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Loop Quantum Gravity on Wed Oct 14, 2009 6:43 pm
Loop Quantum Gravity
http://www.google.com/search?hl=en&q=Loop+Quantum+Gravity+&btnG=Search&aq=f&oq=&aqi=g-p1g9
http://en.wikipedia.org/wiki/Loop_quantum_gravity
Loop quantum gravity (LQG), also known as loop gravity and quantum geometry, is a proposed quantum theory of spacetime which attempts to reconcile the theories of quantum mechanics and general relativity. Loop quantum gravity suggests that space can be viewed as an extremely fine fabric or network "weaved" of finite quantised loops of excited gravitational fields called spin networks. When viewed over time, these spin networks are called spin foam, which should not be confused with quantum foam. A major contender with string theory, loop quantum gravity incorporates general relativity and does not require string theory's higher dimensions.
LQG preserves many of the important features of general relativity, while at the same time employing quantization of both space and time at the Planck scale in the tradition of quantum mechanics. The technique of loop quantization was developed for the nonperturbative quantization of diffeomorphism-invariant gauge theory. Roughly, LQG tries to establish a quantum theory of gravity in which the very space where all other physical phenomena occur becomes quantized.
LQG is one of a family of theories called canonical quantum gravity. The LQG theory includes also matter and forces, but the theory does not address the problem of the unification of all physical forces, as do some other quantum gravity such as string theory.
Loop Quantum Gravity
http://relativity.livingreviews.org/Articles/lrr-1998-1/
The problem of finding the quantum theory of the gravitational field, and thus understanding what is quantum spacetime, is still open. One of the most active of the current approaches is loop quantum gravity. Loop quantum gravity is a mathematically well-defined, non-perturbative and background independent quantization of general relativity, with its conventional matter couplings. Research in loop quantum gravity today forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained are: (i) The computation of the physical spectra of geometrical quantities such as area and volume, which yields quantitative predictions on Planck-scale physics. (ii) A derivation of the Bekenstein-Hawking black hole entropy formula. (iii) An intriguing physical picture of the microstructure of quantum physical space, characterized by a polymer-like Planck scale discreteness. This discreteness emerges naturally from the quantum theory and provides a mathematically well-defined realization of Wheeler's intuition of a spacetime ``foam''. Long standing open problems within the approach (lack of a scalar product, over-completeness of the loop basis, implementation of reality conditions) have been fully solved. The weak part of the approach is the treatment of the dynamics: at present there exist several proposals, which are intensely debated. Here, I provide a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.
Videos :
http://www.youtube.com/results?search_query=Loop+Quantum+Gravity&search_type=&aq=f
http://www.google.com/search?hl=en&q=Loop+Quantum+Gravity+&btnG=Search&aq=f&oq=&aqi=g-p1g9
http://en.wikipedia.org/wiki/Loop_quantum_gravity
Loop quantum gravity (LQG), also known as loop gravity and quantum geometry, is a proposed quantum theory of spacetime which attempts to reconcile the theories of quantum mechanics and general relativity. Loop quantum gravity suggests that space can be viewed as an extremely fine fabric or network "weaved" of finite quantised loops of excited gravitational fields called spin networks. When viewed over time, these spin networks are called spin foam, which should not be confused with quantum foam. A major contender with string theory, loop quantum gravity incorporates general relativity and does not require string theory's higher dimensions.
LQG preserves many of the important features of general relativity, while at the same time employing quantization of both space and time at the Planck scale in the tradition of quantum mechanics. The technique of loop quantization was developed for the nonperturbative quantization of diffeomorphism-invariant gauge theory. Roughly, LQG tries to establish a quantum theory of gravity in which the very space where all other physical phenomena occur becomes quantized.
LQG is one of a family of theories called canonical quantum gravity. The LQG theory includes also matter and forces, but the theory does not address the problem of the unification of all physical forces, as do some other quantum gravity such as string theory.
Loop Quantum Gravity
http://relativity.livingreviews.org/Articles/lrr-1998-1/
The problem of finding the quantum theory of the gravitational field, and thus understanding what is quantum spacetime, is still open. One of the most active of the current approaches is loop quantum gravity. Loop quantum gravity is a mathematically well-defined, non-perturbative and background independent quantization of general relativity, with its conventional matter couplings. Research in loop quantum gravity today forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained are: (i) The computation of the physical spectra of geometrical quantities such as area and volume, which yields quantitative predictions on Planck-scale physics. (ii) A derivation of the Bekenstein-Hawking black hole entropy formula. (iii) An intriguing physical picture of the microstructure of quantum physical space, characterized by a polymer-like Planck scale discreteness. This discreteness emerges naturally from the quantum theory and provides a mathematically well-defined realization of Wheeler's intuition of a spacetime ``foam''. Long standing open problems within the approach (lack of a scalar product, over-completeness of the loop basis, implementation of reality conditions) have been fully solved. The weak part of the approach is the treatment of the dynamics: at present there exist several proposals, which are intensely debated. Here, I provide a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.
Videos :
http://www.youtube.com/results?search_query=Loop+Quantum+Gravity&search_type=&aq=f
