Four Attitudes Towards Singularities in the Search for a Theory of Quantum Gravity

Understand

Singularities in general relativity and quantum field theory are often taken not only to motivate the search for a more-fundamental theory (quantum gravity, QG), but also to characterise this new theory and shape expectations of what it is to achieve.

• Here, we first evaluate how particular types of singularities may suggest an incompleteness of current theories.
• We then classify four different `attitudes' towards singularities in the search for QG, and show, through examples in the physics literature, that these lead to different scenarios for the new theory.
• Two of the attitudes prompt singularity resolution, but only one suggests the need for a theory of QG.