29,486 research outputs found
Polydispersity Effects in the Dynamics and Stability of Bubbling Flows
The occurrence of swarms of small bubbles in a variety of industrial systems
enhances their performance. However, the effects that size polydispersity may
produce on the stability of kinematic waves, the gain factor, mean bubble
velocity, kinematic and dynamic wave velocities is, to our knowledge, not yet
well established. We found that size polydispersity enhances the stability of a
bubble column by a factor of about 23% as a function of frequency and for a
particular type of bubble column. In this way our model predicts effects that
might be verified experimentally but this, however, remain to be assessed. Our
results reinforce the point of view advocated in this work in the sense that a
description of a bubble column based on the concept of randomness of a bubble
cloud and average properties of the fluid motion, may be a useful approach that
has not been exploited in engineering systems.Comment: 11 pages, 2 figures, presented at the 3rd NEXT-SigmaPhi International
Conference, 13-18 August, 2005, Kolymbari, Cret
Interplay between Zeeman interaction and spin-orbit coupling in a two-dimensional semiconductor system
We analyse the interplay between Dresselhaus, Bychkov-Rashba, and Zeeman
interactions in a two-dimensional semiconductor quantum system under the action
of a magnetic field. When a vertical magnetic field is considered, we predict
that the interplay results in an effective cyclotron frequency that depends on
a spin-dependent contribution. For in-plane magnetic fields, we found that the
interplay induces an anisotropic effective gyromagnetic factor that depends on
the orientation of the applied field as well as on the orientation of the
electron momentum.Comment: 5 page
Radiative capture reaction for Ne formation within a full three-body model
Background: The breakout from the hot Carbon-Nitrogen-Oxigen (CNO) cycles can
trigger the rp-process in type I x-ray bursts. In this environment, a
competition between and the
two-proton capture reaction is
expected.
Purpose: Determine the three-body radiative capture reaction rate for
formation including sequential and direct, resonant and
non-resonant contributions on an equal footing.
Method: Two different discretization methods have been applied to generate
Ne states in a full three-body model: the analytical transformed
harmonic oscillator method and the hyperspherical adiabatic expansion method.
The binary --O interaction has been adjusted to reproduce the known
spectrum of the unbound F nucleus. The dominant contributions to
the reaction rate have been
calculated from the inverse photodissociation process.
Results: Three-body calculations provide a reliable description of Ne
states. The agreement with the available experimental data on Ne is
discussed. It is shown that the
reaction rates computed within the two methods agree in a broad range of
temperatures. The present calculations are compared with a previous theoretical
estimation of the reaction rate.
Conclusions: It is found that the full three-body model provides a reaction
rate several orders of magnitude larger than the only previous estimation. The
implications for the rp-process in type I x-ray bursts should be investigated.Comment: 10 pages, 10 figures. Corrected versio
Anomalous quartic couplings in collisions at the LHeC and the FCC-he
We conducted a study on measuring production and on the sensitivity
limits at Confidence Level on thirteen anomalous couplings obtained by
dimension-8 operators which are related to the anomalous quartic
couplings. We consider the main reaction with the sub-process at
the Large Hadron electron Collider (LHeC) and the Future Circular
Collider-hadron electron (FCC-he). For the LHeC, energies of the beams
are taken to be and 140 GeV and the energy of the beams is taken
to be TeV. For the FCC-he, energies of the beams are taken to
be and 140 GeV and the energy of the beams is taken to be TeV, respectively. It is interesting to notice that the LHeC and the FCC-he
will lead to model-independent limits on the anomalous quartic
couplings which are one order of magnitude stringent than the CMS Collaboration
limits, in addition to being competitive with other limits reported in the
literature.Comment: 28 pages, 10 Figures and 13 Table
Chern-Simons and Born-Infeld gravity theories and Maxwell algebras type
Recently was shown that standard odd and even-dimensional General Relativity
can be obtained from a -dimensional Chern-Simons Lagrangian invariant
under the algebra and from a -dimensional Born-Infeld
Lagrangian invariant under a subalgebra respectively. Very
Recently, it was shown that the generalized In\"on\"u-Wigner contraction of the
generalized AdS-Maxwell algebras provides Maxwell algebras types
which correspond to the so called Lie algebras. In this article we
report on a simple model that suggests a mechanism by which standard
odd-dimensional General Relativity may emerge as a weak coupling constant limit
of a -dimensional Chern-Simons Lagrangian invariant under the Maxwell
algebra type , if and only if . Similarly, we show
that standard even-dimensional General Relativity emerges as a weak coupling
constant limit of a -dimensional Born-Infeld type Lagrangian invariant
under a subalgebra of the Maxwell algebra type, if and
only if . It is shown that when this is not possible for a
-dimensional Chern-Simons Lagrangian invariant under the
and for a -dimensional Born-Infeld type Lagrangian
invariant under algebra.Comment: 30 pages, accepted for publication in Eur.Phys.J.C. arXiv admin note:
text overlap with arXiv:1309.006
- …