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A vanishing theorem for a class of logarithmic D-modules
Let OX (resp. DX) be the sheaf of holomorphic functions (resp. the
sheaf of linear differential operators with holomorphic coefficients) on X =
Cn. Let D X be a locally weakly quasi-homogeneous free divisor defined
by a polynomial f. In this paper we prove that, locally, the annihilating
ideal of 1/fk over DX is generated by linear differential operators of order
1 (for k big enough). For this purpose we prove a vanishing theorem for
the extension groups of a certain logarithmic DX–module with OX. The
logarithmic DX–module is naturally associated with D (see Notation 1.1).
This result is related to the so called Logarithmic Comparison Theorem
V centers in MgAl2O4 spinels
V centers induced by ionizing irradiation at 80 or 300 K in single-crystal and polycrystalline MgAl2O4 samples have been studied by use of electron paramagnetic resonance and optical absorption. Vt- and Vo2- centers, as a result of hole trapping at tetrahedral and octahedral cation vacancies, respectively, have been found to be responsible for two EPR bands centered at g=2.011 and optical absorption bands involved in the complex absorption spectrum at about 3.4 eV. These centers anneal thermally in a very wide step from 220 to 575 K. © 1991 The American Physical SocietyPeer Reviewe
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