74,393 research outputs found
Higher order relations in Fedosov supermanifolds
Higher order relations existing in normal coordinates between affine
extensions of the curvature tensor and basic objects for any Fedosov
supermanifolds are derived. Representation of these relations in general
coordinates is discussed.Comment: 11 LaTex pages, no figure
Using TPA to count linear extensions
A linear extension of a poset is a permutation of the elements of the set
that respects the partial order. Let denote the number of linear
extensions. It is a #P complete problem to determine exactly for an
arbitrary poset, and so randomized approximation algorithms that draw randomly
from the set of linear extensions are used. In this work, the set of linear
extensions is embedded in a larger state space with a continuous parameter ?.
The introduction of a continuous parameter allows for the use of a more
efficient method for approximating called TPA. Our primary result is
that it is possible to sample from this continuous embedding in time that as
fast or faster than the best known methods for sampling uniformly from linear
extensions. For a poset containing elements, this means we can approximate
to within a factor of with probability at least using an expected number of random bits and comparisons in the poset
which is at most Comment: 12 pages, 4 algorithm
Pade-resummed high-order perturbation theory for nuclear structure calculations
We apply high-order many-body perturbation theory for the calculation of
ground-state energies of closed-shell nuclei using realistic nuclear
interactions. Using a simple recursive formulation, we compute the perturbative
energy contributions up to 30th order and compare to exact no-core shell model
calculations for the same model space and Hamiltonian. Generally, finite
partial sums of this perturbation series do not show convergence with
increasing order, but tend to diverge exponentially. Nevertheless, through a
simple resummation via Pade approximants it is possible to extract rapidly
converging and highly accurate results for the ground state energy.Comment: 6 pages, 2 figures, 1 tabl
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