We study a variant of poly-nuclear growth where the level boundaries perform continuous-time, discrete-space random walks,
and study how its asymptotic behavior is affected by the presence of a columnar defect on the line. We prove that there is
a non-trivial phase transition in the strength of the perturbation, above which the law of large numbers for the height function
is modified.
Keywords Poly-nuclear growth - Interacting random walks - Zero-temperature Glauber dynamics - Polymer pinning
Mathematics Subject Classification (2000) 60K35 - 60K37