1,233 research outputs found
Phase diagram of frustrated mixed-spin ladders in the strong-coupling limit
We study the ground-state properties of frustrated Heisenberg ferrimagnetic
ladders with antiferromagnetic exchange interactions and two types of
alternating sublattice spins. In the limit of strong rung couplings, we show
that the mixed spin-1/2 and spin-1 ladders can be systematically mapped onto a
spin-1/2 Heisenberg model with additional next-nearest-neighbor exchanges. The
system is either in a ferrimagnetic state or in a critical spin-liquid state
depending on the competition between the spin exchanges along the legs and the
diagonal exchanges.Comment: 6 pages, 2 figur
Nested off-diagonal Bethe ansatz and exact solutions of the su(n) spin chain with generic integrable boundaries
The nested off-diagonal Bethe ansatz method is proposed to diagonalize
multi-component integrable models with generic integrable boundaries. As an
example, the exact solutions of the su(n)-invariant spin chain model with both
periodic and non-diagonal boundaries are derived by constructing the nested T-Q
relations based on the operator product identities among the fused transfer
matrices and the asymptotic behavior of the transfer matrices.Comment: Published versio
Exact solution of the one-dimensional Hubbard model with arbitrary boundary magnetic fields
The one-dimensional Hubbard model with arbitrary boundary magnetic fields is
solved exactly via the Bethe ansatz methods. With the coordinate Bethe ansatz
in the charge sector, the second eigenvalue problem associated with the spin
sector is constructed. It is shown that the second eigenvalue problem can be
transformed into that of the inhomogeneous XXX spin chain with arbitrary
boundary fields which can be solved via the off-diagonal Bethe ansatz method.Comment: published version, 15 pages, no figur
A Vector Matroid-Theoretic Approach in the Study of Structural Controllability Over F(z)
In this paper, the structural controllability of the systems over F(z) is
studied using a new mathematical method-matroids. Firstly, a vector matroid is
defined over F(z). Secondly, the full rank conditions of [sI-A|B] are derived
in terms of the concept related to matroid theory, such as rank, base and
union. Then the sufficient condition for the linear system and composite system
over F(z) to be structurally controllable is obtained. Finally, this paper
gives several examples to demonstrate that the married-theoretic approach is
simpler than other existing approaches
Impact of Economic Factors and Policy Interventions on the COVID-19 Pandemic
This paper studies how policy interventions and economic factors affect COVID-19 infections and deaths, using generalized linear regression (GLM) models. We seek to explain the containment differences by countries’ inherent economic factors, especially the labor market structure, utilizing data from multiple sources. The results show that countries heavily relying on the service sector and international trade suffer more from the spreading, possibly due to the fact that COVID-19 is a communicable disease and spreads quickly through physical contact. Further, we find that these countries could benefit more from stringent policies compared to others
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