30 research outputs found
Photoabsorption spectra of the diamagnetic hydrogen atom in the transition regime to chaos: Closed orbit theory with bifurcating orbits
With increasing energy the diamagnetic hydrogen atom undergoes a transition
from regular to chaotic classical dynamics, and the closed orbits pass through
various cascades of bifurcations. Closed orbit theory allows for the
semiclassical calculation of photoabsorption spectra of the diamagnetic
hydrogen atom. However, at the bifurcations the closed orbit contributions
diverge. The singularities can be removed with the help of uniform
semiclassical approximations which are constructed over a wide energy range for
different types of codimension one and two catastrophes. Using the uniform
approximations and applying the high-resolution harmonic inversion method we
calculate fully resolved semiclassical photoabsorption spectra, i.e.,
individual eigenenergies and transition matrix elements at laboratory magnetic
field strengths, and compare them with the results of exact quantum
calculations.Comment: 26 pages, 9 figures, submitted to J. Phys.
Outliers: Multicolour photometry guiding the search for evolved binary systems in the globular cluster 47 Tucanae
We use Hubble Space Telescope multicolour photometry of the globular cluster
47 Tucanae to uncover a population of 24 objects with no previous
classification that are outliers from the single-star model tracks in the
colour-magnitude diagram and yet are likely cluster members. By comparing those
sources with evolutionary models and X-ray source catalogues, we were able to
show that the majority of those sources are likely binary systems that do not
have any X-ray source detected nearby, most possibly formed by a white dwarf
and a main-sequence star and a small number of possible double-degenerate
systems.Comment: 13 pages, 8 figures, 2 tables. Accepted for publication in MNRAS on
September 18, 201
Spatial modeling of techno-economic potential of biojet fuel production in Brazil
It is expected that Brazil could play an important role in biojet fuel (BJF) production in the future due to the long experience in biofuel production and the good agro-ecological conditions. However, it is difficult to quantify the techno-economic potential of BJF because of the high spatiotemporal variability of available land, biomass yield, and infrastructure as well as the technological developments in BJF production pathways. The objective of this research is to assess the recent and future techno-economic potential of BJF production in Brazil and to identify location-specific optimal combinations of biomass crops and technological conversion pathways. In total, 13 production routes (supply chains) are assessed through the combination of various biomass crops and BJF technologies. We consider temporal land use data to identify potential land availability for biomass production. With the spatial distribution of the land availability and potential yield of biomass crops, biomass production potential and costs are calculated. The BJF production cost is calculated by taking into account the development in the technological pathways and in plant scales. We estimate the techno-economic potential by determining the minimum BJF total costs and comparing this with the range of fossil jet fuel prices. The techno-economic potential of BJF production ranges from 0 to 6.4 EJ in 2015 and between 1.2 and 7.8 EJ in 2030, depending on the reference fossil jet fuel price, which varies from 19 to 65 US$/GJ across the airports. The techno-economic potential consists of a diverse set of production routes. The Northeast and Southeast region of Brazil present the highest potentials with several viable production routes, whereas the remaining regions only have a few promising production routes. The maximum techno-economic potential of BJF in Brazil could meet almost half of the projected global jet fuel demand toward 2030