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SUMMARY:Steady Warps: Linear\, Nonlinear\, and Breaking
DTSTART:20251202T060000Z
DTEND:20251202T063000Z
DTSTAMP:20261016T172100Z
UID:indico-event-4610@indico-tdli.sjtu.edu.cn
DESCRIPTION:Speakers: Jiaru Li(李佳儒）\n\nHost: Dong LaiJoin Tencent 
 Meeting：https://meeting.tencent.com/dm/T9ag0lXOPfDQMeeting ID: 72316316
 5 (no password）Abstract:An increasing number of protoplanetary disks sho
 ws observational signatures of warps and misalignments\, raising questions
  of how disks sustain coherent warps and how they may break into misaligne
 d pieces. We study the steady-state structures and breaking conditions of 
 warped disks. To focus on the hydrodynamics\, while remaining agnostic abo
 ut what forces the warp\, we adopt a simple but physically motivated setup
 : rather than including an explicit perturber or external torque\, we fix 
 the disk's inner and outer boundaries at different inclinations. The disk 
 is hence constrained to accommodate a warp between the boundaries. By vary
 ing the boundary misalignment\, we can explore the linear regime\, the non
 linear regime\, and the onset of breaking\, while having good control over
  the warp amplitude. Combining this model with analytical theories and thr
 ee-dimensional hydrodynamic simulations\, we carry out a clean and systema
 tic investigation of the hydrodynamic behaviors of warped disks. We find t
 hat\, with small warps\, disks settle into warp steady states that are wel
 l described by the linear theory. Moderately warped disks enter the nonlin
 ear regime\, showing several distinct features such as torque saturation\,
  vertical “bouncing” motion of gas\, and enhanced mass accretion rates
 . Measurements of these effects in our simulations show good quantitative 
 agreement with nonlinear theories. Strongly warped disks are unstable: the
 se disks are susceptible to a runaway growth of warp amplitude that ultima
 tely leads to disk breaking. This instability may be caused by the nonline
 ar saturation of the disk's internal torque\, which occurs roughly when th
 e warp amplitude exceeds a critical value ~2\\sqrt{\\alpha} for Keplerian 
 disks.Biography:Jiaru Li is a CIERA Postdoctoral Fellow at Northwestern Un
 iversity. His research interests include exoplanetary dynamics\, protoplan
 etary disks\, and compact objects embedded in AGN disks\, while he primari
 ly studies these topics using N-body and hydrodynamics simulations.\n\nhtt
 ps://indico-tdli.sjtu.edu.cn/event/4610/
LOCATION:Tsung-Dao Lee Institute/N6F-N601 - Meeting Room (Tsung-Dao Lee In
 stitute)
URL:https://indico-tdli.sjtu.edu.cn/event/4610/
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