Discrete Math Seminar: Rami Tabbara

We will describe a class of two directed and friendly walks along the square lattice that are restricted to the upper half-plane. Onemotivation for studying this class is that it can be used  to model an idealised thermodynamic system of a DNA strand in a solvent near an attractive surface. We will solve the combinatorial problem of finding a closed-form expression for the number of $N$ paired walks that contain $L$ lower-walk-to-$x$-axis and $M$ lower-walk-to-upper-walk shared site contacts.