In this paper, we survey some of latest developments in using preconditioned conjugate gradient methods for solving mildly ill-conditioned Toeplitz systems where the condition numbers of the systems grow like O(n) for some > 0. This corresponds to Toeplitz matrices generated by functions having zeros of order. Because of the ill-conditioning, the number of iterations required for convergence in...

For a Toeplitz or Toeplitz-like matrix T, we define a preconditioning applied to the symmetrized matrix TnT, which decreases the condition number compared to the one of TnT and even the one of T. This enables us to accelerate the conjugate gradient algorithm for solving Toepiltz and Toeplitz-like linear systems, thus extending the previous results of [1], restricted to the Hermitian positive de...

Toeplitz operators (or equivalently, Wiener-Hopf operators; more generally, block Toeplitz operators; and particularly, Toeplitz determinants) are of importance in connection with a variety of problems in physics, and in particular, in the field of quantum mechanics. For example, a study of solvable models in quantum mechanics uses the spectral theory of Toeplitz operators (cf. [Pr]); the one-d...

Computations with Toeplitz and Toeplitz-like matrices are fundamental for many areas of algebraic and numerical computing. The list of computational problems reducible to Toeplitz and Toeplitz-like computations includes, in particular, the evaluation of the greatest common divisor (gcd), the least common multiple (lcm), and the resultant of two polynomials, computing Padé approximation and the ...

Let E be a row-finite directed graph. We prove that there exists a C∗algebra C∗ min (E) with the following co-universal property: given any C∗-algebra B generated by a Toeplitz-Cuntz-Krieger E-family in which all the vertex projections are nonzero, there is a canonical homomorphism from B onto C∗ min (E). We also identify when a homomorphism from B to C∗ min (E) obtained from the co-universal p...

We extend the theory of Multigrid methods developed for PDE, Toeplitz and related matrices to the Block Toeplitz case. Prolongations and restrictions are defined depending on the zeroes of the generating function of the Block Toeplitz matrix. On numerical examples we compare different choices for prolongations and restrictions.

We compute the Dixmier trace of pseudo-Toeplitz operators on the Fock space. As an application we find a formula for the Dixmier trace of the product of commutators of Toeplitz operators on the Hardy and weighted Bergman spaces on the unit ball of C. This generalizes an earlier work of Helton-Howe for the usual trace of the anti-symmetrization of Toeplitz operators.

In this paper we completely characterize compact Toeplitz operators on the harmonic Bergman space. By using this result we establish the short exact sequences associated with the Toeplitz algebra and the Hankel algebra. We show that the Fredholm index of each Fredholm operator in the Toeplitz algebra or the Hankel algebra is zero.  2002 Elsevier Science (USA). All rights reserved.

We study three different problems in the area of Toeplitz operators on the Segal-Bargmann space in C. Extending results obtained previously by the first author and Y.L. Lee, and by the second author, we first determine the commutant of a given Toeplitz operator with a radial symbol belonging to the class Sym>0(C ) of symbols having certain growth at infinity. We then provide explicit examples o...

During a recent conversation, R . P. Agnew suggested a determination of the validity of the proposition that row-infinite Toeplitz transformations are more powerful than row-finite transformations . Before this proposition is examined, it is necessary to assign a precise meaning to it. Corresponding to every sequence s a regular rowfinite Toeplitz transformation A can be constructed such that t...