631 research outputs found
Die Bedeutung des Messeplatzes Deutschland
Die volkswirtschaftliche Bedeutung des deutschen Messewesens ist grundsĂ€tzlich unbestritten, weniger klar ist jedoch die GröĂenordnung des gesamtwirtschaftlichen Effekts. Auch die EigentĂŒmerstrukturen deutscher Messegesellschaften werden zurzeit diskutiert: Die meisten deutschen Messegesellschaften sind im Eigentum von StĂ€dten und LĂ€ndern, die sich finanziell sehr unterschiedlich engagieren. Dr. Hermann Kresse, AUMA, sieht die Voraussetzungen fĂŒr eine komplette Privatisierung des MessegeschĂ€fts gegenwĂ€rtig nicht gegeben. FĂŒr Prof. Dr. Robert K. von WeizsĂ€cker, Technische UniversitĂ€t MĂŒnchen, ist eine Vollprivatisierung der deutschen Messeindustrie der einzig sinnvolle Privatisierungsansatz. Horst Penzkofer, ifo Institut, weist darauf hin, dass VeranstaltungsgeschĂ€ft und Messeinfrastruktur noch nicht als Wettbewerbseinheit betrachtet werden können: "WĂ€hrend die meisten Messegesellschaften schon wie private Messeveranstalter auf dem Markt agieren und im VeranstaltungsgeschĂ€ft ErtrĂ€ge erwirtschaften, somit eine Privatisierung des DurchfĂŒhrungsgeschĂ€fts durchaus vorstellbar ist, sind die Voraussetzungen fĂŒr eine wettbewerbsadĂ€quate Vermarktung der Immobilien bzw. Messeinfrastruktur zurzeit noch nicht gegeben."Messestandort, Messewirtschaft, Auslandsmesse, Privatisierung, Deutschland
Finite size corrections to scaling in high Reynolds number turbulence
We study analytically and numerically the corrections to scaling in
turbulence which arise due to the finite ratio of the outer scale of
turbulence to the viscous scale , i.e., they are due to finite size
effects as anisotropic forcing or boundary conditions at large scales. We find
that the deviations \dzm from the classical Kolmogorov scaling of the velocity moments \langle |\u(\k)|^m\rangle \propto k^{-\zeta_m}
decrease like . Our numerics employ a
reduced wave vector set approximation for which the small scale structures are
not fully resolved. Within this approximation we do not find independent
anomalous scaling within the inertial subrange. If anomalous scaling in the
inertial subrange can be verified in the large limit, this supports the
suggestion that small scale structures should be responsible, originating from
viscosity either in the bulk (vortex tubes or sheets) or from the boundary
layers (plumes or swirls)
Mass splittings of nuclear isotopes in chiral soliton approach
The differences of the masses of nuclear isotopes with atomic numbers between
\~10 and ~30 can be described within the chiral soliton approach in
satisfactory agreement with data. Rescaling of the model is necessary for this
purpose - decrease of the Skyrme constant by about 30%, providing the "nuclear
variant" of the model. The asymmetric term in Weizsaecker-Bethe- Bacher mass
formula for nuclei can be obtained as the isospin dependent quantum correction
to the nucleus energy. Some predictions for the binding energies of neutron
rich nuclides are made in this way, from, e.g. Be-16 and B-19 to Ne-31 and
Na-32. Neutron rich nuclides with high values of isospin are unstable relative
to strong interactions. The SK4 (Skyrme) variant of the model, as well as SK6
variant (6-th order term in chiral derivatives in the lagrangian as solitons
stabilizer) are considered, and the rational map approximation is used to
describe multiskyrmions.Comment: 16 pages, 10 tables, 2 figures. Figures are added and few misprints
are removed. Submitted to Phys. Atom. Nucl. (Yad. Fiz.
J/psi plus prompt-photon associated production in two-photon collisions at next-to-leading order
We calculate the cross section of J/psi plus prompt-photon inclusive
production in gamma gamma collisions at next-to-leading order within the
factorization formalism of nonrelativistic quantum chromodynamics (NRQCD)
focusing on direct photoproduction. Apart from direct J/psi production, we also
include the feed-down from directly-produced chi_{cJ} and psi' mesons. We
discuss the analytical calculation, in particular the treatment of the various
types of singularities and the NRQCD operator renormalization, in some detail.
We present theoretical predictions for the future e^+e^- linear collider TESLA,
taking into account both brems- and beamstrahlung.Comment: 31 pages, 9 figure
Necessary Optimality Conditions for Higher-Order Infinite Horizon Variational Problems on Time Scales
We obtain Euler-Lagrange and transversality optimality conditions for
higher-order infinite horizon variational problems on a time scale. The new
necessary optimality conditions improve the classical results both in the
continuous and discrete settings: our results seem new and interesting even in
the particular cases when the time scale is the set of real numbers or the set
of integers.Comment: This is a preprint of a paper whose final and definite form will
appear in Journal of Optimization Theory and Applications (JOTA). Paper
submitted 17-Nov-2011; revised 24-March-2012 and 10-April-2012; accepted for
publication 15-April-201
Predicting Neutron Production from Cosmic-ray Muons
Fast neutrons from cosmic-ray muons are an important background to
underground low energy experiments. The estimate of such background is often
hampered by the difficulty of measuring and calculating neutron production with
sufficient accuracy. Indeed substantial disagreement exists between the
different analytical calculations performed so far, while data reported by
different experiments is not always consistent. We discuss a new unified
approach to estimate the neutron yield, the energy spectrum, the multiplicity
and the angular distribution from cosmic muons using the Monte Carlo simulation
package FLUKA and show that it gives a good description of most of the existing
measurements once the appropriate corrections have been applied.Comment: 8 pages, 7 figure
DC and AC Josephson effects with superfluid Fermi atoms across a Feshbach resonance
We show that both DC and AC Josephson effects with superfluid Fermi atoms in
the BCS-BEC crossover can be described at zero temperature by a nonlinear
Schrodinger equation (NLSE). By comparing our NLSE with mean-field extended BCS
calculations, we find that the NLSE is reliable in the BEC side of the
crossover up to the unitarity limit. The NLSE can be used for weakly-linked
atomic superfluids also in the BCS side of the crossover by taking the
tunneling energy as a phenomenological parameter.Comment: 8 pages, 4 figures, presented at the Scientific Seminar on Physics of
Cold Trapped Atoms, 17th International Laser Physics Workshop (Trondheim,
June 30 - July 4, 2008
Financial Transaction Tax: Small is Beautiful
The case for taxing financial transactions merely to raise more revenues from the financial sector is not particularly strong. Better alternatives to tax the financial sector are likely to be available. However, a tax on financial transactions could be justified in order to limit socially
undesirable transactions when more direct means of doing so are unavailable for political or
practical reasons. Some financial transactions are indeed likely to do more harm than good,
especially when they contribute to the systemic risk of the financial system. However, such a
financial transaction tax should be very small, much smaller than the negative externalities in
question, because it is a blunt instrument that also drives out socially useful transactions.
There is a case for taxing over-the-counter derivative transactions at a somewhat higher rate
than exchange-based derivative transactions. More targeted remedies to drive out socially
undesirable transactions should be sought in parallel, which would allow, after their
implementation, to reduce or even phase out financialtransaction taxes
Photoproduction in Ultra-Peripheral Relativistic Heavy Ion Collisions with STAR
We present a summary of recent photoproduction results in ultra peripheral
relativistic heavy ions collisions with STAR. These collisions have impact
parameters larger then twice the nuclear radius; the nuclei do not physically
collide, but interact via long-range electromagnetic fields. We observe
exclusive production as well as with
accompanying mutual nuclear excitation at GeV. We report
the production cross section for both coherent and incoherent coupling
accompanied by mutual nuclear excitation. We have studied the cross section as
a function of , and and compared it to
theoretical models. In addition, we measured the helicity matrix
elements. They are found to be consistent with s-channel helicity conservation.
The ratio of coherent and direct pair photoproduction has
been measured and found to be consistent with earlier measurements. The 4-pion
final state state has also been observed.Comment: 6 pages, 6 figures, Photon 2007 Proceeding
Hadronic Cross-sections in two photon Processes at a Future Linear Collider
In this note we address the issue of measurability of the hadronic
cross-sections at a future photon collider as well as for the two-photon
processes at a future high energy linear collider. We extend, to
higher energy, our previous estimates of the accuracy with which the \gamgam\
cross-section needs to be measured, in order to distinguish between different
theoretical models of energy dependence of the total cross-sections. We show
that the necessary precision to discriminate among these models is indeed
possible at future linear colliders in the Photon Collider option. Further we
note that even in the option a measurement of the hadron production
cross-section via \gamgam processes, with an accuracy necessary to allow
discrimination between different theoretical models, should be possible. We
also comment briefly on the implications of these predictions for hadronic
backgrounds at the future TeV energy collider CLIC.Comment: 20 pages, 5 figures, LaTeX. Added an acknowledgemen
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