Results 1 - 10 of 32
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[en] The magnetic susceptibility of systems from a class of integrable models for doped spin-S Heisenberg chains is calculated in the limit of vanishing magnetic field. For small concentrations xh of the mobile spin-(S-1/2) charge carriers we find an explicit expression for the contribution of the gapless mode associated to the magnetic degrees of freedom of these holes to the susceptibility which exhibits a singularity for xh→0 for sufficiently large S. We prove a sum rule for the contributions of the two gapless magnetic modes in the system to the susceptibility which holds for arbitrary hole concentration. This sum rule complements the one for the low temperature specific heat which has been obtained previously
[en] We derive exact inversion identities satisfied by the transfer matrix of inhomogeneous interaction-round-a-face (IRF) models with arbitrary boundary conditions using the underlying integrable structure and crossing properties of the local Boltzmann weights. For the critical restricted solid-on-solid (RSOS) models these identities together with some information on the analytical properties of the transfer matrix determine the spectrum completely and allow to derive the Bethe equations for both periodic and general open boundary conditions
[en] Starting from the fusion rules for the algebra SO(5)2 we construct one-dimensional lattice models of interacting anyons with commuting transfer matrices of ‘interactions round the face’ (IRF) type. The conserved topological charges of the anyon chain are recovered from the transfer matrices in the limit of large spectral parameter. The properties of the models in the thermodynamic limit and the low energy excitations are studied using Bethe ansatz methods. Two of the anyon models are critical at zero temperature. From the analysis of the finite size spectrum we find that they are effectively described by rational conformal field theories invariant under extensions of the Virasoro algebra, namely WB2 and WD5, respectively. The latter contains primaries with half and quarter spin. The modular partition function and fusion rules are derived and found to be consistent with the results for the lattice model
[en] A family of exactly solvable models describing a spin S Heisenberg chain doped with mobile spin-(S - ((1)/(2))) carriers is constructed from gl(2|1)-invariant solutions of the Yang-Baxter equation. The models are generalizations of the supersymmetric t-J model which is obtained for S ((1)/(2)). We solve the model by means of the algebraic Bethe Ansatz and present results for the zero temperature and thermodynamic properties. At low temperatures the models show spin charge separation, i.e. contain contributions of a free bosonic theory in the charge sector and an SU(2)-invariant theory describing the magnetic excitations. For small carrier concentration the latter can be decomposed further into an SU(2) level-2S Wess-Zumino-Novikov-Witten model and the minimal unitary model Mp with p 2S + 1
[en] The flow of the low energy eigenstates of a Usl(21) superspin chain with alternating fundamental (3) and dual () representations is studied as function of a twist angle determining the boundary conditions. The finite size spectrum is characterized in terms of scaling dimensions and quasi momenta representing the two families of commuting transfer matrices for the model which are even and odd under the interchange 3 , respectively. Based on the extrapolation of our finite size data we find that under a variation of the boundary conditions from antiperiodic to periodic for the fermionic degrees of freedom levels from the continuous part of the spectrum flow into discrete levels and vice versa. The implications of our results on the underlying conformal field theory which describes the continuum limit are discussed.
[en] We use the Bethe ansatz solution for the one-dimensional Hubbard model with open boundary conditions and applied boundary fields to study the spectrum of bound states at the boundary. Depending on the strength of the boundary potentials, one finds that the true ground state contains a single charge or, for boundary potentials comparable with the Hubbard interaction, a pair of electrons in a bound state. If these are left unoccupied one finds holon and spinon bound states. We compute the finite size corrections to the low-lying energies in this system and use the predictions of boundary conformal field theory to study the exponents related to the orthogonality catastrophe. (author)
[en] The contribution of anyonic degrees of freedom emerging in the non-Abelian spin sector of a one-dimensional system of interacting fermions carrying both SU(3) and SU(N) degrees of freedom to the thermodynamic properties of the latter is studied based on the exact solution of the model. For sufficiently small temperatures and fields the anyons appear as zero energy modes localized at the massive kink excitations. From their quantum dimension they are identified as SU(3) anyons. The density of kinks (and anyons) can be controlled by external fields leading to the formation of collective states of these anyons described by various conformal embeddings of the SU(3) WZNW model for large fields. Based on the numerical analysis of the thermodynamic Bethe ansatz equations we propose a phase diagram for the anyonic modes.
[en] We calculate the asymptotic behavior of correlators as a function of the microscopic parameters for an integrable Bose-Fermi mixture with repulsive interaction in one dimension. For two cases, namely polarized and unpolarized fermions the singularities of the momentum distribution functions are characterized as a function of the coupling constant and the relative density of bosons
[en] We derive functional equations for the eigenvalues of the XXZ model subject to anti-diagonal twisted boundary conditions by means of fusion of transfer matrices and by Sklyanin's method of separation of variables. Our findings coincide with those obtained using Baxter's method and are compared to the recent solution of Galleas. As an application we study the finite size scaling of the ground-state energy of the model in the critical regime
[en] The flow of the low energy eigenstates of a superspin chain with alternating fundamental (3) and dual () representations is studied as function of a twist angle determining the boundary conditions. The finite size spectrum is characterized in terms of scaling dimensions and quasi momenta representing the two families of commuting transfer matrices for the model which are even and odd under the interchange , respectively. Based on the extrapolation of our finite size data we find that under a variation of the boundary conditions from periodic to antiperiodic for the fermionic degrees of freedom levels from the continuous part of the spectrum flow into discrete levels and vice versa. (paper)