Multiplicity of Radial Ground States for the Scalar Curvature Equation Without Reciprocal Symmetry

We study existence and multiplicity of positive ground states for the scalar curvature equation $$\begin{aligned} \varDelta u+ K(|x|)\, u^{\frac{n+2}{n-2}}=0, \quad x\in {{\mathbb {R}}}^n\,, \quad n>2, \end{aligned}$$ Δ u + K ( | x | ) u n + 2 n - 2 = 0 , x ∈ R n , n > 2 , when the function $$K:{{\mathbb {R}}}^+\rightarrow {{\mathbb {R}}}^+$$ K : R + → R + is bounded above and below by two positive constants, i.e. $$0<\underline{K} \le K(r) \le \overline{K}$$ 0 < K ̲ ≤ K ( r ) ≤ K ¯ for every $$r > 0$$ r > 0 , it is decreasing in $$(0,{{{\mathcal {R}}}})$$ ( 0 , R ) and increasing in $$({{{\mathcal {R}}}},+\infty )$$ ( R , + ∞ ) for a certain $${{{\mathcal {R}}}}>0$$ R > 0 . We recall that in this case ground states have to be radial, so the problem is reduced to an ODE and, then, to a dynamical system via Fowler transformation. We provide a smallness non perturbative (i.e. computable) condition on the ratio $$\overline{K}/\underline{K}$$ K ¯ / K ̲ which guarantees the existence of a large number of ground states with fast decay, i.e. such that $$u(|x|) \sim |x|^{2-n}$$ u ( | x | ) ∼ | x | 2 - n as $$|x| \rightarrow +\infty $$ | x | → + ∞ , which are of bubble-tower type. We emphasize that if K(r) has a unique critical point and it is a maximum the radial ground state with fast decay, if it exists, is unique.

On an optimal replenishment policy for inventory models for non-instantaneous deteriorating items with stock dependent demand and partial backlogging

This paper proposes a procedure for determining the optimal replenishment policy for the simple inventory model with stock-dependent demand items, non-instantaneous deteriorating items and partial backlogging. The optimal policy is shown to be of a threshold form. That is, (i) if the time of the onset of deterioration is greater than or equal to the time at which partial-backlogging begins in the basic model (with no deterioration), then the optimal policy is determined by the parameters of the basic model, else (ii) The optimal policy corresponds to the unique critical point of the objective function for the model with non-instantaneous deterioration. Moreover, a simple test for deciding in favor of the former model is given. The procedure obtained is simpler and easier to implement than those existing in the literature. Numerical examples are presented for illustration.

Economic-order-type inventory models for non-instantaneous deteriorating items and backlogging

This paper is concerned with finding the optimal economic order quantity for the basic (EOQ) inventory model with backlogging in the presence of non-instantaneous deterioration. It is shown that the optimal EOQ is a threshold policy. That is, (i) if the time at which deterioration begins in the non-instantaneous deterioration model is greater than or equal to the time at which backlogging begins in the basic (EOQ) model, then the optimal policy is determined by the parameters of the basic (EOQ) model, else (ii) the optimal policy corresponds to the unique critical point of the objective function for the model with non-instantaneous deterioration. An approach for determining this policy is proposed. This approach is simple and easy to implement. Moreover, it does not suffer from the shortcomings of existing approaches in the literature. A numerical example is presented for illustration.

On the allowed symmetries of all distorted forms of conformers, molecules, and transition structures

Based on the catchment region point symmetry theorem, a general framework and some new results are presented on symmetry constraints of deformations preserving chemical identity. The point symmetries of the unique critical point (equilibrium) nuclear arrangement corresponding to a conformer, molecule, or a transition structure and those of a family of nuclear arrangements with an arbitrarily small limit on the allowed distortions provide a complete symmetry characterization of the entire potential surface catchment region of the chemical species. Consequently, the point symmetries of all distorted molecular forms that preserve chemical identity can be deduced by testing symmetry conditions only within an arbitrarily small domain of the potential surface, in the vicinity of the equilibrium arrangement. Additional constraints are deduced on the point symmetries of transition structures obtained directly from the given conformer. Keywords: molecular distortions, symmetry, catchment regions, new symmetry theorems, framework groups, point groups.