in this paper, we deal with the subdierential concept onhadamard spaces. flat hadamard spaces are characterized, and nec-essary and sucient conditions are presented to prove that the subdif-ferential set in hadamard spaces is nonempty. proximal subdierentialin hadamard spaces is addressed and some basic properties are high-lighted. finally, a density theorem for subdierential set is establi...

abstract. let x be a vector space over a field k of real or complex numbers.we will prove the superstability of the following golab-schinzel type equationf(x + g(x)y) = f(x)f(y); x; y 2 x;where f; g are unknown functions (satisfying some assumptions). then we generalize the superstability result for this equation with values in the field of complex numbers to the case of an arbitrary hilbert spac...

From past literature it is evident that the search for self-dual codes has been hampered by the computational difficulty of generating the Hadamard matrices required. The use of the cocyclic construction of Hadamard matrices has permitted substantial cut-downs in the search time, but the search space still grows exponentially. Here we look at an adaptation of image-processing techniques for the...

Given a definite nonnegative matrix A ∈ Mn(C), we study the minimal index of A : I(A) = max{λ ≥ 0 : A ◦ B ≥ λB for all 0 ≤ B}, where A ◦ B denotes the Hadamard product (A ◦ B)ij = AijBij . For any unitary invariant norm N in Mn(C), we consider the Nindex of A: I(N,A) = min{N(A ◦ B) : B ≥ 0 and N(B) = 1} If A has nonnegative entries, then I(A) = I(‖ · ‖sp, A) if and only if there exists a vector...

We give some sufficient and necessary conditions for an analytic function f on the unit ball B with Hadamard gaps, that is, for f (z)=∑k=1Pnk (z) (the homogeneous polynomial expansion of f ) satisfying nk+1/nk ≥ λ > 1 for all k ∈N, to belong to the space p(B)= { f |sup0<r<1(1− r2)‖R fr‖p <∞, f ∈H(B)}, p = 1,2,∞ as well as to the corresponding little space. A remark on analytic functions with Ha...

A proof is presented that in a spatially flat Robertson-Walker spacetime the adia-batic vacuum of scalar quantum field is a Hadamard state only if it is of infinite order and vice versa every Hadamard state lies in the Fock space based on an adiabatic vacuum.

Let M be a Hadamard manifold, that is, a complete simply connected riemannian manifold with non-positive sectional curvatures. Then every geodesic segment α : [0, a] → M from α(0) to α(a) can be extended to a geodesic ray α : [0,∞) → M . We say then that the Hadamard manifold M is geodesically complete. Note that, in this case, all geodesic rays are proper maps. CAT(0) spaces are generalization...

Applications of well-known matrix theory reveal some interesting and possibly useful invariant properties of the real Hadamard matrix and transform (including the Walsh matrix and transform). Subject to certain conditions that can be fulfilled for many orders of the matrix, the space it defines can be decomposed into two invariant subspaces defined by two real, singular, mutually orthogonal (al...

Fej'{e}r  Hadamard  inequality is generalization of Hadamard inequality. In this paper we prove certain Fej'{e}r  Hadamard  inequalities for $k$-fractional integrals. We deduce Fej'{e}r  Hadamard-type  inequalities for Riemann-Liouville fractional integrals. Also as special case Hadamard inequalities for $k$-fractional as well as fractional integrals are given.