The p-Laplacian evolution equation in metric measure spaces has been studied as the gradient flow in L2 of the p-Cheeger energy (for 1<p<∞). In this paper, using the first-order differential structure on a metric measure space introduced by Gigli, we characterise the subdifferential in L2 of the p-Cheeger energy. This gives rise to a new definition of the p-Laplacian operator in metric measure spaces, which allows us to work with this operator in more detail. In this way, we introduce a new notion of solutions to the p-Laplacian evolution equation in metric measure spaces. For p=1, we obtain a Green-Gauss formula similar to the one by Anzellotti for Euclidean spaces, and use it to characterise the 1-Laplacian operator and study the total variation flow. We also study the asymptotic behaviour of the solutions of the p-Laplacian evolution equation, showing that for 1≤p<2 we have finite extinction time.
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