We develop an analytical approach for the study of the quench dynamics of the anisotropic Heisenberg model (XXZ model) on the infinite line. We present the exact time-dependent wave functions after a quench in an integral form for any initial state and for any anisotropy Δ by means of a generalized Yudson contour representation. We calculate the evolution of several observables from two particu...

We consider the (2+1)-dimensional gauged Thirring model in the Heisenberg picture. In this context we evaluate the vacuum polarization tensor as well as the corrected gauge boson propagator and address the issues of generation of mass and dynamics for the gauge boson (in the limits of QED3 and Thirring model as a gauge theory, respectively) due to the radiative corrections. On leave from Depart...

We investigate a two-dimensional classical N-vector model with a nonlinear interaction (1+sigma(i) x sigma(j))(p) in the large-N limit. As observed for N=3 by Blöte et al. [Phys. Rev. Lett. 88, 047203 (2002)], we find a first-order transition for p>p(c) and no finite-temperature phase transitions for pp(c), both phases have short-range order, the correlation length showing a finite...

We propose a nonlinear integral equation (NLIE) with only one unknown function, which gives the free energy of the integrable one dimensional Heisenberg model with arbitrary spin. In deriving the NLIE, the quantum Jacobi-Trudi and Giambelli formula (BazhanovReshetikhin formula), which gives the solution of the T -system, plays an important role. In addition, we also calculate the high temperatu...

Magnetization measurements of Sr14−xCaxCu24O41 with 0 ≤ x ≤ 12 in magnetic fields up to 16 T show that the low-temperature magnetic response of the CuO2 spin chains changes strongly upon Ca doping. For x = 0 quantum statistical simulations yield that the temperature and field dependence of the magnetization can be well described by an effective Heisenberg model in which the ground state configu...

Solides Heisenberg Antiferromagnetic model on 2D quasiperiodic tilings Thèse presentée pour obtenir le grade de

We introduce a transformation which allows the fermionization of operators of any onedimensional spin-chain. This fermionization procedure is independent of any eventual integrable structure and is compatible with it. We illustrate this method on various integrable and non-integrable chains, and deduce some general results. In particular, we fermionize XXC spin-chains and study their symmetries...

Type-I quantum impurities are investigated in the context of the integrable Heisenberg model. This type of defects is associated to the (q)-harmonic oscillator algebra. The transmission matrices associated to this particular type of defects are computed via the Bethe ansatz methodology for the XXX model, as well as for the critical and non-critical XXZ spin chain. In the attractive regime of th...

We consider the highly anisotropic ferromagnetic spin 1/2 Heisenberg chain with periodic boundary conditions. In each sector of constant total z component of the spin, we develop convergent expansions for the lowest band of eigenvalues and eigenfunctions. These eigenstates describe droplet states in which the spins essentially form a single linear droplet which can move. Our results also give a...

The magnetization process of the S = 1 and 1/2 kagomé Heisenberg antiferromagnet is studied by means of the numerical exact diagonalization method. It is found that the magnetization curve at zero temperature has a plateau at 1/3 of the full magnetization. In the presence of √ 3 × √ 3 lattice distortion, this plateau is enhanced and eventually the ferrimagnetic state is realized. There also app...