> show me your concrete evidence for many worlds. You can't do it.

Most people would agree that the sun emits light in all directions, but there is no way to prove it with concrete evidence. The only thing you can prove with concrete evidence is that the sun emits light in the direction of objects in our solar system that we can see. We infer that the sun emits light in all directions because that is the best explanation that accounts for the data that we have.

Many-worlds is the same. We can't demonstrate their existence, we infer it from the current-best explanation that accounts for the data that we have.

My understanding is that the best current interpretation of quantum mechanics is that there is no interpretation and that you just have to do the math.

Yes, that's right. But if you want to assign any meaning to the math, and in particular if you want to adopt an ontology where you exist, then the math leaves you no alternative than to conclude that parallel universes also exist (unless you resort to special pleading like the Copenhagen interpretation).

I mean, just doing the math and being agnostic about the strengths of different interpretations seems to be an interpretation. Maybe it's more of an epistemic position than a metaphysical one, but it still kinda counts.

> current-best explanation

Many-worlds is by far not accepted to be the "current-best explanation".

It's a candidate. It's not clear it's right.

Sorry, I wasn't clear. The current-best explanation is not many worlds, it's the mathematical formalism of QM. Many-worlds is a logical consequence of that.

Many worlds is one possible interpretation of the logical consequences of that. It's not nearly as definite or clear-cut as you're making it sound.

It seems pretty clear cut to me. I've seen no argument against it that doesn't involve some logical fallacy. If you think you know of one please enlighten me.

Well, I'm not an expert. But I know that, among those who are experts, many-worlds is not the consensus or even the majority view. So, while it may seem clear cut to you, it doesn't to everyone. That's why I keep saying that no, it's not clear.

I realize that's argument by authority, and that's considered a fallacy...

I'm not an expert either. I'm a computer scientist, not a physicist. But the math behind QM -- at least the parts that matter for this discussion -- is pretty straightforward linear algebra. Really, anyone can learn it. So don't take my word for it, look into it and decide for yourself. You can start here:

https://www.amazon.com/Philosophy-Physics-Princeton-Foundati...

https://www.amazon.com/Quantum-Mechanics-Experience-David-Al...

Or, if you don't feel like buying a book:

https://flownet.com/ron/QM.pdf

Or, if you prefer a video:

https://www.youtube.com/watch?v=dEaecUuEqfc

BTW, it may come as a surprise to learn that I am actually not a big proponent of many-worlds despite recognizing that it is in fact a logical consequence of the math. If so, you may find this interesting too:

https://blog.rongarret.info/2009/04/on-shadow-photons-and-re...

and a follow-up written ten years later:

https://blog.rongarret.info/2019/07/the-trouble-with-many-wo...

>QM is pretty straightforward linear algebra

The chasm between my grades in linear algebra and my grades in quantum begs to differ... :(

There are two different ways of approaching QM: the physicist's way and the computer scienctist's way. You were probably taught it the physicist's way, which is not wrong, but obscures the parts you need to know to understand the MWI. That part really is pretty simple. You should try again.

According to Einstein nature is parsimonious:many worlds is proliferate.

Sure, but parsimony only applies when all else is equal, and here all else is not equal. Newtonian mechanics is a lot more parsimonious than GR.

That’s human theories which is way downstream of the classical interpretation/paradigm of nature being defined as physical processes.