Large mass expansion in two-loop QCD corrections of para-charmonium decay

We calculate the two-loop QCD corrections to paracharmonium decays $eta_{c} rightarrow gamma gamma$ and $eta_{c} rightarrow g g$ involving light-by-light scattering diagrams with light quark loops. Artificial large mass expansion and convergence improvement techniques are used to evaluate these corrections. The obtained corrections to the decays $eta_{c} rightarrow gamma gamma$ and $eta_{c} rightarrow g g$ account for $-1.25$ and $-0.73$ of the leading order contribution, respectively.Comment: 24 pages, 10 figures; REVTeX version; Version to appear in Phys. Rev. D, 9 pages, 4 figure

Error-driven Global Transition in a Competitive Population on a Network

We show, both analytically and numerically, that erroneous data transmission generates a global transition within a competitive population playing the Minority Game on a network. This transition, which resembles a phase transition, is driven by a `temporal symmetry breaking' in the global outcome series. The phase boundary, which is a function of the network connectivity $p$ and the error probability $q$, is described quantitatively by the Crowd-Anticrowd theory.Comment: 4 pages, 3 figure

Internal character dictates phase transition dynamics between isolation and cohesive grouping

We show that accounting for internal character among interacting, heterogeneous entities generates rich phase transition behavior between isolation and cohesive dynamical grouping. Our analytical and numerical calculations reveal different critical points arising for different character-dependent grouping mechanisms. These critical points move in opposite directions as the population's diversity decreases. Our analytical theory helps explain why a particular class of universality is so common in the real world, despite fundamental differences in the underlying entities. Furthermore, it correctly predicts the non-monotonic temporal variation in connectivity observed recently in one such system