Trigonometric diophantine equations (On vanishing sums of roots of unity)
Von Neumann operators are reflexive.
Stable invariant subspaces for operators on Hilbert space
If T is a bounded operator on a separable complex Hilbert space ℋ, an invariant subspace ℳ for T is stable provided that whenever is a sequence of operators such that , there is a sequence of subspaces , with in for all n, such that in the strong operator topology. If the projections converge in norm, ℳ is called a norm stable invariant subspace. This paper characterizes the stable invariant subspaces of the unilateral shift of finite multiplicity and normal operators. It also shows that...
On λ-commuting operators
For a scalar λ, two operators T and S are said to λ-commute if TS = λST. In this note we explore the pervasiveness of the operators that λ-commute with a compact operator by characterizing the closure and the interior of the set of operators with this property.
The primary pretenders
Packing lines, planes, etc.: Packings in Grassmannian spaces.
The Mathieu group and its pseudogroup extension .
On three-dimensional space groups.
Page 1