Uniqueness of lower semicontinuous viscosity solutions for the minimum time problem

We obtain the uniqueness of lower semicontinuous (LSC) viscosity solutions of the transformed minimum time problem assuming that they converge to zero on a "reachable" part of the target in appropriate directions. We present a counter-example which shows that the uniqueness does not hold without thi s convergence assumption. It was shown by Soravia that the uniqueness of LSC viscosity solutions havi ng a "subsolution property" on the target holds. In order to verify this su bsolution property, we show that the dynamic programming principle (DPP) ho lds inside for any LSC viscosity solutions. In order to obtain the DPP, we prepare appropriate approximate PDEs derived through Barles' inf-convolution and its variant.