84,974 research outputs found
Generalised hyperbolicity in spacetimes with string-like singularities
In this paper we present well-posedness results of the wave equation in
for spacetimes that contain string-like singularities. These results
extend a framework able to characterise gravitational singularities as
obstruction to the dynamics of test fields rather than point particles. In
particular, we discuss spacetimes with cosmic strings and the relation of our
results to the Strong Cosmic Censorship Conjecture.Comment: Accepted for publication in Classical and Quantum Gravit
Hypernuclear Physics at PANDA
Hypernuclear research will be one of the main topics addressed by the PANDA
experiment at the planned Facility for Anti-proton and Ion Research FAIR at
Darmstadt, Germany. A copious production of Xi-hyperons at a dedicated internal
target in the stored anti-proton beam is expected, which will enable the
high-precision gamma-spectroscopy of double strange systems for the first time.
In addition to the general purpose PANDA setup, the hypernuclear experiments
require an active secondary target of silicon layers and absorber material as
well as high purity germanium (HPGe) crystals as gamma-detectors. The design of
the setup and the development of these detectors is progressing: a first HPGe
crystal with a new electromechanical cooling system was prepared and the
properties of a silicon strip detector as a prototype to be used in the
secondary target were studied. Simultaneously to the hardware projects,
detailed Monte Carlo simulations were performed to predict the yield of
particle stable hypernuclei. With the help of the Monte Carlo a procedure for
Lambda-Lambda-hypernuclei identification by the detection and correlation of
the weak decay pions was developed.Comment: prepared for the International Conference on Exotic Atoms and Related
Topics (EXA2011), Vienna, Sept. 5-9, 201
The legal form of labour conflicts and their time persistence: an empirical analysis with a large firms' panel
Using a panel of large firms from Spain, we check the relative time persistence of different types of labour conflicts such as strikes, collective conflicts, lockouts and other conflicts with lost working hours but without the previous stated legal forms for labour conflicts. We present random-effects probit estimations comparing observations with each type of conflicts with the same set of observations without any type of conflict. The results show that no legal form labour conflicts do not have long-term persistence (persistence is only in the short-term, from quarter to quarter), and the other types of conflicts suffer short and long-term persistence of confliction at the firm level, corresponds to strikes the higher size of both types of persistence. As short and long term persistence of strikes have almost the same size these results do not support asymmetric information theories of strike.Strike; labour conflict; time persistence; asymmetric information
Near field and far field scattering of surface plasmon polaritons by one-dimensional surface defects
A rigorous formulation for the scattering of surface plasmon polaritons (SPP)
from a one-dimensional surface defect of any shape that yields the
electromagnetic field in the vacuum half-space above the vacuum-metal interface
is developed by the use of an impedance boundary condition. The electric and
magnetic near fields, the angular distribution of the far-field radiation into
vacuum due to SPP-photon coupling, and the SPP reflection and transmission
coefficients are calculated by numerically solving the k-space integral
equation upon which the formulation is based. In particular, we consider
Gaussian-shaped defects and study the dependence of the above mentioned
physical quantities on their 1/e half-width a and height h. SPP reflection is
significant for narrow defects; maximum reflection (plasmon mirrors) is
achieved for a~lambda/10. For increasing defect widths, protuberances and
indentations behave differently. The former give rise to a monotonic increase
of radiation at the expense of SPP transmission for increasing defect
half-width. Indentations exhibit a significant increase of radiation (decrease
of SPP transmission) for half-widths of the order of or smaller than the
wavelength, but tend to total SPP transmission in an oscillatory manner upon
further increasing the half-width. Light-emitters might thus be associated with
either wide indentations, or protuberances with widths that are of the order of
or smaller than the wavelength.Comment: REVTeX 3.1, 10 pages with 9 EPS figures (epsf macro
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