Showing posts with the label physics

Comments on symmetric monoidal categories by John Baez

I recently watched a talk by John Baez titled " Symmetric Monoidal Categories " [1]. Baez presents new mathematical material that he considers provides a common foundation for the description of different scientific and engineering topics, material that he considers to be a kind of " Rosetta stone ". Baez is correct that scientists and engineers like to describe processes or composite systems using diagrams: flow charts, Petri nets, electrical circuit diagrams, signal-flow graphs, chemical reaction networks, Feynman diagrams, etc. He claims that many of these diagrams fit into a common framework, the mathematics of symmetric monoidal categories, and that when we accept this achievement, we begin to see connections between seemingly different topics. Baez also claims that this new viewpoint introduces a paradigm shift in science. Let us go over all those interesting claims. My comments will focus on the scientific side of his talk. To get started, Baez says that s

Common misconceptions in physics (book)

This book does not offer an idealized view of physics, but a realistic view with its problems, inconsistencies, and limitations. Popular science books written by physicists, physics textbooks, and the professional physics literature contain misleading or easily misinterpreted claims, and such misconceptions and myths are preventing a fundamental understanding of Nature. This book identifies over two hundred common misconceptions in classical electrodynamics, thermodynamics, statistical mechanics, general relativity, quantum mechanics, and quantum field theory. The claims that the Coulomb gauge is not a physical gauge, that mass increases with velocity, that entropy is a quantity characterizing disorder, that general relativity is equivalent to the theory of a massless self-interacting spin-2 field, that molecular chaos is the source of irreversibility, that electrons and protons are sometimes particles and sometimes waves, and that relativistic quantum electrodynamics is a Lagrangian