Owners of developed land versus owners of undeveloped land: why land use is more constrained in the Bay Area than in Pittsburgh

We model residential land use constraints as the outcome of a political economy game between owners of developed and owners of undeveloped land. Land use constraints are interpreted as shadow taxes that increase the land rent of already developed plots and reduce the amount of new housing developments. In general equilibrium, locations with nicer amenities are more developed and, as a consequence, more regulated. We test our model predictions by geographically matching amenity, land use, and historical Census data to metropolitan area level survey data on regulatory restrictiveness. Following the predictions of the model, we use amenities as instrumental variables and demonstrate that metropolitan areas with better amenities are more developed and more tightly regulated than other areas. Consistent with theory, metropolitan areas that are more regulated also grow more slowly

Discrete modelling of capillary mechanisms in multi-phase granular media

A numerical study of multi-phase granular materials based upon micro-mechanical modelling is proposed. Discrete element simulations are used to investigate capillary induced effects on the friction properties of a granular assembly in the pendular regime. Capillary forces are described at the local scale through the Young-Laplace equation and are superimposed to the standard dry particle interaction usually well simulated through an elastic-plastic relationship. Both effects of the pressure difference between liquid and gas phases and of the surface tension at the interface are integrated into the interaction model. Hydraulic hysteresis is accounted for based on the possible mechanism of formation and breakage of capillary menisci at contacts. In order to upscale the interparticular model, triaxial loading paths are simulated on a granular assembly and the results interpreted through the Mohr-Coulomb criterion. The micro-mechanical approach is validated with a capillary cohesion induced at the macroscopic scale. It is shown that interparticular menisci contribute to the soil resistance by increasing normal forces at contacts. In addition, more than the capillary pressure level or the degree of saturation, our findings highlight the importance of the density number of liquid bonds on the overall behaviour of the material

On the Origins of Land Use Regulations: Theory and Evidence from US Metro Areas

We model residential land use constraints as the outcome of a political economy game between owners of developed and owners of undeveloped land. Land use constraints benefit the former group (via increasing property prices) but hurt the latter (via increasing development costs). More desirable locations are more developed and, as a consequence of political economy forces, more regulated. Using an IV approach that directly follows from our model we find strong and robust support for our predictions. The data provide weak or no support for alternative hypotheses whereby regulations reflect the wishes of the majority of households or efficiency motives.Land use regulations, zoning, land ownership, housing supply

A new magnetic field dependence of Landau levels on a graphene like structure

We consider a tight-binding model on the honeycomb lattice in a magnetic field. For special values of the hopping integrals, the dispersion relation is linear in one direction and quadratic in the other. We find that, in this case, the energy of the Landau levels varies with the field B as E_n(B) ~ [(n+\gamma)B]^{2/3}. This result is obtained from the low-field study of the tight-binding spectrum on the honeycomb lattice in a magnetic field (Hofstadter spectrum) as well as from a calculation in the continuum approximation at low field. The latter links the new spectrum to the one of a modified quartic oscillator. The obtained value $\gamma=1/2$ is found to result from the cancellation of a Berry phase.Comment: 4 pages, 4 figure

Characterization of high-current pulsed arcs ranging from 100--250 kA peak

In this paper, we present the laboratory study on three experimental setups that produce a free arc channel subjected to the transient phase of a lightning current waveform. This work extends the high-current pulsed arc characterization performed in previous studies for peak levels up to 100 kA. Eleven high-current waveforms with peak value ranging from 100--250 kA with different growth rates and action integrals are studied, allowing the comparison of different test benches. These waveforms correspond to standard lightning ones used in aircraft certification processes. Hydrodynamic properties such as arc channel evolution and shock-wave propagation are determined by high-speed video imaging and the background-oriented Schlieren method. The arc diameter reaches around 90mm at 50 $\mu$s for a current of 250 kA peak. Space- and time-resolved measurements of temperature, electron density and pressure are assessed by optical emission spectroscopy associated with the radiative transfer equation. It is solved across the arc column and takes into account the assumption of non-optically thin plasma at local thermodynamic equilibrium. For a 250 kA waveform, temperatures up to 43000K are found, with pressures in the order of 50 bar. The influence of current waveform parameters on the arc properties are analyzed and discussed

Lifshitz tails for alloy type models in a constant magnetic field

In this note, we study Lifshitz tails for a 2D Landau Hamiltonian perturbed by a random alloy-type potential constructed with single site potentials decaying at least at a Gaussian speed. We prove that, if the Landau level stays preserved as a band edge for the perturbed Hamiltonian, at the Landau levels, the integrated density of states has a Lifshitz behavior of the type $e^{-\log^2|E-2bq|}$

p-Wave Polaron

We consider the properties of a single impurity immersed in a Fermi sea close to an interspecies p-wave Feshbach resonance. We calculate its dispersion and spectral response to a radiofrequency pulse. In the presence of a magnetic field, dipolar interactions split the resonance and lead to the appearance of two novel features with respect to the s-wave case: a third polaron branch in the excitation spectrum, in addition to the usual attractive and repulsive ones; and an anisotropic dispersion of the impurity characterized by different effective masses perpendicular and parallel to the magnetic field. The anisotropy can be tuned as a function of the field strength and the two effective masses may have opposite signs, or become smaller than the bare mass

Modélisation 3D d'un composite UD par la Méthode des Eléments Discrets

Dans ces travaux, la Méthode des Eléments Discrets (MED) est mise à profit pour la modélisation 3D d'un matériau composite unidirectionnel. %L'intérêt d'introduire les Eléments Discrets (ED) à l'échelle des constituants (fibre et matrice) est de pouvoir, à terme, rendre compte de mécanismes de dégradation locaux (micro-fissuration matricielle, décohésion fibre/matrice, rupture de fibre) propres à ce type de matériau. L'objectif à court terme est d'utiliser cette méthode pour traiter localement les endommagements induits par un choc tout en l'associant, au delà de la zone endommagée à une modélisation plus conventionnelle de type Eléments Finis (EF) [1]. Les modélisations géométriques de la fibre et de la matrice sont d'abord présentées. La phase de calibration des paramètres intrinsèques du modèle par ED régissant le comportement matériel des milieux fibre et matrice d'une part, et de l'interface fibre/matrice d'autre part, est ensuite détaillée. Le comportement de chaque constituant est à ce stade supposé élastique fragile. Une analyse, à la fois qualitative et quantitative, est finalement réalisée sur les cas tests de traction longitudinale et transverse, et de cisaillement dans le plan des fibres et hors plan, pour une cellule élémentaire représentative. Les résultats sont comparés à ceux connus de la littérature [2].Dans ces travaux, la Méthode des Eléments Discrets (MED) est mise à profit pour la modélisation 3D d'un matériau composite unidirectionnel. %L'intérêt d'introduire les Eléments Discrets (ED) à l'échelle des constituants (fibre et matrice) est de pouvoir, à terme, rendre compte de mécanismes de dégradation locaux (micro-fissuration matricielle, décohésion fibre/matrice, rupture de fibre) propres à ce type de matériau. L'objectif à court terme est d'utiliser cette méthode pour traiter localement les endommagements induits par un choc tout en l'associant, au delà de la zone endommagée à une modélisation plus conventionnelle de type Eléments Finis (EF) [1]. Les modélisations géométriques de la fibre et de la matrice sont d'abord présentées. La phase de calibration des paramètres intrinsèques du modèle par ED régissant le comportement matériel des milieux fibre et matrice d'une part, et de l'interface fibre/matrice d'autre part, est ensuite détaillée. Le comportement de chaque constituant est à ce stade supposé élastique fragile. Une analyse, à la fois qualitative et quantitative, est finalement réalisée sur les cas tests de traction longitudinale et transverse, et de cisaillement dans le plan des fibres et hors plan, pour une cellule élémentaire représentative. Les résultats sont comparés à ceux connus de la littérature [2]