103,524 research outputs found
Sharp bounds on enstrophy growth in the viscous Burgers equation
We use the Cole--Hopf transformation and the Laplace method for the heat
equation to justify the numerical results on enstrophy growth in the viscous
Burgers equation on the unit circle. We show that the maximum enstrophy
achieved in the time evolution is scaled as , where
is the large initial enstrophy, whereas the time needed for
reaching the maximal enstrophy is scaled as . These bounds
are sharp for sufficiently smooth initial conditions.Comment: 12 page
Determining masses of supersymmetric particles
If supersymmetric particles are produced at the Large Hadron Collider it
becomes very important not only to identify them, but also to determine their
masses with the highest possible precision, since this may lead to an
understanding of the SUSY-breaking mechanism and the physics at some higher
scale. We here report on studies of how such mass measurements are obtained,
and how the precision can be optimized.Comment: 11 pages, contribution to the proceedings "II. Southeastern European
Workshop Challenges Beyond The Standard Model", 19-23 May 2005, Vrnjacka
Banja, Serbi
Digital curation and the cloud
Digital curation involves a wide range of activities, many of which could benefit from cloud
deployment to a greater or lesser extent. These range from infrequent, resource-intensive tasks
which benefit from the ability to rapidly provision resources to day-to-day collaborative activities
which can be facilitated by networked cloud services. Associated benefits are offset by risks
such as loss of data or service level, legal and governance incompatibilities and transfer
bottlenecks. There is considerable variability across both risks and benefits according to the
service and deployment models being adopted and the context in which activities are
performed. Some risks, such as legal liabilities, are mitigated by the use of alternative, e.g.,
private cloud models, but this is typically at the expense of benefits such as resource elasticity
and economies of scale. Infrastructure as a Service model may provide a basis on which more
specialised software services may be provided.
There is considerable work to be done in helping institutions understand the cloud and its
associated costs, risks and benefits, and how these compare to their current working methods,
in order that the most beneficial uses of cloud technologies may be identified. Specific
proposals, echoing recent work coordinated by EPSRC and JISC are the development of
advisory, costing and brokering services to facilitate appropriate cloud deployments, the
exploration of opportunities for certifying or accrediting cloud preservation providers, and
the targeted publicity of outputs from pilot studies to the full range of stakeholders within the
curation lifecycle, including data creators and owners, repositories, institutional IT support
professionals and senior manager
Resolving ambiguities in mass determinations at future colliders
The measurements of kinematical endpoints, in cascade decays of
supersymmetric particles, in principle allow for a determination of the masses
of the unstable particles. However, in this procedure ambiguities often arise.
We here illustrate how such ambiguities arise. They can be resolved by a
precise determination of the LSP mass, provided by the Linear Collider.Comment: 6 pages, 6 figures, to appear in the proceedings of the 2005
International Linear Collider Workshop, Stanford, U.S.
1,2-Dimethyl-4,5-diphenylbenzene determined on a Bruker SMART X2S benchtop crystallographic system
The title compound, C(20)H(18), has two crystallographically independent molecules in the asymmetric unit. The phenyl substituents of molecule A are twisted away from the plane defined by the central benzene ring by 131.8 (2) and -52.7 (3)degrees. The phenyl substituents of molecule B are twisted by -133.3 (2) and 50.9 (3)degrees. Each molecule is stabilized by a pair of intraMolecular C(aryl, sp(2))-H center dot center dot center dot pi interactions, as well as by several interMolecular C(methyl, sp(3))-H center dot center dot center dot pi interactions
Muon g-2: Review of Theory and Experiment
A review of the experimental and theoretical determinations of the anomalous
magnetic moment of the muon is given. The anomaly is defined by a=(g-2)/2,
where the Land\'e g-factor is the proportionality constant that relates the
spin to the magnetic moment. For the muon, as well as for the electron and
tauon, the anomaly a differs slightly from zero (of order 10^{-3}) because of
radiative corrections. In the Standard Model, contributions to the anomaly come
from virtual `loops' containing photons and the known massive particles. The
relative contribution from heavy particles scales as the square of the lepton
mass over the heavy mass, leading to small differences in the anomaly for e,
\mu, and \tau. If there are heavy new particles outside the Standard Model
which couple to photons and/or leptons, the relative effect on the muon anomaly
will be \sim (m_\mu/ m_e)^2 \approx 43\times 10^3 larger compared with the
electron anomaly. Because both the theoretical and experimental values of the
muon anomaly are determined to high precision, it is an excellent place to
search for the effects of new physics, or to constrain speculative extensions
to the Standard Model. Details of the current theoretical evaluation, and of
the series of experiments that culminates with E821 at the Brookhaven National
Laboratory are given. At present the theoretical and the experimental values
are known with a similar relative precision of 0.5 ppm. There is, however, a
3.4 standard deviation difference between the two, strongly suggesting the need
for continued experimental and theoretical studyComment: 103 pages, 57 figures, submitted to Reports on Progress in Physics
Final version as published, several minor clarifications to text and a number
of references were correcte
2,3-Bis(bromomethyl)-1,4-diphenylbenzene
In the title compound, C(20)H(16)Br(2), the terminal phenyl groups are twisted away from the central ring by approximately 55 and -125 degrees (average of four dihedral angles each), respectively. The crystal structure is stabilized by a combination of interMolecular and intraMolecular interactions including interMolecular pi-pi stacking interactions [C atoms of closest contact = 3.423 ( 5) angstrom]
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