Three Roads To Quantum Gravity
Three Roads To Quantum Gravity
Three Roads To Quantum Gravity
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238 THREE ROADS TO QUANTUM GRAVITY<br />
The mathematically rigorous approach to loop quantum gravity is<br />
presented in Abhay Ashtekar, Jerzy Lewandowski, Donald Marolf, Jose<br />
Mourao and Thomas Thiemann, `Quantization of diffeomorphism<br />
invariant theories of connections with local degrees of freedom', Journal<br />
of Mathematical Physics 36 (1995) 6456, gr-qc/9504018; Abhay Ashtekar,<br />
Jerzy Lewandowski, `<strong>Quantum</strong> ®eld theory of geometry', hep-th/<br />
9603083; and T. Thiemann, `<strong>Quantum</strong> spin dynamics I and II', gr-qc/<br />
9606089, gr-qc/9606090, Classical and <strong>Quantum</strong> <strong>Gravity</strong> 15 (1998) 839,<br />
875.<br />
The original references for the Ashtekar±Sen formalism are in A. Sen,<br />
Physics. Letters B119 (1982) 89; International Journal; of Theoretical<br />
Physics 21 (1982) 1; A. Ashtekar, Physical Review Letters 57 (1986)<br />
2244; A. Ashtekar, Physical. Review D36 (1987) 1587.<br />
CHAPTER 11<br />
This is all standard material in string theory, to which Brian Greene's<br />
The Elegant Universe (Norton, 1999) is an excellent introduction. The<br />
best textbook is J. Polchinksi, String Theory (Cambridge University<br />
Press, 1998).<br />
CHAPTER 12<br />
The original references for the holographic principle are Gerard 't Hooft,<br />
`Dimensional reduction in quantum gravity', gr-qc/9310006, in Salanfestschrift,<br />
edited by A. Alo, J. Ellis, S. Randjbar-Daemi (World<br />
Scienti®c, 1993); and Leonard Susskind, `The world as a hologram',<br />
hep-th/9409089, Journal of Mathematical Physics 36 (1995) 6377. Ideas<br />
closely related to the holographic principle were presented earlier by<br />
L. Crane in `Categorical physics', hep-th/9301061 and hep-th/9308126<br />
in Knots and <strong>Quantum</strong> <strong>Gravity</strong>, edited by J. Baez (Oxford University<br />
Press, 1994); L. Crane, `Clocks and categories: is quantum gravity<br />
algebraic?' Journal of Mathematical Physics 36 (1995) 6180, gr-qc/<br />
9504038.<br />
The Bekenstein bound was proposed in J.D. Bekenstein, Lettere<br />
Nuovo Cimento 4 (1972) 737, Physical Review D7 (1973), 2333;<br />
Physical Review D9 (1974) 3292. Ted Jacobson's paper deriving<br />
general relativity from the Bekenstein bound and the laws of<br />
thermodynamics is `Thermodynamics of spacetime: the Einstein<br />
equation of state', gr-qc/9504004, Physical Review Letters 75 (1995)<br />
1260. The derivation of the Bekenstein bound in loop quantum gravity<br />
is in L. Smolin, `Linking topological quantum ®eld theory and<br />
nonperturbative quantum gravity', gr-qc/9505028, Journal of Mathematical<br />
Physics 36 (1995) 6417. Another very promising version of the<br />
holographic principle was proposed by Rafael Bousso in `A covariant