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SUMMARY:New Aspects of spontaneous scalarization of black holes beyond Gen
 eral relativity - Zakaria Belkhadria\, University of Geneva / Università 
 di Cagliari
DTSTART:20260213T130000Z
DTEND:20260213T140000Z
UID:TALK244639@talks.cam.ac.uk
CONTACT:Lorenzo Gavassino
DESCRIPTION:Spontaneous scalarization is a mechanism that allows black hol
 es to develop a non-trivial profile of a scalar field “scalar hair” be
 cause of tachyonic instabilities\, enabling tests of gravity beyond Genera
 l Relativity. Motivated by stability and threshold issues in Gauss-Bonnet 
 scalarization\, we propose a new model characterized by two nonminimal cou
 plings of the scalar field to both Gauss-Bonnet curvature and a U(1) gauge
  field (e.g. electromagnetic field). The presence of two distinct sources 
 of tachyonic instability broadens the conditions for spontaneous scalariza
 tion. We track how the electric charge and the coupling constants govern t
 he onset of the scalar field and derive new solution branches with nontriv
 ial scalar profiles. Numerical integration shows multiple coexisting scala
 rized black hole solutions with adjustable thresholds\, influenced by the 
 relative strengths of curvature and matter couplings. We examine their sca
 lar charge\, horizon properties\, and thermodynamic characteristics\, demo
 nstrating how the model can selectively activate or suppress scalarization
  phenomena. The matter source term modifies the scalarization onset and pr
 omotes stable solutions\, as indicated by the evolution of the scalar char
 ge and horizon quantities. These findings suggest an alternative approach 
 to scalarization\, may avoid the instabilities of curvature-only or matter
 -only models\, and offer new ways to test strong-gravity effects in upcomi
 ng observations.\n
LOCATION:Potter Room / Zoom :  https://cam-ac-uk.zoom.us/j/85131795570
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