In Tikhonov-Phillips regularization of general form the given ill-posed linear system is replaced by a Least Squares problem including a minimization of the solution vector x, relative to a seminorm ‖Lx‖2 with some regularization matrix L. Based on the finite difference matrix Lk, given by a discretization of the first or second derivative, we introduce the seminorm ‖LkD x̃ x‖2 where the diagona...

We introduce the T -restricted weighted generalized inverse of a singular matrix A with respect to a positive semidefinite matrix T , which defines a seminorm for the space. The new approach proposed is that since T is positive semidefinite, the minimal seminorm solution is considered for all vectors perpendicular to the kernel of T .

In this note we prove a trace theorem in fractional spaces with variable exponents. To be more precise, we show that if p : Ω × Ω → (1,∞) and q : ∂Ω→ (1,∞) are continuous functions such that (n− 1)p(x, x) n− sp(x, x) > q(x) in ∂Ω ∩ {x ∈ Ω: n− sp(x, x) > 0}, then the inequality ‖f‖Lq(·)(∂Ω) ≤ C { ‖f‖Lp̄(·)(Ω) + [f ]s,p(·,·) } holds. Here p̄(x) = p(x, x) and [f ]s,p(·,·) denotes the fractional semi...

We extend some previous results of our work [1] on the error of the averaging method, in the one-frequency case. The new error estimates apply to any separating family of seminorms on the space of the actions; they generalize our previous estimates in terms of the Euclidean norm. For example, one can use the new approach to get separate error estimates for each action coordinate. An application...

The notion of (unbounded) C∗-seminorms plays a relevant role in the representation theory of ∗-algebras and partial ∗-algebras. A rather complete analysis of the case of ∗-algebras has given rise to a series of interesting concepts like that of semifinite C∗seminorm and spectral C∗-seminorm that give information on the properties of ∗-representations of the given ∗-algebra A and also on the str...

Let Lm,p(Rn) be the homogeneous Sobolev space for p?(n,?), ? a Borel regular measure on Rn, and Lm,p(Rn)+Lp(d?) of measurable functions with finite seminorm ?f?Lm,p(Rn)+Lp(d?):=inff1+f2=f?{?f1?Lm,p(Rn)p+?Rn|f2|pd?}1/p. We construct linear operator T:Lm,p(Rn)+Lp(d?)?Lm,p(Rn), that nearly optimally decomposes every function in sum space: ?Tf?Lm,p(Rn)p+?Rn|Tf?f|pd??C?f?Lm,p(Rn)+Lp(d?)p C dependent...

Let I be a finite interval and r ∈ N. Denote by ∆ s + L q the subset of all functions y ∈ L q such that the s-difference ∆ s τ y(·) is nonnegative on I, ∀τ > 0. Further, denote by ∆ s + W r p , the class of functions x on I with the seminorm x (r) L p ≤ 1, such that ∆ s τ x ≥ 0, τ > 0. For s = 3,. .. , r + 1, we obtain two-sided estimates of the shape preserving widths