The pre-inflationary dynamics of LQC confronting quantum gravity with observations

Abhay Ashtekar

Research output: Contribution to conferencePaperpeer-review


• The early universe provides an ideal setting to test quantum gravity ideas. The inflationary paradigm provides a telescope to peer into the Planck regime. Furthermore, it has been extremely successful with structure formation. Can one provide a quantum gravity completion of the inflationary paradigm thereby overcoming some of its limitations? In LQG the answer is yes in the following precise sense: • Background geometry: Singularity Resolution and precise quantum geometry for the Planck regime. • Perturbations: Since they propagate on quantum geometry using QFT on cosmological quantum geometries (aa, Lewandowski, Kaminski), trans-Planckian issues can be handled systematically provided the test field approximation holds. Analyzed in detail using the renormalized stress-energy of (1)(2) on the quantum geometry of Ψ. Detailed numerics show that the approximation does hold if φ p1. (Agullo, AA, Nelson) • Extension: If ΦB P1 & ψ is a 'permissible vacuum,' modes of observational interest are all in the Bunch Davis vacuum at the onset of the WMAP slow roll → Predictions of the standard inflationary scenario for the power spectra, spectral indices & ratio of tensor to scalar modes are recovered starting from the deep Planck era. (Agullo, AA, Nelson) • Non-Gaussianity: There is a small window in φB for which at the onset of inflation ψ has excitations over the Bunch-Davis vacuum. These give rise to specific 3-point functions ('bi-spectrum') which are important for the 'halo bias'. Could be observed in principle: Link between observations and the initial state! A window to probe the Planck era around the LQC bounce. (Agullo, AA, Nelson, Shandera, Ganc, Komatsu) • Note: LQG does not imply that inflation must have occurred because it does not address particle physics issues. The analysis simply assumes that there is an inflaton with a suitable potential. But it does show concretely that many of the standard criticisms (e.g. due to Brandenberger) of inflation can be addressed in LQG by facing the Planck regime squarely.

Original languageEnglish (US)
Number of pages1
StatePublished - Dec 1 2012
Event22nd Workshop on General Relativity and Gravitation in Japan 2012, JGRG 22 - Hongo, Tokyo, Japan
Duration: Nov 12 2012Nov 16 2012


Other22nd Workshop on General Relativity and Gravitation in Japan 2012, JGRG 22
CityHongo, Tokyo

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics


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