Let
q
∈
0,1
. We know that, when
q
tends to 1, we recover “classical” quantum mechanics. However, when
q
is not equal to one, we have a theory of quantum mechanics in a spacetime, i.e., a theory where the vacuum has a nonzero energy density. As a
q
-analogue on the space variable of the wave equation, we introduce the
q
-space wave equation. Solutions of these equations are given for
q
∈
0,1
and for
q
⟶
0
. Since some states have more spin degrees of freedom than the physical particle has, the
q
-space wave equations remove the additional degrees of freedom.