16,146 research outputs found
On Ptolemaic metric simplicial complexes
We show that under certain mild conditions, a metric simplicial complex which
satisfies the Ptolemy inequality is a CAT(0) space. Ptolemy's inequality is
closely related to inversions of metric spaces. For a large class of metric
simplicial complexes, we characterize those which are isometric to Euclidean
space in terms of metric inversions.Comment: 13 page
HepData and JetWeb: HEP data archiving and model validation
The CEDAR collaboration is extending and combining the JetWeb and HepData
systems to provide a single service for tuning and validating models of
high-energy physics processes. The centrepiece of this activity is the fitting
by JetWeb of observables computed from Monte Carlo event generator events
against their experimentally determined distributions, as stored in HepData.
Caching the results of the JetWeb simulation and comparison stages provides a
single cumulative database of event generator tunings, fitted against a wide
range of experimental quantities. An important feature of this integration is a
family of XML data formats, called HepML.Comment: 4 pages, 0 figures. To be published in proceedings of CHEP0
HepForge: A lightweight development environment for HEP software
Setting up the infrastructure to manage a software project can become a task
as significant writing the software itself. A variety of useful open source
tools are available, such as Web-based viewers for version control systems,
"wikis" for collaborative discussions and bug-tracking systems, but their use
in high-energy physics, outside large collaborations, is insubstantial.
Understandably, physicists would rather do physics than configure project
management tools.
We introduce the CEDAR HepForge system, which provides a lightweight
development environment for HEP software. Services available as part of
HepForge include the above-mentioned tools as well as mailing lists, shell
accounts, archiving of releases and low-maintenance Web space. HepForge also
exists to promote best-practice software development methods and to provide a
central repository for re-usable HEP software and phenomenology codes.Comment: 3 pages, 0 figures. To be published in proceedings of CHEP06. Refers
to the HepForge facility at http://hepforge.cedar.ac.u
Are There Hints of Light Stops in Recent Higgs Search Results?
The recent discovery at the LHC by the CMS and ATLAS collaborations of the
Higgs boson presents, at long last, direct probes of the mechanism for
electroweak symmetry breaking. While it is clear from the observations that the
new particle plays some role in this process, it is not yet apparent whether
the couplings and widths of the observed particle match those predicted by the
Standard Model. In this paper, we perform a global fit of the Higgs results
from the LHC and Tevatron. While these results could be subject to
as-yet-unknown systematics, we find that the data are significantly better fit
by a Higgs with a suppressed width to gluon-gluon and an enhanced width to
gamma gamma, relative to the predictions of the Standard Model. After
considering a variety of new physics scenarios which could potenially modify
these widths, we find that the most promising possibility is the addition of a
new colored, charged particle, with a large coupling to the Higgs. Of
particular interest is a light, and highly mixed, stop, which we show can
provide the required alterations to the combination of gg and gamma gamma
widths.Comment: 6 pages, 5 figure
Genetic diversity at the FMR1 locus in the Indonesian population
We report an analysis of allelic diversity at short tandem repeat polymorphisms within the fragile XA locus in 1069 male volunteers from twelve Indonesian sub-populations. An odd numbered allele of DXS548 was found at high frequency in all Indonesian populations. Greater allelic diversity was identified at the loci under study than has been previously reported for an Asian population. These differences distinguish the Indonesian population from all previously reported Asian, European and African populations. A high frequency of small premutation alleles, 4/120 (3.3%, 95% CI 0.9–8.3%), was identified in the Moluccan population of Hiri Island
Optical studies of two LMC X-ray transients : RX J0544.1-7100 and RX J0520.5-6932
We report observations which confirm the identities of the optical
counterpart to the transient sources RX J0544.1-7100 and RX J0520.5-6932. The
counterparts are suggested to be a B-type stars. Optical data from the
observations carried out at ESO and SAAO, together with results from the OGLE
data base, are presented. In addition, X-ray data from the RXTE all-sky monitor
are investigated for long term periodicities. A strong suggestion for a binary
period of 24.4d is seen in RX J0520.5-6932 from the OGLE data.Comment: 6 pages, 7 figure
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