RE: First collisions at the LHC with unprecedented Energy! (Ask a particle physisicist)
September 2, 2015 at 10:57 pm
(This post was last modified: September 2, 2015 at 11:24 pm by Alex K.)
JuliaL
Haha, yes, I'm like Feynman
Anyways... So, in reverse order.
I simply meant just that, the two experiments take place in places at times that one can not send a light beam from.the earlier to the later one, i.e. they are not in each other's light cone as you say more correctly.
QCD: indeed, QCD has the curious property that the interaction becomes stronger at large distances/low energies, which makes studying it much harder. Why QCD has this property is hard to explain visually. Possibly because I don't understand it well enough. Maybe this: the larger the distance and the longer one waits, the more time the virtual particles between say two quarks have to build up force. It indeed ends up looking like a sticky mass of glue between them. Fun fact: string theory was originally invented to describe those "rubber bands", before it wqs completely repurposed and put in 10 spacetime dimensions.
The question about the relation between quantum wave functions and fields is not specific to QCD, but generally to quantum field theory. It is a very technical question that I struggle answering without maths. Ok, field and wave function are somewhat different categories. A wave function is a function that assigns the (sqrt of) probabilities to a place and time
f(x;t)
Strictly speaking that is just the 1-particle wave function. If there are three particles, say, the wave function is
f(x1,x2,x3;t)
It assigns a probability to a combination of three places for the respective particles. It becomes more complex very quickly for many particles, and impossible to visualize. Now, a field is a mathematical object
F(x,t)
which always depends on just one coordinate. It *very roughly speaking* tells you how to make one more particle at place x if you already have n of them, and how the probability wave function changes in going from n to n+1 particles.
f(x1,x2.... xn, x_n+1) = F(x_n+1)( f(x1,...xn) )
As such it encodes the behavior of an arbitrary collection of particles of the theory, but not the detailed state in which the system is in. Sigh, such an inadequate answer.
Haha, yes, I'm like Feynman
Anyways... So, in reverse order.
I simply meant just that, the two experiments take place in places at times that one can not send a light beam from.the earlier to the later one, i.e. they are not in each other's light cone as you say more correctly.
QCD: indeed, QCD has the curious property that the interaction becomes stronger at large distances/low energies, which makes studying it much harder. Why QCD has this property is hard to explain visually. Possibly because I don't understand it well enough. Maybe this: the larger the distance and the longer one waits, the more time the virtual particles between say two quarks have to build up force. It indeed ends up looking like a sticky mass of glue between them. Fun fact: string theory was originally invented to describe those "rubber bands", before it wqs completely repurposed and put in 10 spacetime dimensions.
The question about the relation between quantum wave functions and fields is not specific to QCD, but generally to quantum field theory. It is a very technical question that I struggle answering without maths. Ok, field and wave function are somewhat different categories. A wave function is a function that assigns the (sqrt of) probabilities to a place and time
f(x;t)
Strictly speaking that is just the 1-particle wave function. If there are three particles, say, the wave function is
f(x1,x2,x3;t)
It assigns a probability to a combination of three places for the respective particles. It becomes more complex very quickly for many particles, and impossible to visualize. Now, a field is a mathematical object
F(x,t)
which always depends on just one coordinate. It *very roughly speaking* tells you how to make one more particle at place x if you already have n of them, and how the probability wave function changes in going from n to n+1 particles.
f(x1,x2.... xn, x_n+1) = F(x_n+1)( f(x1,...xn) )
As such it encodes the behavior of an arbitrary collection of particles of the theory, but not the detailed state in which the system is in. Sigh, such an inadequate answer.
The fool hath said in his heart, There is a God. They are corrupt, they have done abominable works, there is none that doeth good.
Psalm 14, KJV revised edition
