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String theory is a theoretical framework that attempts to address these questions. The starting point for string theory is the idea that the point-like particles of particle physics can also be modeled as one-dimensional objects called strings. String theory describes how strings propagate through space and interact with each other.
This is true for string theory as well, but in string theory it is often more intuitive to understand why the non-physical states should be disposed of. The simplest example is the photon: a photon is a vector particle (it has an inner "arrow" which points to some direction, its polarization). Mathematically, it can point towards any direction ...
In string theory, the strings may be open (forming a segment with two endpoints) or closed (forming a loop like a circle) and may have other special properties. [1] Prior to 1995, there were five known versions of string theory incorporating the idea of supersymmetry (these five are known as superstring theories) and two versions without supersymmetry known as bosonic string theories, which ...
String theory is a branch of theoretical physics that attempts to build a theory of quantum gravity using one-dimensional strings rather than zero-dimensional point particles as fundamental building blocks. The name string theory is somewhat of a misnomer since the modern theory also includes higher dimensional objects known as branes
In 1974, Joël Scherk and John Schwarz suggested that string theory was therefore not a theory of nuclear physics as many theorists had thought but instead a theory of quantum gravity. [53] At the same time, it was realized that hadrons are actually made of quarks, and the string theory approach was abandoned in favor of quantum chromodynamics.
Bosonic string theory; Superstring theory. Type I string; Type II string. Type IIA string theory; Type IIB string theory; Heterotic string; N=2 superstring; M-theory. Matrix theory; Introduction to M-theory; F-theory; String field theory; Matrix string theory; Nonlinear sigma model; Tachyon condensation; RNS formalism; String theory landscape ...
Polchinski, Joseph (1998) String Theory. Cambridge University Press. Vol. 1: An introduction to the bosonic string. ISBN 0-521-63303-6. Vol. 2: Superstring theory and beyond. ISBN 0-521-63304-4. Szabo, Richard J. (Reprinted 2007) An Introduction to String Theory and D-brane Dynamics. Imperial College Press. ISBN 978-1-86094-427-7.
Topological string theory is obtained by a topological twist of the worldsheet description of ordinary string theory: the operators are given different spins. The operation is fully analogous to the construction of topological field theory which is a related concept. Consequently, there are no local degrees of freedom in topological string theory.