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SUMMARY:The Softer Side of Disc Gravity - Antranik A. Sefilian
DTSTART:20181127T130000Z
DTEND:20181127T140000Z
UID:TALK112099@talks.cam.ac.uk
CONTACT:Dr William Béthune
DESCRIPTION:Astrophysical discs encircling a central mass are ubiquitous i
 n a variety of contexts – galactic\, stellar and planetary. In many inst
 ances\, such discs are observed to contain a total mass much less than tha
 t of the dominant central object. Despite this fact\, discs – through th
 eir gravity – can play an important dynamical role in the orbital evolut
 ion of their constituent particles\, as well as external objects (e.g. tes
 t-particles)\, by driving orbital precession and exchange of angular momen
 tum over long (secular) time-scales. Thus\, analytic quantification of the
  secular gravitational effects due to discs represents a vital necessity. 
 One of the direct means for achieving this goal relies on the well-known L
 aplace-Lagrange theory. Nevertheless\, this approach is ill-posed as it re
 sults in the divergence of the disc potential. This divergence has motivat
 ed the development of alternative approaches: one that resorts to softened
  forms of gravity (i.e. modifying the Newtonian potential with the introdu
 ction of an ad hoc softening parameter)\, and another which – by constru
 ction – does not suffer from the classical singularity inherent to Lapla
 ce-Lagrange theory.\n\nIn this talk\, I will introduce these two methods a
 nd present results indicating that softened disc potentials can reproduce 
 the expected secular dynamics of test-particles provided that the softenin
 g prescription (1) is implemented properly\, and (2) satisfies certain mat
 hematical and physical conditions. Building up on this finding\, I will pr
 esent preliminary results touching on the outstanding question pertinent t
 o the sustenance of rigidly precessing self-gravitating eccentric discs su
 ch as the inferred stellar disc in the centre of M31 galaxy.
LOCATION:MR14\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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