61 Facts About String theory

In physics, string theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings.

String theory describes how these strings propagate through space and interact with each other.

String theory is a broad and varied subject that attempts to address a number of deep questions of fundamental physics.

String theory has contributed a number of advances to mathematical physics, which have been applied to a variety of problems in black hole physics, early universe cosmology, nuclear physics, and condensed matter physics, and it has stimulated a number of major developments in pure mathematics.

String theory was first studied in the late 1960s as a theory of the strong nuclear force, before being abandoned in favor of quantum chromodynamics.

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Five consistent versions of superstring theory were developed before it was conjectured in the mid-1990s that they were all different limiting cases of a single theory in 11 dimensions known as M-theory.

One of the challenges of string theory is that the full theory does not have a satisfactory definition in all circumstances.

String theory is a theoretical framework that attempts to address these questions and many others.

The starting point for string theory is the idea that the point-like particles of particle physics can be modeled as one-dimensional objects called strings.

String theory describes how strings propagate through space and interact with each other.

Studies of string theory have yielded a number of results on the nature of black holes and the gravitational interaction.

One of the goals of current research in string theory is to find a solution of the theory that reproduces the observed spectrum of elementary particles, with a small cosmological constant, containing dark matter and a plausible mechanism for cosmic inflation.

One of the challenges of string theory is that the full theory does not have a satisfactory definition in all circumstances.

Original version of string theory was bosonic string theory, but this version described only bosons, a class of particles that transmit forces between the matter particles, or fermions.

Bosonic string theory was eventually superseded by theories called superstring theories.

The type I theory includes both open strings and closed strings, while types IIA, IIB and heterotic include only closed strings.

In some cases, by modeling spacetime in a different number of dimensions, a String theory becomes more mathematically tractable, and one can perform calculations and gain general insights more easily.

String theory theories require extra dimensions of spacetime for their mathematical consistency.

In bosonic string theory, spacetime is 26-dimensional, while in superstring theory it is 10-dimensional, and in M-theory it is 11-dimensional.

Notable fact about string theory is that the different versions of the theory all turn out to be related in highly nontrivial ways.

Type I string theory turns out to be equivalent by S-duality to the heterotic string theory.

Similarly, type IIB string theory is related to itself in a nontrivial way by S-duality.

In string theory and other related theories, a brane is a physical object that generalizes the notion of a point particle to higher dimensions.

String theory's announcement led to a flurry of research activity now known as the second superstring revolution.

Unlike supergravity theory, string theory was able to accommodate the chirality of the standard model, and it provided a theory of gravity consistent with quantum effects.

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String theory has proved to be an important tool for investigating the theoretical properties of black holes because it provides a framework in which theorists can study their thermodynamics.

The claim is that this quantum field theory is equivalent to a gravitational theory, such as string theory, in the bulk anti-de Sitter space in the sense that there is a "dictionary" for translating entities and calculations in one theory into their counterparts in the other theory.

For example, a single particle in the gravitational String theory might correspond to some collection of particles in the boundary String theory.

Physics of the quark–gluon plasma is governed by a String theory called quantum chromodynamics, but this String theory is mathematically intractable in problems involving the quark–gluon plasma.

Currently accepted String theory describing elementary particles and their interactions is known as the standard model of particle physics.

String theory has been used to construct a variety of models of particle physics going beyond the standard model.

One popular way of deriving realistic physics from string theory is to start with the heterotic theory in ten dimensions and assume that the six extra dimensions of spacetime are shaped like a six-dimensional Calabi–Yau manifold.

Big Bang String theory is the prevailing cosmological model for the universe from the earliest known periods through its subsequent large-scale evolution.

Currently, the leading candidate for a String theory going beyond the Big Bang is the String theory of cosmic inflation.

The String theory has received striking support from observations of the cosmic microwave background, the radiation that has filled the sky since around 380,000 years after the Big Bang.

Regardless of whether Calabi–Yau compactifications of string theory provide a correct description of nature, the existence of the mirror duality between different string theories has significant mathematical consequences.

The Calabi–Yau manifolds used in string theory are of interest in pure mathematics, and mirror symmetry allows mathematicians to solve problems in enumerative geometry, a branch of mathematics concerned with counting the numbers of solutions to geometric questions.

Group String theory is the branch of mathematics that studies the concept of symmetry.

One of the major achievements of contemporary group String theory is the classification of finite simple groups, a mathematical theorem that provides a list of all possible finite simple groups.

Witten has speculated that the version of string theory appearing in monstrous moonshine might be related to a certain simplified model of gravity in three spacetime dimensions.

Some structures reintroduced by string theory arose for the first time much earlier as part of the program of classical unification started by Albert Einstein.

String theory was originally developed during the late 1960s and early 1970s as a never completely successful theory of hadrons, the subatomic particles like the proton and neutron that feel the strong interaction.

The S-matrix approach was started by Werner Heisenberg in the 1940s as a way of constructing a String theory that did not rely on the local notions of space and time, which Heisenberg believed break down at the nuclear scale.

String theory eventually made it out of the dustbin, but for the following decade, all work on the theory was completely ignored.

Still, the String theory continued to develop at a steady pace thanks to the work of a handful of devotees.

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The resulting String theory did not have a tachyon and was proven to have space-time supersymmetry by John Schwarz and Michael Green in 1984.

The consistency conditions had been so strong, that the entire String theory was nearly uniquely determined, with only a few discrete choices.

In coming to understand this calculation, Edward Witten became convinced that string theory was truly a consistent theory of gravity, and he became a high-profile advocate.

Stephen Shenker showed it diverged much faster than in field String theory suggesting that new non-perturbative objects were missing.

M-String theory was foreshadowed in the work of Paul Townsend at approximately the same time.

Witten noted that the effective description of the physics of D-branes at low energies is by a supersymmetric gauge String theory, and found geometrical interpretations of mathematical structures in gauge String theory that he and Nathan Seiberg had earlier discovered in terms of the location of the branes.

String theory noted that in this limit the gauge theory describes the string excitations near the branes.

Many critics of string theory have expressed concerns about the large number of possible universes described by string theory.

Possible existence of, say, consistent different vacuum states for superstring theory probably destroys the hope of using the theory to predict anything.

String theorist Leonard Susskind has argued that string theory provides a natural anthropic explanation of the small value of the cosmological constant.

However, string theory is likely compatible with certain types of quintessence, where dark energy is caused by a new field with exotic properties.

Since the superstring revolutions of the 1980s and 1990s, string theory has been one of dominant paradigms of high energy theoretical physics.

Some string theorists have expressed the view that there does not exist an equally successful alternative theory addressing the deep questions of fundamental physics.

String theory argues that the extreme popularity of string theory among theoretical physicists is partly a consequence of the financial structure of academia and the fierce competition for scarce resources.

Lee Smolin expresses a slightly different position in his critique, claiming that string theory grew out of a tradition of particle physics which discourages speculation about the foundations of physics, while his preferred approach, loop quantum gravity, encourages more radical thinking.

String theory is a powerful, well-motivated idea and deserves much of the work that has been devoted to it.