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Encyclopedia > Type IIB string theory

In theoretical physics, type II string theory is a unified term that includes both type IIA strings and type IIB strings. These account for two of the five consistent superstring theories in ten dimensions. Both theories have the maximal amount of supersymmetry — namely 32 supercharges — in ten dimensions. Both theories are base on oriented closed strings. Theoretical physics attempts to understand the world by making a model of reality, used for rationalizing, explaining, and predicting physical phenomena through a physical theory. There are three types of theories in physics: mainstream theories, proposed theories and fringe theories. ... Superstring theory is an attempt to explain all of the particles and fundamental forces of nature in one theory by modeling them as vibrations of tiny supersymmetric strings. ... In particle physics, supersymmetry is a hypothetical symmetry that relates bosons and fermions. ... Supercharge may mean: Supercharge, the rock and roll band In theoretical physics, a supercharge is a generator of supersymmetry transformations. ... A closed string is a one-dimensional fundamental object in string theory that has no end-points, and therefore is topologically equivalent to a circle. ...

## Contents

At low energies, type IIA string theory is described by type IIA supergravity in ten dimensions which is a non-chiral theory (i.e. left-right symmetric) with (1,1) d=10 supersymmetry; the fact that the anomalies in this theory cancel is therefore trivial. A supergravity theory is a field theory combining supersymmetry and general relativity. ... A phenomenon is said to be chiral if it is not identical to its mirror image (see Chirality (mathematics)). The fundamental laws of physics may be chiral, as the weak charge is not invariant under a reflection unless particles are replaced by their antiparticles as well, and kaon decay appears... In particle physics, supersymmetry is a hypothetical symmetry that relates bosons and fermions. ... An anomaly is a deviation from the common rule. ...

In the 1990s it was realized by Edward Witten (building on previous insights by Michael Duff, Paul Townsend, and others) that the limit of type IIA string theory in which the string coupling goes to infinity becomes a new 11-dimensional theory called M-theory. Edward Witten at Harvard University Edward Witten (born August 26, 1951) is a professor at the Institute for Advanced Study and one of the leading researchers in string theory (M-theory). ... M-theory is a solution proposed for the unknown theory of everything which would combine all five superstring theories and 11-dimensional supergravity together. ...

## Type IIB string

At low energies, type IIB string theory is described by type IIB supergravity in ten dimensions which is a chiral theory (left-right asymmetric) with (2,0) d=10 supersymmetry; the fact that the anomalies in this theory cancel is therefore nontrivial. A supergravity theory is a field theory combining supersymmetry and general relativity. ... A phenomenon is said to be chiral if it is not identical to its mirror image (see Chirality (mathematics)). The fundamental laws of physics may be chiral, as the weak charge is not invariant under a reflection unless particles are replaced by their antiparticles as well, and kaon decay appears... In particle physics, supersymmetry is a hypothetical symmetry that relates bosons and fermions. ... An anomaly is a deviation from the common rule. ...

In the 1990s it was realized that type II string theory with the string coupling constant g is equivalent to the same theory with the coupling 1 / g. This equivalence is known as S-duality. In theoretical physics, S-duality (also a strong-weak duality) is an equivalence of two quantum field theories, string theories, or M-theory. ...

Orientifold of type IIB string theory leads to type I string theory. In theoretical physics, orientifold is a generalization of the notion of orbifold. ... In theoretical physics, type I string theory is one of five consistent supersymmetric string theories in ten dimensions. ...

## Relationship between the type II theories

In the late 1980s, it was realized that type IIA string theory is related to type IIB string theory by T-duality. T-duality is a symmetry of string theory, relating type IIA and type IIB string theory, and the two heterotic string theories. ... Results from FactBites:

 String theory - Facts, Information, and Encyclopedia Reference article (2690 words) String theory is a model of fundamental physics whose building blocks are one-dimensional extended objects (strings) rather than the zero-dimensional points (particles) that are the basis of the Standard Model of particle physics. String theories which include fermionic vibrations are now known as superstring theories; several different kinds have been described. Since string theory may not be tested in the foreseeable future, some scientists have asked if it even deserves to be called a scientific theory: it is not yet a falsifiable theory in the sense of Popper.
 String theory - Wikipedia, the free encyclopedia (2656 words) String theory is a model of fundamental physics whose building blocks are one-dimensional extended objects (strings) rather than the zero-dimensional points (particles) that are the basis of the Standard Model of particle physics. String theories which include fermionic vibrations are now known as superstring theories; several different kinds have been described. Since string theory may not be tested in the foreseeable future, some scientists have asked if it even deserves to be called a scientific theory: it is not yet a falsifiable theory in the sense of Popper.
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