relation: http://eprints.imtlucca.it/1182/ title: Branching processes and evolution at the ends of a food chain creator: Caldarelli, Guido creator: Tebaldi, Claudio creator: Stella, Attilio subject: QC Physics description: In a critically self-organized model of punctuated equilibrium, boundaries determine peculiar scaling of the size distribution of evolutionary avalanches. This is derived by an inhomogeneous generalization of standard branching processes, extending previous mean field descriptions and yielding ν = 1/2 together with τ′ = 7/4, as distribution exponent of avalanches starting from species at the ends of a food chain. For the nearest neighbor chain one obtains numerically τ′ = 1.25±0.01, and τfirst′ = 1.35±0.01 for the first return times of activity, again distinct from bulk exponents. publisher: American Physical Society date: 1996-06 type: Article type: PeerReviewed format: application/pdf language: en identifier: http://eprints.imtlucca.it/1182/1/PRL_Caldarelli_1996.pdf identifier: Caldarelli, Guido and Tebaldi, Claudio and Stella, Attilio Branching processes and evolution at the ends of a food chain. Physical Review Letters, 76 (26). pp. 4983-4986. ISSN 0031-9007 (1996) relation: http://dx.doi.org/10.1103/PhysRevLett.76.4983 relation: 10.1103/PhysRevLett.76.4983