Calling antimatter 'regular particles going back in time' is cute but only really helpful if you've got a Feynman diagram and you want to spin it around to face a different direction.

Zanthius, which of us has actually taken a graduate school class in quantum field theory? You keep pulling out pop-sci explanation videos. I've derived the time-propagator and proven causality for quantum fields.

Matt O'Dowd is an Australian-born astrophysicist. He is an assistant professor at the Physics and Astronomy Department at the Lehman College of the City University of New York[1] and writer and host of PBS Space Time on YouTube.[2] He is a frequent guest on Science Goes to the Movies on CUNY TV, and StarTalk radio with Neil deGrasse Tyson.[3]

The Hamiltonian in classical mechanics is derived from a Lagrangian, which is a more fundamental quantity relative to special relativity. The Hamiltonian indicates how to march forward in time, but the time is different in different reference frames. The Lagrangian is a Lorentz scalar, while the Hamiltonian is the time component of a four-vector. So the Hamiltonian is different in different frames, and this type of symmetry is not apparent in the original formulation of quantum mechanics.

If the Lagrangian is invariant under a symmetry, then the resulting equations of motion are also invariant under that symmetry. This characteristic is very helpful in showing that theories are consistent with either special relativity or general relativity.

Antimatter is in every precise meaningful sense matter moving backward in time. The notion of "moving backward in time" is nonsensical in a Hamiltonian formulation, because the whole description can only go forward in time. That's the definition of what the Hamiltonian does--- it takes you forward in time a little bit. So if you formulate quantum mechanics the Hamiltonian way, this idea is difficult to understand (still it can be done--- Stueckelberg discovered this connection before the path integral, when field Hamiltonians were the only tool).

You can describe it that way for discussions of individual interactions because it's convenient - I'm not saying those people are wrong - , but when you get to discussions of macro-scale phenomena like thermodynamics, talking of actual propagation backwards in time is a mistake.

The propagation operator itself points straight back to time being pointed away from simple boundary conditions.

New particle links dark matter with missing antimatter

Physicists in the US and Canada have proposed a new particle that could solve two important mysteries of modern physics: what is dark matter and why is there much more matter than antimatter in the universe?

The yet-to-be-discovered “X” particle is expected to decay mostly to normal matter, whereas its antiparticle is expected decay mostly to “hidden” antimatter. The team claims that its existence in the early universe could explain why there is more matter than antimatter in the universe – and that dark matter is in fact hidden antimatter.

Sure. I am not arguing that they aren't equivalent. But don't you get twice as many possibilities if you include both the forward possibilities and the backward possibilities? Why do you think the g-factor is around 2 and not around 1?

You need to include those in one way or another; taking the time-travel interpretation of the mathematics is not necessary.



Well, well... the path integral formulation is based on mathematics, not a diagram. But diagrams and mathematical formulations can be equivalent. For example, you can use regression or a machine learning algorithm to find a formula that fits a graph or geometrical shape. You can use the Schrödinger equation to visualize atomic orbitals, but you could probably also use a machine learning algorithm to find the Schrödinger equation from the shapes of the atomic orbitals.

You might think that graphs and geometrical shapes are "dumbed down" mathematics…