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9

OP wrote(v4): [...] Strings in string theory also seem to possess a rather complicated and certainly non-trivial suite materials-like properties such as length, rigidity, tension, and I'm sure others (e.g. some analog of angular momentum?). [...] Well, the relativistic string should not be confused with the non-relativistic material string, compare ...


8

The question "what is xxx made of" is really asking "what can xxx be decomposed into"? For example we know matter is made of atoms because it can be decomposed into atoms. We know atoms are made of electrons, protons and neutrons because atoms can be broken down into electrons, protons and neutrons. But electrons can't be decomposed into anything, so it's ...


8

An original article is Ashoke Sen, Barton Zwiebach, Quantum Background Independence of Closed String Field Theory (arXiv:hep-th/9311009) An old spr comment by Sabbir Rahman gives a survey of the history of some of these developments. More references are here.


7

Lenny Susskind explains that the answer to this question depends on the parameters of the theory at 1:10:50 to the end of this video. He makes use of the fact that the question if strings are fundamental or if they are composed of something else is analogous to the question if in electrodynamics, electrons or magnetic monopols have to be considered ...


4

Dear Andrew, despite Moshe's expectations, I fully agree with him, but let me say it differently. In QFT, we're talking about "first quantization" - this is not yet a quantum field theory but either a classical field theory or quantum mechanics for 1 particle. Those two have different interpretations - but a similar description. When it is ...


2

Some cases to ponder over. A closed string splits into two closed strings, which then merge again into a single closed string. The overall string worldsheet has the topology of a torus. There is an SL(2,Z) group of large diffeomorphisms acting upon this worldsheet. The contribution to the partition function comes from summing up over all contributions with ...


2

This is to complete @Dilaton 's answer. The very basic reason theoretical physicist are entranced by string models and their extensions is because they promise to be the framework of the Theory Of Everything, the holy grail of theoretical physics. String theories and their extensions provide for the quantization of gravity, the long standing difficulty in ...


2

In string theory the strings are fundamental objects and cannot be made of anything. However, the strings of string theory, like more general extended objects --e.g., the membranes in brane theory--, can be considered to be made of more fundamental point-like objects. An interesting picture is given in Point-Like Structure in Strings I would finally ...


1

The disk and upper half plane are related by an SL(2,R) transformation. Therefore correlators evaluated on the respective surfaces are identical.


1

In short, string is a dislocation defect of the vacuum crystalline structure. This by the way explains why apparent full angle around a string seems to be smaller than $2 \pi$.


1

String field theory can't deal with the modular invariance. Indeed, that's a reason that there is no known consistent string field theory which contains and describes external physical closed string states. This is a paradoxical proposition from me because the first string theory paper in my life that I studied in detail, one about the Kyoto group string ...



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