What is String Theory ?

String theory, in particle physics, a theory that attempts to merge quantum mechanics with Albert Einstein’s general theory of relativity. The name string theory comes from the modeling of subatomic particles as tiny one-dimensional “stringlike” entities rather than the more conventional approach in which they are modeled as zero-dimensional point particles.

Because string theory potentially provides a unified description of gravity and particle physics, it is a candidate for a theory of everything, a self-contained mathematical model that describes all fundamental forces and forms of matter.

The Elegant Universe: The companion site for the 3 hour PBS series based on Brian Greene's book. You can even watch the series online.

The announcement was universally ignored. String theory had already failed in its first incarnation as a description of the strong force, and many felt it was unlikely that it would now prevail as the solution to an even more difficult problem.

The theory envisions that a string undergoing a particular mode of vibration corresponds to a particle with definite properties such as mass and charge. In the 1980s, physicists realized that string theory had the potential to incorporate all four of nature’s forces—gravity, electromagnetism, strong force, and weak force—and all types of matter in a single quantum mechanical framework, suggesting that it might be the long-sought unified field theory.

Particle Adventure: A very nice tour through the main ideas of the Standard Model of particle physics.(Also available in Spanish and other languages).

This view was bolstered by string theory’s suffering from its own theoretical problems.

Despite much work on these problems, it is not known to what extent string theory describes the real world or how much freedom the theory allows in the choice of its details.

The Science of Matter, Space and Time: Another nice presentation of the concepts of particle physics.

string theory is still a vibrant area of research that is undergoing rapid development, it remains primarily a mathematical construct because it has yet to make contact with experimental observations.

For one, some of its equations showed signs of being inconsistent; for another, the mathematics of the theory demanded the universe have not just the three spatial dimensions of common experience but six others (for a total of nine spatial dimensions, or a total of ten space-time dimensions).

Einstein's Unfinished Symphony: An article on string theory that appeared recently in TIME magazine, on occasion of TIME's designation of Einstein as the person of the 20th century.

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.

Strings '00 Pictures: Photos of some of the world's leading string theorists, at the most important yearly conference on the subject (see also the ITP M Theory Program and Strings 96 pictures).

Black Holes, Strings and Quantum Gravity: A public lecture by Prof. Juan Maldacena, undoubtedly the most influential string theorist in the last few years (also available in Spanish).

Subsequently, it was realized that the very properties that made string theory unsuitable as a theory of nuclear physics made it a promising candidate for a quantum theory of gravity. The earliest version of string theory, bosonic string theory, incorporated only the class of particles known as bosons.

Superstrings! Home Page: A nice site where many aspects of string theory are explained.

Duality, Spacetime and Quantum Mechanics: A public lecture by Prof. Edward Witten (IAS Princeton), arguably the world's most influential theoretical physicist, and a leading contributor to string theory.

In late 1997, theorists discovered an important relationship called the AdS/CFT correspondence, which relates string theory to another type of physical theory called a quantum field theory.

The Theory of Strings--- A Detailed Introduction: An extensive description of the basic ideas of the theory, by Prof. Sunil Mukhi, a leading string theorist.

One of the challenges of string theory is that the full theory does not have a satisfactory definition in all circumstances. Another issue is that the theory is thought to describe an enormous landscape of possible universes, and this has complicated efforts to develop theories of particle physics based on string theory. These issues have led some in the community to criticize these approaches to physics and question the value of continued research on string theory unification.

String Reviews: List of downloadable review articles on various topics in string theory. Most of them are highly technical, but some of the articles in the "Colloquia/Semipopular" category are intended for a wider audience.

String Theory and the Unification of Forces: An explanation of the ambitious goal of string theory, by Prof. S. Mukhi.

The Second Superstring Revolution: A (somewhat technical) report on the latest developments in string theory, due to Prof. John Schwarz, one of the fathers of the theory.

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 also be modeled as one-dimensional objects called strings.