The integrability condition called shape invariance is shown to have an underlying algebraic structure and the associated Lie algebras are identified. These shape-invariance algebras transform the parameters of the potentials such as strength and range. Shape-invariance algebras, in general, are shown to be infinite-dimensional. The conditions under which they become finitedimensional are explo...

It is shown that the previously known N = 3 and N = 4 superconformal algebras can be contracted consistently by singular scaling of some of the generators. For the later case, by a contraction which depends on the central term, we obtain a new N = 4 superconformal algebra which contains an SU(2)×U(1) Kac-Moody subalgebra and has nonzero central extension.

We examine price competition under product-specific network effects, in a duopoly where the products are differentiated horizontally and vertically. When consumers’ expectations are not affected by prices, firms may share the market equally, or one firm (possibly even the low-quality one) may capture the entire market. When product qualities are different, we may also have interior asymmetric e...

In global seismology Earth’s properties of fractal nature occur. Zygmund classes appear as the most appropriate and systematic way to measure this local fractality. For the purpose of seismic wave propagation, we model the Earth’s properties as Colombeau generalized functions. In one spatial dimension, we have a precise characterization of Zygmund regularity in Colombeau algebras. This is made ...

It is shown how to embed the polydisk algebras (finite and infinite ones) into the disk algebra A(D). As a consequence, one obtains uniform closed subalgebras of A(D) which have arbitrarily prescribed stable ranks.

A discrete-delayed model of plasmid-bearing, plasmid-free organisms competing for a single-limited nutrient in a chemostat is established. Rigorous mathematical analysis of the asymptotic behavior of this model is presented. An interesting method to analyze the local stability of interior equilibrium is developed. The argument is also applicable to a model of plasmidbearing, plasmid-free organi...

In the present paper, two light sources commonly used in interior lighting system: incandescent light and light emitting diode (LED) were chosen to evaluate their influences on three kinds of mammalian cells, together with UVA and UVB, and the mechanism of the photocytotoxicity was investigated in terms of intracellular ROS production, lipid peroxidation, SOD activity and GSH level assays. The ...