BEGIN:VCALENDAR VERSION:2.0 PRODID:-//linuxsoftware.nz//NONSGML Joyous v1.4//EN BEGIN:VEVENT SUMMARY:Nonlinear echoes from black holes in Einstein-Maxwell-scalar theor y DTSTART:20250515T143000Z DTEND:20250515T160000Z DTSTAMP:20260731T131016Z UID:f9bced53-0249-4cb2-a67e-7a0bc8fdc0f1 SEQUENCE:2 CREATED:20250509T142147Z DESCRIPTION:The post-merger portion of the gravitational wave emitted in a binary coalescence encodes precious information about the structure of th e remnant. While in the case of a black hole in General Relativity the sig nal is described by a standard ringdown\, when considering different objec ts\, or alternative theories of gravity\, new features might emerge. In th is context an interesting possibility is the appearance of echoes. While t hey are generally studied for exotic compact objects\, it has recently bee n found that they might arise also for black holes in the Einstein-Maxwell -scalar extension to General Relativity. Indeed\, in a particular region o f the parameter space\, this theory admits hairy black hole configurations whose effective potential under scalar or gravitational perturbations fea tures cavity-like structures\, where radiation can be trapped and echoes c an be generated. In a recent work\, carried out in collaboration with Marc o Melis\, Robin Croft and Paolo Pani\, we computed the quasi-normal freque ncies of such black hole solutions\, for radial and axial modes. Furthermo re\, by performing simulations of the spherical collapse of scalar wave pa ckets\, we have been able to observe the presence of echo patterns in the time-domain behavior of the scalar field\, even in the regime where nonlin earities are significant. In this talk I will present the results of our s tudy and discuss our follow-up project\, in which we will simulate the hea d-on collision process with the aim of investigating whether echoes are pr eserved in such a scenario\, or they are quenched by other dynamical effec ts. LAST-MODIFIED:20250509T142203Z LOCATION:DF Seminar Room (2-8.3)\, 2nd floor of Physics Building URL:http://df.vps.tecnico.ulisboa.pt/pt/eventos/nonlinear-echoes-from-blac k-holes-in-einstein-maxwell-scalar-theory/ X-ALT-DESC;FMTTYPE=text/html:

The post-merger por tion of the gravitational wave emitted in a binary coalescence encodes pre cious information about the structure of the remnant. While in the case of a black hole in General Relativity the signal is described by a standard ringdown\, when considering different objects\, or alternative theories of gravity\, new features might emerge. In this context an interesting possi bility is the appearance of echoes.

While they are generally stu died for exotic compact objects\, it has recently been found that they mig ht arise also for black holes in the Einstein-Maxwell-scalar extension to General Relativity. Indeed\, in a particular region of the parameter space \, this theory admits hairy black hole configurations whose effective pote ntial under scalar or gravitational perturbations features cavity-like str uctures\, where radiation can be trapped and echoes can be generated.

In a recent work\, carried out in collaboration with Marco Melis\, R obin Croft and Paolo Pani\, we computed the quasi-normal frequencies of su ch black hole solutions\, for radial and axial modes. Furthermore\, by per forming simulations of the spherical collapse of scalar wave packets\, we have been able to observe the presence of echo patterns in the time-domain behavior of the scalar field\, even in the regime where nonlinearities ar e significant.

In this talk I will present the results of our st udy and discuss our follow-up project\, in which we will simulate the head -on collision process with the aim of investigating whether echoes are pre served in such a scenario\, or they are quenched by other dynamical effect s.

END:VEVENT END:VCALENDAR