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arXiv · 1411.4793

Torsional instanton effects in quantum gravity

Romesh K. Kaul·Sandipan Sengupta
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Abstract

We show that, in the first order gravity theory coupled to axions, the instanton number of the Giddings-Strominger wormhole can be interpreted as the Nieh-Yan topological index. The axion charge of the baby universes is quantized in terms of the Nieh-Yan integers. Tunneling between universes of different Nieh-Yan charges implies a nonperturbative vacuum state. The associated topological vacuum angle can be identified with the Barbero-Immirzi parameter.

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Romesh K. Kaul, Sandipan Sengupta. 2015-01-05. Torsional instanton effects in quantum gravity. https://doi.org/10.1103/physrevd.90.124081

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