2,564 research outputs found
First-principles prediction of a decagonal quasicrystal containing boron
We interpret experimentally known B-Mg-Ru crystals as quasicrystal
approximants. These approximant structures imply a deterministic decoration of
tiles by atoms that can be extended quasiperiodically. Experimentally observed
structural disorder corresponds to phason (tile flip) fluctuations.
First-principles total energy calculations reveal that many distinct tilings
lie close to stability at low temperatures. Transfer matrix calculations based
on these energies suggest a phase transition from a crystalline state at low
temperatures to a high temperature state characterized by tile fluctuations. We
predict BMgRu forms a decagonal quasicrystal that is
metastable at low temperatures and may be thermodynamically stable at high
temperatures.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Depleted pyrochlore antiferromagnets
I consider the class of "depleted pyrochlore" lattices of corner-sharing
triangles, made by removing spins from a pyrochlore lattice such that every
tetrahedron loses exactly one. Previously known examples are the "hyperkagome"
and "kagome staircase". I give criteria in terms of loops for whether a given
depleted lattice can order analogous to the kagome \sqrt{3} \times \sqrt{three}
state, and also show how the pseudo-dipolar correlations (due to local
constraints) generalize to even the random depleted case.Comment: 6pp IOP latex, 1 figure; Proc. "Highly Frustrated Magnetism 2008",
Sept 2008, Braunschwei
Method of fabricating an object with a thin wall having a precisely shaped slit
A method is described for making a structure with a cavity and a thin wall with a precisely shaped slit. An object with a cavity having two openings, one of which is to be closed by a thin wall with a slit, is placed on the surface of a fixture. The fixture surface has a slot conforming to the size and shape of the slit to be formed in the thin wall
Bethe Ansatz solution of a decagonal rectangle triangle random tiling
A random tiling of rectangles and triangles displaying a decagonal phase is
solved by Bethe Ansatz. Analogously to the solutions of the dodecagonal square
triangle and the octagonal rectangle triangle tiling an exact expression for
the maximum of the entropy is found.Comment: 17 pages, 4 figures, some remarks added and typos correcte
Methods for obtaining and handling marine eggs and embryos
2nd EditionFrom the Preface: The Introduction to the first edition of this book (1957) (see page viii) stated
that the volume was admittedly incomplete, and that new methods for obtaining,
handling and studying marine eggs and embryos would undoubtedly be forthcoming.
This prediction has been abundantly borne out in the intervening 14 years, and a
complete revision of the book is clearly called for. A major re-writing is now
(June, 1971) in progress. However, steadily continuing sales have resulted in the
first edition going out of print, and it seemed advisable to re-issue it, with certain
minor changes, as a stopgap measure, pending the major re-writing in progress. In
the interim, it is appropriate here to point out some of the newer sources of information
now available, and to note a few of the advances which have been made
since 1957.Preparation of the first edition was completed under a National Science
Foundation grant (NSF-G2477); the present revision was made possible, in part, by
a grant from the National Institutes of Health, GM 15311
Non-relativistic Lee Model on two Dimensional Riemannian Manifolds
This work is a continuation of our previous work (JMP, Vol. 48, 12, pp.
122103-1-122103-20, 2007), where we constructed the non-relativistic Lee model
in three dimensional Riemannian manifolds. Here we renormalize the two
dimensional version by using the same methods and the results are shortly given
since the calculations are basically the same as in the three dimensional
model. We also show that the ground state energy is bounded from below due to
the upper bound of the heat kernel for compact and Cartan-Hadamard manifolds.
In contrast to the construction of the model and the proof of the lower bound
of the ground state energy, the mean field approximation to the two dimensional
model is not similar to the one in three dimensions and it requires a deeper
analysis, which is the main result of this paper.Comment: 18 pages, no figure
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