Modified Theories of Quantum Gravity

In General > see BF theory; clifford algebra; gravity; modified general relativity [strong coupling]; newton-cartan; Non-Symmetric Gravity.
@ Modified dynamics: Smolin CQG(92) [G → 0]; Wang gq/05-in [conformally symmetric]; Broda et al PLB(07) [abelian theory].
@ Other dimensions: Bjerrum-Bohr NPB(04)ht/03 [D → ]; Nieto a0704 [8D, background-independent Kaluza-Klein à la lqg]; > s.a. 2D and 3D quantum gravity, regge calculus.

Linearized Gravity > s.a. [perturbations]; canonical and covariant quantum gravity.
@ Approaches: Ashtekar et al PRD(91) [lqg]; Grigore CQG(00)ht/99; Shojai & Shojai PS(03)gq [Bohmian approach]; Quevedo & Tafoya GRG(05)gq/04 [deformation]; Bomstad & Klauder CQG(06)gq [projection operator].
@ Ground state: Kuchar JMP(70) [canonical]; Hartle PRD(84) [Euclidean path integral].
@ Gravitons: Varadarajan PRD(02)gq [loop and Fock space]; Speziale JHEP(06)gq/05 [2-point function from spin foam, 3D model]; > s.a. quantum field theory in curved spacetime [graviton].
@ Around FRW backgrounds: Ford & Parker PRD(77); Bojowald et al a0806 [in lqg].
@ Related topics: Moncrief GRG(79) [linearization instabilities]; > s.a. quantum regge calculus.

Higher-Order Theories > s.a. classical higher-order theories; covariant quantum gravity [stability of Minkowski].
* Results: It is renormalizable and asymptotically free [@ Tomboulis], but nonunitary (due to quartic terms in R² that give ghosts in the propagators) and with H unbounded below [@ Stelle, etc].
@ General references: Mazzitelli PRD(92), Tomboulis PLB(96)ht [relationship with general relativity, and renormalization]; Asorey et al IJMPA(97); Mielke a0707 [topological action].
@ Renormalizability: Utiyama & DeWitt JMP(62); Stelle PRD(77); de Berredo-Peixoto & Shapiro PRD(05)ht/04 [Gauss-Bonnet term, 4–]; > s.a. renormalization of quantum gravity [UV fixed points].
@ Around de Sitter: Cognola et al JCAP(05)ht, Cognola & Zerbini JPA(06)in [one-loop covariant f(R) gravity].
@ In quantum cosmology: Hawking & Luttrell NPB(84); van Elst et al CQG(94)gq [R + R³ action]; Pimentel et al CQG(97) [pure R² action]; Davis GRG(00) [string-motivated]; Fabris & Reuter GRG(00); Sanyal & Modak PRD(01)gq, CQG(02)gq/01 [R + R² action]; Shojai & Shojai a0801-GRG [spatially flat].
@ FRW minisuperspace: Sanyal PLB(02)gq [Schrödinger equation and interpretation].
@ Related topics: Accioly et al IJTP(00) [propagator]; Kleidis et al PLB(02)ht [with massive scalar].
> Related topics: see higher-order gravity; path integral quantum gravity; quantum gravity; semiclassical quantum gravity.

Other Theories of Gravity > s.a. classical theories of gravity; quantum cosmology [varying constants].
@ Scalar-tensor: Pimentel & Mora gq/00 [Bergmann-Wagoner theory].

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