A new kind of comparison theorem in which an SDE is compared with two deterministic ODEs is established by means of the generalized sample solutions of SDEs. Using this theorem, we can compare solutions of two SDEs with different diffusion coefficients and obtain some asymptotic estimations for the paths of diffusion processes. In the investigation of solutions of stochastic differential equati...

A singular stochastic control problem with state constraints in two-dimensions is studied. We show that the free boundary between the control and no-action regions is approximately linear away from the state constraining boundaries. Proof of this result relies on connections with related optimal stopping problems. We provide an explicit solution to one such optimal stopping problem. Results of ...

This paper focus aspects connected to the optimal control of a renewable resource modelled by a stochastic differential equation. The main point is to show how small changes of the problem may cause severe changes in the properties of the control. In particular we show how the introduction of uncertainty may lead to a less conservative policy. In this context we introduce the notion “induced cr...

and Applied Analysis 3 Fix an open solvency set S ⊂ R. Let τS = inf {t > 0; Y (t) ∉ S} (10) be the bankruptcy time. τS is the first time at which the stochastic process Y(t) exits the solvency set S. Similar optimal control problems in which the terminal time is governed by a stopping criterion are considered in [19–21] in the deterministic case. Let f i : Rk × K → R and g i : Rk → R be given f...

We consider a stochastic control problem that has emerged in the economics literature as an investment model under uncertainty. This problem combines features of both stochastic impulse control and optimal stopping. The aim is to discover the form of the optimal strategy. It turns out that this has a priori rather unexpected features. The results that we establish are of an explicit nature. We ...

We study the stochastic model for bioremediation in a bioreactor with ideal mixing. The dynamics of the examined system is described by stochastic differential equations. We consider an optimal control problem with quadratic costs functional for the linearized model of a well-stirred bioreactor. The optimal control is based on the optimal robust state estimates. The approximate optimal solution...

This work develops a new framework for a class of stochastic control problems with optimal stopping. One of our main motivations stems from dealing with the option pricing of American type. The value function is characterized as the unique solution of a partial differential equation in a Sobolev space. Together with certain regularities and estimates of the value function, the existence of the ...

This paper is devoted to the study of the connections among risk-sensitive stochastic optimal control, dynamic game optimal control, risk-neutral stochastic optimal control and deterministic optimal control in a nonlinear, discrete-time context with complete state information. The analysis worked out sheds light on the profound links among these control strategies, which remain hidden in the li...

Abstract. We consider a mean field linear-quadratic-Gaussian game with a major player and a large number of minor players parametrized by a continuum set. The mean field generated by the minor players is approximated by a random process depending only on the initial state and the Brownian motion of the major player, and this leads to two limiting optimal control problems with random coefficient...

The productive sector of the economy, represented by a single firm employing labour to produce the consumption good, is studied in a stochastic continuous time model on a finite time interval. The firm must choose the optimal level of employment and capital investment in order to maximize its expected total profits. In this stochastic control problem the firm’s capacity is modelled as an Itô pr...