441 research outputs found
Dynamical symmetry of isobaric analog 0+ states in medium mass nuclei
An algebraic sp(4) shell model is introduced to achieve a deeper
understanding and interpretation of the properties of pairing-governed 0+
states in medium mass atomic nuclei. The theory, which embodies the simplicity
of a dynamical symmetry approach to nuclear structure, is shown to reproduce
the excitation spectra and fine structure effects driven by proton-neutron
interactions and isovector pairing correlations across a broad range of nuclei.Comment: 7 pages, 5 figure
Branon search in hadronic colliders
In the context of the brane-world scenarios with compactified extra
dimensions, we study the production of brane fluctuations (branons) in hadron
colliders (, and ) in terms of the brane tension
parameter , the branon mass and the number of branons . From the
absence of monojets events at HERA and Tevatron (run I), we set bounds on these
parameters and we also study how such bounds could be improved at Tevatron (run
II) and the future LHC. The single photon channel is also analyzed for the two
last colliders.Comment: 17 pages, 10 figures, LaTeX. New comments and figures included. Final
version to appear in Phys. Rev.
Towards nonlinear quantum Fokker-Planck equations
It is demonstrated how the equilibrium semiclassical approach of Coffey et
al. can be improved to describe more correctly the evolution. As a result a new
semiclassical Klein-Kramers equation for the Wigner function is derived, which
remains quantum for a free quantum Brownian particle as well. It is transformed
to a semiclassical Smoluchowski equation, which leads to our semiclassical
generalization of the classical Einstein law of Brownian motion derived before.
A possibility is discussed how to extend these semiclassical equations to
nonlinear quantum Fokker-Planck equations based on the Fisher information
Particle Aggregation in a turbulent Keplerian flow
In the problem of planetary formation one seeks a mechanism to gather small
solid particles together into larger accumulations of solid matter. Here we
describe a scenario in which turbulence mediates this process by aggregating
particles into anticyclonic regions. If, as our simulations suggest,
anticyclonic vortices form as long-lived coherent structures, the process
becomes more powerful because such vortices trap particles effectively. Even if
the turbulence is decaying, following the upheaval that formed the disk, there
is enough time to make the dust distribution quite lumpy.Comment: 16 pages, 9 figure
Nuclear masses set bounds on quantum chaos
It has been suggested that chaotic motion inside the nucleus may
significantly limit the accuracy with which nuclear masses can be calculated.
Using a power spectrum analysis we show that the inclusion of additional
physical contributions in mass calculations, through many-body interactions or
local information, removes the chaotic signal in the discrepancies between
calculated and measured masses. Furthermore, a systematic application of global
mass formulas and of a set of relationships among neighboring nuclei to more
than 2000 nuclear masses allows to set an unambiguous upper bound for the
average errors in calculated masses which turn out to be almost an order of
magnitude smaller than estimated chaotic components.Comment: 4 pages, Accepted for publication in Physical Review Letter
Inclusive particle production at HERA: Higher-order QCD corrections to the resolved quasi-real photon contribution
We calculate in next-to-leading order inclusive cross sections of
single-particle production via resolved photons in collisions at HERA.
Transverse-momentum and rapidity distributions are presented and the scale
dependence is studied. The results are compared with first experimental data
from the H1 Collaboration at HERA.Comment: 11 pages with 15 uuencoded PS figures. Preprint DESY 93-03
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
Variational bound on energy dissipation in plane Couette flow
We present numerical solutions to the extended Doering-Constantin variational
principle for upper bounds on the energy dissipation rate in turbulent plane
Couette flow. Using the compound matrix technique in order to reformulate this
principle's spectral constraint, we derive a system of equations that is
amenable to numerical treatment in the entire range from low to asymptotically
high Reynolds numbers. Our variational bound exhibits a minimum at intermediate
Reynolds numbers, and reproduces the Busse bound in the asymptotic regime. As a
consequence of a bifurcation of the minimizing wavenumbers, there exist two
length scales that determine the optimal upper bound: the effective width of
the variational profile's boundary segments, and the extension of their flat
interior part.Comment: 22 pages, RevTeX, 11 postscript figures are available as one
uuencoded .tar.gz file from [email protected]
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
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.
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