Background independence

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The term background independence comes from theoretical physics and is a characteristic of spacetime in general relativity . The opposite background from dependent thinking goes on the considerations u. a. by Isaac Newton and is derived from the somewhat imprecise physical notion that space and time are, so to speak, the backdrop against which the physical phenomena take place.

Background independence was given a special meaning because it was anticipated by the general theory of relativity, and every covariant quantum gravity was implied. The spacetime background is not static in general relativity, but changes due to the influence of moving masses and energies.

On the one hand, the behavior of spacetime results directly from the theory, and on the other hand, it is even coupled to the environment in such a way that, for example, in black holes according to Stephen Hawking, “time ends inside a black hole”. This contradicts the intuitive idea of ​​a space-time unaffected by the processes in the universe.

Example of string theory and loop quantum gravity

The loop quantum gravity is, for example, a background-independent theory, since it does not assume a spacetime background, but first constructs it through the theory.

Current string theory approaches, on the other hand, assume that strings oscillate through a given space-time that is inserted “by hand” into the theory. Therefore, string theory is currently not background-independent. The string theorist Brian Greene hopes, however, that in the future it could be possible to transfer the background-independent techniques used in loop quantum gravity to string theory. To what extent this is possible is currently still completely open.

credentials

  1. ↑ “When the nuclear fuel of a massive star is depleted, it loses heat and shrinks. The curvature of spacetime can become so great that a black hole is created from which no light can escape. Time ends inside the black hole. ”, Stephen Hawking, The Universe in a Nutshell, Hoffmann & Campe, 2001, Chapter 1, p. 33

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