No information flow using statistical fluctuations, and quantum cryptography

The communication protocol of Home and Whitaker [Phys. Rev. A 67, 022306 (2003)] is examined in some detail, and found to work equally well using a separable state. The protocol is in fact completely classical, based on simple post-selection of suitable experimental runs. The quantum cryptography protocol proposed in the same publication is also examined, and is found to indeed need quantum properties for the system to be secure. However, the security test proposed in the mentioned paper is found to be insufficient, and a modification is proposed here that will ensure security.Comment: revtex4, 9 page

P is not equal to NP

SAT is not in P, is true and provable in a simply consistent extension B' of a first order theory B of computing, with a single finite axiom characterizing a universal Turing machine. Therefore, P is not equal to NP, is true and provable in a simply consistent extension B" of B.Comment: In the 2nd printing the proof, in the 1st printing, of theorem 1 is divided into three parts a new lemma 4, a new corollary 8, and the remaining part of the original proof. The 2nd printing contains some simplifications, more explanations, but no error has been correcte

A Kochen-Specker inequality

By probabilistic means, the concept of contextuality is extended so that it can be used in non-ideal situations. An inequality is presented, which at least in principle enables a test to discard non-contextual hidden-variable models at low error rates, in the spirit of the Kochen-Specker theorem. Assuming that the errors are independent, an explicit error bound of 1.42% is derived, below which a Kochen-Specker contradiction occurs.Comment: revtex, 5 pages, 1 figure. v2: journal version (results extended somewhat), epl LaTeX class, 8 pages, 1 figur

Exciton coupling in molecular crystals

The implications of perfect exciton coupling and molecular vibrations were investigated, as well as the effect they have on the lifetime of singlet and triplet excitons coupled in a limiting geometry. Crystalline bibenzyl, Cl4Hl4, provided a situation in which these mechanisms involving exciton coupling can be studied in the limit of perfect coupling between units due to the crystal's geometry. This geometry leads to a coupling between the two halves of the molecule resulting in a splitting of the molecular excited states. The study reported involves an experimental spectroscopic approach and begins with the purification of the bibenzyl. The principal experimental apparatus was an emission spectrometer. A closed cycle cryogenic system was used to vary the temperature of the sample between 20 K and 300 K. The desired results are the temperature-dependent emission spectra of the bibenzyl; in addition, the lifetimes and quantum yields measured at each temperature reveal the effect of competing radiationless processes

Computational solution of chemistry problems

AB initio quantum chemical techniques have been used to investigate weakly bound complexes of H2O and SO2. An energy gradient program was used to locate stable structures for the H2O, SO2 complexes, and SCF calculations were carried out to determine the binding energies of complexes with multiple water molecules. A 4-31G basis set was used for most potential energy searches. More accurate basis sets including a generally contracted basis set with d orbitals on the sulfur were used for geometry and binding energy verification. For single water complexes, five different stable geometries were located with binding energies between 4 and 11 Kcal mol(-1), suggesting a binding shell for H2O around SO2 and a mechanism for the formation of an SO2-containing water droplet. Calculations on one of the complexes utilizing a larger double zeta basis and d functions on the sulfur atom lead to adjusted binding energies in the range 3 to 8 Kcal mol(-1). Very little charge transfer between SO2 and H2O was present. Addition of more than one H2O was found to be energetically favorable although the addition of the fourth water in certain geometries did not increase the stability of the complex. An alternative mechanism for the tropospheric gas phase production of acid rain is suggested

IUE observations of the 1982-84 eclipse of Epsilon Aurigae

The major characteristics in the ultraviolet of the 1982-84 eclipse of Eps Aur as observed with IUE by various workers are summarized. This star can be observed over the entire IUE wavelength range, from 1200 to 3200 A, in low dispersion, allowing eclipse light curves to be obtained in broadband regions, but due to its steep spectral gradient and the sensitivities of IUE cameras, high resolution exposures adequately cover only the regions from 1700-1900 and 2400-3200 A. In many ways, the UV data confirms or expands upon interpretations of the stem made from observations in other wavelength regions, but in other respects the system remains as enigmatic as before

The Danish Model and the Globalizing Learning Economy: Lessons for Developing Countries

Although Denmark shares with the other four Nordic countries certain attributes, such as pragmatic protestant religion, small and homogenous population, strong social democratic parties and ambitious welfare states, it also has its own characteristics. High degree of specialization in the so-called low-tech sectors, combined with high mobility and income security in labour markets (flexicurity), contributes to making the Danish system unique in the world. Denmark has experienced some stagnation in its growth over the last decade but still ranks among the top ten in the world in terms of GNP per capita, registered unemployment is less than 2 per cent (as of June 2008) while the inflation rate has remained moderate. These goals for economic policy have been realized in an environment with a high degree of income equality. In this paper we use the concepts .innovation system., .the learning economy. and .learning modes. to analyse the evolution of the Danish model and what can be learnt from it.economic development, welfare state, social cohesion, innovation