Quantum Mechanics vs Crisis of Modern Physics

Schrödinger cancelled by Bohr

The roots of the present crisis of modern physics can be traced 100 years back to the discovery of quantum mechanics based on the Schrödinger's equation in 1925, which directly triggered a fierce controversy concerning its physical meaning. Here Schrödinger/Einstein were outmanoeuvred by Bohr/Born/Heisenberg declaring the Copenhagen Interpretation CI to be the belief all physicists had and still have to confess to. But Schrödinger/Einstein never accepted CI and the unresolved trauma is today manifested in particular in a discussion about Identity, Individuality and Indistinguishability in Physics and Mathematics.

In classical mechanics particles follow continuous trajectories in space-time, which do not overlap, and so can be used to identify particles even of the same type in all other respects.  Particles do not jump from place to place and so can be distinguished. 

This is not so in quantum mechanics: A solution to the Schrödinger equations for a system of $N$ particles (electrons) takes the form of a multi-dimensional wave function $\Psi (t, x_1,...,x_n)$ depending on $N$ three-dimensional coordinates $x_1,x_2,...,x_N,$ and a common time coordinate $t$. In CI the square of the wave function is supposed to represent the probability of a realisation of quantum particle configuration at time $t$, with quantum particle $n$ appearing at position $x_n$ for $n=1,...,N$. Wave functions are either symmetric in the variables $x_n$ representing bosons such as photons, or anti-symmetric representing fermions such as electrons. In CI it is not possible to identify particle trajectories and so quantum particle identity is lost. Yet quantum particles are labeled and have identity in the sense that two quantum particles (electrons with the same spin) cannot share position in space-time. Quantum particles appear as possibilities without identity and continuity in time, to be compared with  classical particles as actualities with identity continuous in time. 

CI is not an ontological model of what is, but something very different still without scientific meaning despite 100 years of brooding by the greatest of human minds. A basic difficulty is that there are so many more possibilities than actualities. Interaction of actualities like collision of classical particles has meaning, while interaction of possibilities appears to be meaningless. Documentation of actualities may be possible, while documentation of all possibilities is impossible. CI is uncomputable.

The nightmare of CI is the idea of collapse of the wave function as the step from possibility to actuality or from anonymity to identity believed to take place upon observation. This is the event of an Observer opening Schrödinger's cat box to find the cat either dead or alive, convinced that before the opening the cat is in a state of all possibilities or superposition of both alive and dead. Schrödinger thus demonstrated the absurdity of CI, but was cancelled by Bohr and there we are today. 

All the questions from 1925 remain about the possible meaning of a physics without identity and continuity in time. In particular the possibility of self-destruction by self-interaction in the absence of individuality and identity discussed in recent posts.   

Real Quantum Mechanics presents a new form of quantum mechanics where identity and continuity in time is restored, a form of physics which is computable.  

Suddenly the Wave Function Collapsed into a Rabbit.