We compute the boundary energy and the Casimir energy for both the spin-12 XXZ quantum spin chain and (by means of the light-cone lattice construction) the massive sine-Gordon model with both left and right boundaries. We also derive a nonlinear integral equation for the ground state of the sine-Gordon model on a finite interval. These results, which are based on a recently-proposed Bethe Ansat...

We present an alternative to the conventional matrix product state representation, which allows us to avoid the explicit local Hilbert space truncation many numerical methods employ. Utilizing chain mappings corresponding to linear and logarithmic discretizations of the spin-boson model onto a semi-infinite chain, we apply the newmethod to the sub-ohmic spin-boson model. We are able to reproduc...

The electronic structure of the enigmatic iron-based superconductor FeSe has puzzled researchers since spectroscopic probes failed to observe expected electron pocket at $Y$ point in 1-Fe Brillouin zone. It been speculated that this pocket, essential for an understanding superconducting state, is either absent or incoherent. Here, we perform a theoretical study preferred nematic order originati...

We consider the Heisenberg spin chain in the presence of integrable spin defects. Using the Bethe ansatz methodology, we extract the associated transmission amplitudes, that describe the interaction between the particle-like excitations displayed by the models and the spin impurity. In the attractive regime of the XXZ model, we also derive the breather’s transmission amplitude. We compare our f...