Indulgence to quantum mechanics

JUAN CAMILO MARTÍNEZ GONZÁLEZ; OLIMPIA LOMBARDI

Bristol

Congreso; 2018 ISPC Annual Symposium; 2018

University of Bristol

In this presentation we want to stress that, although optical isomerism makes the impossibility of reduction more explicit, when quantum mechanics in its standard version is taken seriously, the same obstacle is found in the case of structural isomers, since they have the same Hamiltonians. The idea that the case of optical isomerism is more serious is based on the idea that the definite positions of the nuclei introduce a difference in the Hamiltonians of distinct structural isomers because the distances between those positions are not the same in the different isomers. But this idea inadmissibly introduces classical assumptions into quantum mechanics. From an exclusively quantum viewpoint, once the components of the molecule are given, the Hamiltonian is fixed and is the same for all the isomers. In Woolley?s words: ?we return to the example of C3H4; in the present terms this represents a collection of 3 carbon nuclei, 4 protons and 22 electrons. [?] Suppose we apply quantum mechanics to all the particles in one go, what do we get? It is easier to say what we have never found so far ?no suggestion of three distinct isomers for the molecules of allene, cyclopropene and methyl acetylene.? (Woolley 1998, p. 11).But, what is the appropriate treatment for this diagnosis? The most reductionist temperaments assume that the idea of a neatly defined molecular structure is a ?metaphor.? Others suppose that the obstacles will be overcome and the concept of molecular structure will arise when the simplifications will be removed and the quantum description will be completed with the interactions with other molecules, or with decoherence, or with more detailed Hamiltonians, etc. Independently of the dubious conclusions about the success of those strategies, it is interesting to notice that almost nobody seriously considers the possibility of modifying quantum mechanics itself. But, if the concept of molecular structure is so fruitful in chemistry and the shape of the molecules is so clearly detected by experimental means, why not think that molecules do have geometrical shape as described by chemistry?, why not consider that we must be indulgent with quantum mechanics, since it is a mere calculation tool that must be replaced in the future by a new theory that really describes microscopic reality?