Selected Scientific Discoveries upto 2013

funded by ARO

 

Generalized Jacobi Coordinates based on a graph-theoretic algorithm on subclass of sign-nonsingular patterns involving Binary Trees (also related to the Kastelyn-Percus theorems for counting perfect matchings and Exact combinatorial solutions of the 2D Ising Model) and used to simplify the calculations of the KAM-nondegeneracy condition in N-body problems, have recently appeared in two different directions - (1) Entangled Fock Space in Einstein-Podolsky-Rosen states (J. Katriel et al Molecular Phys 2008), (2) Shape Dynamics in classical and quantum gravity (cf J. Barbour et al Perimeter Institute) :

C. Lim, Binary trees, symplectic matrices and the Jacobi coordinates of celestial mechanics, Arch. Rat. Mech. Anal. 115 (1991), 153-165; C. Lim, Canonical transformations and graph theory, Physics Letters A, 138 1989, 258-266.

Exact solutions of an energy-enstrophy theory (based on Kac's spherical model) in the statistical physics of quasi-2D flows, using the newly discovered equivalence of the canonical and microcanonical ensembles for long-range interactions on compact oriented manifolds (via Hodge Theory), leads to results that are applicable to Planetary Atmospheres in extra-solar systems such as "Super-rotators are more common than Sub-rotators in Nearly Barotropic Planetary Atmospheres", and to the enigmatic super-rotation of Venus and Titan:

C. C. Lim, "Phase Transition to Super-rotating Atmospheres in a Simple Planetary Model for a Non-Rotating Massive Planet - Exact Solution", Physical Review E 86 (6)(2012) click here to download from APS.

For details on the rotating case, see submitted Phys Rev article, 2013.

Anomalous Expansion and Negative Specific Heat in quasi-2D trapped vortex filament bundles in an unbounded horizontal domain was discovered by Tim Andersen and Chjan Lim and applied to the confinement and stability of hot Tokamak plasmas; see for example:

T. Andersen and C. Lim, "Negative Specific Heat in a Quasi-2D Generalized Vorticity Model'', Phys. Rev. Lett. 99, 165001, Oct 2007.

Tipping Points in Social Opinion Dynamics PRE 11:

J. Xie, S. Sreenivasan, G. Korniss, W. Zhang, C. Lim, and B.K. Szymanski, "Social consensus through the influence of committed minorities", Physical Review E 84, 011130 (2011).

Time-Reversible Dynamical System, see for example:

M. Krupa, C. Lim, and M. Golubitsky, "Time-reversibility and particle sedimentation'', SIAM J. Applied Math. 51(1), 49-72 (1991).

Other resuts 0n Network Science and Applied Probability:

[1] W. Zhang and C.C. Lim, "The Concentration and Stability of the Community Detecting Functions on Random Networks", Internet Math, Accepted December 2012, appeared online March 2013. click here to download

[2] W. Zhang, C.C. Lim and B. Szymanski, "Analytic Treatment of Tipping Points for Social Consensus in Large Random Networks", Phys. Rev. E, Appeared December 2012, Phys. Rev. E. December 2012

[3] C.C. Lim, "Social forums with strong neutrals- exact solutions for expected times to multi-consensus", Phys. Rev. E, submitted May 31 2013, for diffusion-driven cases

[4] C.C. Lim and W. Zhang, "Monotonicity of Social Opinion Dynamics on Large Networks", submitted July 31 2013, for the role of monotonicity in math. sociology where pure diffusion is secondary to drift.

New Scientific Discoveries 2008-2011

funded by ARO

 

My recent work on Network Science in collaboration with SCNARC at RPI funded by the ARL have focussed on social and mathematical questions on Tipping Fractions of Minority Opinion in Social Influencing: (1) Robustness wrt local rules in multi-agents models and smallness (5 - 10%) of tipping fractions, (2) Scalability of tipping points to large networks and different topologies including scale-free and small world, (3) Rigorous methods for calculating mean times to agreement (synchronization rates) and their fluctuations (Martingale estimates for variance of consensus times), (4) Diffusion (SDE) models for social influencing based on Dynkin formula and the relationship between SDE and semielliptic PDEs with Dirichlet BC.

Our recent papers below and in my cv have received some public attention such as from Freakonomics.com and the Atlantic Monthly - for a large sample of websites linking to these results and papers, please type in GOOGLE: Chjan Lim, Tipping Point or click here for a description of our research group.

[1] J. Xie, S. Sreenivasan, G. Korniss, W. Zhang, C. Lim, and B.K. Szymanski, "Social consensus through the influence of committed minorities", Physical Review E 84, 011130 (2011).

[2] W. Zhang, C. Lim, S. Sreenivasan, J. Xie, B.K. Szymanski, and G. Korniss, "Social Influencing and Associated Random Walk Models: Asymptotic Consensus Times on the Complete Graph", Chaos 21, 025115 (2011).

[3] C. Lim, and W. Zhang, "Noisy Naming Games, Partial Synchonization and Coarse Graining", IEEE NSW Proc. West Point, NY, 25-29, DOI:10.1109/NSW.2011.6004654 (2011).

[4] Weituo Zhang, Chjan C. Lim, Noise in Naming Games, partial synchronization and community detection in social networks arXiv:1008.4115, 2010.

New Scientific Discoveries 2004-2008

funded by ARO and ARL

 

(I) Anomalous Expansion and Negative Specific Heat in quasi-2D trapped vortex filament bundles - this was discovered by Tim Andersen and Chjan Lim and applied to a large class of problems where wriggly vortex lines play dominant roles such as Electron Magneto-Hydrodynamics (EMH), London's theory of superconductivity and Plasma Physics. The original negative specific heat was discovered in gravo-thermal collapse of star clusters (cf. Lynden-Bell etal) where a sufficiently dense gravitational core transfers energy to a halo and increases in temperature (the halo gains energy but cools), leading to a run-away process. A similar process in vortex line bundles was found first by Path-Integral MC simulations and later confirmed by an elegant series of mean field and steepest descent calculations based squarely on applications of Kac's SPHERICAL CONSTRAINT (cf. preprints/papers by Andersen and Lim 2005 - ). Important scientific and technological consequences of these discoveries by the PI and co-workers will be discussed in a series of papers, talks and funding seminars, including applications to super-confinement of plasmas in EMH and other MHD systems considered to be significant for thermonuclear fusion.

(II) Orientation asymmetry from planetary spin is introduced naturally in a unified statistical mechanics for the Barotropic Vorticity Equation and the Shallow Water Equations on a rotating sphere and used to predict the phase transitions to super-rotating solid-body flows at high energy to enstrophy ratios, and the non-symmetrical phase transitions to antirotating solid-body flows when the planetary spin is large. This new statistical mechanics uses a canonical path-integral where the action is given by the Lagrangian L of the BVE model and microcanonical constraint on circulation and enstrophy. L = H + AM where H is the Hamiltonian that is conserved even over nontrivial topography and AM is the fluid's angular momentum that is not conserved except over trivial topography by the BVE. The analogy and connections are made clear in the following article which gives an exact non-mean field solution using Kac's spherical model method to the problem of the inverse cascade of energy to large scales while angular momentum is exchanged with a massive spinning sphere in a quasi-2d atmospheric flow. Several papers discuss further the significant results obtained by Xueru Ding and Chjan Lim using Monte-Carlo methods, including applications to Venusian and Titan super-rotation and the enigma of the absence of sub-rotating atmospheres amongst slowly-rotating terrestrial planets and to the cyclonic-anticyclonic debate around the large coherent spots on the Gas Giants - see Physica A 2007, Physics Fluids 2008.