Can we conceive a quantum field theory without classical spacetime underpinnings? -- Conceptual issues in gauging gravity: from Utiyama to the spin form approach

When a quantum theory ventures into dealing with gravity, whose classical treatment was formulated by Einstein's general theory of relativity, it inevitably encounters numerous constraints, most severe among them is the non-availability of a spacetime underpinning that is the precondition for any quantum theory, or for any scientific theory, traditionally (meaning up-to-now) conceived. Implications of this constraint will be examined, and ways of addressing some of them, which require radical modifications of foundations of quantum field theory and clearer conception of the most fundamental quantum principle will be suggested in the talk.