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SUMMARY:Photon sphere for a  dyonic black hole  corresponding to A_2 Toda 
 chain
DTSTART;VALUE=DATE-TIME:20261030T064500Z
DTEND;VALUE=DATE-TIME:20261030T070000Z
DTSTAMP;VALUE=DATE-TIME:20261025T223310Z
UID:indico-contribution-6271@cern.ch
DESCRIPTION:Speakers: Vladimir Ivashchuk (SRCAM Rostest/RUDN University)\n
 We consider a dilatonic dyon black hole solution\n with a gravitational ra
 dius of  $2 \\mu$ and two charges\, \n $Q_1$  (electric) and $Q_2$ (magnet
 ic)\, within the framework \n of a four-dimensional gravitational model co
 mprising one scalar field and one 2-form.  The dilaton coupling constant $
 \\lambda$ is fixed by $\\lambda^2 = \\frac{3}{2}$. This solution  is relat
 ed to the $A_2$ Toda chain. \n The circular orbits of null geodesics are e
 xplored\, and the fifth-order polynomial  master equation governing the ph
 oton sphere radius $R_0$\n is analyzed. It is shown to admit a unique solu
 tion satisfying $R_0 > 2 \\mu$. \n The circular null geodesics are proven 
 to be unstable. \n Finally\, the black hole shadow is examined\, yielding 
 relations \n for the shadow angle  and the critical impact parameter.\n\nh
 ttps://indico.particle.mephi.ru/event/626/contributions/6271/
LOCATION: Conference Hall 4
URL:https://indico.particle.mephi.ru/event/626/contributions/6271/
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