Spectral variation conjecture for normal operators and differentiator compressions

From papers

Let AA be a normal operator on a complex Hilbert space of dimension n2n\ge 2. Let ρ(A)\rho(A) denote the radius of the smallest closed disk containing the spectrum of AA, let AA' be the compression of AA to the orthogonal complement of a trace vector of AA, and let s(A,A)s(A,A') denote the spectral variation between AA and AA'. The spectral variation conjecture. One has

s(A,A)ρ(A),s(A,A')\le \rho(A),

and equality occurs if and only if either A=0A=0, or AA has simple eigenvalues and AnA^n is a non-zero scalar operator. The claim reformulates the polynomial conjectures in terms of spectra of a normal operator and its compression. The source gives no resolution, so the conjecture remains open there.

Progress summary

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Sources & referencesView supporting material

Primary source

Julius Borcea, “Maximal and inextensible polynomials and the geometry of the spectra of normal operators”, arXiv:math/0309233 (2007).

Solutions 0

No solutions have been posted yet.