Connection Formulation of Canonical General Relativity  

In General > s.a. BRST; initial value formulation; numerical general relativity; [connection formulation of quantum gravity].
* Ashtekar variables: Based on self-dual action; A complex SO(3) connection Aai(x) and a densitized triad Eai(x) (initially, a densitized SU(2) soldering form, to be used with coupled spinorial matter), with Poisson brackets {Aai(x), Ebj(y)} = –i ab ij (xy); In a solution of the fields equations, Aai = –1 (ai + i Kai), with the connection of E, and K the extrinsic curvature.
* Ashtekar-Barbero variables: Using the Immirzi parameter , the connection can be generalized to

Aai = –1 (ai + Kai) ;

Notice however that for i this spatial connection is not the pull-pack of a spacetime connection.
* Action:

S = dt Sigma d3x [–2i Eai Aai + 2i Na Ebi Fabi – 2i N a Eai + N Eai Ebj ijk Fabk] + boundary terms .

* Constraints and evolution:

a Ea = 0 ,   tr Ea Fab = 0 ,   tr Ea Eb Fab = 0 .

* And geometry: The surface element of a 2-surface xa(r,s) is (Eai Eib fa fb )1/2 dr ds, where fa:= abc xbxc.
* SU(2) vs SO(3): The idea that the contribution from j = 1 edges of spin networks dominates black hole areas, as opposed to j = 1/2, suggests (but does not imply – an exclusion principle argument might apply) that the true gauge group involved might be SO(3) rather than SU(2).

General References > s.a. higher-order gravity.
@ Bibliography: Beetle & Corichi gq/97, Corichi & Hauser gq/05.
@ Complex variables: Sen PLB(82); Ashtekar PRL(86), PRD(87), in(87), in(90); Jacobson & Smolin PLB(87); Dolan PLB(89); Herdegen CQG(89); Bergmann & Smith PRD(91); Soloviev PLB(92); Wallner PRD(92); Chang & Soo IJMPD(93)ht; Romano GRG(93)gq [vs geometrodynamics]; Khatsymovsky gq/93, PLB(97)gq/96 [and self-duality]; Kerrick PRL(95); Nieto MPLA(05) [form of the action].
@ Real variables: Barbero PRD(94)gq/93, PRD(95)gq/94; Holst PRD(96)gq/95; Loll gq/97-in; Samuel CQG(00)gq, PRD(01).
@ Immirzi parameter: Immirzi CQG(97)gq/96; Rovelli & Thiemann PRD(98)gq/97; Krasnov CQG(98)gq/97; Corichi & Krasnov MPLA(98); Barros e Sá IJMPD(01)gq/00; Samuel PRD(01); Mena CQG(02)gq [not local]; Garay & Mena PRD(02)gq [and black hole entropy]; Dreyer PRL(03)gq/02 [and black hole entropy]; Oppenheim PRD(04)gq/03 [and quasinormal modes]; Pérez & Rovelli PRD(06)gq/05 [physical effects]; Chou et al PRD(05)gq [meaning, scalar vs pseudo-scalar]; Fatibene et al CQG(07)-a0706 [action]; > s.a. Conformal Gravity, models [Dirac fields, Immirzi parameter as local field], regge calculus.
@ SU(2) vs SO(3): Swain IJMPD(03)gq-GRF and gq/04, gq/04-MGX; Chou et al PLB(06)gq/05.
@ Compared to metric variables: Anandan gq/95; Zagermann CQG(98)gq/97 [2 Killing vectors].
@ Nature of equations: Iriondo et al PRL(97)gq, ATMP(98)gq; Yoneda & Shinkai PRL(99)gq/98; Shinkai & Yoneda PRD(99)gq [stable form].
@ Reality conditions: Bengtsson TMP(93); Mena IJMPD(94)gq/93 [and quantization]; Immirzi CQG(93); Barbero PRD(95)gq/94, PRD(95)gq/94; Morales-Técotl et al CQG(96)gq [as Dirac constraints]; Yoneda & Shinkai CQG(96)gq [with cosmological constant]; Pons et al PRD(00)gq/99; Alexandrov CQG(06)gq/05 [and Lorentz-covariant formulation].
@ Euclidean / Lorentzian: Ashtekar PRD(96)gq/95; Barbero PRD(96)gq [2-parameter action]; Barnich & Husain CQG(97)gq/96; Mena G&C(98)gq/97 [generalized Wick transform]; Garay & Mena CQG(98)gq.
@ Solving the constraints: Thiemann CQG(93)gq; Barbero CQG(95)gq/94; Goldberg PRD(96) [gauge and diffeomorphism].
@ Initial value problem: Saraykar & Wagh pr(89); Robinson & Soteriou CQG(90); Capovilla et al gq/93.
@ Gauge issues: Manojlovic & Mikovic NPB(92) [fixing]; Montesinos & Vergara GRG(01)gq/00 [invariance].
@ Related topics: Giannopoulos & Daftardar CQG(92) [algebraic evaluation]; Chang & Soo PRD(92) [and 4-manifolds]; Rovelli PRD(93) [and surface areas]; > s.a. holonomy.

Variations and Generalizations > s.a. 3D gravity; higher-dimensional; loop variables; models [including matter]; Topological Gravity.
@ Linearized: Ashtekar & Lee IJMPD(94).
@ Covariant formulation: Fatibene et al CQG(07)gq.
@ 2+2 decomposition: d'Inverno & Vickers CQG(95); d'Inverno et al CQG(06) [double-null, Hamiltonian].
@ Based on threading: Fodor & Pejés in(91); > s.a. modified canonical formalism.
@ As BF theory: Capovilla et al CQG(01)gq [and Immirzi parameter].
@ Other similar variables: Rosas-Rodríguez IJMPA(08) [Eai and Bai].
@ And torsion: Maluf JMP(92); Montesinos JMP(99).


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