Bares 2.0 wave buoy and sustainable buoy network

The aim of this article is to show the operation of the Bares 2.0 wave buoy and the Bares network developed by HCTech. In the marine sector it is highly important to know the state of the sea for applications such as the construction of ports, the study of the impact of waves in coastal areas, the development and calibration of forecasting wave models, the knowledge of the state of the maritime navigation channels, etc. Some of the great difficulties that exist in order to obtain the information of ocean waves is the high cost of the buoys, installation and maintenance. The Bares network aims to cover areas of high oceanographic interest, the target is a sustainable network of buoys that facilitate the access to wave data. The features of this network are the optimized cost, high reliability and reduced maintenance.Peer Reviewe

Hubbard chain with a Kondo impurity

A Bethe Ansatz solution of a (modified) Hubbard chain with a Kondo impurity of arbitrary spin S at a highly symmetric line of parameter space is proposed and explored. Our results confirm the existence of a strong-coupling (line of) fixed-point(s) with ferromagnetic Kondo coupling as first hypothetized by Furusaki and Nagaosa on the basis of perturbative renormalization group calculations. For on-site Hubbard repulsion and ferromagnetic Kondo exchange, the ground state has spin S-1/2, i.e., is a singlet when S=1/2. The contributions of the impurity to the magnetic susceptibility and low-temperature specific heat are discussed. While the Wilson ratio is unity in the half-filled band, it is found to be a function of density and interaction away from half-filling.Comment: 5 pages, Revte

Scalar Symmetries of the Hubbard Models with Variable Range Hopping

Examples of scalar conserved currents are presented for trigonometric, hyperbolic and elliptic versions of the Hubbard model with non-nearest neighbour variable range hopping. They support for the first time the hypothesis about the integrability of the elliptic version. The two- electron wave functions are constructed in an explicit form.Comment: 9 pages, LaTex2e, no figure

Algebraic Bethe ansatz for the supersymmetric t−Jt-J model with reflecting boundary conditions

In the framework of the graded quantum inverse scattering method (QISM), we obtain the eigenvalues and eigenvectors of the supersymmetric $t-J$ model with reflecting boundary conditions in FFB background. The corresponding Bethe ansatz equations are obtained.Comment: Latex file, 23 Page

Doped Heisenberg chains: spin-S generalizations of the supersymmetric t-J model

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 M_p with p=2S+1.Comment: LaTeX, 24 pp. incl. 4 figure

Exact thermodynamics and Luttinger liquid properties of the integrable t-J model

A Trotter-Suzuki mapping is used to calculate the finite-temperature properties of the one-dimensional supersymmetric $t-J$ model. This approach allows for the exact calculation of various thermodynamical properties by means of the quantum transfer matrix (QTM). The free energy and other interesting quantities are obtained such as the specific heat and compressibility. For the largest eigenvalue of the QTM leading to the free energy a set of just two non-linear integral equations is presented. These equations are studied analytically and numerically for different particle densities and temperatures. The structure of the specific heat is discussed in terms of the elementary charge as well as spin excitations. Special emphasis is placed on the study of the low-temperature behavior confirming scaling predictions by conformal field theory and Luttinger liquid theory. To our knowledge this is the first complete investigation of a strongly correlated electron system on a lattice at finite temperature.Comment: 27 pages, Latex, 9 Post-Script figures, uses graphicx and amsmat

Exact solutions of graded Temperley-Lieb Hamiltonians

Orthosympletic Hamiltonians derived from representations of the Temperley-Lieb algebra are presented and solved via the coordinate Bethe Ansatz. The spectra of these Hamiltonians are obtained using open and closed boundary conditions.Comment: 39 pages, LaTe

Yangian Symmetry and Quantum Inverse Scattering Method for the One-Dimensional Hubbard Model

We develop the quantum inverse scattering method for the one-dimensional Hubbard model on the infinite interval at zero density. $R$-matrix and monodromy matrix are obtained as limits from their known counterparts on the finite interval. The $R$-matrix greatly simplifies in the considered limit. The new $R$-matrix contains a submatrix which turns into the rational $R$-matrix of the XXX-chain by an appropriate reparametrization. The corresponding submatrix of the monodromy matrix thus provides a representation of the Y(su(2)) Yangian. From its quantum determinant we obtain an infinite series of mutually commuting Yangian invariant operators which includes the Hamiltonian.Comment: 14 pages, LaTeX, no figures, minor change