Stringy black holes and Wald entropy

by Prof. Tomás Ortín (IFT (UAM/CSIC) Madrid)

Monday 18 Sept 2023, 16:00 → 17:00 Europe/Rome

AULA PAOLUZI

 In order to test whether the microscopic entropy computed by string/(AdS/CFT) methods
matches the macroscopic one for stringy black holes at higher orders in alpha' it is
crucial to have a reliable computation of the latter.  A prominent candidate is the
quantity that plays the role of the entropy in the first law of black hole thermodynamics
for any matter-free diff-invariant theory: the Wald entropy. Iyer and Wald gave a widely
used prescription to compute it when the matter fields are tensors. However, in the case
of the black-hole solutions of the heterotic superstring effective action to first order
in alpha' the entropy obtained using this prescription fails to satisfy the first law.

The main reason for this failure is the fact that most matter fields have gauge freedoms
and, therefore, they are not tensors.

In this talk I will show how to compute the diffeomorphism Noether charge (Wald entropy)
by dealing correctly with the gauge freedoms of the matter fields. I will apply this
methodology to different theories including the heterotic superstring effective action to
first order in alpha'. The resulting formula will be used to compute the alpha'
corrections to the entropy of the several black-hole solutions of the heterotic
superstring effective action to first order in alpha'.

A presto, A.