can the lowest time of a node never be greater than its discovery time ?
Discovery time and lowest time
No because it is an array which stores, for every vertex v , the discovery time of the earliest discovered vertex to which v or any of the vertices in the subtree rooted at v is having a back edge.
It is just how it is defined. Also if you see the code, we initialise it same as discovery time, after this it is updated only when we get something smaller than the current value.
Yeah i saw the code and that is the reason i asked the question to confirm its definition.Thanks for ths clarification.