String Theory  

All Roads Lead to String Theory (Polchinski)  
Prior to the First Superstring Revolution
 
Early History  SMatrix Theory Regge Trajectory  
Bosonic String Theory  Worldsheet String Bosonic String Theory String Perturbation Theory Tachyon Condensation  
Supersymmetric Revolution  Supersymmetry RNS Formalism GS Formalism BPS  
Superstring Revolutions


First Superstring Revolution  GSO Projection Type II String Theory Type IIB String Theory Type IIA String Theory Type I String Theory Type H String Theory Type HO String Theory Type HE String Theory 

Second Superstring Revolution  TDuality DBrane SDuality HoravaWitten String Theory MTheory Holographic Principle N=4 SuperYangMills Theory AdS CFT BFSS Matrix Theory Matrix String Theory (2,0) Theory Twistor String Theory FTheory String Field Theory Pure Spinor Formalism 

After the Revolutions
 
Phenomenology  String Theory Landscape Minimal Supersymmetric Standard Model String Phenomenology  
This article or section 's content is very similar or exactly the same as that at Wikipedia. This is because the contributor of this article had initially contributed it to wikipedia. 
Type IIB String Theory is a consistent 10dimensional Superstring Theory. It has a Supersymmetry of (32 supercharges), or more specifically, , in string  theoretical terms, as opposed to Supergravity terms. It is GSO Truncated, so it does not have a Tachyon in its ground state. It is distinguished from the Type IIA String Theory by its same Ramond Sector GSO Projection on both left and right moving components of the state. This makes the theory nonchiral.^{[1]}
Action Principle
The Lagrangian Density (across the Worldsheet) of the Type IIB String Theory is the RNS Lagrangian Density:
Consequently, the action is:^{[1]}
GSO Projection
The GSO Projection in the NeveuSchwarz Sector is obviously the Standard NeveuSchwarz GSO Projection:^{[2]}
However, the GSO Projection in the Ramond Sector is more complicated. We may either use the following pair of projections:^{[2]}
Or the following pair:^{[2]}
I.e. both the leftmoving components and the rightmoving components must be GSO truncated in the same way.^{[2]} This is what makes the theory nonchiral.^{[3]}
Cancellation of Conformal Anomaly
Since the Type IIB String Theory is only a GSO Truncated version of the naive RNS String Theory, its normal ordering constant is in the Ramond Sector and and its critical dimension is in order for cancellation of conformal anomaly to occur.
Gauge Group and Unsuitabilitiy as a Theory of Everything
The Type IIB String Theory is nonchiral, and consequently has no gauge group (unless the identity group is counted). This is fine as a theory of quantum gravity, because a gauge group isn't required to describe gravity (in fact, it can be checked, that since it is a GSO Truncated version of naive RNS String Theory, getting rid of Supersymmetry from the naive RNS String Theory results in the Bosonic String Theory, and when its beta function is set to 0 to preserve Conformal invariance, one obtains the Einstein Field Equations, and thus General Relativity at the lowenergylimit). However, this would describe the other interactions, such as the strong force, the weak force and the Electromagnetic force incorrectly, as the experimentally verified Standard Model requires them to have gauge groups of , and respectively.^{[1]}
Therefore, the Type IIB String Theory, even when compactified on a CalabiYau Manifold, cannot be a Theory of Everything. This initiated the main part of the First Superstring Revolution and the Type H String Theoryies. The Type HE string theory satisfies this requirement.^{[1]}
Tduality with the Type IIA string theory
Prior to the Second Superstring Revolution, the only known relationship between the Type IIB String Theory and the Type IIA String Theory was that both of them were GSO Truncated versions of the naive RNS String Theory, by applying the same and opposite GSO Projections to the left and right moving components of the state respectively. However, this relationship, was not a duality or an equivalence, and thus, it could not be used to derive one theory from the other.
During the start of the Second Superstring Revolution, it was realized that Type IIA String Theory is related to Type IIB String Theory by TDuality.^{[4]}
The reason is that it is clear that TDuality negates the sign of the massless bosonic directional dimensional field , much as how Sduality negates the sign of the Dilaton field . Thus, by Worldsheet Supersymmetry, it should also negate the massless fermionic directional dimensional field and therefore the Fermionic operator  valued modes of oscillation of the string are Wickrotated. So, therefore, the fermion number operator is also negated, and therefore, thus, the Klein Operator is also negated, and hence, thus, the GSO Projection transforms from the same on the leftmoving component and the rightmoving component to the opposite on the left and right components. This clearly transforms between the Type IIA String Theory and the Type IIB String Theory, unifying them into a single Type II String Theory.
Sduality with the "Sen string theory"
It is generally very difficult to find the strongcoupling limit of any theory, if it is in the peturbative regime, because this strongcoupling limit would obviously diverge.^{[5]} However, if one anaanalyses the massless fields of Type IIB String Theory, one sees that the fields , at strong coupling become unchanged, except with the F1 Strings transforming into the D1 Branes. Thus, the Sdual of the Type IIB String Theory is the Type IIB String Theory with the F1 Strings replaced with the D1 branes, which is occasionally called the Sen String Theory.
GS Formalism
In the GS Formalism, Type IIB String Theory, being a Type II String Theory, has Supersymmetry, which means that the spinor has two components.
Furthermore, it is uniquely identified by the projection:
Which makes it nonchiral.
References
 ↑ ^{1.0} ^{1.1} ^{1.2} ^{1.3} Mohaupt, Thomas. Introduction to String theory. http://arxiv.org/pdf/hepth/0207249v1.pdf.
 ↑ ^{2.0} ^{2.1} ^{2.2} ^{2.3} Szabo, Richard, J.. Introduction to String theory and Dbrane Dynamics. http://arxiv.org/pdf/hepth/0207142v1.pdf.
 ↑ Wray, Kevin. An Introduction to String Theory. http://math.berkeley.edu/~kwray/papers/string_theory.pdf.
 ↑ McMohan, David (2009). String theory DeMystified. Chicago: McGrawHill. ISBN 9780071498708. http://www.nucleares.unam.mx/~alberto/apuntes/mcmahon.pdf.
 ↑ Feynman, Richard; Albert (2005). Styer. ed. Quantum Mechanics and Path Integrals (2 ed.). New York: Dover. p. 356. ISBN 9780486477220.