We show that control systems with an analytic semigroup and control and observation operators that are not too unbounded have a Hankel operator that belongs to the Schatten class Sp for all positive p. This implies that the Hankel singular values converge to zero faster than any polynomial rate. This in turn implies fast convergence of balanced truncations. As a corollary, decay rates for the e...

The Langlands functoriality conjecture, as reformulated in the “beyond endoscopy” program, predicts comparisons between (stable) trace formulas of different groups G1,G2 for every morphism G1L→LG2 their L-groups. This conjecture can be seen a special case more general which replaces reductive by spherical varieties and formula its generalization, relative formula. goal this article precursor [1...

We consider the problem of solving least squares problems involving a matrix M of small displacement rank with respect to two matrices Z 1 and Z 2. We develop formulas for the generators of the matrix M (H) M in terms of the generators of M and show that the Cholesky factorization of the matrix M (H) M can be computed quickly if Z 1 is close to unitary and Z 2 is triangular and nilpotent. These...

This paper presents stability results for various fast trigonometric transforms. We consider the numerical stability of the classical fast Fourier transform (FFT) with respect to diierent precomputation methods for the involved twiddle factors and show the strong innuence of precomputation errors on the numerical stability of the FFT. The examinations are extended to fast algorithms for the com...

For μ≥-1/2, the authors have developed elsewhere a scheme for interpolation by Hankel translates of a basis function Φ in certain spaces of continuous functions Yn(n∈ℕ) depending on a weight w. The functions Φ and w are connected through the distributional identity t4n(hμ'Φ)(t)=1/w(t), where hμ' denotes the generalized Hankel transform of order μ. In this paper, we use the projection operators ...

In this paper Mersenne number transforms are converted into cyclic convolutions, in which form they are amendable to simple hardware interpretation. Such realisation structures are proposed that can make the computation of Mersenne number transforms very fast indeed. This new approach can be extended to the implementation of other number theoretic transforms, in particular to Fermat number tran...