Open Quantum Systems in Noninertial Frames

We study the effects of decoherence on the entanglement generated by Unruh effect in noninertial frames by using bit flip, phase damping and depolarizing channels. It is shown that decoherence strongly influences the initial state entanglement. The entanglement sudden death can happens irrespective of the acceleration of the noninertial frame under the action of phase flip and phase damping channels. It is investigated that an early sudden death happens for large acceleration under the depolarizing environment. Moreover, the entanglement increases for a highly decohered phase flip channel.Comment: 11 pages, 6 eps figure

The Dynamics of International R & D spillovers

Coe and Helpman (1995) among others report positive and equivalent R&D spillovers across groups of countries. However, the nature of their econometric tests does not address the heterogeneity of knowledge diffusion across countries. We empirically examine these issues in a sample of 10 OECD countries by extending both the time span and the coverage of R&D activities in the data set. We find that the elasticity of total factor productivity with respect to domestic and foreign R&D stocks is extremely heterogeneous across countries and that data cannot be pooled. Thus, panel estimates conceal important cross-country differences. The US appears to be a net loser in terms of international R&D spillovers. Our interpretation is that when competitors ‘catch-up’ technologically, they challenge US market shares and investments worldwide. This has implications for US productivity

Are international R&D spillovers costly for the US?

Coe and Helpman (1995) and others report positive and equivalent R&D spillovers across G7 countries. We argue that their homogeneity constraint on spillovers across G7 countries is inappropriate, and show that it is rejected by the data. Extending the data set and applying new empirical approaches, we find: (i) R&D spillovers are extremely heterogeneous across G7 countries; (ii) panel estimates do not correspond to country specific estimates and conceal important cross-country differences in knowledge diffusion; and (iii) the US is a net loser in terms of international R&D spillovers. Our interpretation is that when competitors ‘catch-up’ technologically, they challenge US market shares and investments worldwide and this has implications for US productivity