Hořava–Lifshitz gravity

Hořava–Lifshitz gravity (or Hořava gravity) is a theory of quantum gravity proposed by Petr Hořava in 2009.^[1] It solves the problem of different concepts of time in quantum field theory and general relativity by treating the quantum concept as the more fundamental so that space and time are not equivalent (anisotropic) at high energy level. The relativistic concept of time with its Lorentz invariance emerges at large distances. The theory relies on the theory of foliations to produce its causal structure. It is related to topologically massive gravity and the Cotton tensor. It is a possible UV completion of general relativity. Also, the speed of light goes to infinity at high energies. The novelty of this approach, compared to previous approaches to quantum gravity such as Loop quantum gravity, is that it uses concepts from condensed matter physics such as quantum critical phenomena. Hořava's initial formulation was found to have side-effects such as predicting very different results for a spherical Sun compared to a slightly non-spherical Sun, so others have modified the theory. Inconsistencies remain.^[2]^[3]^[4]

The detailed balance condition

Hořava originally imposed the theory to satisfy the detailed balance condition which considerably reduces the number of terms in the action.

References

↑ Hořava, Petr (2009). "Quantum gravity at a Lifshitz point". Phys. Rev. D. 79 (8): 084008. arXiv:0901.3775. Bibcode:2009PhRvD..79h4008H. doi:10.1103/PhysRevD.79.084008.
↑ Charmousis, C.; Niz, G.; Padilla, A.; Saffin, P. (2009). "Strong coupling in Horava gravity". Journal of High Energy Physics. 2009 (08): 070. arXiv:0905.2579. Bibcode:2009JHEP...08..070C. doi:10.1088/1126-6708/2009/08/070.
↑ Blas, D.; Pujolàs, O.; Sibiryakov, S. (2009). "On the extra mode and inconsistency of Hořava gravity". Journal of High Energy Physics. 2009 (10): 029. arXiv:0906.3046. Bibcode:2009JHEP...10..029B. doi:10.1088/1126-6708/2009/10/029.
↑ Koyama, Kazuya; Arroja, Frederico (2010). "Pathological behaviour of the scalar graviton in Hořava–Lifshitz gravity". Journal of High Energy Physics. 2010 (3): 1–11. arXiv:0910.1998. Bibcode:2010JHEP...03..061K. doi:10.1007/JHEP03(2010)061.

External links

Zeeya Merali, "Splitting Time from Space—New Quantum Theory Topples Einstein's Spacetime". Scientific American, December, 2009

Theories of gravitation

Standard

Newtonian gravity (NG)	Newton's law of universal gravitation History of gravitational theory

General relativity (GR)	Introduction History Mathematics Resources Tests Post-Newtonian formalism Linearized gravity ADM formalism Gibbons–Hawking–York boundary term

Alternatives to
general relativity

Paradigms	Classical theories of gravitation Quantum gravity Theory of everything

Classical	Einstein–Cartan Bimetric theories Gauge theory gravity Teleparallelism Composite gravity f(R) gravity Massive gravity Modified Newtonian dynamics (MOND) Nonsymmetric gravitation Scalar–tensor theories Brans–Dicke Scalar–tensor–vector Conformal gravity Scalar theories Nordström Whitehead Geometrodynamics Induced gravity Tensor–vector–scalar Chameleon Pressuron

Quantisation	Euclidean quantum gravity Canonical quantum gravity Wheeler–DeWitt equation Loop quantum gravity Spin foam Causal dynamical triangulation Causal sets DGP model

Unification	Kaluza–Klein theory Dilaton Supergravity

Unification and quantisation	Noncommutative geometry Self-creation cosmology Semiclassical gravity Superfluid vacuum theory Logarithmic BEC vacuum String theory M-theory F-theory Heterotic string theory Type I string theory Type 0 string theory Bosonic string theory Type II string theory Little string theory Twistor theory Twistor string theory

Generalisations / Extensions of GR	Scale relativity Liouville gravity Lovelock theory (2+1)-dimensional topological gravity Gauss–Bonnet gravity Jackiw–Teitelboim gravity

Pre-Newtonian theories
and Toy models

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