CONAN -- the cruncher of local exchange coefficients for strongly interacting confined systems in one dimension

We consider a one-dimensional system of particles with strong zero-range interactions. This system can be mapped onto a spin chain of the Heisenberg type with exchange coefficients that depend on the external trap. In this paper, we present an algorithm that can be used to compute these exchange coefficients. We introduce an open source code CONAN (Coefficients of One-dimensional N-Atom Networks) which is based on this algorithm. CONAN works with arbitrary external potentials and we have tested its reliability for system sizes up to around 35 particles. As illustrative examples, we consider a harmonic trap and a box trap with a superimposed asymmetric tilted potential. For these examples, the computation time typically scales with the number of particles as $O(N^{3.5 \pm 0.4})$. Computation times are around 10 seconds for $N=10$ particles and less than 10 minutes for $N=20$ particles.Comment: 16 pages, 3 figures, 4 technical appendices, revised version with updated examples and appendices. Source code and compiled versions of CONAN can be found at http://phys.au.dk/forskning/forskningsomraader/amo/few-body-physics-in-a-many-body-world/cona

An assessment framework for REDD+ benefit sharing mechanisms within a forest policy mix

Policy instruments for implementing the Reducing Emissions from Deforestation and Forest Degradation and the enhancement of forest carbon stocks (REDD+) mechanism operate within an orchestra of national contexts and policy mixes that affect the forest and other land sectors. How will policymakers choose between the myriad of options for distributing REDD+ benefits, and be able to evaluate its potential effectiveness, efficiency and equity (3Es) within the various institutional and governance structures a where such a REDD+ benefit sharing mechanism is situated? This is a pressing issue given the results- based aspect of REDD+. We present here a three-element assessment framework for evaluating outcomes and performance of REDD+ benefit sharing mechanisms, using the criteria of effectiveness, efficiency and equity: (1) the structures (objective and policies) of a REDD+ benefit sharing mechanism; (2) the broader institutional and policy contexts underlying forest governance; and (3) outcomes of REDD+ including emissions reductions, ecosystem service provision and poverty alleviation. A strength of the assessment framework is its flexible design to incorporate indicators relevant to different contexts; this helps to generate a shared working understanding of what is to be evaluated in the different REDD+ benefit sharing mechanisms (BSMs) across complex socio- political contexts. In applying the framework to case studies, the assessment highlights trade-offs among the 3Es, and the need to better manage access to information, monitoring and evaluation, consideration of local perceptions of equity and inclusive decision-making processes. The framework aims not to simplify complexity but rather, serves to identify actionable ways forward towards a more efficient, effective and equitable implementation and re- evaluation of REDD+ BSMs as part of reflexive policymaking

Annihilation of Charged Particles

The kinetics of irreversible annihilation of charged particles performing overdamped motion induced by long-range interaction force, $F(r)\sim r^{-\lambda}$, is investigated. The system exhibits rich kinetic behaviors depending on the force exponent $\lambda$. In one dimension we find that the densities decay as $t^{-1/(2+\lambda)}$ and $t^{-1/(1+2\lambda)}$ when $\lambda>1$ and $1/2<\lambda<1$, respectively, with logarithmic correction at $\lambda=1$. For $\lambda \leq 1/2$, the asymptotic behavior is shown to be dependent on system size.Comment: 17 pages, plain TeX, 3 figures available upon request from [email protected]

Green tea extract only affects markers of oxidative status postprandially: lasting antioxidant effect of flavonoid-free diet

Epidemiological studies suggest that foods rich in flavonoids might reduce the risk of cardiovascular disease and cancer. The objective of the present study was to investigate the effect of green tea extract (GTE) used as a food antioxidant on markers of oxidative status after dietary depletion of flavonoids and catechins. The study was designed as a 2×3 weeks blinded human cross-over intervention study (eight smokers, eight non-smokers) with GTE corresponding to a daily intake of 18·6 mg catechins/d. The GTE was incorporated into meat patties and consumed with a strictly controlled diet otherwise low in flavonoids. GTE intervention increased plasma antioxidant capacity from 1·35 to 1·56 (P<0·02) in postprandially collected plasma, most prominently in smokers. The intervention did not significantly affect markers in fasting blood samples, including plasma or haemoglobin protein oxidation, plasma oxidation lagtime, or activities of the erythrocyte superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase. Neither were fasting plasma triacylglycerol, cholesterol, α-tocopherol, retinol, β-carotene, or ascorbic acid affected by intervention. Urinary 8-oxo-deoxyguanosine excretion was also unaffected. Catechins from the extract were excreted into urine with a half-life of less than 2 h in accordance with the short-term effects on plasma antioxidant capacity. Since no long-term effects of GTE were observed, the study essentially served as a fruit and vegetables depletion study. The overall effect of the 10-week period without dietary fruits and vegetables was a decrease in oxidative damage to DNA, blood proteins, and plasma lipids, concomitantly with marked changes in antioxidative defenc

Emergence of Order in Textured Patterns

A characterization of textured patterns, referred to as the disorder function \bar\delta(\beta), is used to study properties of patterns generated in the Swift-Hohenberg equation (SHE). It is shown to be an intensive, configuration-independent measure. The evolution of random initial states under the SHE exhibits two stages of relaxation. The initial phase, where local striped domains emerge from a noisy background, is quantified by a power law decay \bar\delta(\beta) \sim t^{-{1/2} \beta}. Beyond a sharp transition a slower power law decay of \bar\delta(\beta), which corresponds to the coarsening of striped domains, is observed. The transition between the phases advances as the system is driven further from the onset of patterns, and suitable scaling of time and \bar\delta(\beta) leads to the collapse of distinct curves. The decay of $\bar\delta(\beta)$ during the initial phase remains unchanged when nonvariational terms are added to the underlying equations, suggesting the possibility of observing it in experimental systems. In contrast, the rate of relaxation during domain coarsening increases with the coefficient of the nonvariational term.Comment: 9 Pages, 8 Postscript Figures, 3 gif Figure

Relaxation and Coarsening Dynamics in Superconducting Arrays

We investigate the nonequilibrium coarsening dynamics in two-dimensional overdamped superconducting arrays under zero external current, where ohmic dissipation occurs on junctions between superconducting islands through uniform resistance. The nonequilibrium relaxation of the unfrustrated array and also of the fully frustrated array, quenched to low temperature ordered states or quasi-ordered ones, is dominated by characteristic features of coarsening processes via decay of point and line defects, respectively. In the case of unfrustrated arrays, it is argued that due to finiteness of the friction constant for a vortex (in the limit of large spatial extent of the vortex), the typical length scale grows as $\ell_s \sim t^{1/2}$ accompanied by the number of point vortices decaying as $N_v \sim 1/t$. This is in contrast with the case that dominant dissipation occurs between each island and the substrate, where the friction constant diverges logarithmically and the length scale exhibits diffusive growth with a logarithmic correction term. We perform extensive numerical simulations, to obtain results in reasonable agreement. In the case of fully frustrated arrays, the domain growth of Ising-like chiral order exhibits the low-temperature behavior $\ell_q \sim t^{1/z_q}$, with the growth exponent $1/z_q$ apparently showing a strong temperature dependence in the low-temperature limit.Comment: 9 pages, 5 figures, to be published in Phys. Rev.