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04 June, 2017

posted 14 Sept 2017, 07:21 by Scott Melville   [ updated 14 Sept 2017, 07:22 ]
Soft Hair as a Soft Wig
(20 pages)

A canonical transformation is identified which decouples the soft degrees of freedom in classical gravity and electromagnetism. These soft dynamics are constrained by asymptotic symmetries (large gauge or BMS transformations), but this need not have any bearing on the hard dynamics nor the black hole information paradox. A quantum analog is also discussed.


Recent relations between soft theorems and asymptotic symmetries were hoped to shed light on the black hole information paradox by offering a mechanism by which information could be stored in the soft degrees of freedom at infinty (the memory effect). Here it is argued that this was overly optimistic, as a decoupling between soft and hard sectors prevents this kind of `soft hair' from encoding `hard information'.

Sub-subleading Soft Graviton Theorem in Generic Theories of Quantum Gravity
(52 pages)

A general expression for soft graviton emission is given at NNLO, written as a universal piece (proportional to the amplitude without soft emission) plus a non-universal piece (sensitive to the vertices of the underlying theory).


While supertranslations and superrotations are enough to give universal LO and NLO soft factors, it was suspected that beyond NLO there would be non-universal features for soft emission amplitudes. Here we can explicitly see that this is the case in generic gravitational theories.