1,606 research outputs found
The strong Lefschetz property for Artinian algebras with non-standard grading
We define the strong Lefschetz property for finite graded modules over graded
Artinian algebras whose grading is not necessarily standard. We show that most
results which have been obtained for Artinian algebras with standard grading
can be extended for non-standard grading. Our results on the strong Lefschetz
property for non-standard grading can be used to prove that certain Artinian
complete intersections with standard grading have the strong Lefschetz
property.Comment: 24 pages, To appear in Journal of Algebr
The central simple modules of Artinian Gorenstein algebras
Let A be a standard graded Artinian algebra over a field of characteristic
zero and let z be a linear form in A. We define the central simple modules for
each such pair (A, z). Assume that A is Gorenstein. Then we prove that A has
the strong Lefschetz property if and only if there exists a linear form z in A
such that all central simple modules of the pair (A,z) have the strong
Lefschetz property. In the course of proof we need to extend the definition of
the strong Lefschetz property to finite graded modules over graded Artinian
algebra, which previously was defined only for standard graded Artinian
algebras.Comment: 20 pages, To be published in Journal of Pure and Applied Algebr
Theory of Metal-Insulator Transition in PrRu4P12 and PrFe4P12
All symmetry allowed couplings between the 4f^2-electron ground state doublet
of trivalent praseodymium in PrRu4P12 and PrFe4P12 and displacements of the
phosphorus, iron or ruthenium ions are considered. Two types of displacements
can change the crystal lattice from body-centred cubic to simple orthorhombic
or to simple cubic. The first type lowers the point group symmetry from
tetrahedral to orthorhombic, while the second type leaves it unchanged, with
corresponding space group reductions Im3 --> Pmmm and Im3 --> Pm3 respectively.
In former case, the lower point-group symmetry splits the degeneracy of the
4f^2 doublet into states with opposite quadrupole moment, which then leads to
anti-quadrupolar ordering, as in PrFe4P12. Either kind of displacement may
conspire with nesting of the Fermi surface to cause the metal-insulator or
partial metal-insulator transition observed in PrFe4P12 and PrRu4P12. We
investigate this scenario using band-structure calculations, and it is found
that displacements of the phosphorus ions in PrRu4P12 (with space group
reduction Im3 --> Pm3) open a gap everywhere on the Fermi surface.Comment: 6 page
Multipole Fluctuations in Filled Skutterudites
In order to clarify exotic multipole properties of filled skutterudites, we
evaluate multipole susceptibility for =15, where is the local
-electron number, on the basis of a multiorbital Anderson model constructed
using the - coupling scheme. For =1, magnetic fluctuations dominate
over low-temperature electronic properties, while for =2 and 4, electronic
states are dominated by both magnetic and quadrupole fluctuations. For =3
and 5, octupole fluctuations are found to be significant, depending on the
crystalline electric field potential. We discuss possible relevance of the
results to actual materials.Comment: 4 pages, 3 figures, JPSJ2.cls. To be published in J. Phys. Soc. Jp
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