Pseudo-RNA with parallel aligned single-strands and periodic base sequence as a new universality class

This work investigates a field theory for RNA-like polymers with periodic base sequence GCGCG..., where only single-strands aligned in the same direction form double strands. The field theory is derived from a lattice model that incorporates excluded volume effects, base sequence, and temperature dependent denaturation - renaturation. The artificial directionality leads to a novel universality class, not related to conventional branched polymers and Lee-Yang field theory. This universality class is unstable against natural pairing, where oppositely aligned single-strands form double strands. Near the upper critical dimension \(d=6\) the denaturation - renaturation transition is a continuous crossover between two \(\varphi _{n=0}^{4}\) critical points and the critical point of the new universality class. However, the behavior for \(d\le 5\) remains unclear.