Referring to the attached set of equations,
Wave function of the "Schrodinger equation for two-particles [equation 1]" can be separated using separation of variable method, when they are distinguishable. And two separate "one particle" equations must be [equation 3]. In this form, the physical meaning must be, the particle 1 is in the potential field "V", and particle 2 feels no potential at all, unless I assume V=V1+V2 where particle 1 is in facing V1 and particle 2 is facing V2 potential. I mean V1 and V2 could be any real value that I choose!!!! But is it?
However for distinguishable particles this mathematical derivation is fairly simple. But how people come up with the composite wave function for indistinguishable particles [equation 4]? Is it just a guess or there is any formal mathematical derivation?