in this paper we studied the thermal negativity in a two-qubit xx spin ½ chain model and xxx spin1/2 chain model(isotropic heisenberg model)spin-1/2 chain subjected to an external magnetic field inz direction. we calculate analytical relation for the thermal negativity for two qubit xx and xxx spinchain models in the external magnetic field. effects of the magnetic field and temperature on then...

In this paper we studied the thermal negativity in a two-qubit XX spin ½ chain model and XXX spin1/2 chain model(isotropic Heisenberg model)spin-1/2 chain subjected to an external magnetic field inz direction. We calculate analytical relation for the thermal negativity for two qubit XX and XXX spinchain models in the external magnetic field. Effects of the magnetic field and temperature on then...

For the integrable higher-spin XXX and XXZ spin chains we show an explicit formula for the multiple-integral representations of the emptiness formation probability (EFP) in the massless ground-state at zero temperature. We first derive it for the inhomogeneous spin-s XXZ chain, and then for the homogeneous chain, sending the spin-s inhomogeneous parameters to zero. We assume 2s-strings for the ...

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...

On the Algebraic Bethe Ansatz for XXX spin chain: creation operators " beyond the equator ". Abstract Considering the XXX spin-1/2 chain in the framework of the Algebraic Bethe Ansatz (ABA) we make the following short comment: the product of the creation operators corresponding to the recently found solution of the Bethe equations " on the wrong side of the equator " [1] is just zero (not only ...

The form of the spectral curve for 4d N = 2 supersymmetric Yang-Mills theory with matter fields in the fundamental representation of the gauge group suggests that its 1d integrable counterpart should be looked for among (inhomogeneous) sl(2) spin chains with the length of the chain being equal to the number of colours Nc. For N f < 2Nc the relevant spin chain is the simplest XXX-model, and this...

A unified treatment is developed for the XXX-Heisenberg model and a long-ranged interaction model (the H2 in Haldane-Shastry model) from the point of view of shift operators (or raising and lowering operators), based on which the energy spectra of the spin-chain models are determined. Some physical discussions are also made. PACS numbers: 75.10.Jm, 03.65.Fd

We study the local conserved charges in integrable spin chains of the XYZ type with nontrivial boundary conditions. The general structure of these charges consists of a bulk part, whose density is identical to that of a periodic chain, and a boundary part. In contrast with the periodic case, only the charges corresponding to the interactions of even number of spins exist for the open chain. Hen...

This is a very elementary introduction to the Heisenberg (XXX) quantum spin chain, the Yang-Baxter equation, and the algebraic Bethe Ansatz.