Boundary renormalization flow in symmetry-enriched Ising criticality

We investigate how time-reversal--breaking boundary fields destabilize topological edge modes and induce universal boundary renormalization-group (RG) flows in an interacting Majorana chain of BDI symmetry class. Using large-scale density-matrix renormalization-group (DMRG) calculations, we map the zero-temperature phase diagram and identify three phases---a two-Majorana topological phase, a four-Majorana symmetry-protected phase, and an antiferromagnet---separated by Ising-type critical lines with central charge c=1/2. Introducing a boundary term that couples to the edge Majorana modes produces a continuous flow between free and fixed boundary conditions. Finite-size corrections to the ground-state energy collapse onto a universal scaling function f(g) of the single variable g = B L^1/2, demonstrating a conformal-to-conformal crossover. Entanglement entropy and spectral analysis further reveal that boundary primary operators evolve smoothly between their Ising conformal field theory (CFT) limits. These results establish that universal boundary RG flows and their finite-size signatures persist in symmetry-enriched topological chains, highlighting the robustness of Ising boundary criticality against interactions.