5 research outputs found
Renormalized SO(5) symmetry in ladders with next-nearest-neighbor hopping
We study the occurrence of SO(5) symmetry in the low-energy sector of
two-chain Hubbard-like systems by analyzing the flow of the running couplings
(-ology) under renormalization group in the weak-interaction limit. It is
shown that SO(5) is asymptotically restored for low energies for rather general
parameters of the bare Hamiltonian. This holds also with inclusion of a
next-nearest-neighbor hopping which explicitly breaks particle-hole symmetry
provided one accounts for a different single-particle weight for the
quasiparticles of the two bands of the system. The physical significance of
this renormalized SO(5) symmetry is discussed.Comment: Final version: to appear in Phys. Rev. Lett., sched. Mar. 9
Third Order Renormalization Group applied to the attractive one-dimensional Fermi Gas
We consider a Callan-Symanzik and a Wilson Renormalization Group approach to
the infrared problem for interacting fermions in one dimension with
backscattering. We compute the third order (two-loop) approximation of the beta
function using both methods and compare it with the well known multiplicative
Gell-Mann Low approach. We point out a previously unnoticed qualitative
dependence of the third order fixed point on an arbitrary dimensionless
parameter, which strongly suggest the spurious nature of the fixed point.Comment: 16 pages, Revised version, added comment