20,706 research outputs found
Stationary quantum Markov process for the Wigner function
As a stochastic model for quantum mechanics we present a stationary quantum
Markov process for the time evolution of the Wigner function on a lattice phase
space Z_N x Z_N with N odd. By introducing a phase factor extension to the
phase space, each particle can be treated independently. This is an improvement
on earlier methods that require the whole distribution function to determine
the evolution of a constituent particle. The process has branching and
vanishing points, though a finite time interval can be maintained between the
branchings. The procedure to perform a simulation using the process is
presented.Comment: 12 pages, no figures; replaced with version accepted for publication
in J. Phys. A, title changed, an example adde
Optimal estimation of a physical observable's expectation value for pure states
We study the optimal way to estimate the quantum expectation value of a
physical observable when a finite number of copies of a quantum pure state are
presented. The optimal estimation is determined by minimizing the squared error
averaged over all pure states distributed in a unitary invariant way. We find
that the optimal estimation is "biased", though the optimal measurement is
given by successive projective measurements of the observable. The optimal
estimate is not the sample average of observed data, but the arithmetic average
of observed and "default nonobserved" data, with the latter consisting of all
eigenvalues of the observable.Comment: v2: 5pages, typos corrected, journal versio
Stringy Derivation of Nahm Construction of Monopoles
We derive the Nahm construction of monopoles from exact tachyon condensation
on unstable D-branes. The Dirac operator used in the Nahm construction is
identified with the tachyon profile in our D-brane approach, and we provide
physical interpretation of the procedures Nahm gave. Crucial is the
introduction of infinite number of brane-antibranes from which arbitrary
D-brane can be constrcuted, exhibitting a unified view of various D-branes. We
explicitly show the equivalence of the D3-brane boundary state with the
monopole profile and the D1-brane boundary state with the Nahm data as
transverse scalars.Comment: 18 pages, 4 eps figures, JHEP style, comments about low energy limits
added, references adde
A Multiobjective Approach to Allocating Water Resource for Municipal, Agricultural and Recreational Uses
A water resource allocation problem in Western Skane, Sweden, is formulated as a two-level multiobjective program, which reflects a decentralized institutional framework of the region. The upper level model deals with the region as a whole and seeks for technically feasible alternatives and their associated costs. The lower level models are concerned with activities of different water users which often conflict each other.
Both the upper and the lower level problems are solved in a stepwise manner using reference objective methods. Advantages of this class of multiobjective methods as a tool for aiding decision-making and conflict resolution are noted. Uses of the model and further extensions are also mentioned
Robustness Criterion for Planning Water Supply/Demand Systems
Water resource systems have been an important part of resources and environment related research at IIASA since its inception. As demands for water increase relative to supply, the intensity and efficiency of water resources management must be developed further. This in turn requires an increase in the degree of detail and sophistication of the analysis, including economic, social and environmental evaluation of water resources development alternatives aided by application of mathematical modeling techniques, to generate inputs for planning, design, and operational decisions.
During the year of 1978 it was decided that parallel to the continuation of demand studies, an attempt would be made to integrate the results of our studies on water demands with water supply considerations. This new task was named "Regional Water Management (Task 1, Resources and Environment Area)".
This paper is concerned with the robustness of the integrated water supply/water demand systems which is defined as the system ability to perform under different future events than originally expected at a relatively small incremental costs. It is shown how the robustness criterion may be used (in addition to the cost-effectiveness criterion) for screening long lead-time investment alternatives
Real-time simulation of jet engines with digital computer. 1: Fabrication and characteristics of the simulator
The fabrication and performance of a real time jet engine simulator using a digital computer are discussed. The use of the simulator in developing the components and control system of a jet engine is described. Comparison of data from jet engine simulation tests with actual engine tests was conducted with good agreement
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