19,268 research outputs found
Low-momentum interactions in three- and four-nucleon scattering
Low momentum two-nucleon interactions obtained with the renormalization group
method and the similarity renormalization group method are used to study the
cutoff dependence of low energy 3N and 4N scattering observables. The residual
cutoff dependence arises from omitted short-ranged 3N (and higher) forces that
are induced by the renormalization group transformations, and may help to
estimate the sensitivity of various 3N and 4N scattering observables to
short-ranged many-body forces.Comment: 5 pages, 8 figures, to be published in Phys. Rev.
Cosmic Sculpture: A new way to visualise the Cosmic Microwave Background
3D printing presents an attractive alternative to visual representation of
physical datasets such as astronomical images that can be used for research,
outreach or teaching purposes, and is especially relevant to people with a
visual disability. We here report the use of 3D printing technology to produce
a representation of the all-sky Cosmic Microwave Background (CMB) intensity
anisotropy maps produced by the Planck mission. The success of this work in
representing key features of the CMB is discussed as is the potential of this
approach for representing other astrophysical data sets. 3D printing such
datasets represents a highly complementary approach to the usual 2D projections
used in teaching and outreach work, and can also form the basis of
undergraduate projects. The CAD files used to produce the models discussed in
this paper are made available.Comment: Accepted for publication in the European Journal of Physic
Multiobjective analysis for the design and control of an electromagnetic valve actuator
The electromagnetic valve actuator can deliver much improved fuel efficiency and reduced emissions in spark ignition (SI) engines owing to the potential for variable valve timing when compared with cam-operated, or conventional, variable valve strategies. The possibility exists to reduce pumping losses by throttle-free operation, along with closed-valve engine braking. However, further development is required to make the technology suitable for accept- ance into the mass production market. This paper investigates the application of multiobjective optimization techniques to the conflicting objective functions inherent in the operation of such a device. The techniques are utilized to derive the optimal force–displacement characteristic for the solenoid actuator, along with its controllability and dynamic/steady state performance
The ion motion in self-modulated plasma wakefield accelerators
The effects of plasma ion motion in self-modulated plasma based accelerators
is examined. An analytical model describing ion motion in the narrow beam limit
is developed, and confirmed through multi-dimensional particle-in-cell
simulations. It is shown that the ion motion can lead to the early saturation
of the self-modulation instability, and to the suppression of the accelerating
gradients. This can reduce the total energy that can be transformed into
kinetic energy of accelerated particles. For the parameters of future
proton-driven plasma accelerator experiments, the ion dynamics can have a
strong impact. Possible methods to mitigate the effects of the ion motion in
future experiments are demonstrated.Comment: 11 pages, 3 figures, accepted for publication in Phys. Rev. Let
Three-body Faddeev-Alt-Grassberger-Sandhas approach to direct nuclear reactions
Momentum space three-body Faddeev-like equations are used to calculate
elastic, transfer and charge exchange reactions resulting from the scattering
of deuterons on 12C and 16O or protons on 13C and 17O; 12C and 16O are treated
as inert cores. All possible reactions are calculated in the framework of the
same model space. Comparison with previous calculations based on approximate
methods used in nuclear reaction theory is discussed.Comment: 10 pages, 13 figures, to be published in Phys. Rev.
Very High Mach Number Electrostatic Shocks in Collisionless Plasmas
The kinetic theory of collisionless electrostatic shocks resulting from the
collision of plasma slabs with different temperatures and densities is
presented. The theoretical results are confirmed by self-consistent
particle-in-cell simulations, revealing the formation and stable propagation of
electrostatic shocks with very high Mach numbers (), well above the
predictions of the classical theories for electrostatic shocks.Comment: 6 pages, submitted to Phys. Rev. Let
New calculation schemes for proton-deuteron scattering including the Coulomb interaction
The Coulomb interaction between the protons is included in the description of
proton-deuteron scattering using the screening and renormalization approach in
the framework of momentum-space integral equations. Two new calculational
schemes are presented that confirm the reliability of the perturbative approach
for treating the screened Coulomb interaction in high partial waves, used by us
in earlier works.Comment: To be published in Phys. Rev.
Photodisintegration of the triton with realistic potentials
The process is treated by means of three-body integral
equations employing in their kernel the W-Matrix representation of the
subsystem amplitudes. As compared to the plane wave (Born) approximation the
full solution of the integral equations, which takes into account the final
state interaction, shows at low energies a 24% enhancement. The calculations
are based on the semirealistic Malfliet-Tjon and the realistic Paris and Bonn B
potentials. For comparison with earlier calculations we also present results
for the Yamaguchi potential. In the low-energy region a remarkable potential
dependence is observed, which vanishes at higher energies.Comment: 16 pages REVTeX, 8 postscript figures included, uses epsfig.st
Multiple scattering effects in quasi free scattering from halo nuclei: a test to Distorted Wave Impulse Approximation
Full Faddeev-type calculations are performed for Be breakup on proton
target at 38.4, 100, and 200 MeV/u incident energies. The convergence of the
multiple scattering expansion is investigated. The results are compared with
those of other frameworks like Distorted Wave Impulse Approximation that are
based on an incomplete and truncated multiple scattering expansion.Comment: 7 pages, 16 figures, to be published in Phys. Rev.
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