1,896 research outputs found
Continuous control of ionization wave chaos by spatially derived feedback signals
In the positive column of a neon glow discharge, two different types of
ionization waves occur simultaneously. The low-dimensional chaos arising from
the nonlinear interaction between the two waves is controlled by a continuous
feedback technique. The control strategy is derived from the time-delayed
autosynchronization method. Two spatially displaced points of observation are
used to obtain the control information, using the propagation characteristics
of the chaotic wave.Comment: Elsevier-Tex-File, 8 pages, 6 figures, submitted to PL
Kaon Distribution Amplitude from QCD Sum Rules
We present a new calculation of the first Gegenbauer moment of the
kaon light-cone distribution amplitude. This moment is determined by the
difference between the average momenta of strange and nonstrange valence quarks
in the kaon. To calculate , QCD sum rule for the diagonal correlation
function of local and nonlocal axial-vector currents is used. Contributions of
condensates up to dimension six are taken into account, including
-corrections to the quark-condensate term. We obtain
, differing by the sign and magnitude from the recent
sum-rule estimate from the nondiagonal correlation function of pseudoscalar and
axial-vector currents. We argue that the nondiagonal sum rule is numerically
not reliable. Furthermore, an independent indication for a positive is
given, based on the matching of two different light-cone sum rules for the
form factor. With the new interval of we update our previous
numerical predictions for SU(3)-violating effects in form
factors and charmless (B) decays.Comment: a comment and a reference added, version to appear in Phys.Rev.D, 17
pages, 7 figure
The Implementation of the Sustainable Development Goals in the Nordic Arctic (ISDeGoNA)
This report assesses the status of the implementation of the Sustainable Development Goals (SDGs) in the Nordic Arctic. The 17 SDG’s can be seen as the most comprehensive international effort for sustainable development, however the process of implementing them in an Arctic context is still a research- and policy gap. In response, a comparative study has been carried out with a more specific focus on SDG implementation in Arctic Finland, Iceland, and Norway. Here, the research findings are based on small literature reviews and extensive semi-structured interviews with regional governments, local authorities, and business organizations. From this perspective, different contexts were thematized such as SDG awareness, most relevant SDGs within the focus areas, respective achievements and shortcomings, governance processes as well as essential stakeholders enabling SDG implementation.publishedVersio
Exclusive radiative and electroweak b->d and b->s penguin decays at NLO
We provide Standard Model expectations for the rare radiative decays B->K^*
gamma, B->rho gamma and B-> omega gamma, and the electroweak penguin decays
B->K^* l^+ l^- and B->rho l^+ l^- at the next-to-leading order (NLO), extending
our previous results to b->d transitions. We consider branching fractions,
isospin asymmetries and direct CP asymmetries. For the electroweak penguin
decays, the lepton-invariant mass spectrum and forward-backward asymmetry is
also included. Radiative and electroweak penguin transitions in b->d are mainly
interesting in the search for new flavour-changing neutral current
interactions, but in addition the B->rho gamma decays provide constraints on
the CKM parameters (\bar\rho,\bar\eta). The potential impact of these
constraints is discussed.Comment: 29 pages, LaTe
Symmetry-breaking corrections to heavy-to-light B meson form factors at large recoil
Recently it has been shown that symmetries emerging in the heavy quark and
large recoil energy limit impose various relations on form factors that
parametrise the decay of B mesons into light mesons. These symmetries are
broken by perturbative effects. In this paper we discuss the structure of
heavy-to-light form factors including such effects and compute
symmetry-breaking corrections to first order in the strong coupling. As an
application of our results we consider the forward-backward asymmetry zero in
the rare decay B -> V l^+ l^- and the possibility to constrain potential new
physics contributions to the Wilson coefficient C_9.Comment: 30 pages, LaTeX (typos in eq. (44), (46) corrected
-invariant two-fermion Dirac equation with extended hyperfine operator
For the S-states of muonium and positronium, the hyperfine shifts to the
order of a recently derived two-fermion equation with explicit -invariance are checked against the results of a nonrelativistic reduction,
and the leading shifts are calculated. An additional hyperfine
operator is discovered which can milden the singularity for of the
Dirac hyperfine operator, such that the resulting extended operator can be used
nonperturbatively. The binding correction to magnetic moments is mentioned
How much charm can PANDA produce?
We consider the production of charmed baryons and mesons in the
proton-antiproton binary reactions at the energies of the future ANDA
experiment. To describe these processes in terms of hadronic interaction
models, one needs strong couplings of the initial nucleons with the
intermediate and final charmed hadrons. Similar couplings enter the models of
binary reactions with strange hadrons. For both charmed and strange hadrons we
employ the strong couplings and their ratios calculated from QCD light-cone sum
rules. In this method finite masses of and quarks are taken into
account. Employing the Kaidalov's quark-gluon string model with Regge poles and
adjusting the normalization of the amplitudes in this model to the calculated
strong couplings, we estimate the production cross section of charmed hadrons.
For it can reach several tens of at
, whereas the cross sections of and pair
production are predicted to be smaller.Comment: 22 pages, 6 figures, matches published versio
Light-cone sum rules for form factors revisited
We reconsider and update the QCD light-cone sum rules for form
factors. The gluon radiative corrections to the twist-2 and twist-3 terms in
the correlation functions are calculated. The -quark mass is
employed, instead of the one-loop pole mass used in the previous analyses. The
light-cone sum rule for is fitted to the measured
-distribution in , fixing the input parameters with the
largest uncertainty: the Gegenbauer moments of the pion distribution amplitude.
For the vector form factor at zero momentum transfer we predict
. Combining it with the value of the
product extracted from experiment, we obtain
. In addition, the scalar
and penguin form factors and are
calculated.Comment: 33 pages, 7 figures, one figure and a few comments added, version to
appear in JHE
Interaction of matter-wave gap solitons in optical lattices
We study mobility and interaction of gap solitons in a Bose-Einstein
condensate (BEC) confined by an optical lattice potential. Such localized
wavepackets can exist only in the gaps of the matter-wave band-gap spectrum and
their interaction properties are shown to serve as a measure of discreteness
imposed onto a BEC by the lattice potential. We show that inelastic collisions
of two weakly localized near-the-band-edge gap solitons provide simple and
effective means for generating strongly localized in-gap solitons through
soliton fusion.Comment: 12 pages, 7 figure
Kinetic equation with exact charge conservation
We formulate the kinetic master equation describing the production of charged
particles which are created or destroyed only in pairs due to the conservation
of their Abelian charge.Our equation applies to arbitrary particle
multiplicities and reproduces the equilibrium results for both canonical (rare
particles) and grand canonical (abundant particles) systems. For canonical
systems, the equilibrium multiplicity is much lower and the relaxation time is
much shorter than the naive extrapolation from the grand canonical ensemble
results. Implications for particle chemical equilibration in heavy-ion
collisions are discussed.Comment: 4 Pages in RevTe
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