In modern theoretical physics, taking into account the symmetry relations associated with various physical phenomena plays a very important role. Similar symmetry relations arise in physical problems in two ways. First of all, any physical process proceeds in space (and in time), so when describing such processes, you have to use some coordinate system. Space has certain symmetry properties: it is homogeneous and isotropic (i.e. all its points are equal between themselves and at each point all directions are equal to each other). In connection with these properties of space, each physical theory should not depend on the choice of the original coordinate system, that is, it should be invariant with respect to any parallel transfers and rotations of this system...