Vector Meson Dominance | Hacker News Reader

Vector Meson Dominance

johncarlosbaez.wordpress.com

52 pointschmaynard12 comments

Very cool! The suggestion to consider how the standard model came to be rather than starting with the result sounds like an excellent idea.

But of course i have to disagree with this: "A spin-1/2 particle is described by a spinor, which is a bit weird, but spin-1 particle is described by something more familiar: a vector!"

In my view a spinor is even more familiar than a vector: it's like a hand - it comes back to itself after 720° of rotation. Just like a vector is like an arrow or a mirror, which come back after 360°. What could be more familiar than a hand?

"a spinor is like a hand" is about as intuitive as "a monad is like a burrito"

Spinors are so intuitive that you need a 1 hour video full of animations to explain them: https://www.youtube.com/watch?v=b7OIbMCIfs4

The whole assumption of the video is that one cannot understand spinors. He does a good job with the mathematics but i disagree with the premise.

My hand comes back after 360°.

Attempting to spin my hand by 360° may result in me coming back from the hospital, unless I spin my entire body along with it.

But with a twist in the arm. After another 360 the arm is back too.

> it's like a hand - it comes back to itself after 720° of rotation

The analogy is a bit broken in a way that may add confusion. The hand comes back to it's starting configuration after two 360° rotations, each along a different axis. A spinor's symmetry has 720° of rotation along a single axis.

No, around a single axis. if you hold your hand palm up you can rotate in the (vertical) z axis around 360° and get a twist in the arm. another 360° undoes the twist, that's 720° around a single axis.

No. The first rotation is along an axis in the direction in which your fingers point. The second rotation is along an axis normal to your palm.

If you're rotating around your fingers you're doing something else, not what i mean. I'm just talking palm up, rotating in the vertical axis, 720°. like the cup dance.

> In my view a spinor is even more familiar than a vector

Okay... Pauli and Dirac both received Nobel Prizes for discovering spinors. Nobody needed to discover pointing in some direction.

Sometimes the simplest things are hidden in plain sight :) Most people point with their fingers/hands. Unlike rayman, who has vector-like hands, biological beings have them connected to their body, which makes them behave like spinors. But Dirac actually knew about this, after all there is a belt trick named after him.

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