Recent content by Alwi

Dear nrqed, Can you tolerate a symmetry operation generated by degrees of freedom that are NOT found in your Lagrangian ? My answer is NO ! I think that lies at the heart of the question. How do you deal with such a symmetry ? What about the Noether currents and so on ? Conserved charges ? I...

Dear Demystifier, I think the biggest problem from a Physics point of view - is that you would have left out some degrees of freedom that could possibly generate a symmetry operation. In that sense - an algebra that is not closed is not very satisfactory from a Physics perspective. The notion...

Dear nrqed, If the algebra does not close - then you have to introduce new degrees of freedom so that the symmetry can be preserved with the new set of fields. Otherwise you lose the symmetry because you miss out on degrees of freedom which must be part of the symmetry. There would be...

Dear Xepma, Here is also another reason why I think knotted strings ought to be considered. Its not clear to me that one can always find a homotopy involving the compact extra dimension - that will unknot the knotted string. What makes you think that there will be no obstructions ? Maybe the...

Dear xepma, No I disagree with your statement that every string will be topologically equivalent to the unknot. Knottedness can take place totally in the large 3+1 dimensions. The compact extra dimensions need not unravel that knottedness. It all depends on how we do our compactification and...

Dear anuradha, Well the Nambu-Goto action is itself non-polynomial - because of the square-root. In the Nambu-Goto formalism, there is a topological term that we can add - the self-linking number. It is non-linear. But I have never seen a quantisation of the Nambu-Goto action with this knot...

Well the introduction of the world-sheet metric is to simplify the problem at hand. One can begin with the Nabu-Goto action and then impose Weyl symmetry etc. However it will be ugly and terribly messy owing to the non-polynomial nature of the Nambu-Goto action. However - in the Nambu-Goto...

Hi all ! I am curious about the possibility of knotted strings. If we can accept the propagation of closed loop strings, then shouldn't we consider the possibility of knotted, closed loop strings ? I do not see - offhand - any reason why a closed string cannot be knotted. Think of a...