272,293 research outputs found
Two-stage Turing model for generating pigment patterns on the leopard and the jaguar
Based on the results of phylogenetic analysis, which showed that flecks are the primitive pattern of the felid family and all other patterns including rosettes and blotches develop from it, we construct a Turing reaction-diffusion model which generates spot patterns initially. Starting from this spotted pattern, we successfully generate patterns of adult leopards and jaguars by tuning parameters of the model in the subsequent phase of patterning
Oscillatory Turing Patterns in a Simple Reaction-Diffusion System
Turing suggested that, under certain conditions, chemicals can react and diffuse in such a way as to produce steady-state inhomogeneous spatial patterns of chemical concentrations. We consider a simple two-variable reaction-diffusion system and find there is a spatio-temporally oscillating solution (STOS) in parameter regions where linear analysis predicts a pure Turing instability and no Hopf instability. We compute the boundary of the STOS and spatially non-uniform solution (SSNS) regions and investigate what features control its behavior
The color-singlet contribution to e^+ e^- ->J/psi + X at the endpoint
Recent observations of the J/psi spectrum produced in e^+e^- collisions at
the Upsilon(4S) resonance are in conflict with fixed-order calculations using
Non-Relativsitic QCD effective theory (NRQCD). One problem is an enhancement in
the cross section when the J/psi has maximal energy, due to large perturbative
corrections (Sudakov logarithms). In a recent paper, the Sudakov logarithms in
the color-octet contribution were summed by combining NRQCD with the
Soft-Collinear Effective Theory. However to be consistent, the color-singlet
contributions must also be summed in the endpoint region which was not done in
that paper. In this paper, we sum the leading and next-to-leading logarithms in
the color-singlet contribution to the J/psi production cross section. We find
that the color-singlet cross section is suppressed near endpoint compared to
the fixed order NRQCD prediction.Comment: 17 pages, 7 figure
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