We show that the homomorphism preservation theorem fails for LFP, both in general and in restriction to finite structures. That is, there is a formula of LFP that is preserved under homomorphisms (in the finite) but is not equivalent (in the finite) to a Datalog program. This resolves a question posed by Atserias. The results are established by two different methods: (1) a method of diagonalisa...

The two-site Bose–Hubbard model is a simple model used to study Josephson tunneling between two Bose–Einstein condensates. In this work we give an overview of some mathematical aspects of this model. Using a classical analysis, we study the equations of motion and the level curves of the Hamiltonian. Then, the quantum dynamics of the model is investigated using direct diagonalisation of the Ham...

The Higgs mode is expected to exist in any system with the spontaneous symmetry breaking of the continuous symmetry. We make numerical study about the Higgs mode in the Heisenberg antiferromagnet on the square lattice by the exact diagonalisation approach. Since the Higgs mode can couple with a pair of the Nambu-Goldstone modes, we calculate the dynamical correlation of the two spin operators, ...

The polynomial matrix EVD (PEVD) is an extension of the conventional eigenvalue decomposition (EVD) to polynomial matrices. The purpose of this article is to provide a review of the theoretical foundations of the PEVD and to highlight practical applications in the area of broadband blind source separation (BSS). Based on basic definitions of polynomial matrix terminology such as parahermitian a...

We consider a system of coupled harmonic oscillators on a cubic lattice. The force constants are supposed to take two distinct values at random according to a bond concentration x. The density of states (DOS) is evaluated both by numerical diagonalisation and in coherent-potential approximation (CPA). There is excellent agreement between the results of the two methods. Near the concentration, w...

A novel blind DS-CDMA array channel estimator is presented which is capable of handling severe frequency-selective channels, where the multipath delay spread can be comparable with the data symbol period. By employing the concept of the spatiotemporal array (STAR) manifold, a subspace-type estimation algorithm is proposed, in conjunction with an onedimensional temporal smoothing procedure, to j...

The free algebra adjunction, between the category of algebras of a monad and the underlying category, induces a comonad on the category of algebras. The coalgebras of this comonad are the topic of study in this paper (following earlier work). It is illustrated how such coalgebras-on-algebras can be understood as bases, decomposing each element x into primitives elements from which x can be reco...

We calculate positions and predissociation widths for quasi-bound states of HOCl with total angular momentum of J 1⁄4 0 and J 1⁄4 3. An ab initio potential energy surface is used in conjunction with a complex absorbing potential (CAP). These calculations are performed by diagonalising a complex symmetric Hamiltonian using our discrete variable representation (DVR) based parallel code, PDVR3D, a...

A class F of partial recursive functions is called recursively enumerable if there exists an r.e. set J ⊆ N such that F = {φi | i ∈ J}. We prove that every r.e. class F of partial recursive functions with infinite domains must have a recursive witness array, i.e. there is a computable array of finite sets X = [Xn]n∈ω such that (i) for every f ∈ F one has f(n) ∈ Xn for infinitely many n and (ii)...

The two-site Bose–Hubbard model is a simple model used to study Josephson tunneling between two Bose–Einstein condensates. In this work we give an overview of some mathematical aspects of this model. Using a classical analysis, we study the equations of motion and the level curves of the Hamiltonian. Then, the quantum dynamics of the model is investigated using direct diagonalisation of the Ham...