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The way renormalisation is mostly covered in popular media, made me think you can’t do quantum physics without dirty tricks to get rid of infinites. Then I rea

by audunw 3y ago

The way renormalisation is mostly covered in popular media, made me think you can’t do quantum physics without dirty tricks to get rid of infinites. Then I read The Road to Reality by Roger Penrose and in the chapter on renormalisation it mentions just “by the way“ that the problem goes away if you assume the universe has a minimum scale, or something like that. Why isn’t this common knowledge? Why isn’t this one of the first things that gets told when talking about renormalisation? Why is the default assumption that the universe is continuous? Doesn’t seem like we have a good reason for it, other than the fact that we use integration as a tool and that assumes continuity by default. Does it make mathematical analysis easier all-in-all? Why not just pick the Planck length as a reasonable assumption for the quantisation of space? Might not be correct but probably a more reasonable guess than assuming that it’s continuous?

eigenspace 3y ago
> Why isn’t this common knowledge? Why isn’t this one of the first things that gets told when talking about renormalisation? It's because of the historical development where it really did start off as a nasty bag of mathematical tricks. It wasn't until much later that Wilson and co put renormalization procedures on firm footing, and by that time it had a quite bad reputation.
ndsipa_pomu 3y ago
I thought it was due to relativity which assumes a continuous space. There's a lot of evidence to back up relativity, though it does have issues with not working in a black hole, so it would be questionable to throw it out without something better to replace it.
BoiledCabbage 3y ago
> other than the fact that we use integration as a tool and that assumes continuity by default. Is there really no equivalent of calculus that works on a "quantized"/discreet numberline? The seems really hard to believe.
ko27 3y ago
> Why is the default assumption that the universe is continuous? Why is your default assumption that physicists haven't tried to make it discrete? You need to break Lorentz invariance to have the universe be discrete, which is an effort that's worth a Nobel prize. > Doesn’t seem like we have a good reason for it We have many good reasons for it. https://www.forbes.com/sites/startswithabang/2020/04/17/this-is-why-space-needs-to-be-continuous-not-discrete/ https://www.forbes.com/sites/startswithabang/2020/04/17/this... From the article: "If space is discrete, then the principle of relativity is wrong"

by audunw 3y ago

eigenspace 3y ago

> Why isn’t this common knowledge? Why isn’t this one of the first things that gets told when talking about renormalisation? It's because of the historical development where it really did start off as a nasty bag of mathematical tricks. It wasn't until much later that Wilson and co put renormalization procedures on firm footing, and by that time it had a quite bad reputation.

ndsipa_pomu 3y ago

I thought it was due to relativity which assumes a continuous space. There's a lot of evidence to back up relativity, though it does have issues with not working in a black hole, so it would be questionable to throw it out without something better to replace it.

BoiledCabbage 3y ago

> other than the fact that we use integration as a tool and that assumes continuity by default. Is there really no equivalent of calculus that works on a "quantized"/discreet numberline? The seems really hard to believe.

ko27 3y ago

> Why is the default assumption that the universe is continuous? Why is your default assumption that physicists haven't tried to make it discrete? You need to break Lorentz invariance to have the universe be discrete, which is an effort that's worth a Nobel prize. > Doesn’t seem like we have a good reason for it We have many good reasons for it. https://www.forbes.com/sites/startswithabang/2020/04/17/this-is-why-space-needs-to-be-continuous-not-discrete/ https://www.forbes.com/sites/startswithabang/2020/04/17/this... From the article: "If space is discrete, then the principle of relativity is wrong"