3,053 research outputs found
A study of the effectiveness of a phonetic and activity approach to the teaching of spelling in grade four,
Includes appendices.
Thesis (M.A.)--Boston Universit
Analytical solution of a model for complex food webs
We investigate numerically and analytically a recently proposed model for
food webs [Nature {\bf 404}, 180 (2000)] in the limit of large web sizes and
sparse interaction matrices. We obtain analytical expressions for several
quantities with ecological interest, in particular the probability
distributions for the number of prey and the number of predators. We find that
these distributions have fast-decaying exponential and Gaussian tails,
respectively. We also find that our analytical expressions are robust to
changes in the details of the model.Comment: 4 pages (RevTeX). Final versio
A bipartite class of entanglement monotones for N-qubit pure states
We construct a class of algebraic invariants for N-qubit pure states based on
bipartite decompositions of the system.
We show that they are entanglement monotones, and that they differ from the
well know linear entropies of the sub-systems. They therefore capture new
information on the non-local properties of multipartite systems.Comment: 6 page
The invariant-comb approach and its relation to the balancedness of multipartite entangled states
The invariant-comb approach is a method to construct entanglement measures
for multipartite systems of qubits. The essential step is the construction of
an antilinear operator that we call {\em comb} in reference to the {\em
hairy-ball theorem}. An appealing feature of this approach is that for qubits
(or spins 1/2) the combs are automatically invariant under SL(2,\CC), which
implies that the obtained invariants are entanglement monotones by
construction. By asking which property of a state determines whether or not it
is detected by a polynomial SL(2,\CC) invariant we find that it is the
presence of a {\em balanced part} that persists under local unitary
transformations. We present a detailed analysis for the maximally entangled
states detected by such polynomial invariants, which leads to the concept of
{\em irreducibly balanced} states. The latter indicates a tight connection with
SLOCC classifications of qubit entanglement. \\ Combs may also help to define
measures for multipartite entanglement of higher-dimensional subsystems.
However, for higher spins there are many independent combs such that it is
non-trivial to find an invariant one. By restricting the allowed local
operations to rotations of the coordinate system (i.e. again to the
SL(2,\CC)) we manage to define a unique extension of the concurrence to
general half-integer spin with an analytic convex-roof expression for mixed
states.Comment: 17 pages, revtex4. Substantially extended manuscript (e.g. proofs
have been added); title and abstract modified
Talking Story: Using Culture to Educate Pacific Islander Men about Health and Aging
Abstract Relatively little attention has been paid in the literature to strategies promoting the health of Native Hawaiian and other Pacific Islander (NHPI) men. To fill this void, a Native Hawaiian cancer survivor and a Marshallese minister in Orange County, California, founded the Kane Group to promote men's health information and support. This group is comprised of 10 to 15 NHPI men, ages 35 to 83, with a diverse background of experiences in the U.S. healthcare system and health conditions, including multiple site cancer survivors and/or co-morbidity and chronic condition, like high blood pressure, diabetes. The Kane Group provides social support and engages in discussions, using the island tradition of "talk story", to relate a variety of men's health issues from prostate cancer to physical fitness to end-of-life decision making in a supportive and safe environment. The group weaves Pacific Islander culture and values into the process and conduct of the support groups. This community commentary describes the innovative strategies, successes, and challenges that emerged with the development of the group that were designed to celebrate Pacific Islander men's health, provide information, fellowship, and support for the many who are facing health crises
Algebraic invariants of five qubits
The Hilbert series of the algebra of polynomial invariants of pure states of
five qubits is obtained, and the simplest invariants are computed.Comment: 4 pages, revtex. Short discussion of quant-ph/0506073 include
Can we avoid high coupling?
It is considered good software design practice to organize source code into modules and to favour within-module connections (cohesion) over between-module connections (coupling), leading to the oft-repeated maxim "low coupling/high cohesion". Prior research into network theory and its application to software systems has found evidence that many important properties in real software systems exhibit approximately scale-free structure, including coupling; researchers have claimed that such scale-free structures are ubiquitous. This implies that high coupling must be unavoidable, statistically speaking, apparently contradicting standard ideas about software structure. We present a model that leads to the simple predictions that approximately scale-free structures ought to arise both for between-module connectivity and overall connectivity, and not as the result of poor design or optimization shortcuts. These predictions are borne out by our large-scale empirical study. Hence we conclude that high coupling is not avoidable--and that this is in fact quite reasonable
Classification of qubit entanglement: SL(2,C) versus SU(2) invariance
The role of SU(2) invariants for the classification of multiparty
entanglement is discussed and exemplified for the Kempe invariant I_5 of pure
three-qubit states. It is found to being an independent invariant only in
presence of both W-type entanglement and threetangle. In this case, constant
I_5 admits for a wide range of both threetangle and concurrences. Furthermore,
the present analysis indicates that an SL^3 orbit of states with equal tangles
but continuously varying I_5 must exist. This means that I_5 provides no
information on the entanglement in the system in addition to that contained in
the tangles (concurrences and threetangle) themselves. Together with the
numerical evidence that I_5 is an entanglement monotone this implies that SU(2)
invariance or the monotone property are too weak requirements for the
characterization and quantification of entanglement for systems of three
qubits, and that SL(2,C) invariance is required. This conclusion can be
extended to general multipartite systems (including higher local dimension)
because the entanglement classes of three-qubit systems appear as subclasses.Comment: 9 pages, 10 figures, revtex
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