BEGIN:VCALENDAR VERSION:2.0 PRODID:-//linuxsoftware.nz//NONSGML Joyous v1.4//EN BEGIN:VEVENT SUMMARY:Self-Similar Collapse in Spherically Symmetric Elasticity DTSTART:20250909T140000Z DTEND:20250909T160000Z DTSTAMP:20260801T185119Z UID:92625f34-5652-44b7-a677-a930429ed45e SEQUENCE:2 CREATED:20250908T203203Z DESCRIPTION:Perfect fluids have been widely used in the simulation of real istic astrophysical phenomena\, such as collapse and binary coalescence. N evertheless\, these fluid models are very simple and their use to describe the full extension of a compact object\, from core to envelope\, may not be adequate and leave out more complex aspects of stellar dynamics. Elasti c matter models generalize perfect fluids by also taking into account devi ations from a relaxed state and\, furthermore\, allow for a smooth matchin g at separation surfaces. Thus\, elasticity can be used to model compact o bjects with complex compositions.Despite showing promise\, there are few r esults using elasticity. To this end we studied this matter model in the c ontext of self-similar spherically symmetric gravitational collapse. Self- similarity pertains to systems displaying invariance with regards to scale changes. In the context of collapse it provides two advantages. On the on e hand\, the description of the system depends only on the scale variable\ , removing the need to solve PDEs\, while still retaining many properties of collapse. On the other hand\, self-similarity is closely linked with cr itical collapse\, the study and understanding of collapse at the threshold of black hole formation and associated processes.In this talk I will go o ver the results obtained for self-similar collapse. I will show how elasti city compares with perfect fluid models\, and how the tuning of the materi al parameters affects the spacetime through the material'\;s response to the collapse\, specifically in the generalization of the well known Eva ns-Coleman solution\, as well as in the case of other modes of collapse. I will also show how the material'\;s characteristics affect the regula rity of the spacetime\, and how they may forbid the existence of self-simi larity altogether. LAST-MODIFIED:20250908T203221Z LOCATION:Sala de Seminários do Departamento de Física (2-8.3 - 2º Piso do Edíficio de Física)/Online URL:http://df.vps.tecnico.ulisboa.pt/pt/eventos/self-similar-collapse-in-s pherically-symmetric-elasticity/ X-ALT-DESC;FMTTYPE=text/html:

Perfect fluids have been widely used in the simulation of realistic astrophysical phenomena\, such as collapse and binary coalescence. Nevertheless\, these fluid model s are very simple and their use to describe the full extension of a compac t object\, from core to envelope\, may not be adequate and leave out more complex aspects of stellar dynamics. Elastic matter models generalize perf ect fluids by also taking into account deviations from a relaxed state and \, furthermore\, allow for a smooth matching at separation surfaces. Thus\ , elasticity can be used to model compact objects with complex composition s.

Despite showing promise\, there are f ew results using elasticity. To this end we studied this matter model in t he context of self-similar spherically symmetric gravitational collapse. S elf-similarity pertains to systems displaying invariance with regards to s cale changes. In the context of collapse it provides two advantages. On th e one hand\, the description of the system depends only on the scale varia ble\, removing the need to solve PDEs\, while still retaining many propert ies of collapse. On the other hand\, self-similarity is closely linked wit h critical collapse\, the study and understanding of collapse at the thres hold of black hole formation and associated processes.

In this talk I will go over the results obtained for self-s imilar collapse. I will show how elasticity compares with perfect fluid mo dels\, and how the tuning of the material parameters affects the spacetime through the material'\;s response to the collapse\, specifically in t he generalization of the well known Evans-Coleman solution\, as well as in the case of other modes of collapse. I will also show how the material&#x 27\;s characteristics affect the regularity of the spacetime\, and how the y may forbid the existence of self-similarity altogether.

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