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SUMMARY:Contributory: Dynamical analysis of Bianchi type-IX cosmology with
  a scalar field mediated dark sector interaction
DTSTART;VALUE=DATE-TIME:20261116T071500Z
DTEND;VALUE=DATE-TIME:20261116T073000Z
DTSTAMP;VALUE=DATE-TIME:20261026T204249Z
UID:indico-contribution-964@indico.narit.or.th
DESCRIPTION:Speakers: Ashmita . (Khon Kaen University)\nThe recent DESI DR
 2 preference for a time-varying dark-energy equation of state\, together w
 ith the long-standing difficulty of explaining why an initially anisotropi
 c universe should evolve toward isotropy\, motivates the study of interact
 ing dark-sector models in anisotropic backgrounds. We investigate the dyna
 mics of Bianchi type-IX cosmologies containing pressureless dark matter co
 upled to dark energy in the form of a quintessence scalar field $\\phi$ wi
 th exponential potential $V(\\phi)=V_0\\\,e^{-\\lambda\\phi}$. Energy exch
 ange between the two dark components is mediated by the scalar field throu
 gh the interaction term $Q=\\kappa\\beta\\dot\\phi\\\,\\rho_{\\rm DM}$\, w
 here $\\kappa^2=8\\pi G$ and $\\beta$ is a dimensionless coupling. Because
  Bianchi-IX models generically recollapse\, the Hubble scalar $H$ vanishes
  at the moment of maximum expansion\, where the expansion-normalized varia
 bles of the standard Wainwright-Ellis formalism diverge. We therefore adop
 t the $D$-normalized phase-space formalism of Hewitt\, Uggla\, and Wainwri
 ght\, which compactifies the state space and remains regular through the r
 ecollapse\, including the moment of maximum expansion at which $H = 0$. To
 gether with the modified conservation equations for the two dark component
 s\, the Einstein Klein Gordon system reduces to a closed autonomous polyno
 mial dynamical system\, whose fixed points we classify by linear stability
  analysis\, supplemented by center-manifold theory for the non-hyperbolic 
 points. The fixed points shows the kinetic-dominated\, coupling modified m
 atter dominated\, curvature scalar\, scalar field dominated and coupled sc
 aling families\; the last is the anisotropic analogue of the Amendola scal
 ing attractor. Restricting to the initially expanding\, isotropizing traje
 ctories\, we map the region of the $(\\lambda\,\\beta)$ plane in which ani
 sotropic Bianchi-IX models approach an accelerating Friedmann Robertson Wa
 lker state.\n\nhttps://indico.narit.or.th/event/234/contributions/964/
LOCATION:Pattaya\, Thailand D Varee Jomtien Beach Pattaya Hotel
URL:https://indico.narit.or.th/event/234/contributions/964/
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