In this paper, we derive a TTˉ deformed soft graviton theorem in the
context of celestial holography. As a concrete example, it illustrates that a
two-dimensional irrelevant deformation can be applied to a four-dimensional
theory at the level of amplitudes. We argue that the TTˉ deformation has
a close relation to the loop-correction from the amplitude side which could
provide an alternative way to construct an ultraviolet complete quantum theory
of gravity.Comment: v2: Interpretation improved significantly, discussions on the
connection between loop corrections and deformations added, extra with
respect to the version accepted for publication in journal due to the page
limit