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Phase field theory of interfaces and crystal nucleation in a eutectic system of fcc structure: II. Nucleation in the metastable liquid immiscibility region
The official version of this Article can be accessed from the link below - Copyright @ 2007 American Institute of PhysicsIn the second part of our paper, we address crystal nucleation in the metastable liquid miscibility region of eutectic systems that is always present, though experimentally often inaccessible. While this situation resembles the one seen in single component crystal nucleation in the presence of a metastable vapor-liquid critical point addressed in previous works, it is more complex because of the fact that here two crystal phases of significantly different compositions may nucleate. Accordingly, at a fixed temperature below the critical point, six different types of nuclei may form: two liquid-liquid nuclei: two solid-liquid nuclei; and two types of composite nuclei, in which the crystalline core has a liquid "skirt," whose composition falls in between the compositions of the solid and the initial liquid phases, in addition to nuclei with concentric alternating composition shells of prohibitively high free energy. We discuss crystalline phase selection via exploring/identifying the possible pathways for crystal nucleation.This work has been supported by the Hungarian Academy of Sciences under contract No. OTKA-K-62588 and by the ESA PECS Nos. 98021 and 98043
Note on a Conjecture of Wegner
The optimal packings of n unit discs in the plane are known for those natural
numbers n, which satisfy certain number theoretic conditions. Their geometric
realizations are the extremal Groemer packings (or Wegner packings). But an
extremal Groemer packing of n unit discs does not exist for all natural numbers
n and in this case, the number n is called exceptional. We are interested in
number theoretic characterizations of the exceptional numbers. A counterexample
is given to a conjecture of Wegner concerning such a characterization. We
further give a characterization of the exceptional numbers, whose shape is
closely related to that of Wegner's conjecture.Comment: 5 pages; Contributions to Algebra and Geometry, Vol.52 No1 April 201
Az ÁBÉCÉ tanításának hasznosságáról (A célnyelvû tanítási közeg megteremtésének fontosságáért)
Jelzések NYIK-es tanulók olvasmánymegértéséről
Ez a dolgozatom „Az olvasás: fölfedezés” – Egy korosztály irodalomértésének alakulása című, 1997-ben megvédett kandidátusi értekezésem (Magyar Tudományos Akadémia Doktori Tanácsa, Budapest) alapján készült. Köszönettel tartozom témavezetőmnek, A. Jászó Anna egyetemi tanárnak a kutatásaim kritikai szemléletű irányításáért és Zsolnai József professzor úrnak, a Nyelvi, irodalmi és kommunikációs program (NYIK) kidolgozójának, aki az értekezésem elkészültét megkülönböztetett figyelemmel, nem egyszer bátorító észrevételeivel kísérte
Toward the Jamming Threshold of Sphere Packings: Tunneled Crystals
We have discovered a new family of three-dimensional crystal sphere packings
that are strictly jammed (i.e., mechanically stable) and yet possess an
anomalously low density. This family constitutes an uncountably infinite number
of crystal packings that are subpackings of the densest crystal packings and
are characterized by a high concentration of self-avoiding "tunnels" (chains of
vacancies) that permeate the structures. The fundamental geometric
characteristics of these tunneled crystals command interest in their own right
and are described here in some detail. These include the lattice vectors (that
specify the packing configurations), coordination structure, Voronoi cells, and
density fluctuations. The tunneled crystals are not only candidate structures
for achieving the jamming threshold (lowest-density rigid packing), but may
have substantially broader significance for condensed matter physics and
materials science.Comment: 19 pages, 5 figure
Entanglement and permutational symmetry
We study the separability of permutationally symmetric quantum states. We
show that for bipartite symmetric systems most of the relevant entanglement
criteria coincide. However, we provide a method to generate examples of bound
entangled states in symmetric systems, for the bipartite and the multipartite
case. These states shed some new light on the nature of bound entanglement.Comment: 5 pages, no figures, revtex4; v3: published versio
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