4,939 research outputs found
Stochastic Target Games and Dynamic Programming via Regularized Viscosity Solutions
We study a class of stochastic target games where one player tries to find a
strategy such that the state process almost-surely reaches a given target, no
matter which action is chosen by the opponent. Our main result is a geometric
dynamic programming principle which allows us to characterize the value
function as the viscosity solution of a non-linear partial differential
equation. Because abstract mea-surable selection arguments cannot be used in
this context, the main obstacle is the construction of measurable
almost-optimal strategies. We propose a novel approach where smooth
supersolutions are used to define almost-optimal strategies of Markovian type,
similarly as in ver-ification arguments for classical solutions of
Hamilton--Jacobi--Bellman equations. The smooth supersolutions are constructed
by an exten-sion of Krylov's method of shaken coefficients. We apply our
results to a problem of option pricing under model uncertainty with different
interest rates for borrowing and lending.Comment: To appear in MO
Singular mean-field control games with applications to optimal harvesting and investment problems
This paper studies singular mean field control problems and singular mean
field stochastic differential games. Both sufficient and necessary conditions
for the optimal controls and for the Nash equilibrium are obtained. Under some
assumptions the optimality conditions for singular mean-field control are
reduced to a reflected Skorohod problem, whose solution is proved to exist
uniquely. Applications are given to optimal harvesting of stochastic mean-field
systems, optimal irreversible investments under uncertainty and to mean-field
singular investment games. In particular, a simple singular mean-field
investment game is studied where the Nash equilibrium exists but is not unique
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