An axiomatic approach to gradients with applications to Dirichlet and obstacle problems beyond function spaces
Keywords: primary, 49J27; secondary, 31E05, 35J50, 35J66, 49Q20, 46L51, 46L52Dirichlet problem; First eigenvalue; Generalized Sobolev space; Gradient relation; Lattice; Metric space; Noncommutative function; Obstacle problem; Operator-valued function; Partial order