16,120 research outputs found
Progressive managerial bonuses in a spatial Bertrand duopoly
The relationship of managerial bonuses and profit maximization is interesting both from an economic and a managerial viewpoint. Our contribution to this literature is showing that progressive managerial bonuses can increase profits in a spatial Bertrand competition, and furthermore they can help collusion
Field-reversed bubble in deep plasma channels for high quality electron acceleration
We study hollow plasma channels with smooth boundaries for laser-driven
electron acceleration in the bubble regime. Contrary to the uniform plasma
case, the laser forms no optical shock and no etching at the front. This
increases the effective bubble phase velocity and energy gain. The longitudinal
field has a plateau that allows for mono-energetic acceleration. We observe as
low as 10^{-3} r.m.s. relative witness beam energy uncertainty in each
cross-section and 0.3% total energy spread. By varying plasma density profile
inside a deep channel, the bubble fields can be adjusted to balance the laser
depletion and dephasing lengths. Bubble scaling laws for the deep channel are
derived. Ultra-short pancake-like laser pulses lead to the highest energies of
accelerated electrons per Joule of laser pulse energy
On the efficient numerical solution of lattice systems with low-order couplings
We apply the Quasi Monte Carlo (QMC) and recursive numerical integration
methods to evaluate the Euclidean, discretized time path-integral for the
quantum mechanical anharmonic oscillator and a topological quantum mechanical
rotor model. For the anharmonic oscillator both methods outperform standard
Markov Chain Monte Carlo methods and show a significantly improved error
scaling. For the quantum mechanical rotor we could, however, not find a
successful way employing QMC. On the other hand, the recursive numerical
integration method works extremely well for this model and shows an at least
exponentially fast error scaling
Scaling relations of exciton diffusion in linear aggregates with static and dynamic disorder
Exciton diffusion plays an important role in many opto-electronic processes and phenomena. Understanding the interplay of intermolecular coupling, static energetic disorder, and dephasing caused by environmental fluctuations (dynamic disorder) is crucial to optimize exciton diffusion under various physical conditions. We report on a systematic analysis of the exciton diffusion constant in linear aggregates using the Haken-Strobl-Reineker model to describe this interplay. We numerically investigate the static-disorder scaling of (i) the diffusion constant in the limit of small dephasing rate, (ii) the dephasing rate at which the diffusion is optimized, and (iii) the value of the diffusion constant at the optimal dephasing rate. Three scaling regimes are found, associated with, respectively, fully delocalized exciton states (finite-size effects), weakly localized states, and strongly localized states. The scaling powers agree well with analytically estimated ones. In particular, in the weakly localized regime, the numerical results corroborate the so-called quantum Goldilocks principle to find the optimal dephasing rate and maximum diffusion constant as a function of static disorder, while in the strong-localization regime, these quantities can be derived fully analytically
Anomalous temperature evolution of the internal magnetic field distribution in the charge-ordered triangular antiferromagnet AgNiO2
Zero-field muon-spin relaxation measurements of the frustrated triangular
quantum magnet AgNiO2 are consistent with a model of charge disproportionation
that has been advanced to explain the structural and magnetic properties of
this compound. Below an ordering temperature of T_N=19.9(2) K we observe six
distinct muon precession frequencies, due to the magnetic order, which can be
accounted for with a model describing the probable muon sites. The precession
frequencies show an unusual temperature evolution which is suggestive of the
separate evolution of two opposing magnetic sublattices.Comment: 4 pages, 3 figure
Improved Fixed-Budget Results via Drift Analysis
Fixed-budget theory is concerned with computing or bounding the fitness value
achievable by randomized search heuristics within a given budget of fitness
function evaluations. Despite recent progress in fixed-budget theory, there is
a lack of general tools to derive such results. We transfer drift theory, the
key tool to derive expected optimization times, to the fixed-budged
perspective. A first and easy-to-use statement concerned with iterating drift
in so-called greed-admitting scenarios immediately translates into bounds on
the expected function value. Afterwards, we consider a more general tool based
on the well-known variable drift theorem. Applications of this technique to the
LeadingOnes benchmark function yield statements that are more precise than the
previous state of the art.Comment: 25 pages. An extended abstract of this paper will be published in the
proceedings of PPSN 202
Molecular abundances and low-mass star formation. I: Si- and S-bearing species toward IRAS 16293-2422
Results from millimeter and submillimeter spectral line surveys of the protobinary source IRAS 16293-2422 are presented. Here we outline the abundances of silicon- and sulfur-containing species. A combination of rotation diagram and full statistical equilibrium/radiative transfer calculations is used to constrain the physical conditions toward IRAS 16293 and to construct its beam-averaged chemical composition over a 10-20" (1600-3200 AU) scale. The chemical complexity as judged by species such as SiO, OCS, and H_2S, is mtermedtate between that of dark molecular clouds such as Ll34N and hot molecular cloud cores such as Orion KL. From the richness of the spectra compared to other young stellar objects of similar luminosity, it is clear that molecular abundances do not scale simply with mass; rather, the chemistry is a strong function of evolutionary state, i.e., age
Structure of the lightest tin isotopes
We link the structure of nuclei around Sn, the heaviest doubly magic
nucleus with equal neutron and proton numbers (), to nucleon-nucleon
() and three-nucleon () forces constrained by data of few-nucleon
systems. Our results indicate that Sn is doubly magic, and we predict
its quadrupole collectivity. We present precise computations of Sn
based on three-particle--two-hole excitations of Sn, and reproduce the
small splitting between the lowest and states. Our
results are consistent with the sparse available data.Comment: 8 pages, 4 figure
- …