Signature change in loop quantum gravity: General midisuperspace models and dilaton gravity

Understand

Models of loop quantum gravity based on real connections have a deformed notion of general covariance, which leads to the phenomenon of signature change.

• This result is confirmed here in a general analysis of all midisuperspace models without local degrees of freedom.
• As a subclass of models, 2-dimensional theories of dilaton gravity appear, but a larger set of examples is possible based only on the condition of anomaly freedom.
• While the classical dilaton gravity models are the only such systems without deformed covariance, they do give rise to signature change when holonomy modifications are included.