American University of Beirut

Dr. Jihad Touma


Short Bio

Jihad Touma is a Professor of Physics at AUB. His work in astrophysical dynamics has brought to light the chaotic rotation of Mars (with dramatic implications for the evolution of climate, and life on the red planet), potential episodes of large scale volcanism on Earth and Venus (touching on mass extinction on Earth, and resurfacing of Venus), the early resonant forcing of the lunar orbit (towards a solution of a then thirty-year-old puzzle), the chaotic orbital architecture of extrasolar planets, a process for the doubling of stellar black hole nuclei, and more recently: instabilities in multi-planet systems in binaries; a novel mechanism for shepherding trans-Neptunian objects, and the complete mapping of critical phase transitions in self-gravitating stellar clusters around super-massive black holes.


Building on longstanding interests in social dynamics, he has, together with colleague Leonid Klushin (Physics, AUB ), students and collaborators, explored self-organized flocking regimes in models of coupled self-propelled particles, and identified novel trapping attractors in leader-follower models with cone of vision coupling.

Particle-Mesh Approach to Secular Self-Gravitating Clusters around Black Holes [work in collaboration with Stephane Colombi, IAP, France]

In his work, elegant mathematical models and associated physical insights are often accompanied by the design and deployment of tailor-made numerical algorithms, exploiting the symmetries, the geometry, of the problems at hand to allow for remarkably accurate and efficient exploration of complex dynamical systems. Such is the case of: Lie-Poisson algorithms for spin-orbit dynamics of planets and their satellites, including a full nonlinear analysis of numerical stability [with Jack Wisdom, MIT]; Lie-Poisson algorithms for Poincare’s model of the coupled dynamics between a solid mantle filled with a fluid of uniform vorticity [with Jack Wisdom, MIT); Generalized (and modernized) Gauss’ algorithm for the orbit averaged evolution of self-gravitating nearly-Keplerian systems, allowing for softened gravitational encounters in hot stellar systems [with Scott Tremaine, IAS, Princeton, and Mher Kazandjian, Leiden Observatory, Leiden], allowing for Post Newtonian corrections, spins, tides, radiation pressure…etc; Waterbag algorithm for the gravitational Poisson-Vlasov system (with Stephane Colombi, IAP, Paris); Micro-canonical Monte-Carlo algorithms for self-gravitating stellar clusters around supermassive black holes [with Mher Kazandjian, Leiden Observatory, Leiden]; Particle-Mesh algorithms for truncated secular dynamics [with Stephane Colombi, IAP, Paris].


Particle-Mesh Algorithm for Secular Self-Gravitating Clusters around Black Holes: Instability and Relaxation of Counter-Rotating Cluster [work with Stephane Colombi, IAP, France]


Non-linear dynamics, out-of-equilibrium physics, astrophysics, computational physics, Self-organization, dynamical systems

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