James Fodor

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3,084 appearances 4 recordings 1 series first heard Jun 2026 last heard 30 Aug

James Fodor’s voice in public audio — every appearance, attributed to the second.

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Recordings per month over the last 12 months — 4 in all, peaking in Aug 2026 with 2.

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The Science of Everything Podcast · Episode 164: Gauge Theory and the Higgs Boson · 30 Aug 2026 podcast

There's this connection between symmetries and conservation.

So there's already a kind of a a a a a reason to keep the redundancy in the theory, because uh there has this sort of nice property that we can read off a a conservation law off off of the theory.

It also just makes the theory easier if we can, you know, give each photon field its own uh its own phase instead of having to somehow like subtract that off, which would make the theory more complicated to work with mathematically.

So there's there's a bunch of reasons to maintain the gauge invariance and even more as we'll see going forward.

But but here's the really interesting part.

That we need to understand.

And this is something that took me many years to sort of get, because the way this is taught is often quite poor, I think.

So let me try to develop the idea.

When physicists were developing quantum electrodynamics, they already had a classical template to use, which is

Maxwell's theories of electromagnetism, right?

We already had those equations.

And so they knew what they should expect to find, particularly when we're talking about interactions between electrons and photons, like light and matter.

They knew what those equations should look like, and so they wrote the Lagrangian to reproduce those equations of motion just with in the quantized version, right?

We talked about how quantization is done in previous episodes again, I won't get into that.

But basically, you you can take your equations of motion.

uh work out what the Lagrangian should be from those equations of motion, and then just quantize the resulting fields, and then you have a quantum field theory.

This meant that in constructing the Lagrangian for the uh quantum field theory of electromagnetism, physicists started with the equations of motion of classical electromagnetism.

worked backwards to figure out which you can do mathematically to figure out the corresponding Lagrangian, and then they look at the fields there and quantize those and and work forward.

And and then so then we had a quantum field theory of electromagnetism.

But they had this problem that they found where that there was this extra internal degree of freedom.

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