f***@yahoo.co.uk

2006-07-23 18:01:50 UTC

On a blog I came across a strange question:

"Does it make sense to speak about the number of

strings found in a volume of space?"

Could anbody comment on this? I would be

interested if one has to imagine string theory

as filling all of space with strings Or branes),

or whether this is the wrong visualization.

Frank

[Moderator's note: one can construct the "number of strings" operator in a

perturbative treatment of string theory - much like you can talk about

the number of particles and/or the level of the harmonic oscillator.

However, both in quantum field theory and string theory, this quantum

number is a bit problematic. It is certainly not conserved. In QFT, it

depends on the energy scale at which you understand the system - because

with a high enough scale, you find very many gluons inside the proton,

to say an example. The "number of particles" behaves strangely when

you include interactions. The latter statement is also true in string

theory. The real physical objects at nonzero coupling are not just the

"bare 1 string" that you know from g=0. LM]

"Does it make sense to speak about the number of

strings found in a volume of space?"

Could anbody comment on this? I would be

interested if one has to imagine string theory

as filling all of space with strings Or branes),

or whether this is the wrong visualization.

Frank

[Moderator's note: one can construct the "number of strings" operator in a

perturbative treatment of string theory - much like you can talk about

the number of particles and/or the level of the harmonic oscillator.

However, both in quantum field theory and string theory, this quantum

number is a bit problematic. It is certainly not conserved. In QFT, it

depends on the energy scale at which you understand the system - because

with a high enough scale, you find very many gluons inside the proton,

to say an example. The "number of particles" behaves strangely when

you include interactions. The latter statement is also true in string

theory. The real physical objects at nonzero coupling are not just the

"bare 1 string" that you know from g=0. LM]