How do you mean? To clarify: a "point particle" is an object with no internal structure, that is, it can be fully described by its coordinates wrt time (ignori

How do you mean? To clarify: a "point particle" is an object with no internal structure, that is, it can be fully described by its coordinates wrt time (ignoring relativity for now). This is a concept, a model which explains many phenomena, a model on top of which you can build many theories. It does not, however, explain the conjunction of QM with special relativity.