Optimal Control Under Stochastic Target Constraints

Fri, 22/01/2010
14:15
Bruno Bouchard (University Paris Dauphine) Nomura Seminar Add to calendar DH 1st floor SR
Normal 0 false false false EN-GB X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} We study a class of Markovian optimal stochastic control problems in which the controlled process $ Z^\nu $ is constrained to satisfy an a.s.~constraint $ Z^\nu(T)\in G\subset \R^{d+1} $ $ \Pas $ at some final time $ T>0 $.  When the set is of the form $ G:=\{(x,y)\in
\R^d\x \R~:~g(x,y)\ge 0\} $, with $ g $ non-decreasing in $ y $, we provide a Hamilton-Jacobi-Bellman  characterization of the associated value function. It gives rise to a state constraint problem where the constraint can be expressed in terms of an auxiliary value function $ w $ which characterizes the set $ D:=\{(t,Z^\nu(t))\in
[0,T]\x\R^{d+1}~:~Z^\nu(T)\in G\;a.s. $ for some $  \nu\} $. Contrary to standard state constraint problems, the domain $ D $ is not given a-priori and we do not need to impose conditions on its boundary. It is naturally incorporated in the auxiliary value function $ w $ which is itself a viscosity solution of a non-linear parabolic PDE.  Applying ideas recently developed in Bouchard, Elie and Touzi (2008), our general result also allows to consider optimal control problems with moment constraints of the form $ \Esp{g(Z^\nu(T))}\ge 0 $ or $ \Pro{g(Z^\nu(T))\ge 0}\ge p $.