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] though progress was made on the theory.[5] Nevertheless, observations of gravitational waves emitted by the neutron-star merger GW170817 contravene predictions made by this model of gravity.[6][7][8] Some have revised the theory to account for this. [9]
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.
See also
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. S2CID 891685.
- ^ Charmousis, C.; Niz, G.; Padilla, A.; Saffin, P. (2009). "Strong coupling in Horava gravity". Journal of High Energy Physics. 2009 (8): 070. arXiv:0905.2579. Bibcode:2009JHEP...08..070C. doi:10.1088/1126-6708/2009/08/070. S2CID 53363935.
- ^ 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. S2CID 15368805.
- ^ Koyama, Kazuya; Arroja, Frederico (2010). "Pathological behaviour of the scalar graviton in Hořava–Lifshitz gravity". Journal of High Energy Physics. 2010 (3): 61. arXiv:0910.1998. Bibcode:2010JHEP...03..061K. doi:10.1007/JHEP03(2010)061. S2CID 119236847.
- ^ Wang, Anzhong (2017). "Hořava Gravity at a Lifshitz Point: A Progress Report". International Journal of Modern Physics D. 26 (7). arXiv:1701.06087. Bibcode:2017IJMPD..2630014W. doi:10.1142/S0218271817300142. S2CID 119258168.
- ^ Creminelli P, Vernizzi F (December 2017). "Dark Energy after GW170817 and GRB170817A". Physical Review Letters. 119 (25): 251302. arXiv:1710.05877. Bibcode:2017PhRvL.119y1302C. doi:10.1103/PhysRevLett.119.251302. PMID 29303308. S2CID 206304918.
- ^ Sakstein J, Jain B (December 2017). "Implications of the Neutron Star Merger GW170817 for Cosmological Scalar-Tensor Theories". Physical Review Letters. 119 (25): 251303. arXiv:1710.05893. Bibcode:2017PhRvL.119y1303S. doi:10.1103/PhysRevLett.119.251303. PMID 29303345. S2CID 39068360.
- ^ Ezquiaga JM, Zumalacárregui M (December 2017). "Dark Energy After GW170817: Dead Ends and the Road Ahead". Physical Review Letters. 119 (25): 251304. arXiv:1710.05901. Bibcode:2017PhRvL.119y1304E. doi:10.1103/PhysRevLett.119.251304. PMID 29303304. S2CID 38618360.
- ^ Frusciante N, Benetti M (May 2021). "Cosmological constraints on Hořava gravity revised in light of GW170817 and GRB170817A and the degeneracy with massive neutrinos". Phys. Rev. D. 103 (10). arXiv:2005.14705. doi:10.1103/PhysRevD.103.104060.
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