Parameter dependent optimal thresholds, indifference levels and inverse optimal stopping problems

Consider the classic infinite-horizon problem of stopping a one-dimensional diffusion to optimise between running and terminal rewards and suppose we are given a parametrised family of such problems. We provide a general theory of parameter dependence in infinite-horizon stopping problems for which threshold strategies are optimal. The crux of the approach is a supermodularity condition which guarantees that the family of problems is indexable by a set valued map which we call the indifference map. This map is a natural generalisation of the allocation (Gittins) index, a classical quantity in the theory of dynamic allocation. Importantly, the notion of indexability leads to a framework for inverse optimal stopping problems

On Infinite Horizon Optimal Stopping of General Random Walk

The objective of this study is to provide an alternative characterization of the optimal value function of a certain Black- Scholes-type optimal stopping problem where the underlying stochastic process is a general random walk, i.e. the process constituted by partial sums of an IID sequence of random variables. Furthermore, the pasting principle of this optimal stopping problem is studied.General random walk, optimal stopping, minimal functions, continuous pasting

On the Tree-Cutting Problem under Interest Rate and Forest Value Uncertainty

The current literature on optimal forest rotation makes the unrealistic assumption of constant interest rate though harvesting decisions of forest stands are typically subject to long time horizons. We apply the Wicksellian single rotation framework to cover the unexplored case of variable and stochastic interest rate. By modelling the stochastic interest rate according to the Cox-Ingersoll-Ross model and the forest value as a geometric Brownian motion we provide an explicit solution for the Wicksellian single rotation problem and show that increased interest rate volatility increases the optimal exercise threshold of the irreversible harvesting opportunity and thereby prolongs the optimal rotation period. Numerical illustration indicates that the optimal threshold becomes higher at an increasing rate.forest rotation, optimal stopping, stochastic interest rates

The Optimal Stopping Problem of Dupuis and Wang: A Generalization

In this paper, we study the optimal stopping problem of Dupuis and Wang analyzed in [7]. In this problem, the underlying follows a linear diffusion but the decision maker is not allowed to stop at any time she desires but rather on the jump times of an independent Poisson process. In [7], the authors solve this problem in the case where the underlying is a geometric Brownian motion and the payoff function is of American call option type. In the current study, we will this problem under weak assumptions on both the underlying and the payoff. We also demonstrate that the results of [7] are recovered from ours.Optimal stopping, linear diffusion, free boundary problem, Poisson process

Wicksellian Theory of Forest Rotation under Interest Rate Variability

The current literature on optimal forest rotation makes the assumption of constant interest rate. However, the irreversible harvesting decisions of forest stands are typically subject to relatively long time horizons over which interest rates do fluctuate considerably. In this paper we apply the Wicksellian single rotation framework to extend the existing studies to cover the unexplored case of variable interest rate. Given the technical generality of the considered valuation problem, we provide a thorough mathematical characterization of the optimal timing problem and develop new results. We show that even in the deterministic case if the current interest rate deviates from its long-run steady state, interest rate variability changes the rotation age significantly when compared with the constant discounting case. Further, and importantly, allowing for interest rate uncertainty is shown to increase the optimal rotation period when the value of the optimal policy is a convex function of the current interest rate. In line with this finding, we also establish that increased interest rate volatility has a positive impact on the optimal rotation period.Wicksellian rotation, variable interest rates, linear diffusions, optimal stopping, free boundary problems