Crop utilization and fate of fertilizer nitrogen in soil

Non-Peer Reviewe

Competing density-wave orders in a one-dimensional hard-boson model

We describe the zero-temperature phase diagram of a model of bosons, occupying sites of a linear chain, which obey a hard-exclusion constraint: any two nearest-neighbor sites may have at most one boson. A special case of our model was recently proposed as a description of a ``tilted'' Mott insulator of atoms trapped in an optical lattice. Our quantum Hamiltonian is shown to generate the transfer matrix of Baxter's hard-square model. Aided by exact solutions of a number of special cases, and by numerical studies, we obtain a phase diagram containing states with long-range density-wave order with period 2 and period 3, and also a floating incommensurate phase. Critical theories for the various quantum phase transitions are presented. As a byproduct, we show how to compute the Luttinger parameter in integrable theories with hard-exclusion constraints.Comment: 16 page

Mean flow and spiral defect chaos in Rayleigh-Benard convection

We describe a numerical procedure to construct a modified velocity field that does not have any mean flow. Using this procedure, we present two results. Firstly, we show that, in the absence of mean flow, spiral defect chaos collapses to a stationary pattern comprising textures of stripes with angular bends. The quenched patterns are characterized by mean wavenumbers that approach those uniquely selected by focus-type singularities, which, in the absence of mean flow, lie at the zig-zag instability boundary. The quenched patterns also have larger correlation lengths and are comprised of rolls with less curvature. Secondly, we describe how mean flow can contribute to the commonly observed phenomenon of rolls terminating perpendicularly into lateral walls. We show that, in the absence of mean flow, rolls begin to terminate into lateral walls at an oblique angle. This obliqueness increases with Rayleigh number.Comment: 14 pages, 19 figure

Order Parameters of the Dilute A Models

The free energy and local height probabilities of the dilute A models with broken \Integer_2 symmetry are calculated analytically using inversion and corner transfer matrix methods. These models possess four critical branches. The first two branches provide new realisations of the unitary minimal series and the other two branches give a direct product of this series with an Ising model. We identify the integrable perturbations which move the dilute A models away from the critical limit. Generalised order parameters are defined and their critical exponents extracted. The associated conformal weights are found to occur on the diagonal of the relevant Kac table. In an appropriate regime the dilute A$_3$ model lies in the universality class of the Ising model in a magnetic field. In this case we obtain the magnetic exponent $\delta=15$ directly, without the use of scaling relations.Comment: 53 pages, LaTex, ITFA 93-1

Van Afval Af

__Abstract__ Er is in de gemeentelijke afvalwereld consensus dat de toekomst ligt in gesloten materiaalkringlopen. Ook het Verpakkingenakkoord spreekt de ambitie uit dat in de komende tien jaar een versnelling nodig is richting grootschalig hergebruik, sluiten van kringlopen en de ontwikkeling van een goed functionerende circulaire grondstoffenmarkt. Vergelijkbare ambities zijn ook door veel gemeenten individueel en de Rijksoverheid in haar ‘afval is grondstof’ beleid uitgesproken. Die gemeentelijke ambitie – en dan specifiek op het gebied van verpakkingen - is de directe aanleiding voor deze transitie-studie. Het beoogt overzicht en suggesties te bieden aan gemeenten (en andere partijen) over hun rol in de circulaire economie vanuit hun positie in de afvalketen. Veel gemeenten hebben de beleidsvoorbereiding en/of uitvoering bij samenwerkingsverbanden of overheidsgedomineerde bedrijven gelegd. In dit document bedoelen we met gemeenten, tenzij anders vermeld, dus ook de lokale overheid inclusief deze partijen. Tijdens de interviews en sessies bleken de meningen soms verdeeld of het Verpakkingenakkoord op alle punten een stap in de goede richting is. In deze studie gaan we uit er vanuit dat het nu gesloten Verpakkingenakkoord een gegeven is, maar we besteden wel aandacht aan hoe gemeenten de invulling en uitvoering van het Verpakkingenakkoord (en de organisatie van afvalbeheer in het algemeen) de komende jaren kunnen vormgeven en strategisch positie kunnen kiezen

A Point's Point of View of Stringy Geometry

The notion of a "point" is essential to describe the topology of spacetime. Despite this, a point probably does not play a particularly distinguished role in any intrinsic formulation of string theory. We discuss one way to try to determine the notion of a point from a worldsheet point of view. The derived category description of D-branes is the key tool. The case of a flop is analyzed and Pi-stability in this context is tied in to some ideas of Bridgeland. Monodromy associated to the flop is also computed via Pi-stability and shown to be consistent with previous conjectures.Comment: 15 pages, 3 figures, ref adde

Effective actions of a Gauss-Bonnet brane world with brane curvature terms

We consider a warped brane world scenario with two branes, Gauss-Bonnet gravity in the bulk, and brane localised curvature terms. When matter is present on both branes, we investigate the linear equations of motion and distinguish three regimes. At very high energy and for an observer on the positive tension brane, gravity is four dimensional and coupled to the brane bending mode in a Brans-Dicke fashion. The coupling to matter and brane bending on the negative tension brane is exponentially suppressed. In an intermediate regime, gravity appears to be five dimensional while the brane bending mode remains four dimensional. At low energy, matter on both branes couple to gravity for an observer on the positive tension brane, with a Brans-Dicke description similar to the 2--brane Randall-Sundrum setup. We also consider the zero mode truncation at low energy and show that the moduli approximation fails to reproduce the low energy action.Comment: 14 page