We consider the problem of optimal two modes switching in finite horizon in the model with jumps. We first give a verification theorem to shape the problem and later we show that it is satisfied. Finally when randomness comes from a diffusion process we study the the associated PDI variational inequalities with inter-connected obstacles.
Setting of the problemLet (Ω, F , (F t ) t≤T , P ) be a stochastic basis such that F 0 contains all the P -null sets of F and for any t < T , F t+ := ∩ >0 F t+ = F t . We assume that the filtration (F t ) t≤T is generated by a standard d-dimensional Brownian motion B = (B t ) t≤T and a Poisson random measure μ on R + × U where U = R l \ {0}.A problem which underlies the one we consider here is related to management of a power plant. Actually assume we have a power station (or plant) which produces electricity whose selling price in the market is an F t -adapted stochastic process (X t ) t≤T . Electricity is non-storable, then once produced it should be almost immediately consumed. As a result, the station will produce electricity only when the production is profitable in relation with the level of X. Otherwise the production is stopped until the market selling price reaches a level which makes it profitable again and it will be resumed. Therefore a management strategy δ of this power plant is an increasing sequence of F t -stopping times (τ n ) n≥1 where lim n→∞ τ n = T , P − a.s.. For any n ≥ 1, τ 2n−1 (resp. τ 2n ) are the times when the manager of the plant makes the decision to stop (resp. resume) the production. We suppose that at t = 0 the production is open.When a strategy δ := (τ n ) n≥1 is implemented its yield is given by:the process u is bind to δ by u t = 1 if the production is open at time t and 0 otherwise ; Ψ(t, x, 1) = ψ 1 (t, x) and Ψ(t, x, 0) = ψ 2 (t, x) where ψ 1 (t, X t )dt (resp. ψ 2 (t, X t )dt) is the yield provided by the power station in a short time dt when open (resp. closed) ; a 12 > 0 (resp. a 21 > 0) is the cost when the plant is switched from the operating mode to the mothballed one (resp. conversely). The problem is to find a strategy δ * such that J(δ * ) = sup δ J(δ). The quantity J(δ * ) is the price of the power plant in the energy market. 2
Verification Theoremwhere T t is the set of F t -stopping times τ ≥ t, P − a.s.. Then Y 1 0 = sup δ J(δ) and the strategy δ * = (τ * n ) n≥1 defined as follows: τ * 0 = 0 and for n ≥ 1,