[Astro] [CAPT] Extra seminar today: Javier Carballo

[Laura Sberna (staff)]

A reminder: in 30 minutes in C05 Physics.

> On 5 Dec 2025, at 12:05, Laura Sberna (staff) <Laura.Sberna at nottingham.ac.uk> wrote:
> 
> Dear all, 
> 
> We will have an extra seminar next week. The speaker, Javier Carballo, together with Paolo Arnaudo, will be visiting us from 9 December to 11 December from the University of Southampton. Please get in touch with them (cc'd) if you would like to arrange a meeting.
> 
> When: 11am, Wednesday December 10th
> Where: C05 Physics
> 
> Javier Carballo (U of Southampton)
> 
> "A complete mode decomposition of black hole perturbations"
> 
> It is well known that quasinormal modes (QNMs) do not form a complete basis for linear black hole perturbations. In particular, retarded Green's functions of black holes can only be decomposed as a convergent sum of QNMs at sufficiently late times. In this talk, I will show that Green's functions can be expanded as a convergent mode sum everywhere in spacetime. When QNMs fail at early times, a sum of Matusbara modes (MMs) associated to the horizon temperature converges instead. I will present the case of the Schwarzschild black hole, where the branch cut is resolved into a set of de Sitter modes by adding a small positive cosmological constant. Based on 2510.18956.
> 
> Best, 
> Laura

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