When I was young, I was taught in the university class as the usual textbook says; if we measure the position of a quantum mechanical particle, then its wave function shrinks to a Dirac' delta function of positional variable.
But in the recent book of John Gribbin, it is written that; "the collapse of wave function is a device introduced by Niels Bohr without evidence whatsoever." And the book further introduces other theory that can avoid the necessity of introducing the collapse of wave function. It is "transaction interaction"proposed by John Cramer.
Which is true at all? Is there surelly the collapse of the wave function or not?
Please someone tell me the truth.
Old poor stray sheep