What is immirzi parameter?

Immirzi Parameter

The Immirzi parameter (also known as the Barbero-Immirzi parameter) is a numerical coefficient appearing in loop quantum gravity, a nonperturbative theory of quantum gravity. The Immirzi parameter measures the size of the quantum of area in Planck units. As a result, its value is currently fixed by matching the semiclassical black hole entropy, as calculated by Stephen Hawking, and the counting of microstates in loop quantum gravity.

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Some articles on immirzi parameter:

Immirzi Parameter - Interpretation
... The parameter may be viewed as a renormalization of Newton's constant ... Various speculative proposals to explain this parameter have been suggested for example, an argument due to Olaf Dreyer based on quasinormal modes ... at long distance) were found requiring a different value of the Immirzi parameter, it would constitute evidence that loop quantum gravity cannot reproduce the physics of ...
Loop Quantum Gravity - Key Concepts - Black Hole Entropy
... The problem is that a crucial free parameter in the theory, known as the Immirzi parameter, can only be computed by demanding agreement with Bekenstein and Hawking's calculation of the black hole entropy ... but does not obtain the Bekenstein-Hawking formula S = A/4 unless the Immirzi parameter is chosen to give this value ... of all non singular black holes directly from theory and independent of Immirzi parameter ...