Pure classical physics can explain quantum phenomena, study shows

Amazing stuff!

"A reformulation of the classical Hamilton-Jacobi equation, incorporating density and multiple least-action paths, can exactly reproduce quantum phenomena such as the double-slit experiment, quantum tunneling, and hydrogen atom wave functions. This approach mathematically bridges classical and quantum mechanics, showing that quantum behavior can be computed using classical principles without approximations."

" ... MIT scientists have now shown that certain mathematical ideas from everyday classical physics can be used to describe the often weird and nonintuitive behavior that occurs at the quantum, subatomic scale.

In a paper appearing today in the journal Proceedings of the Royal Society A Mathematical Physical and Engineering Science, the team shows that the motion of a quantum object can be calculated by applying an idea from classical physics known as "least action." With their new formulation, they show they can arrive at exactly the same solution as the Schrödinger equation—the main description of quantum mechanics—for a number of textbook quantum-mechanical scenarios, including the double-slit experiment and quantum tunneling. ..."

From the abstract:

"We show that the Schrödinger equation can be solved exactly based only on classical least action.

Fundamental postulates of quantum mechanics can in turn be derived directly from this construction. The results extend to the relativistic Klein-Gordon, Pauli, and Dirac equations, and suggest a smooth transition between physics across scales. 

Most quantum mechanics problems have classical versions which involve multiple least action solutions. The associated classical multipaths stem either from the initial position or momentum distribution, or from branch points, generated, e.g. by a multiply connected manifold (double slit experiment), by spatial inequality constraints (particle in a box), or by a singularity (Coulomb potential). We show that the exact Schrödinger wave function  can be constructed by combining this classical multi-valued action with the classical density ⁠, computed analytically from  along each extremal action path.

The construction is general and does not involve any semi-classical approximation.

Quantum wave collapse at measurement can be derived from the classical density change. Entanglement corresponds to a sum of classical particle actions mapping to a tensor product of spinors. The results also provide a simpler computational alternative to Feynman path integrals, as they use only a minimal subset of classical paths."

Classical physics can explain quantum weirdness, study shows

On computing quantum waves exactly from classical action (open access)

New study bridges the worlds of classical and quantum physics (original news release) "The weird quantum behavior of subatomic particles can be understood through everyday classical ideas, MIT researchers show."

On computing quantum waves exactly from classical and relativistic action (prepint, first published 5/10/2024, open access)