail media access and prohibit the filming of executions, discusses legal challenges to such laws, and explores freedom of the press jurisprudence. In particular, the article analyzes First Amendment case law and right-of-access cases. The author also discusses the Eighth Amendment\u27s relationship to First Amendment case law in the area of media coverage of executions
Non-perturbative Renormalisation of Domain Wall Fermions: Quark Bilinears
We find the renormalisation coefficients of the quark field and the flavour
non-singlet fermion bilinear operators for the domain wall fermion action, in
the regularisation independent (RI) renormalisation scheme. Our results are
from a quenched simulation, on a 16^3x32 lattice, with beta=6.0 and an extent
in the fifth dimension of 16. We also discuss the expected effects of the
residual chiral symmetry breaking inherent in a domain wall fermion simulation
with a finite fifth dimension, and study the evidence for both explicit and
spontaneous chiral symmetry breaking effects in our numerical results. We find
that the relations between different renormalisation factors predicted by
chiral symmetry are, to a good approximation, satisfied by our results and that
systematic effects due to the (low energy) spontaneous chiral symmetry breaking
and zero-modes can be controlled. Our results are compared against the
perturbative predictions for both their absolute value and renormalisation
scale dependence.Comment: 53 pages, 21 figures, revte
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