Time discretization from noncommutativity

We show that a particular noncommutative geometry, sometimes called angular or ρ-Minkowski, requires that the spectrum of time be discrete. In this noncommutative space the time variable is not commuting with the angular variable in cylindrical coordinates. The possible values that the variable can take go from minus infinity to plus infinity, equally spaced by the scale of noncommutativity. Possible self-adjoint extensions of the “time operator” are discussed. They give that a measurement of time can be any real value, but time intervals are still quantized.