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Loop Quantum Cosmology with Complex Ashtekar Variables

Abstract : We construct and study Loop Quantum Cosmology (LQC) when the Barbero-Immirzi parameter takes the complex value $\gamma=\pm i$. We refer to this new quantum cosmology as complex Loop Quantum Cosmology. We proceed in making an analytic continuation of the Hamiltonian constraint (with no inverse volume corrections) from real $\gamma$ to $\gamma=\pm i$ in the simple case of a flat FLRW Universe coupled to a massless scalar field with no cosmological constant. For that purpose, we first compute the non-local curvature operator (defined by the trace of the holonomy of the connection around a fundamental plaquette) evaluated in any spin $j$ representation and we find a new close formula for it. This allows to define explicitly a one parameter family of regularizations of the Hamiltonian constraint in LQC, parametrized by the spin $j$. It is immediate to see that any spin $j$ regularization leads to a bounce scenario. Then, motivated particularly by previous results on black hole thermodynamics, we perform the analytic continuation of the Hamiltonian constraint defined by $\gamma=\pm i$ and $j=-1/2+is$ where $s$ is real. Even if the area spectrum is now continuous, we show that the so-defined complex LQC removes also the original singularity which is replaced by a quantum bounce. In addition, the maximal density and the minimal volume of the Universe are obviously independent of $\gamma$. Furthermore, the dynamics before and after the bounce are no more symmetric, which makes a clear distinction between these two phases of the evolution of the Universe.
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Contributor : Karim Noui <>
Submitted on : Monday, July 14, 2014 - 8:37:58 PM
Last modification on : Friday, February 19, 2021 - 4:10:02 PM
Long-term archiving on: : Thursday, November 20, 2014 - 6:37:41 PM


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Jibril Ben Achour, Julien Grain, Karim Noui. Loop Quantum Cosmology with Complex Ashtekar Variables. Classical and Quantum Gravity, IOP Publishing, 2015, 32, pp.025011. ⟨10.1088/0264-9381/32/2/025011⟩. ⟨hal-01023613⟩



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