Information about Bosonic String Theory
| String theory |
| Key topics |
| Superstring theory |
| Theory |
| Bosonic string theory M-theory (simplified) Type I string Type II string String field theory Heterotic string |
| Concepts |
| Strings Branes |
| Related Topics |
| Supersymmetry Supergravity Quantum gravity |
| Scientists |
| Witten others |
Bosonic string theory is the original version of string theory, developed in the late 1960s. Although it has many attractive features, it has a pair of features that render it unattractive as a physical model. Firstly it predicts only the existence of bosons whereas we know many physical particles are fermions. Secondly, it predicts the existence of a particle whose mass is imaginary implying that it travels faster than light. The existence of such a particle, commonly known as a tachyon, would conflict with much of what we know about physics, and such particles have never been observed.
Another feature of bosonic string theory is that in general the theory displays inconsistencies due to the conformal anomaly. In a spacetime of 26 dimensions, however, with 25 dimensions of space and one of time, the inconsistencies cancel. Another way to look at this is that in general bosonic string theory predicts unphysical particle states called 'ghosts'. In 26 dimensions the no-ghost theorem predicts that these ghost states have no interaction whatsoever with any other states and hence that they can be ignored leaving a consistent theory. So bosonic string theory predicts a 26 dimensional spacetime. This high dimensionality isn't a problem for bosonic string theory because it can be formulated in such a way that along the 22 excess dimensions, spacetime is folded up to form a small torus. This would leave only the familiar four dimensions of spacetime visible.
In the early 1970s, supersymmetry was discovered in the context of string theory, and a new version of string theory called superstring theory (supersymmetric string theory) became the real focus. Nevertheless, bosonic string theory remains a very useful "toy model" to understand many general features of perturbative string theory, and string theory textbooks usually start with the bosonic string. The first volume of Polchinski's String Theory and Zwiebach's A First Course in String Theory are good examples.
See also
String theory is a model of fundamental physics, whose building blocks are one-dimensional extended objects called strings, rather than the zero-dimensional point particles that form the basis for the standard model of particle physics.
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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. It is considered one of the most promising candidate theories of quantum gravity.
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M-theory is a proposed "master theory" that unifies the five superstring theories.
Drawing on the work of a number of string theorists (including Ashoke Sen, Chris Hull, Paul Townsend, Michael Duff and John Schwarz); Edward Witten of the Institute for Advanced Study
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Drawing on the work of a number of string theorists (including Ashoke Sen, Chris Hull, Paul Townsend, Michael Duff and John Schwarz); Edward Witten of the Institute for Advanced Study
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M-theory is a theory of physics that deals with the extension of superstring theory. It is somewhat contentious in the physics community, as it lacks empirical evidence. If ever experimentally verified, M-theory and string theory would represent remarkable advances in science.
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In theoretical physics, type I string theory is one of five consistent supersymmetric string theories in ten dimensions. It is the only one whose strings are unoriented (both orientations of a string are equivalent) and which contains not only closed strings, but also open
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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.
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In theoretical physics, string field theory is a proposal to define string theory in such a way that the background independence is respected. String field theory can be understood as a quantum field theory with infinitely many fields which are unified into one master
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In physics, a heterotic string is a peculiar mixture (or hybrid) of the bosonic string and the superstring (the adjective heterotic comes from the Greek word heterosis, hybrid vigour).
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A string is one of the main objects of study in a branch of theoretical physics called string theory. There are different string theories, many of which are unified by M-theory.
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In theoretical physics, a brane or p-brane is a spatially extended, mathematical concept that appears in string theory and its relatives (M-theory and brane cosmology). The variable p refers to the spatial dimension of the brane.
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For the Angel episode, see .
In particle physics, supersymmetry (often abbreviated SUSY) is a novel symmetry that relates elementary particles of one spin to another particle that differs by half a unit of spin and are known as superpartners.
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In theoretical physics, supergravity (supergravity theory) is a field theory that combines the principles of supersymmetry and general relativity. Together, these imply that, in supergravity, the supersymmetry is a local symmetry (in contrast to non-gravitational
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Quantum gravity is the field of theoretical physics attempting to unify quantum mechanics, which describes three of the fundamental forces of nature, with general relativity, the theory of the fourth fundamental force: gravity.
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Edward Witten
Born July 26 1951
Baltimore, Maryland
Nationality American
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Born July 26 1951
Baltimore, Maryland
Nationality American
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String theory is a model of fundamental physics, whose building blocks are one-dimensional extended objects called strings, rather than the zero-dimensional point particles that form the basis for the standard model of particle physics.
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In particle physics, bosons are force carrier particles, such as the photon. They may be either elementary or composite. They are distinguished from fermions (matter particles) by their integer spin. Bosons are named after Indian physicist Satyendra Nath Bose.
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In particle physics, fermions are particles with half-integer spin, such as protons and electrons. They are named after Enrico Fermi. In the Standard Model there are two types of elementary fermions: quarks and leptons.
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imaginary number (or purely imaginary number) is a complex number whose square is a negative real number. Imaginary numbers were defined in 1572 by Rafael Bombelli. At the time, such numbers were thought not to exist, much as zero and the negative numbers were regarded by
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A tachyon (from the Greek ταχυόνιον, takhyónion, from ταχύς, takhýs, i.e.
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Conformal anomaly is an anomaly i.e. a quantum phenomenon that breaks the conformal symmetry of the classical theory.
In string theory, conformal symmetry on the worldsheet is a local Weyl symmetry and must therefore cancel if the theory is to be consistent.
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In string theory, conformal symmetry on the worldsheet is a local Weyl symmetry and must therefore cancel if the theory is to be consistent.
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In mathematics, and in particular, in the mathematical background of string theory, the Goddard-Thorn theorem (also called the no-ghost theorem) is a theorem about certain vector spaces. It is named after P. Goddard and C. B. Thorn.
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In geometry, a torus (pl. tori) is a surface of revolution generated by revolving a circle in three dimensional space about an axis coplanar with the circle, which does not touch the circle. Examples of tori include the surfaces of doughnuts and inner tubes.
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For the Angel episode, see .
In particle physics, supersymmetry (often abbreviated SUSY) is a novel symmetry that relates elementary particles of one spin to another particle that differs by half a unit of spin and are known as superpartners.
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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. It is considered one of the most promising candidate theories of quantum gravity.
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In physics, a toy model is a simplified set of objects and equations relating them that can nevertheless be used to understand a mechanism that is also useful in the full, non-simplified theory.
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In quantum mechanics, perturbation theory is a set of approximation schemes directly related to mathematical perturbation for describing a complicated quantum system in terms of a simpler one.
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Joseph Polchinski (born on May 16, 1954 in White Plains, New York) is a physicist working on string theory. He graduated from Canyon del Oro High School in Tucson, Arizona in 1971, obtained his B.S. degree from Caltech in 1975, and his Ph.D.
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The Nambu-Goto action is the simplest invariant action in bosonic string theory. It is the starting point of the analysis of string behavior, using the principles of Lagrangian mechanics. Just as the action for a free point particle is proportional to its proper time—i.e.
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In physics, the Polyakov action is the two-dimensional action of a conformal field theory describing the worldsheet of a string in string theory. It was introduced by S.Deser and B.Zumino and independently by L.Brink, P.Di Vecchia and P.S.
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