Invariant R-matrix Research Articles

On exact overlaps for [formula omitted] symmetric spin chains

We study the integrable two-site states of the quantum integrable models solvable by the nested algebraic Bethe ansatz and possessing gl(N)-invariant R-matrix. We investigate the overlaps between the integrable two-site states and the wave-functions. To find exact derivations for the factorized overlap formulas for the nested integrable systems is a longstanding unsolved problem. In this paper we give a derivation for a large class of the integrable states of the gl(N) symmetric spin chain. The first part of the derivation is to calculate recurrence relations for the off-shell overlap that uniquely fix it. Using these recursions we prove that the normalized overlaps of the multi-particle states have factorized forms which contain the products of the one-particle overlaps and the ratio of the Gaudin-like determinants. We also show that the previously proposed overlap formulas agree with our general formula.

New R-matrices with non-additive spectral parameters and integrable models of strongly correlated fermions

We present a general formula for constructing R-matrices with non-additive spectral parameters associated with a type-I quantum superalgebra. The spectral parameters originate from two one-parameter families of inequivalent finite-dimensional irreducible representations of the quantum superalgebra upon which the R-matrix acts. Applying to the quantum superalgebra Uq(gl(2|1)), we obtain the explicit expression for the Uq(gl(2|1))− invariant R-matrix which is of non-difference form in spectral parameters. Using this R­ matrix we derive a new two-parameter integrable model of strongly correlated electrons with pure imaginary pair hopping terms.

New symmetries of -invariant Bethe vectors

We consider quantum integrable models solvable by the nested algebraic Bethe ansatz and possessing -invariant R-matrix. We study two types of Bethe vectors. The first type corresponds to the original monodromy matrix. The second type is associated to a monodromy matrix closely related to the inverse of the monodromy matrix. We show that these two types of Bethe vectors are identical up to normalization and reshuffling of the Bethe parameters. To prove this correspondence we use the current approach. This identity gives new combinatorial relations for the scalar products of the Bethe vectors. The q-deformed case, as well as the superalgebra case, are also evoked in the conclusion.

On Bethe vectors in mathfrak{g}{mathfrak{l}}_3 -invariant integrable models

We consider quantum integrable models solvable by the nested algebraic Bethe ansatz and possessing mathfrak{g}{mathfrak{l}}_3 -invariant R-matrix. We study a new recently proposed approach to construct on-shell Bethe vectors of these models. We prove that the vectors constructed by this method are semi-on-shell Bethe vectors for arbitrary values of Bethe parameters. They thus do become on-shell vectors provided the system of Bethe equations is fulfilled.

Norm of Bethe vectors in models with [formula omitted] symmetry

We study quantum integrable models solvable by the nested algebraic Bethe ansatz and possessing gl(m|n)-invariant R-matrix. We compute the norm of the Hamiltonian eigenstates. Using the notion of a generalized model we show that the square of the norm obeys a number of properties that uniquely fix it. We also show that a Jacobian of the system of Bethe equations obeys the same properties. In this way we prove a generalized Gaudin hypothesis for the norm of the Hamiltonian eigenstates.

GL(3) -Based Quantum Integrable Composite Models. II. Form Factors of Local Operators

We study integrable models solvable by the nested algebraic Bethe ansatz and possessing the GL(3)-invariant R-matrix. We consider a composite model where the total monodromy matrix of the model is presented as a product of two partial monodromy matrices. Assuming that the last ones can be expanded into series with respect to the inverse spectral parameter we calculate matrix elements of the local operators in the basis of the transfer matrix eigenstates. We obtain determinant representations for these matrix elements. Thus, we solve the inverse scattering problem in a weak sense.

Bethe states for the two-site Bose–Hubbard model: A binomial approach

We calculate explicitly the Bethe vectors states by the algebraic Bethe ansatz method with the gl(2)-invariant R-matrix for the two-site Bose–Hubbard model. Using a binomial expansion of the n-th power of a sum of two operators we get and solve a recursion equation. We calculate the scalar product and the norm of the Bethe vectors states. The form factors of the imbalance current operator are also computed.

Zero modes method and form factors in quantum integrable models

We study integrable models solvable by the nested algebraic Bethe ansatz and possessing GL(3)-invariant R-matrix. Assuming that the monodromy matrix of the model can be expanded into series with respect to the inverse spectral parameter, we define zero modes of the monodromy matrix entries as the first nontrivial coefficients of this series. Using these zero modes we establish new relations between form factors of the elements of the monodromy matrix. We prove that all of them can be obtained from the form factor of a diagonal matrix element in special limits of Bethe parameters. As a result we obtain determinant representations for form factors of all the entries of the monodromy matrix.

Determinant representations for form factors in quantum integrable models with the GL(3)-invariant R-matrix

We obtain determinant representations for the form factors of the monodromy matrix entries in quantum integrable models solvable by the nested algebraic Bethe ansatz and possessing $GL(3)$-invariant $R$-matrix. These representations can be used for the calculation of correlation functions in the models of physical interest.

Jordanian deformation of the open sℓ(2) Gaudin model

We derive a deformed sℓ(2) Gaudin model with integrable boundaries. Starting from the Jordanian deformation of the SL(2)-invariant Yang R-matrix and generic solutions of the associated reflection equation and the dual reflection equation, we obtain the corresponding inhomogeneous spin-1/2 XXX chain. The semiclassical expansion of the transfer matrix yields the deformed sℓ(2) Gaudin Hamiltonians with boundary terms.

Scalar Products in Generalized Models with SU(3)-Symmetry

We consider a generalized model with SU(3)-invariant R-matrix, and review the nested Bethe Ansatz for constructing eigenvectors of the transfer matrix. A sum formula for the scalar product between generic Bethe vectors, originally obtained by Reshetikhin, is discussed. This formula depends on a certain partition function Z({λ}, {μ}|{w}, {v}), which we evaluate explicitly. In the limit when the variables {μ} or \({\{v\}\rightarrow \infty}\), this object reduces to the domain wall partition function of the six-vertex model Z({λ}|{w}). Using this fact, we obtain a new expression for the off-shell scalar product (between a generic Bethe vector and a Bethe eigenvector), in the case when one set of Bethe variables tends to infinity. The expression obtained is a product of determinants, one of which is the Slavnov determinant from SU(2) theory.

Form factors in quantum integrable models with [formula omitted]-invariant R-matrix

We study integrable models solvable by the nested algebraic Bethe ansatz and possessing GL(3)-invariant R-matrix. We obtain determinant representations for form factors of off-diagonal entries of the monodromy matrix. These representations can be used for the calculation of form factors and correlation functions of the XXX SU(3)-invariant Heisenberg chain.

Jordanian deformation of the open XXX spin chain

The general solution to the reflection equation associated with the jordanian deformation of the SL(2) invariant Yang R-matrix is found. The same K-matrix is obtained by the special scaling limit of the XXZ-model with general boundary conditions. The Hamiltonian with the boundary terms is explicitly derived according to the Sklyanin formalism. We discuss the structure of the spectrum of the deformed XXX-model and its dependence on the boundary conditions.

Invariant see-saw models and sequential dominance

We propose an invariant see-saw (ISS) approach to model building, based on the observation that see-saw models of neutrino mass and mixing fall into basis invariant classes labelled by the Casas–Ibarra R-matrix, which we prove to be invariant not only under basis transformations but also non-unitary right-handed neutrino transformations S. According to the ISS approach, given any see-saw model in some particular basis one may determine the invariant R-matrix and hence the invariant class to which that model belongs. The formulation of see-saw models in terms of invariant classes puts them on a firmer theoretical footing, and allows different see-saw models in the same class to be related more easily, while their relation to the R-matrix makes them more easily identifiable in phenomenological studies. To illustrate the ISS approach we show that sequential dominance (SD) models form basis invariant classes in which the R-matrix is approximately related to a permutation of the unit matrix, and quite accurately so in the case of constrained sequential dominance (CSD) and tri-bimaximal mixing. Using the ISS approach we discuss examples of models in which the mixing naturally arises (at least in part) from the charged lepton or right-handed neutrino sectors and show that they are in the same invariant class as SD models. We also discuss the application of our results to flavour-dependent leptogenesis where we show that the case of a real R-matrix is approximately realized in SD, and accurately realized in CSD.

Algebraic Bethe ansatz for the gl(1|2) generalized model and Lieb–Wu equations

We solve the gl(1|2) generalized model by means of the algebraic Bethe ansatz. The resulting eigenvalue of the transfer matrix and the Bethe ansatz equations depend on three complex functions, called the parameters of the generalized model. Specifying the parameters appropriately, we obtain the Bethe ansatz equations of the supersymmetric t- J model, the Hubbard model, or of Yang's model of electrons with delta interaction. This means that the Bethe ansatz equations of these (and many other) models can be obtained from a common algebraic source, namely from the Yang–Baxter algebra generated by the gl(1|2) invariant R-matrix.

Integrable Structure of the Classical Lattice WNAlgebra

Studied is the integrable structure of the classical lattice W N algebra, which formulates the Hamiltonian structure of the N-reduced lattice KPhierarchy. We show that the monodromy matrix satisfies the Poisson algebra with the Z N invariant classical r-matrix.

Bulk and boundary S-matrices for the SU( N) chain

We consider both closed and open integrable antiferromagnetic chains constructed with the SU( N)-invariant R-matrix. For the closed chain, we extend the analyses of Sutherland and Kulish — Reshetikhin by considering also complex “string” solutions of the Bethe ansatz equations. Such solutions are essential to describe general multiparticle excited states. We also explicitly determine the SU( N) quantum numbers of the states. In particular, the model has particle-like excitations in the fundamental representations [ k] of SU( N), with k = 1, …, N − 1. We directly compute the complete two-particle S-matrices for the cases [1] ⊗ [1] and [1] ⊗ [ N − 1 ]. For the open chain with diagonal boundary fields, we show that the transfer matrix has the symmetry SU( l) × SU( N− l) × U(1), as well as a new “duality” symmetry which maps l→ N− l. With the help of these symmetries, we compute by means of the Bethe ansatz for particles of types [1] and [ N − 1 ] the corresponding boundary S-matrices.

Lattice WN algebra and its quantization

We consider the integrable structure of the quantum lattice W N algebras. We introduce the ultralocal Lax matrix, and show that the Yang-Baxter relation is satisfied with a Z N invariant R-matrix.

Cyclic monodromy matrices forsl(n) trigonometricR-matrices

The algebra of monodromy matrices for sl(n) trigonometric R-matrices is studied. It is shown that a generic finite-dimensional polynomial irreducible representation of this algebra is equivalent to a tensor product of L-operators. Cocommutativity of representations is discussed. A special class of representations - factorizable representations is introduced and intertwiners for cocommuting factorizable representations are written through the Boltzmann weights of the sl(n) chiral Potts model. Let us consider an algebra generated by noncommutative entries of the matrix $T(u)$ satisfying the famous bilinear relation originated from the quantum inverse scattering method: $R(\la-\mu)T(\la)T(\mu)=T(\mu)T(\la) R(\la-\mu)$ where $R(\la)$ is R-matrix. For historical reasons this algebra is called the algebra of monodromy matrices. If $\g$ is a simple finite-dimensional Lie algebra and $R(\la)$ is $\g$-invariant R-matrix the algebra of monodromy matrices after a proper specialization gives the Yangian $Y(\g)$ introduced by Drinfeld. If $R(\la)$ is corresponding trigonometric R-matrix this algebra is closely connected with $U_q(\g)$ and $U_q(\hat\g)$ at zero level. If $R(\la)$ is $sl(2)$ elliptic R-matrix the algebra of monodromy matrices gives rise to Sklyanin's algebra. In this paper we shall study algebras of monodromy matrices for $sl(n)$ trigonometric R-matrices at roots of 1. Finite-dimensional cyclic irreducible polynomial representations and their intertwiners are discussed.

The octonionic S-matrix

A new Spin (7) invariant R-matrix is found by solving the Yang-Baxter factorization equation. The solution contains the Spin (7) invariant tensor C abcd which is essentially given by the structure constants of the octonion multiplication table. By imposing unitarity, crossing invariance and analyticity, we obtain two minimal S-matrices, one of which possesses bound states of mass √2 m. In addition, the new R-matrix defines an integrable multistate vertex-model.