15,296 research outputs found
On an atom with a magnetic quadrupole moment in a rotating frame
The quantum description of an atom with a magnetic quadrupole moment in the
presence of a uniform effective magnetic field is analysed. The atom is also
subject to rotation and a scalar potential proportional to the inverse of the
radial distance. It is shown that the spectrum of energy is modified, in
contrast to the Landau-type levels, and there is a restriction on the possible
values of the cyclotron frequency which stems from the influence of the
rotation and scalar potential proportional to the inverse of the radial
distance.Comment: 11 pages. arXiv admin note: text overlap with arXiv:1705.0819
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
Bartering integer commodities with exogenous prices
The analysis of markets with indivisible goods and fixed exogenous prices has
played an important role in economic models, especially in relation to wage
rigidity and unemployment. This research report provides a mathematical and
computational details associated to the mathematical programming based
approaches proposed by Nasini et al. (accepted 2014) to study pure exchange
economies where discrete amounts of commodities are exchanged at fixed prices.
Barter processes, consisting in sequences of elementary reallocations of couple
of commodities among couples of agents, are formalized as local searches
converging to equilibrium allocations. A direct application of the analyzed
processes in the context of computational economics is provided, along with a
Java implementation of the approaches described in this research report.Comment: 30 pages, 5 sections, 10 figures, 3 table
Inelastic scattering and elastic amplitude in Ising field theory in a weak magnetic field at T>T_c. Perturbative analysis
Two-particle scattering in Ising field theory in a weak magnetic field h is
studied in the regime T>T_c, using perturbation theory in h^2. We calculate
explicitly the cross-section of the process 2->3 to the order h^2. To this
order, the corresponding cross-section dominates the total cross-section (the
probability of all inelastic processes) at all energies E. We show that at high
energies the h^2 term in the total cross-section grows as 16 G_3 h^2 log(E)
where G_3 is exactly the third moment of the Euclidean spin-spin correlation
function. Going beyond the leading order, we argue that at small h^2 the
probability of the 2->2 process decays as E^(-16G_3 h^2) as E->infinity.Comment: 20 pages, 3 figures; typos correcte
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
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