For an entirely non-selfadjoint operator with spectrum at zero, the imaginary component of which has an absolutely continuous spectrum (not necessarily dissipative and having lacunas in the spectrum), triangular and ...

For a convex domain D bounded by the hypersurface ∂D in a space of constant curvature we give sharp bounds on the width R - r of a spherical shell with radii R and r that can enclose ∂D, provided that normal curvatures of ...