70,772 research outputs found
Classical and quantum satisfiability
We present the linear algebraic definition of QSAT and propose a direct
logical characterization of such a definition. We then prove that this logical
version of QSAT is not an extension of classical satisfiability problem (SAT).
This shows that QSAT does not allow a direct comparison between the complexity
classes NP and QMA, for which SAT and QSAT are respectively complete.Comment: In Proceedings LSFA 2011, arXiv:1203.542
Phononless thermally activated transport through a disordered array of quantum wires
Phononless plasmon assisted transport through a long disordered array of
finite length quantum wires is investigated analytically. Two temperature
regimes, the low- and the high-temperature ones, with qualitatively different
temperature dependencies of thermally activated resistance are identified. The
characteristics of plasmon assisted and phonon assisted transport mechanisms
are compared. Generically strong electron-electron interaction in quantum wires
results in a qualitative change of the temperature dependence of thermally
activated resistance in comparison to phonon assisted transport. At high
temperatures, the thermally activated resistance is determined by the Luttinger
liquid interaction parameter of the wires.Comment: 15 pages, 1 figur
Soil microbial biomass in organic farming system.
Agricultural production systems have to combine management practices in order to sustain soil's profitability and quality. Organic farming is gaining worldwide acceptance and has been expanding at an annual rate of 20% in the last decade, accounting for over 24 million hectares worldwide. Organic practices avoid applications of synthetic fertilizers and pesticides, rely on organic inputs and recycling for nutrient supply, and emphasize cropping system design and biological processes for pest management, as defined by organic farming regulation in the world. In comparison with conventional farming, organic farming has potential benefits in improving food quality and safety. Plant production in organic farming mainly depends on nutrient release as a function of mineralization processes in soils. The build-up of a large and active soil microbial biomass is important pool of accessible nutrients, therefore, is an important priority in organic farming. In organic farming, there is positive effect of quantity and quality of inputs of organic residues on soil microbial biomass. In this way, the organic systems are extremely important for the increase of the soil fertility and the maintenance of the environmental sustainability
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