Alladi Ramakrishnan Hall

Early Signatures of Sudden Regime Shifts

Sayantari Ghosh

Bose Institute, Kolkata

Recently, a large number of studies have been carried out on the early signatures of sudden
regime shifts in systems as diverse as ecosystems, financial markets, population biology and
complex diseases. The early signatures studied include the critical slowing down as a
transition point is approached, rising variance and the lag-1 autocorrelation
function, skewness and a ratio of two mean first passage times. The signatures of regime shifts
in gene expression dynamics are less systematically investigated. We have considered
sudden regime shifts in the gene expression dynamics described by a fold-bifurcation model
involving bistability and hysteresis. Two alternative models of competence
development in the bacterial population B. subtilis are considered and some early signatures
of the regime shifts between competence and noncompetence are examined. We have used both deterministic
and stochastic formalisms for the purpose of our study. Some of the signatures could
provide the experimental basis for distinguishing between bistability and excitability as the
correct mechanism for the development of competence.