Leadership and self-enforcing international environmental agreements with non-negative emissions

For the widely-used linear-quadratic model of stable IEAs the key results are: (i) if the members of the IEA act in a Cournot fashion with respect to non-signatories, a stable IEA has no more than 2 signatories; (ii) if the signatories act as Stackelberg leaders, a stable IEA can have any number of signatories. These results were derived using numerical simulations and ignored the non-negativity constraint on emissions. Recent papers using analytical approaches and explicitly recognising the non-negativity constraint have suggested that with Stackelberg leadership a stable IEA has at most four signatories. Such papers have introduced non-negativity constraints by restricting parameter values to ensure interior solutions for emissions, which restricts the number of signatories. We use the more appropriate approach of directly imposing the non-negativity constraint on emissions, recognising that for some parameter values this will entail corner solutions, and show, analytically, that the key results from the literature go through

Electronic structure of polychiral carbon nanotubes

Most of the works devoted so far to the electronic band structure of multiwall nanotubes have been restricted to the case where the individual layers have the same helicity. By comparison, much less is known on the electronic properties of multiwall nanotubes that mix different helicities. These are interesting systems, however, since they can be composed of both metallic and semiconducting layers. For the present work, tight-binding calculations were undertaken for polychiral two-layer nanotubes such as (9,6)@(15,10), (6,6)@(18,2), and others. The recursion technique was used to investigate how the densities of states of the individual layers are affected by the intertube coupling. Constant-current STM images were also calculated for these systems. The result obtained is that the image of a two-wall nanotube is pretty much the same as the one of the isolated external layer. It is only in the case of monochiral, commensurate structures like (5,5)@(10,10) that interlayer effects can be seen on the STM topography.Comment: 12 pages plus 6 figures included in the postscript fil

Square root kalman filter with contaminated observations

The algorithm of square root Kalman filtering for the case of contaminated observations is described in the paper. This algorithm is suitable for the parallel computer implementation allowing to treat dynamic linear systems with large number of state variables in a robust recursive way