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In contrast, loop quantum gravity, like general relativity, is manifestly background independent, eliminating the background required in string theory. Loop quantum gravity, like string theory, also aims to overcome the nonrenormalizable divergences of quantum field theories.
(Later, loop quantum gravity inherited this geometric interpretation of gravity, and posits that a quantum theory of gravity is fundamentally a quantum theory of spacetime.) In the 1920s, the French mathematician Élie Cartan formulated Einstein's theory in the language of bundles and connections, [ 1 ] a generalization of Riemannian geometry ...
A quantum theory of gravity is needed in order to reconcile general relativity with the principles of quantum mechanics, but difficulties arise when one attempts to apply the usual prescriptions of quantum theory to the force of gravity. [2] String theory is a theoretical framework that attempts to address these questions.
A very different approach to quantum gravity called loop quantum gravity is fully non-perturbative and manifestly background-independent: geometric quantities, such as area, are predicted without reference to a background metric or asymptotics (e.g. no need for a background metric or anti-de Sitter asymptotics), only a given topology.
Smolin suggests that string theory suffers from serious deficiencies and has an unhealthy near-monopoly in the particle theory community. He called for a diversity of approaches to quantum gravity , and argued that more attention should be paid to loop quantum gravity, an approach Smolin has devised.
Renate Loll: physicist who worked on loop quantum gravity and more recently helped develop the causal dynamical triangulations approach to quantum gravity. Luboš Motl: physicist who worked on string theory. Fotini Markopoulou-Kalamara: physicist who works on loop quantum gravity and spin network models that take causality into account.
Smolin discusses three potential approaches by which a unified theory of quantum gravity, arguably the foremost issue in theoretical physics, may be realized. Approaches discussed include string theory, M-theory, and Smolin's preferred approach, loop quantum gravity. Smolin suggests that these approaches may be approximations of a single ...
Quantum gravity (QG) is a field of theoretical physics that seeks to describe gravity according to the principles of quantum mechanics.It deals with environments in which neither gravitational nor quantum effects can be ignored, [1] such as in the vicinity of black holes or similar compact astrophysical objects, as well as in the early stages of the universe moments after the Big Bang.