Rajan Murgan

Exact solution of the open XXZ chain with general integrable boundary terms at roots of unity

We propose a Bethe-ansatz-type solution of the open spin-1/2 integrable XXZ quantum spin chain with general integrable boundary terms and bulk anisotropy values iπ/(p+1), where p is a positive integer. All six boundary parameters are arbitrary, and need not satisfy any constraint. The solution is in terms of generalized T–Q equations, having more than one Q function. We find numerical evidence that this solution gives the complete set of 2N transfer matrix eigenvalues, where N is the number of spins.

Bethe ansatz of the open spin-s XXZ chain with nondiagonal boundary terms

We consider the open spin-s XXZ quantum spin chain with nondiagonal boundary terms. By exploiting certain functional relations at roots of unity, we propose the Bethe ansatz solution for the transfer matrix eigenvalues for cases where atmost two of the boundary parameters are set to be arbitrary and the bulk anisotropy parameter has values ? = i?/3, i?/5, .... We present numerical evidence to demonstrate completeness of the Bethe ansatz solutions derived for s = 1/2 and s = 1.

q-deformed su(2|2) boundary S-matrices via the ZF algebra

Beisert and Koroteev have recently found a bulk S-matrix corresponding to a q-deformation of the centrally-extended su(2|2) algebra of AdS/CFT. We formulate the associated Zamolodchikov-Faddeev algebra, using which we derive factorizable boundary S-matrices that generalize those of Hofman and Maldacena.

Open-chain transfer matrices for AdS/CFT

We extend Sklyanins construction of commuting open-chain transfer matrices to the SU(2|2) bulk and boundary S-matrices of AdS/CFT. Using the graded version of the S-matrices leads to a transfer matrix of particularly simple form. We also find an SU(1|1) boundary S-matrix which has one free boundary parameter.

Boundary Energy of the Open XXZ Chain from New Exact Solutions

Abstract.Bethe Ansatz solutions of the open spin-

Boundary energy of the general open XXZ chain at roots of unity

\frac{1}{2}

Addendum to 'Bethe ansatz derived from the functional relations of the open XXZ chain for new special cases'

integrable XXZ quantum spin chain at roots of unity with nondiagonal boundary terms containing two free boundary parameters have recently been proposed.We use these solutions to compute the boundary energy (surface energy) in the thermodynamic limit.Communicated by Vincent Rivasseau

The solution of an open XXZ chain with arbitrary spin revisited

Certain solid solutions of perovskite-type ferroelectrics show excellent properties such as giant dielectric response and high electromechanical coupling constant in the vicinity of the morphotropic phase boundary (MPB). These materials are of importance to applications such as electrostrictive actuators and sensors, because of the large dielectric and piezoelectric constants (Jaffe et al., 1971; Sawaguchi, 1953; Kuwata et al., 1982; Newnham, 1997). The term “morphotropic” was originally used to refer to refer to phase transitions due to changes in composition (Ahart et al., 2008). Nowadays, the term ‘morphotropic phase boundaries’ (MPB) is used to refer to the phase transition between the tetragonal and the rhombohedral ferroelectric phases as a result of varying the composition or as a result of mechanical pressure (Jaffe et al., 1954; Yamashita, 1994; Yamamoto & Ohashi, 1994; Cao & Cross, 1993; Amin et al., 1986; Ahart et al., 2008). In the vicinity of the MPB, the crystal structure changes abruptly and the dielectric properties in ferroelectric (FE) materials and the electromechanical properties in piezoelectric materials become maximum. The common ferroelectric materials used for MPB applications is usually complexstructured solid solutions such as lead zirconate titanate PbZr1−xTixO3 (PZT) and Lead Magnesium niobate-lead titanate (1-x)PbMg1/3Nb2/3O3-xPbTiO3), shortly known as PMNPT. For example, PZT is a perovskite ferroelectrics which has a MPB between the tetragonal and rhombohedral FE phases in the temperature-composition phase diagram. However, these materials are complex-structured and require a complicated and costly process to prepare its solid solutions. Furthermore, the study of the microscopic origin of its properties is very complicated. Recently, scientists started to pay attention to the MPB in simple-structured pure compound ferroelectric materials such as ferroelectric oxides. For example, a recent experimental study on lead titanate proved that PbTiO3 can display a large MPB under pressure (Ahart et al., 2008). These experimental results even showed richer phase diagrams than those predicted by first-principle calculations. Therefore, it is of particular importance to study the