769 research outputs found
Moller operators and Lippmann-Schwinger equations for step-like potentials
The Moller operators and the asociated Lippman-Schwinger equations obtained
from different partitionings of the Hamiltonian for a step-like potential
barrier are worked out, compared and related.Comment: 15 pages, 1 inlined figure, iopart.cl
Soybean Aphids Found in Ontario
Originating text in English.Citation: Baute, Tracy. (2001). Soybean Aphids Found in Ontario. CropPest Ontario (OMAF Newsletter), 6(11), 1-6
How institutions shape expectations about the impact of European integration on welfare states
Do Europeans perceive European integration as a threat to their welfare state or as an opportunity? Drawing on comparative survey data, Sharon Baute explains how national and supranational institutions simultaneously shape citizens’ expectations about social protection in the EU
Sources of quantum waves
Due to the space and time dependence of the wave function in the time
dependent Schroedinger equation, different boundary conditions are possible.
The equation is usually solved as an ``initial value problem'', by fixing the
value of the wave function in all space at a given instant. We compare this
standard approach to "source boundary conditions'' that fix the wave at all
times in a given region, in particular at a point in one dimension. In contrast
to the well-known physical interpretation of the initial-value-problem
approach, the interpretation of the source approach has remained unclear, since
it introduces negative energy components, even for ``free motion'', and a
time-dependent norm. This work provides physical meaning to the source method
by finding the link with equivalent initial value problems.Comment: 12 pages, 7 inlined figures; typos correcte
A measurement-based approach to quantum arrival times
For a quantum-mechanically spread-out particle we investigate a method for
determining its arrival time at a specific location. The procedure is based on
the emission of a first photon from a two-level system moving into a
laser-illuminated region. The resulting temporal distribution is explicitly
calculated for the one-dimensional case and compared with axiomatically
proposed expressions. As a main result we show that by means of a deconvolution
one obtains the well known quantum mechanical probability flux of the particle
at the location as a limiting distribution.Comment: 11 pages, 4 figures, submitted to Phys. Rev.
Comment on "Measurement of time of arrival in quantum mechanics"
The analysis of the model quantum clocks proposed by Aharonov et al. [Phys.
Rev. A 57 (1998) 4130 - quant-ph/9709031] requires considering evanescent
components, previously ignored. We also clarify the meaning of the operational
time of arrival distribution which had been investigated.Comment: 3 inlined figures; comment on quant-ph/970903
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