theories:speculative_theories:quantum_gravity
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theories:speculative_theories:quantum_gravity [2018/04/06 16:23] jakobadmin [Intuitive] |
theories:speculative_theories:quantum_gravity [2020/04/03 16:50] (current) 95.168.180.148 Changed table to list structure. In a table the entries in the same row have some relation to each other, that was no the case. |
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| <tabbox Intuitive> | <tabbox Intuitive> | ||
| - | Quantum gravity is the generic term for theories that try to combine the principles of [[theories:quantum_mechanics|quantum theories]] with [[theories:general_relativity|general relativity]]. | + | Quantum gravity is the generic term for theories that try to combine the principles of [[theories:quantum_mechanics:canonical|quantum theories]] with [[models:general_relativity|general relativity]]. |
| So far, no experimentally verified theory of quantum gravity exists. | So far, no experimentally verified theory of quantum gravity exists. | ||
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| * [[https://arxiv.org/abs/1010.5822|Gauge Gravity: a forward-looking introduction]] by Andrew Randono | * [[https://arxiv.org/abs/1010.5822|Gauge Gravity: a forward-looking introduction]] by Andrew Randono | ||
| + | ---- | ||
| + | <blockquote>From a brief analysis of the standard Einstein-Hilbert action, we see that fluctuations of the metric at the Planck scale should become very violent, leading to potential changes in the topology of the spacetime [103, 104]. <cite>https://arxiv.org/abs/1711.00864</cite></blockquote> | ||
| <tabbox Abstract> | <tabbox Abstract> | ||
| Line 36: | Line 38: | ||
| <tabbox Why is it interesting?> | <tabbox Why is it interesting?> | ||
| <blockquote> | <blockquote> | ||
| - | One of the big problems in physics — perhaps the biggest! — is figuring out how our two current best theories fit together. On the one hand we have the [[models:standard_model|Standard Model]], which tries to explain all the forces except gravity, and takes quantum mechanics into account. On the other hand we have [[theories:general_relativity|General Relativity]], which tries to explain gravity, and does not take [[theories:quantum_mechanics|quantum mechanics]] into account. Both theories seem to be more or less on the right track — but until we somehow fit them together, or completely discard one or both, our picture of the world will be deeply schizophrenic. | + | One of the big problems in physics — perhaps the biggest! — is figuring out how our two current best theories fit together. On the one hand we have the [[models:standard_model|Standard Model]], which tries to explain all the forces except gravity, and takes quantum mechanics into account. On the other hand we have [[models:general_relativity|General Relativity]], which tries to explain gravity, and does not take [[theories:quantum_mechanics:canonical|quantum mechanics]] into account. Both theories seem to be more or less on the right track — but until we somehow fit them together, or completely discard one or both, our picture of the world will be deeply schizophrenic. |
| It seems plausible that as a step in the right direction we should figure out a theory of gravity that takes quantum mechanics into account, but reduces to General Relativity when we ignore quantum effects (which should be small in many situations). This is what people mean by "quantum gravity" — the quest for such a theory. | It seems plausible that as a step in the right direction we should figure out a theory of gravity that takes quantum mechanics into account, but reduces to General Relativity when we ignore quantum effects (which should be small in many situations). This is what people mean by "quantum gravity" — the quest for such a theory. | ||
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| - | <blockquote>At the beginning of the XX century,[[theories:general_relativity| General Relativity]] (GR) and [[theories:quantum_mechanics|Quantum Mechanics]] (QM) once | + | <blockquote>At the beginning of the XX century,[[models:general_relativity| General Relativity]] (GR) and [[theories:quantum_mechanics:canonical|Quantum Mechanics]] (QM) once |
| again began reshaping our basic understanding of space and time and, respectively, matter, energy | again began reshaping our basic understanding of space and time and, respectively, matter, energy | ||
| and causality —arguably to a no lesser extent. But we have not been able to combine these new | and causality —arguably to a no lesser extent. But we have not been able to combine these new | ||
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| Here's an incomplete list of popular approaches to formulate a theory of quantum gravity: | Here's an incomplete list of popular approaches to formulate a theory of quantum gravity: | ||
| + | Traditional | ||
| + | * Discrete methods | ||
| + | * Dynamical triangulations | ||
| + | * Regge calculus | ||
| + | * Simplicial models | ||
| + | * Approximate theories | ||
| + | * Euclidean quantum gravity | ||
| + | * Perturbative quantum gravity | ||
| + | * QFT on curved space–times | ||
| + | * Unorthodox approaches | ||
| + | * Sorkin’s Posets | ||
| + | * Finkelstein | ||
| + | * Twistors | ||
| - | ^ Traditional Discrete Methods ^ Traditional Approximate theories ^ Traditional Unorthodox approaches ^ New ^ Most Popular | | + | New |
| - | | Dynamical triangulations | Euclidean quantum gravity | Sorkin’s Posets | Non-commutative geometry | [[theories:speculative_theories:string_theory|String Theory]] | | + | * Non-commutative geometry |
| - | | Regge calculus | Perturbative quantum gravity | Finkelstein | Null surfaces | [[theories:speculative_theories:lqg|Loop Quantum Gravity]] | | + | * Null surfaces |
| - | | Simplicial models | QFT on curved space–times | Twistors | Spin foam models | [[theories:speculative_theories:asymptotic_safety|Asymptotic Safety]] | | + | * Spin foam models |
| - | | | | | | [[theories:speculative_theories:supergravity|Supergravity]]| | + | |
| + | Most popular | ||
| + | * [[theories:speculative_theories:string_theory|String Theory]] | ||
| + | * [[theories:speculative_theories:lqg|Loop Quantum Gravity]] | ||
| + | * [[theories:speculative_theories:asymptotic_safety|Asymptotic Safety]] | ||
| + | * [[models:speculative_models:supergravity|Supergravity]] | ||
| - | Table adapted from [[https://arxiv.org/abs/gr-qc/9803024|Strings, loops and others: a critical survey of the present approaches to quantum gravity]] by Carlo Rovelli | + | List adapted from [[https://arxiv.org/abs/gr-qc/9803024|Strings, loops and others: a critical survey of the present approaches to quantum gravity]] by Carlo Rovelli |
| <tabbox FAQ> | <tabbox FAQ> | ||
| + | |||
| --> What's so difficult about Quantum Gravity?# | --> What's so difficult about Quantum Gravity?# | ||
| Line 100: | Line 120: | ||
| <-- | <-- | ||
| + | -->Why is Gravity Non-Renormalizable?# | ||
| + | see https://arxiv.org/abs/0709.3555 | ||
| + | <-- | ||
| <tabbox History> | <tabbox History> | ||
theories/speculative_theories/quantum_gravity.1523024605.txt.gz · Last modified: 2018/04/06 14:23 (external edit)
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