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arXiv 0803.4500math-phhep-thmath.MP
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非厄米XX自旋链的PT对称性:来自复边界场的非局域体相互作用

PT Symmetry of the non-Hermitian XX Spin-Chain: Non-local Bulk Interaction from Complex Boundary Fields

Christian Korff

摘要:

本文证明了非厄米对角边界条件下的XX自旋链在特定的边界参数值下是准厄米的。这是证明了一个新的内积明确建设采用“准费米子”代数的动量空间中的创造和湮灭运营商是不相关的通过厄米共轭。作为一个特殊的例子,当边界场位于虚轴上时,我们证明了准厄米XX自旋链与非局域费米子模型的谱等价性,其中随着非厄米边界场强度的增加,粒子发生长程跳跃。相应的哈密顿量在自由费米子点处插在开XX和量子群不变XXZ模型之间。对于偶数个位点,已知前者与具有中心荷c=1的CFT相关,而后者与具有中心荷c=-2的对数CFT相关。我们讨论了它的代数结构,并证明了对于奇数个点,超代数对称U(gl(1| 1))可以从单位圆沿虚轴延伸。我们涉及到它的一个中心元素的消失,约旦块的外观在汉密尔顿。

英文摘要:

The XX spin-chain with non-Hermitian diagonal boundary conditions is shown to be quasi-Hermitian for special values of the boundary parameters. This is proved by explicit construction of a new inner product employing a "quasi-fermion" algebra in momentum space where creation and annihilation operators are not related via Hermitian conjugation. For a special example, when the boundary fields lie on the imaginary axis, we show the spectral equivalence of the quasi-Hermitian XX spin-chain with a non-local fermion model, where long range hopping of the particles occurs as the non-Hermitian boundary fields increase in strength. The corresponding Hamiltonian interpolates between the open XX and the quantum group invariant XXZ model at the free fermion point. For an even number of sites the former is known to be related to a CFT with central charge c=1, while the latter has been connected to a logarithmic CFT with central charge c=-2. We discuss the underlying algebraic structures and show that for an odd number of sites the superalgebra symmetry U(gl(1|1)) can be extended from the unit circle along the imaginary axis. We relate the vanishing of one of its central elements to the appearance of Jordan blocks in the Hamiltonian.

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