We introduce a new class of positive linear operators that generalize the classical Bernstein
operators. Specifically, we construct a sequence of operators that preserve the logarithmic
function
,
with
and
.
We prove pointwise and uniform convergence and we derive a quantitative estimate of
the approximation error in terms of the modulus of continuity. We also obtain a
Voronovskaja-type asymptotic formula that is used to establish saturation results
and inverse theorems. In particular, the saturation class of the considered
approximation process is characterized by solving a second order differential
equation. Shape-preserving properties, such as monotonicity, concavity and variation
diminishing, are also investigated. Finally, a simple application to signal denoising is
addressed.
Keywords
asymptotic approximation, positive linear operators,
logarithm preservation, constructive approximation,
saturation by solving differential problems, shape
preserving, denoising