In this paper we consider the solutions of linear systems of saddle point problems‎. ‎By using the spectrum of a quadratic matrix polynomial‎, ‎we study the eigenvalues of the iterative matrix of the Hermitian and skew Hermitian splitting method‎.

We give in this paper some closed-form formulas for the maximal and minimal values of the rank and inertia of the Hermitian matrix expression A − BX ± (BX)∗ with respect to a variable matrix X. As applications, we derive the extremal values of the ranks/inertias of the matrices X and X ± X∗, where X is a (Hermitian) solution to the matrix equation AXB = C, respectively, and give necessary and s...

Let (M, 0) ⊂ C be a complex n -dimensional Hermitian symmetric space endowed with the hyperbolic form ωB . Denote by (M ∗, ω∗ B ) the compact dual of (M,ωB) , where ω ∗ B is the Fubini–Study form on M∗ . Our first result is Theorem 1.1 where, with the aid of the theory of Jordan triple systems, we construct an explicit diffeomorphism ΨM : M → R = C ⊂ M∗ satisfying Ψ∗ M (ω0) = ωB and Ψ ∗ M (ω∗ B...

This paper gives double angle theorems that bound the change in an invariant subspace of an indeenite Hermitian matrix in the graded form H = D AD subject to a perturbation H ! e H = D (A + A)D. These theorems extend recent results on a deenite Hermitian matrix in the graded form (Linear Algebra Appl., 311 (2000), 45{60) but the bounds here are more complicated in that they depend on not only r...

We use Chern–Weil theory for Hermitian holomorphic vector bundles with canonical connections for explicit computation of the Chern forms of trivial bundles with special non-diagonal Hermitian metrics. We prove that every ∂̄∂-exact real form of the type (k, k) on an n-dimensional complexmanifold X arises as a difference of the Chern character forms of trivial Hermitian vector bundles with canonic...

It has been a central problem in the theory of quadratic forms to find integers represented by quadratic forms. The celebrated Four Square Theorem by Lagrange [10] was an outstanding result in this study. Ramanujan generalized this theorem and found 54 positive definite quaternary quadratic forms which represent all positive integers [13]. We call a positive definite quadratic form universal, i...

A generalized non-Hermitian oscillator Hamiltonian is proposed that consists of additional linear terms which break PT -symmetry explicitly. The model is put into an equivalent Hermitian form by means of a similarity transformation and the criterion of N -fold supersymmetry with a position-dependent mass is shown to reside in it.

Let H be any complex inner product space with inner product < ·, · >. We say that f : | C → | C is Hermitian positive definite on H if the matrix ( f(< z,z >) )n r,s=1 (∗) is Hermitian positive definite for all choice of z, . . . ,z in H, all n. It is strictly Hermitian positive definite if the matrix (∗) is also non-singular for any choice of distinct z, . . . ,z in H. In this article we prove...

It is a familiar fact in several complex variables that the hermitian quadratic form Lr,p is invariant under biholomorphism. (Restricted to the complex tangent space, this is exactly the Levi form.) It is less familiar that the non-hermitian form Qr,p is invariant under Möbius transformation when restricted to the complex tangent space. This is established in Section 2. Our main result is the f...

A transformation of the form x → iy; x, y ∈ R, or a Darbouxal-type similarity transformation with a metric operator η are shown to transform non-Hermitian PT -symmetric Hamiltonians (with positive mass m = + |m|) into their Hermitian partner Hamiltonians (with negative mass m = − |m|) in Hilbert space. PACS codes: 03.65.Ge, 03.65.Ca