Euler Incognito

The nonlinear flow equations discussed recently by Bender and Feinberg are all reduced to the well-known Euler equation after change of variables.Comment: 2 page

Characterization of radially symmetric finite time blowup in multidimensional aggregation equations,

This paper studies the transport of a mass $\mu$ in $\real^d, d \geq 2,$ by a flow field $v= -\nabla K*\mu$. We focus on kernels $K=|x|^\alpha/ \alpha$ for $2-d\leq \alpha<2$ for which the smooth densities are known to develop singularities in finite time. For this range This paper studies the transport of a mass $\mu$ in $\real^d, d \geq 2,$ by a flow field $v= -\nabla K*\mu$. We focus on kernels $K=|x|^\alpha/ \alpha$ for $2-d\leq \alpha<2$ for which the smooth densities are known to develop singularities in finite time. For this range we prove the existence for all time of radially symmetric measure solutions that are monotone decreasing as a function of the radius, thus allowing for continuation of the solution past the blowup time. The monotone constraint on the data is consistent with the typical blowup profiles observed in recent numerical studies of these singularities. We prove monotonicity is preserved for all time, even after blowup, in contrast to the case $\alpha >2$ where radially symmetric solutions are known to lose monotonicity. In the case of the Newtonian potential ($\alpha=2-d$), under the assumption of radial symmetry the equation can be transformed into the inviscid Burgers equation on a half line. This enables us to prove preservation of monotonicity using the classical theory of conservation laws. In the case $2 -d < \alpha < 2$ and at the critical exponent $p$ we exhibit initial data in $L^p$ for which the solution immediately develops a Dirac mass singularity. This extends recent work on the local ill-posedness of solutions at the critical exponent.Comment: 30 page

Reciprocal Trade Agreements: Impacts on Bilateral Trade Expansion and Contraction in the World Agricultural Marketplace

The rapid increase in the number of bilateral and regional free-trade agreements since 1995 is a striking development. The proliferation of these agreements has raised questions about whether they have, in fact, opened markets, created trade, promoted economic growth, and/or distorted trade. This study uses panel data from 1975 to 2005 and a gravity framework model to identify the influence of reciprocal trade agreements (RTAs) on bilateral trade in the world agricultural marketplace. A benchmark, Heckman sample-selection and two generalized models, one of which accounts for RTA phase-in effects, are used to gauge the impact on partner trade of mutual as well as asymmetric RTA membership. Empirical results show that RTAs increase agricultural trade between member countries but decrease trade between member and nonmember countries. Interestingly, RTAs were found to be particularly effective at expanding agricultural trade and opening markets in developing countries when developing- country trading partners are part of the same agreement.trade policy, reciprocal trade agreements, bilateral, regional, missing trade, gravity models, Agricultural and Food Policy, International Development, International Relations/Trade,

Economic costs and payoffs of bilateral/regional trade agreements

The rapid increase in the number of bilateral and regional free-trade agreements since 1995 is a striking development. The proliferation of these agreements has raised questions among academicians and policymakers about whether they have, in fact, opened markets, created trade, promoted economic growth, and/or distorted trade. This study uses panel data from the 1975-2005 period and the gravity framework to identify the influence of bilateral/regional free-trade agreements on bilateral trade in merchandise, agriculture, and clothing sectors. A benchmark, Heckman sample-selection, and two generalized models, one of which accounts for reciprocal-free-trade-agreement phase-in effects, are used to gauge the impact on partner trade of mutual as well as asymmetric RTA membership.trade policy, bilateral, regional, missing trade, gravity models, reciprocal trade agreements, Agricultural and Food Policy,

Reflectance spectra of mafic silicates and phyllosilicates from .6 to 4.6 microns

The results of spectral measurements for mafic silicates are given. The study provided valuable spectral reflectance information about mafic silicates and phyllosilicates in the 2.5 to 4.6 micron wavelength region. It was shown that the reflectance of these materials is strongly affected by the presence of H2O and OH. Therefore, the identification of these absorbing species is greatly enhanced

Estimating the weak-lensing rotation signal in radio cosmic shear surveys

Weak lensing has become an increasingly important tool in cosmology and the use of galaxy shapes to measure cosmic shear has become routine. The weak-lensing distortion tensor contains two other effects in addition to the two components of shear: the convergence and rotation. The rotation mode is not measurable using the standard cosmic shear estimators based on galaxy shapes, as there is no information on the original shapes of the images before they were lensed. Due to this, no estimator has been proposed for the rotation mode in cosmological weak-lensing surveys, and the rotation mode has never been constrained. Here, we derive an estimator for this quantity, which is based on the use of radio polarisation measurements of the intrinsic position angles of galaxies. The rotation mode can be sourced by physics beyond $\Lambda$CDM, and also offers the chance to perform consistency checks of $\Lambda$CDM and of weak-lensing surveys themselves. We present simulations of this estimator and show that, for the pedagogical example of cosmic string spectra, this estimator could detect a signal that is consistent with the constraints from Planck. We examine the connection between the rotation mode and the shear $B$-modes and thus how this estimator could help control systematics in future radio weak-lensing surveys

Lidar measurements of thermal structure

Rayleigh backscatter observations at 532 nm and 355 nm of relative atmospheric density above Aberystwyth on a total of 93 nights between Dec. 1982 and Feb. 1985 were used to derive the height variation of temperature in the upper stratosphere and mesosphere. Preliminary results for height up to about 25 km were also obtained from observations of Raman backscattering from nitrogen molecules. Comparisons were carried out for stratospheric heights with satellite borne measurements; good agreement was found between equivalent black body temperatures derived from the lidar observations and those obtained from nadir measurements in three channels of the stratosphere sounder units on NOAA satellites; the lidar based atmospheric temperatures have shown general agreement with but a greater degree of structure than the limb sounding measurements obtained using the SAMS experiment on the NOAA-7 satellite. In summer, stratospheric and mesospheric temperatures showed a smooth height variation similar to that of the CIRA model atmosphere. In contrast, the winter data showed a great variability with height, and marked temperature changes both from night to night and within a given night

Lattice Study of Anisotropic QED-3

We present results from a Monte Carlo simulation of non-compact lattice QED in 3 dimensions on a $16^3$ lattice in which an explicit anisotropy between $x$ and $y$ hopping terms has been introduced into the action. This formulation is inspired by recent formulations of anisotropic QED$_3$ as an effective theory of the non-superconducting portion of the cuprate phase diagram, with relativistic fermion degrees of freedom defined near the nodes of the gap function on the Fermi surface, and massless photon degrees of freedom reproducing the dynamics of the phase disorder of the superconducting order parameter. Using a parameter set corresponding to broken chiral symmetry in the isotropic limit, our results show that the renormalised anisotropy, defined in terms of the ratio of correlation lengths of gauge invariant bound states in the $x$ and $y$ directions, exceeds the explicit anisotropy $\kappa$ introduced in the lattice action, implying in contrast to recent analytic results that anisotropy is a relevant deformation of QED$_3$. There also appears to be a chiral symmetry restoring phase transition at $\kappa_c\simeq4.5$, implying that the pseudogap phase persists down to T=0 in the cuprate phase diagram.Comment: 24 pages, 9 figures, 3 tables. This (the published version) has the following alterations: i) An expanded discussion of the empirical aspects of HT superconductivity, ii) An updated version of Figure 4, iii) The removal of the consistency check in section 3.3.1 for reasons of brevit