70,419 research outputs found
The Measurement of the Muon's Anomalous Magnetic Moment Isn't
Recent results announced as measurements of the muon's anomalous magnetic
moment are in fact measurements of the muon's anomalous spin precession
frequency. This precession frequency receives contributions from both the
muon's anomalous magnetic and electric dipole moments. We note that all
existing data cannot resolve this ambiguity, and the current deviation from
standard model predictions may equally well be interpreted as evidence for new
physics in the muon's anomalous magnetic moment, new physics in the muon's
electric dipole moment, or both.Comment: 2 pages, 1 figure, published versio
Heuristic algorithms for the min-max edge 2-coloring problem
In multi-channel Wireless Mesh Networks (WMN), each node is able to use
multiple non-overlapping frequency channels. Raniwala et al. (MC2R 2004,
INFOCOM 2005) propose and study several such architectures in which a computer
can have multiple network interface cards. These architectures are modeled as a
graph problem named \emph{maximum edge -coloring} and studied in several
papers by Feng et. al (TAMC 2007), Adamaszek and Popa (ISAAC 2010, JDA 2016).
Later on Larjomaa and Popa (IWOCA 2014, JGAA 2015) define and study an
alternative variant, named the \emph{min-max edge -coloring}.
The above mentioned graph problems, namely the maximum edge -coloring and
the min-max edge -coloring are studied mainly from the theoretical
perspective. In this paper, we study the min-max edge 2-coloring problem from a
practical perspective. More precisely, we introduce, implement and test four
heuristic approximation algorithms for the min-max edge -coloring problem.
These algorithms are based on a \emph{Breadth First Search} (BFS)-based
heuristic and on \emph{local search} methods like basic \emph{hill climbing},
\emph{simulated annealing} and \emph{tabu search} techniques, respectively.
Although several algorithms for particular graph classes were proposed by
Larjomaa and Popa (e.g., trees, planar graphs, cliques, bi-cliques,
hypergraphs), we design the first algorithms for general graphs.
We study and compare the running data for all algorithms on Unit Disk Graphs,
as well as some graphs from the DIMACS vertex coloring benchmark dataset.Comment: This is a post-peer-review, pre-copyedit version of an article
published in International Computing and Combinatorics Conference
(COCOON'18). The final authenticated version is available online at:
http://www.doi.org/10.1007/978-3-319-94776-1_5
Solar stereoscopy - where are we and what developments do we require to progress?
Observations from the two STEREO-spacecraft give us for the first time the
possibility to use stereoscopic methods to reconstruct the 3D solar corona.
Classical stereoscopy works best for solid objects with clear edges.
Consequently an application of classical stereoscopic methods to the faint
structures visible in the optically thin coronal plasma is by no means straight
forward and several problems have to be treated adequately: 1.)First there is
the problem of identifying one dimensional structures -e.g. active region
coronal loops or polar plumes- from the two individual EUV-images observed with
STEREO/EUVI. 2.) As a next step one has the association problem to find
corresponding structures in both images. 3.) Within the reconstruction problem
stereoscopic methods are used to compute the 3D-geometry of the identified
structures. Without any prior assumptions, e.g., regarding the footpoints of
coronal loops, the reconstruction problem has not one unique solution. 4.) One
has to estimate the reconstruction error or accuracy of the reconstructed
3D-structure, which depends on the accuracy of the identified structures in 2D,
the separation angle between the spacecraft, but also on the location, e.g.,
for east-west directed coronal loops the reconstruction error is highest close
to the loop top. 5.) Eventually we are not only interested in the 3D-geometry
of loops or plumes, but also in physical parameters like density, temperature,
plasma flow, magnetic field strength etc. Helpful for treating some of these
problems are coronal magnetic field models extrapolated from photospheric
measurements, because observed EUV-loops outline the magnetic field. This
feature has been used for a new method dubbed 'magnetic stereoscopy'. As
examples we show recent application to active region loops.Comment: 12 Pages, 9 Figures, a Review articl
Corrugated structure insertion for extending the SASE bandwidth up to 3% at the European XFEL
The usage of x-ray free electron laser (XFEL) in femtosecond
nanocrystallography involves sequential illumination of many small crystals of
arbitrary orientation. Hence a wide radiation bandwidth will be useful in order
to obtain and to index a larger number of Bragg peaks used for determination of
the crystal orientation. Considering the baseline configuration of the European
XFEL in Hamburg, and based on beam dynamics simulations, we demonstrate here
that the usage of corrugated structures allows for a considerable increase in
radiation bandwidth. Data collection with a 3% bandwidth, a few microjoule
radiation pulse energy, a few femtosecond pulse duration, and a photon energy
of 5.4 keV is possible. For this study we have developed an analytical modal
representation of the short-range wake function of the flat corrugated
structures for arbitrary offsets of the source and the witness particles.Comment: 29 pages, 17 figure
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