A blowing up wave equation with exponential type nonlinearity and arbitrary positive energy

We consider in two space dimensions, the nonexistence of global solutions to the class of Klein-Gordon equations∂ttu−Δu+u=fa(u),(t,x)∈[0,T⁎)×Ω. We give sufficient conditions on the data such that the solution of the above Klein-Gordon equation blows up in finite time.