Maximally monotone operators play a key role in modern optimization and
variational analysis. Two useful subclasses are rectangular (also known as star
monotone) and paramonotone operators, which were introduced by Brezis and
Haraux, and by Censor, Iusem and Zenios, respectively. The former class has
useful range properties while the latter class is of importance for interior
point methods and duality theory.
Monotone linear relations play important roles in variational inequality
problems and quadratic optimizations. In this paper, we give explicit maximally
monotone linear subspace extensions of a monotone linear relation in finite
dimensional spaces. Examples are provided to illustrate our extensions. Our
results generalize a recent result by Crouzeix and Anaya.
The most important open problem in Monotone Operator Theory concerns the
maximal monotonicity of the sum of two maximal monotone operators provided that
Rockafellar's constraint qualification holds. In this paper, we provide a new
maximal monotonicity result for the sum of two maximal monotone operators $A$
and $B$ in this setting satisfying that $A+N_{\bar{\dom B}}$ is of type (FPV)
and $\dom A\cap\bar{\dom B}\subseteq\dom B$. The proof relies on some results
on the Fitzpatrick function.
The most important open problem in Monotone Operator Theory concerns the
maximal monotonicity of the sum of two maximal monotone operators provided that
Rockafellar's constraint qualification holds.
In this note, we provide a new maximal monotonicity result for the sum of a
maximal monotone relation and the subdifferential operator of a proper, lower
semicontinuous, sublinear function. The proof relies on Rockafellar's formula
for the Fenchel conjugate of the sum as well as some results on the Fitzpatrick
function.
Monotone operators are of basic importance in optimization as they generalize
simultaneously subdifferential operators of convex functions and positive
semidefinite (not necessarily symmetric) matrices. In 1970, Asplund studied the
additive decomposition of a maximal monotone operator as the sum of a
subdifferential operator and an "irreducible" monotone operator. In 2007,
Borwein and Wiersma [SIAM J. Optim. 18 (2007), pp.
In this paper, we give two explicit examples of unbounded linear maximal
monotone operators. The first unbounded linear maximal monotone operator $S$ on
$\ell^{2}$ is skew. We show its domain is a proper subset of the domain of its
adjoint $S^*$, and $-S^*$ is not maximal monotone. This gives a negative answer
to a recent question posed by Svaiter. The second unbounded linear maximal
monotone operator is the inverse Volterra operator $T$ on $L^{2}[0,1]$.
In this paper, we give two explicit examples of unbounded linear maximal
monotone operators. The first unbounded linear maximal monotone operator $S$ on
$\ell^{2}$ is skew. We show its domain is a proper subset of the domain of its
adjoint $S^*$, and $-S^*$ is not maximal monotone. This gives a negative answer
to a recent question posed by Svaiter. The second unbounded linear maximal
monotone operator is the inverse Volterra operator $T$ on $L^{2}[0,1]$.