The Johnson Space Center Experimental Impact Lab: Contributions Toward Understanding the Evolution of the Solar System

Impact is the most common and only weathering phenomenon affecting all the planetary bodies (e.g., planets, satellites, asteroids, comets, etc.) in the solar system. NASA Johnson Space Center s Experimental Impact Laboratory (EIL) includes three accelerators that are used in support of research into the effects of impact on the formation and evolution of the solar system. They permit researchers to study a wide variety of phenomena associated with high-velocity impacts into a wide range of geologic targets and materials relevant to astrobiological studies. By studying these processes, researchers can investigate the histories and evolution of planetary bodies and the solar system as a whole. While the majority of research conducted in the EIL addresses questions involving planetary impacts, work involving spacecraft components has been performed on occasion. An example of this is the aerogel collector material flown on the Stardust spacecraft that traveled to Comet Wild-2. This capture medium was tested and flight qualified using the 5 mm Light-Gas Gun located in the EIL

Divergence-free Nonrenormalizable Models

A natural procedure is introduced to replace the traditional, perturbatively generated counter terms to yield a formulation of covariant, self-interacting, nonrenormalizable scalar quantum field theories that has the added virtue of exhibiting a divergence-free perturbation analysis. To achieve this desirable goal it is necessary to reexamine the meaning of the free theory about which such a perturbation takes place.Comment: 22 pages. Version accepted for publication; involves modest addition to the end of Sec.

Crystal structure of chlorido-methanol-(N-(2-(oxy)-3-methoxybenzylidene)pyridine-4-carbohydrazonato-κ3O,N,O′)-(4-methylphenyl)methyl-tin(IV), C23H24ClN3O4Sn

C23H24ClN3O4Sn, triclinic, P¯1 (no. 2), a=9.7536(2) Å, b=10.0755(2) Å, c=12.4215(3) Å, α=84.928(2)°, β=72.544(2)°, γ=74.382(2)°, V =1121.44(4) Å3, Z =2, Rgt(F)=0.021, wRref(F2)=0.054, T =100(2) K

Dynamical Symmetry Breaking in Planar QED

We investigate (2+1)-dimensional QED coupled with Dirac fermions both at zero and finite temperature. We discuss in details two-components (P-odd) and four-components (P-even) fermion fields. We focus on P-odd and P-even Dirac fermions in presence of an external constant magnetic field. In the spontaneous generation of the magnetic condensate survives even at infinite temperature. We also discuss the spontaneous generation of fermion mass in presence of an external magnetic field.Comment: 34 pages, 8 postscript figures, final version to appear on J. Phys.

Diffeomorphism on Horizon as an Asymptotic Isometry of Schwarzschild Black Hole

It is argued that the diffeomorphism on the horizontal sphere can be regarded as a nontrivial asymptotic isometry of the Schwarzschild black hole. We propose a new boundary condition of asymptotic metrics near the horizon and show that the condition admits the local time-shift and diffeomorphism on the horizon as the asymptotic symmetry.Comment: 18 pages, no figures, corrected some typo

Crystal structure of bis(μ2-di-n-butyldithiocarbamato-κ3S,S′:S;κ3S:S:S′)-hexacarbonyl-di-rhenium(I), C24H36N2O6Re2

C24H36N2O6Re2, triclinic, P¯1 (no. 2), a=10.3013(2) Å, b=11.3471(2) Å, c=14.5967(3) Å, α=72.540(2)°, β=73.074(2)°, γ=85.369(2)°, V =1557.05(6) Å3, Z =2, Rgt(F)=0.0214, wRref(F2)=0.0466, T =100(2) K

Non-spiky density of states of an icosahedral quasicrystal

The density of states of the ideal three-dimensional Penrose tiling, a quasicrystalline model, is calculated with a resolution of 10 meV. It is not spiky. This falsifies theoretical predictions so far, that spikes of width 10-20 meV are generic for the density of states of quasicrystals, and it confirms recent experimental findings. The qualitative difference between our results and previous calculations is partly explained by the small number of k points that has usually been included in the evaluation of the density of states of periodic approximants of quasicrystals. It is also shown that both the density of states of a small approximant of the three-dimensional Penrose tiling and the density of states of the ideal two-dimensional Penrose tiling do have spiky features, which also partly explains earlier predictions.Comment: 8 pages, 4 figures. Changes in this version: longer introduction, details of figures shown in inset

Spin Polarizabilities of the Nucleon from Polarized Low Energy Compton Scattering

As guideline for forthcoming experiments, we present predictions from Chiral Effective Field Theory for polarized cross sections in low energy Compton scattering for photon energies below 170 MeV, both on the proton and on the neutron. Special interest is put on the role of the nucleon spin polarizabilities which can be examined especially well in polarized Compton scattering. We present a model-independent way to extract their energy dependence and static values from experiment, interpreting our findings also in terms of the low energy effective degrees of freedom inside the nucleon: The polarizabilities are dominated by chiral dynamics from the pion cloud, except for resonant multipoles, where contributions of the Delta(1232) resonance turn out to be crucial. We therefore include it as an explicit degree of freedom. We also identify some experimental settings which are particularly sensitive to the spin polarizabilities.Comment: 30 pages, 19 figure

On the gravitational field of static and stationary axial symmetric bodies with multi-polar structure

We give a physical interpretation to the multi-polar Erez-Rozen-Quevedo solution of the Einstein Equations in terms of bars. We find that each multi-pole correspond to the Newtonian potential of a bar with linear density proportional to a Legendre Polynomial. We use this fact to find an integral representation of the $\gamma$ function. These integral representations are used in the context of the inverse scattering method to find solutions associated to one or more rotating bodies each one with their own multi-polar structure.Comment: To be published in Classical and Quantum Gravit

Numerical study of a non-equilibrium interface model

We have carried out extensive computer simulations of one-dimensional models related to the low noise (solid-on-solid) non-equilibrium interface of a two dimensional anchored Toom model with unbiased and biased noise. For the unbiased case the computed fluctuations of the interface in this limit provide new numerical evidence for the logarithmic correction to the subnormal L^(1/2) variance which was predicted by the dynamic renormalization group calculations on the modified Edwards-Wilkinson equation. In the biased case the simulations are in close quantitative agreement with the predictions of the Collective Variable Approximation (CVA), which gives the same L^(2/3) behavior of the variance as the KPZ equation.Comment: 15 pages revtex, 4 Postscript Figure