Exponential growth or death
Peter Jagers, Chalmers tekniska högskola och Göteborgs universitet, Sweden
In a famous passage Thomas Malthus argued that populations (not dying out) must increase exponentially. We formulate the correct dichotomy, between unbounded growth and extinction, give conditions for growth to be exponential, and in particular discuss how linear growth can come about. A martingale argument explains the mysterious linear phase of molecule number increase in PCR.