  We consider the influence of a terahertz field on the breathing dynamics of
double-stranded DNA. We model the spontaneous formation of spatially localized
openings of a damped and driven DNA chain, and find that linear instabilities
lead to dynamic dimerization, while true local strand separations require a
threshold amplitude mechanism. Based on our results we argue that a specific
terahertz radiation exposure may significantly affect the natural dynamics of
DNA, and thereby influence intricate molecular processes involved in gene
expression and DNA replication.
