13,239 research outputs found
A new method for suppressing excited-state contaminations on the nucleon form factors
One of the most challenging tasks in lattice calculations of baryon form
factors is the analysis and control of excited-state contaminations. Taking the
isovector axial form factors of the nucleon as an example, both a dispersive
representation and a calculation in chiral effective field theory show that the
excited-state contributions become dominant at fixed source-sink separation
when the axial current is spatially distant from the nucleon source location.
We address this effect with a new method in which the axial current is
localized by a Gaussian wave-packet and apply it on a CLS ensemble with
flavors of O() improved Wilson fermions with a pion mass of
MeV.Comment: 7 pages, 6 figures, 1 table, Proceedings for the 36th Annual
International Symposium on Lattice Field Theory, 22-28 July 2018, Michigan
State University, East Lansing, Michigan, US
International Conference on “Foresight Studies on Work in the Knowledge Society“ in Monte de Caparica (FCT-UNL) on 19-20 October 2006
On 19 and 20 October 2006, the Research Centre on Enterprise and Work Organisation (IET) organised the first international conference on “Foresight Studies on Work in the Knowledge Society”. It took place at the auditorium of the new Library of FCT-UNL and had the support of the research project “CodeWork@VO” (financed by FCT-MCTES and co-ordinated by INESC, Porto). The conference related to the European research project “Work Organisation and Restructuring in the Knowledge Society” (WORKS), which is financed by the European Commission. The main objective of the conference was to analyse and discuss research findings on the trends of work structures in the knowledge society, and to debate on new work organisation models and new forms of work supported by ICT.Knowledge Society; work; Foresight
A Duality Exact Sequence for Legendrian Contact Homology
We establish a long exact sequence for Legendrian submanifolds L in P x R,
where P is an exact symplectic manifold, which admit a Hamiltonian isotopy that
displaces the projection of L off of itself. In this sequence, the singular
homology H_* maps to linearized contact cohomology CH^* which maps to
linearized contact homology CH_* which maps to singular homology. In
particular, the sequence implies a duality between the kernel of the map
(CH_*\to H_*) and the cokernel of the map (H_* \to CH^*). Furthermore, this
duality is compatible with Poincare duality in L in the following sense: the
Poincare dual of a singular class which is the image of a in CH_* maps to a
class \alpha in CH^* such that \alpha(a)=1.
The exact sequence generalizes the duality for Legendrian knots in Euclidean
3-space [24] and leads to a refinement of the Arnold Conjecture for double
points of an exact Lagrangian admitting a Legendrian lift with linearizable
contact homology, first proved in [6].Comment: 57 pages, 10 figures. Improved exposition and expanded analytic
detai
Astrophysical Fluid Dynamics via Direct Statistical Simulation
In this paper we introduce the concept of Direct Statistical Simulation (DSS)
for astrophysical flows. This technique may be appropriate for problems in
astrophysical fluids where the instantaneous dynamics of the flows are of
secondary importance to their statistical properties. We give examples of such
problems including mixing and transport in planets, stars and disks. The method
is described for a general set of evolution equations, before we consider the
specific case of a spectral method optimised for problems on a spherical
surface. The method is illustrated for the simplest non-trivial example of
hydrodynamics and MHD on a rotating spherical surface. We then discuss possible
extensions of the method both in terms of computational methods and the range
of astrophysical problems that are of interest.Comment: 26 pages, 11 figures, added clarifying remarks and references, and
corrected typos. This version is accepted for publication in The
Astrophysical Journa
Interaction-induced corrections to conductance and thermopower in quantum wires
We study transport properties of weakly interacting spinless electrons in
one-dimensional single channel quantum wires. The effects of interaction
manifest as three-particle collisions due to the severe constraints imposed by
the conservation laws on the two-body processes. We focus on short wires where
the effects of equilibration on the distribution function can be neglected and
collision integral can be treated in perturbation theory. We find that
interaction-induced corrections to conductance and thermopower rely on the
scattering processes that change number of right- and left-moving electrons.
The latter requires transition at the bottom of the band which is exponentially
suppressed at low temperatures. Our theory is based on the scattering approach
that is beyond the Luttinger-liquid limit. We emphasize the crucial role of the
exchange terms in the three-particle scattering amplitude that was not
discussed in the previous studies.Comment: 4 pages, 2 figure
Optimal Exploitation of the Sentinel-2 Spectral Capabilities for Crop Leaf Area Index Mapping
The continuously increasing demand of accurate quantitative high quality information on land surface properties will be faced by a new generation of environmental Earth observation (EO) missions. One current example, associated with a high potential to contribute to those demands, is the multi-spectral ESA Sentinel-2 (S2) system. The present study focuses on the evaluation of spectral information content needed for crop leaf area index (LAI) mapping in view of the future sensors. Data from a field campaign were used to determine the optimal spectral sampling from available S2 bands applying inversion of a radiative transfer model (PROSAIL) with look-up table (LUT) and artificial neural network (ANN) approaches. Overall LAI estimation performance of the proposed LUT approach (LUTN₅₀) was comparable in terms of retrieval performances with a tested and approved ANN method. Employing seven- and eight-band combinations, the LUTN₅₀ approach obtained LAI RMSE of 0.53 and normalized LAI RMSE of 0.12, which was comparable to the results of the ANN. However, the LUTN50 method showed a higher robustness and insensitivity to different band settings. Most frequently selected wavebands were located in near infrared and red edge spectral regions. In conclusion, our results emphasize the potential benefits of the Sentinel-2 mission for agricultural applications
- …