It is shown that the dominant trapping sets of regular LDPC codes, which are absorption sets, undergo a two-phased dynamic behavior in the iterative message-passing decoding algorithm. Using a linear dynamic model for the iteration behavior of the dominant absorption sets, it is shown that the sets undergo an initial geometric growth phase which stabilizes in a final bit-flipping behavior where the algorithm comes to a fixed point. This analysis is shown to lead to accurate numerical calculations of the error floor bit error rates down to error rates that are inaccessible by simulation. Search result for the dominant such absorption sets
will be presented for a regular LDPC code.