# Duality

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## Duality (physics)

The state of having two natures, which is often applied in physics. The classic example is wave-particle duality. The elementary constituents of nature—electrons, quarks, photons, gravitons, and so on—behave in some respects like particles and in others like waves.

Duality is often used in a more precise sense. It indicates that two seemingly different, theoretical descriptions of a physical system are actually mathematically equivalent. Such an occurrence is very useful. Various properties and phenomena are clearer in one or the other of the descriptions, and calculations that are difficult or impossible in one description may be simple in the other. In the case of wave-particle duality, the wave description corresponds to a theory of quantized fields, where the field variables are governed by an uncertainty principle. The particle description corresponds to a Feynman integral over all particle paths in spacetime. The quantized-field and path integral theories sound very different but are mathematically equivalent, making identical predictions. See Feynman integral, Quantum field theory, Quantum mechanics, Uncertainty principle, Wave mechanics

#### Weak-strong duality

In some systems, there is weak-strong duality, meaning that when the coupling constant g of the original description is large that of the dual description, g, is small; for example g = 1/g. When g is large, so the interactions in the original description are strong and the perturbation theory in this description is highly inaccurate, then perturbation theory in the dual description gives a very accurate description.

#### Duality in superstring theory

It is believed that a complete theory of all particles and interactions must be based on quantization of one-dimensional objects (loops) rather than points: this is superstring theory. In superstring theory there is again the problem that perturbation theory is the main tool, giving an incomplete description of the physics. The situation has greatly improved with the discovery that weak-strong duality is a general property of string theory. In fact, there are five known string theories, and all are dual to one another. A notable feature in string theory is that in addition to strings and solitons, duality requires certain other objects as well: D-branes, which are local disturbances to which strings become fixed. Remarkably, the same methods have also been used to solve some long-standing problems regarding the quantum mechanics of black holes. See Quantum gravitation;, Superstring theory

References in periodicals archive ?
Dualist philosophers and theologists limit the spiritual life with mind-body or spirit-nature dualities.
Mititelu: New type dualities in PDI and PDE constrained optimization problems , J.
Braithwaite provides us a way to understand the central dualities of the profession, not only as a theoretical matter, but also in light of those practices like conferencing where responsive regulation and restorative justice, formal and informal problem-, conflict-, and injustice-resolving mechanisms, support and constrain each other.
His project rests on its pronounced dualities, which merge strands of mainstream and esoteric American culture while focusing on the clash between the apologists of abstraction and pop culture and the perennial success-versus-failure fixation.
The ballet is about universal energies, essential dualities, and interactions.
The design, which dates back to 1994, seems to evolve around sets of dualities.
The English title is rather strange because, whilst the book presents a history of Egypt after the last traditionally `great' era, the New Kingdom, from 1070 to 323 BC, it does so with an emphasis on the dualities prevalent in ancient Egypt.
First, Schneirov rejects the exaggerated dualities that have too often warped labor histories of this period: trade unions versus the Knights of Labor; independent labor politics versus the two-party system; radicalism versus reform.
black"); second, that the passing figure, once imagined, is capable of exploding these dualities even in spite of the efforts of the author who creates him/her to reinscribe them; and, finally, that the subversive nature of the act of passing itself means that our reading of passing characters is always double - we must read them as fundamentally transgressive of and fundamentally capitulative to both moralistic and racial dualisms.
Erickson sets his argument against the rigid dualities of new historicism, aligning himself with the more flexible revisionist historicists who can see discourse not so exclusively centered on power: "By exposing the poem's multiplicity, the book challenges historicist critics to consider a pluralist perspective and to revaluate their most persistent assumptions: that cultural power conditions and controls representation and interpretation .

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