You guys are making possible sources of confusion between the map and the territory sound like they’re specific to QFT while they actually aren’t. “Oh, I know what a ball is. It’s an object where all the points on the surface are at the same distance from the centre.” “How can there be such a thing? The positions of atoms on the surface would fluctuate due to thermal motion. Then what is it, exactly, that you play billiards with?” (Can you find another example of this in a different recent LW thread?)
Your ball point is very different. My driving point is that there isn’t even a nice, platonic-ideal type definition of particle IN THE MAP, let alone something that connects to the territory. I understand how my above post may lead you to misunderstand what I was trying to get it..
To rephrase my above comment, I might say: some of the features a MAP of a particle needs is that its detectable in some way, and that it can be described in a non-relativistic limit by a Schroedinger equation. The standard QFT definitions for particle lack both these features. Its also not-fully consistent in the case of charged particles.
In QFT there is lots of confusion about how the map works, unlike classical mechanics.
There is no ‘rigid’ in special relativity, the best you can do is Born-rigid. Even so, its trivial to define a ball in special relativity, just define it in the frame of a corotating observer and use four vectors to move to the same collection of events in other frames You learn that a ‘ball’ in special relativity has some observer dependent properties, but thats because length and time are observer dependent in special relativity. So ‘radius’ isn’t a good concept, but ‘the radius so-and-so measures’ IS a good concept.
You guys are making possible sources of confusion between the map and the territory sound like they’re specific to QFT while they actually aren’t. “Oh, I know what a ball is. It’s an object where all the points on the surface are at the same distance from the centre.” “How can there be such a thing? The positions of atoms on the surface would fluctuate due to thermal motion. Then what is it, exactly, that you play billiards with?” (Can you find another example of this in a different recent LW thread?)
Your ball point is very different. My driving point is that there isn’t even a nice, platonic-ideal type definition of particle IN THE MAP, let alone something that connects to the territory. I understand how my above post may lead you to misunderstand what I was trying to get it..
To rephrase my above comment, I might say: some of the features a MAP of a particle needs is that its detectable in some way, and that it can be described in a non-relativistic limit by a Schroedinger equation. The standard QFT definitions for particle lack both these features. Its also not-fully consistent in the case of charged particles.
In QFT there is lots of confusion about how the map works, unlike classical mechanics.
This reminds me of the recent conjecture that the black hole horizon is a firewall, which seems like one of those confusions about the map.
Why, is there a nice, platonic-ideal type definition of a rigid ball in the map (compatible with special relativity)? What happens to its radius when you spin it?
There is no ‘rigid’ in special relativity, the best you can do is Born-rigid. Even so, its trivial to define a ball in special relativity, just define it in the frame of a corotating observer and use four vectors to move to the same collection of events in other frames You learn that a ‘ball’ in special relativity has some observer dependent properties, but thats because length and time are observer dependent in special relativity. So ‘radius’ isn’t a good concept, but ‘the radius so-and-so measures’ IS a good concept.