BEGIN:VCALENDAR VERSION:2.0 PRODID:-//linuxsoftware.nz//NONSGML Joyous v1.4//EN BEGIN:VEVENT SUMMARY:Numerical hyperboloidal compactification: waves on FLRW and neutro n star initial data DTSTART:20250624T110000Z DTEND:20250624T130000Z DTSTAMP:20260503T070140Z UID:d011833c-5a2d-4484-b678-0df2f4ecd909 SEQUENCE:1 CREATED:20250618T134120Z DESCRIPTION: Both parts of this talk involve numerical descriptions on com pactified hyperboloidal slices reaching future null infinity -- the "\ ;location"\; in spacetime where electromagnetic and gravitational radi ation arrives and where global properties of spacetimes can be measured. T he first part\, presenting joint work with Flavio Rossetti\, focuses on th e asymptotic decay of the linear wave equation on flat and hyperbolic FLRW spacetimes with a time-dependent scale factor. I will describe the hyperb oloidal setup\, which allows us to recover decay rates obtained from evolu tions on usual truncated Cauchy slices\, and also consider solutions of a non-linear wave with self-interactions. The second part will describe the construction of initial data for a neutron star on a hyperboloidal slice\, involving spherical symmetry and a polytropic-like equation of state. Con straint-satisfying compactified hyperboloidal initial data are obtained fo r a single neutron star and for a combination of a neutron star with a sma ll black hole in its center. To the best of my knowledge\, this is the fir st time that full hyperboloidal slices including a neutron star are constr ucted. LAST-MODIFIED:20250618T134120Z LOCATION:DF Seminar Room (2-8.3)\, 2nd floor of Physics Building URL:http://df.vps.tecnico.ulisboa.pt/en/events/numerical-hyperboloidal-com pactification-waves-on-flrw-and-neutron-star-initial-data/ X-ALT-DESC;FMTTYPE=text/html:

Both parts of this talk involve numerical descriptions on compactified hyperboloidal slices reaching future null infinity -- the "\;location"\; in spacetime w here electromagnetic and gravitational radiation arrives and where global properties of spacetimes can be measured.

The first part\, prese nting joint work with Flavio Rossetti\, focuses on the asymptotic decay of the linear wave equation on flat and hyperbolic FLRW spacetimes with a ti me-dependent scale factor. I will describe the hyperboloidal setup\, which allows us to recover decay rates obtained from evolutions on usual trunca ted Cauchy slices\, and also consider solutions of a non-linear wave with self-interactions.

The second part will describe the constructio n of initial data for a neutron star on a hyperboloidal slice\, involving spherical symmetry and a polytropic-like equation of state. Constraint-sat isfying compactified hyperboloidal initial data are obtained for a single neutron star and for a combination of a neutron star with a small black ho le in its center. To the best of my knowledge\, this is the first time tha t full hyperboloidal slices including a neutron star are constructed.

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