Uniaxial and biaxial soft deformations of nematic elastomers

We give a geometric interpretation of the soft elastic deformation modes of nematic elastomers, with explicit examples, for both uniaxial and biaxial nematic order. We show the importance of body rotations in this non-classical elasticity and how the invariance under rotations of the reference and target states gives soft elasticity (the Golubovic and Lubensky theorem). The role of rotations makes the Polar Decomposition Theorem vital for decomposing general deformations into body rotations and symmetric strains. The role of the square roots of tensors is discussed in this context and that of finding explicit forms for soft deformations (the approach of Olmsted).Comment: 10 pages, 10 figures, RevTex, AmsTe

Development of a machine protection system for the Superconducting Beam Test Facility at Fermilab

Fermilab's Superconducting RF Beam Test Facility currently under construction will produce electron beams capable of damaging the acceleration structures and the beam line vacuum chambers in the event of an aberrant accelerator pulse. The accelerator is being designed with the capability to operate with up to 3000 bunches per macro-pulse, 5Hz repetition rate and 1.5 GeV beam energy. It will be able to sustain an average beam power of 72 KW at the bunch charge of 3.2 nC. Operation at full intensity will deposit enough energy in niobium material to approach the melting point of 2500 {\deg}C. In the early phase with only 3 cryomodules installed the facility will be capable of generating electron beam energies of 810 MeV and an average beam power that approaches 40 KW. In either case a robust Machine Protection System (MPS) is required to mitigate effects due to such large damage potentials. This paper will describe the MPS system being developed, the system requirements and the controls issues under consideration.Comment: 3 pp. 13th International Conference on Accelerator and Large Experimental Physics Control Systems (ICALEPCS 2011). 10-14 Oct 2011. Grenoble, Franc

Nova Scorpii 1941 (V697 Sco): A Probable Intermediate Polar

V697 Sco, the remnant of Nova Scorpii 1941 and currently at V ~ 20.0, is found from photometric observations to have the characteristics of an intermediate polar (IP) with an orbital period (Porb) of 4.49 h and a rotation period (Prot) of 3.31 h. It therefore appears to be a member of the rare class of IPs where Prot ~ Porb, which are probably discless systems. The prominence of the modulation at 0.5 Prot, and its orbital sidebands, indicates two-pole accretion.Comment: To appear in the November 2002 issue of PAS

KUV 01584-0939: A Helium-transferring Cataclysmic Variable with an Orbital Period of 10 Minutes

High speed photometry of KUV 01584-0939 (alias Cet3) shows that is has a period of 620.26 s. Combined with its hydrogen-deficient spectrum, this implies that it is an AM CVn star. The optical modulation is probably a superhump, in which case the orbital period will be slightly shorter than what we have observed.Comment: Published by PASP. See also the latest Early-Release Research Paper website of the PAS

Finite element solution of low bond number sloshing

The dynamics of liquid propellant in a low Bond number environment which are critical to the design of spacecraft systems with respect to orbital propellant transfer and attitude control system were investigated. Digital computer programs were developed for the determination of liquid free surface equilibrium shape, lateral slosh natural vibration mode shapes, and frequencies for a liquid in a container of arbitrary axisymmetric shape with surface tension forces the same order of magnitude as acceleration forces. A finite volume element representation of the liquid was used for the vibration analysis. The liquid free surface equilibrium shapes were computed for several tanks at various contact angles and ullage volumes. A configuration was selected for vibration analysis and lateral slosh mode shapes and natural frequencies were obtained. Results are documented

The Hilbert Action in Regge Calculus

The Hilbert action is derived for a simplicial geometry. I recover the usual Regge calculus action by way of a decomposition of the simplicial geometry into 4-dimensional cells defined by the simplicial (Delaunay) lattice as well as its dual (Voronoi) lattice. Within the simplicial geometry, the Riemann scalar curvature, the proper 4-volume, and hence, the Regge action is shown to be exact, in the sense that the definition of the action does not require one to introduce an averaging procedure, or a sequence of continuum metrics which were common in all previous derivations. It appears that the unity of these two dual lattice geometries is a salient feature of Regge calculus.Comment: 6 pages, Plain TeX, no figure