| |
 |
|
|
Science Forum Index » Physics - Research Forum » Are superstring vibrations 'atonal' ?
Page 1 of 1
|
| Author |
Message |
| Wilhelm.Busch |
 Posted: Sat Mar 17, 2007 2:33 am |
|
|
|
Guest
|
Hallo
The following question defies my attempts to answer it by ordinary means
and I would very much appreciate your help:
Are there any observable coherent superpositions of d i f f e r e n t
'particles' according to String Theory ? If so: which ? If not: why not
?
In more detail: it is my understanding that different eigenstates of
fundamental strings should correspond to (loosely speaking) different
elementary particles. I also believe that one should be able to create
(at least in principle) string vibrations consisting of a superposition
of eigenmodes - just like a violin string can play music, not only
individual notes. Indeed, the notion of mathematical superpositions is
already commonplace in, for example, the earliest treatments on
quantizing strings via summation of creation/annihilation operators.
Thus one should be able to mathematically generate strings which are
vibrating in a superposition of eigenmodes, hence representing a
superposition of different elementary 'particles'.
Problem: But why don't we observe such a quantum state consisting of a
coherent superposition of different 'particles' ?
Or do we / would we observe them, e.g. in accelerator experiments ?
Or is there a (super-)selection rule at work that forbids this, similar
to forbidding superposing bosonic and fermionic degrees through
enforcing (anti-)symmetry of the quantum state ?
Many thanks for whatever help you can offer
PS:
A. The vertex operators that one uses to construct scattering amplitudes
seem to me to be tuned by hand to represent only incoming/outgoing
strings that are not in a superposition of different fundamental
vibration eigenmodes ('particles'). There is apparently no other reason
(e.g. a dynamical principle) that enforces such a restriction to pure
eigenstates of the string hamiltonian.
B. One can mathematically construct irreducible
representations/excitations that have a specific behavior under Poincare
transformations and that apparently would not mix if one uses input
states displaying no superpositions or reducible representations. But I
still fail to understand why we should see only irreducible
representations. I also cannot see why, at the very least, states in the
subspaces belonging to the same or similar eigenvalues should not
superpose easily.
C. Yet another question: How is the corresponding question answered in
'ordinary' QFT and is it easier to answer it there than in String Theory
where a single string (small set of strings) should represent all the
'particles' ?
D. Thank you all the more for helping out with an answer in case some of
the above questions should only arise due to me confusing concepts. For
example, if all or most of the cited superpositions needed to get a
state corresponding to superposed different particles might indeed be
mathematically impossible then a step by step explanation about how that
arises would be very much appreciated. |
|
|
| Back to top |
|
| |
|
Page 1 of 1
All times are GMT - 5 Hours
The time now is Wed Oct 15, 2008 2:16 pm
|
|