Metrics on the set of semimartingale filtrations

Let X be a stochastic process with cadlag paths. We consider the set of all filtrations under which X is a semimartingale, and we define a distance between such filtrations with the help of the bounded variation parts in the corresponding decompositions of X. We show that this distance is a complete metric on the set of semimartingale filtrations if the given process X is continuous.     

Approximating a common zero of finite family of monotone operators in Hadamard spaces

In this paper, a common zero of a finite family of monotone operators is approximated in Hadamard spaces. Some applications in convex minimization and fixed point theory are also presented.     

Elliptic system with some singular nonlinearity

We investigate multiplicity of solutions for elliptic systems with singular non-linearities. We obtain a theorem which shows that elliptic systems with some singular non-linearities have infinitely many solutions. We get this result by using the variational method, critical point theory and homology theory.     

Endomorphisms of free modules as sums of four quadratic endomorphisms

We will prove that every endomorphism of a free right R-module of infinite rank can be decomposed as a sum of four endomorphisms which satisfy some fixed polynomial identities.