Relativistic Positioning Systems: The Emission Coordinates

This paper introduces some general properties of the gravitational metric and the natural basis of vectors and covectors in 4-dimensional emission coordinates. Emission coordinates are a class of space-time coordinates defined and generated by 4 emitters (satellites) broadcasting their proper time by means of electromagnetic signals. They are a constitutive ingredient of the simplest conceivable relativistic positioning systems. Their study is aimed to develop a theory of these positioning systems, based on the framework and concepts of general relativity, as opposed to introducing `relativistic effects' in a classical framework. In particular, we characterize the causal character of the coordinate vectors, covectors and 2-planes, which are of an unusual type. We obtain the inequality conditions for the contravariant metric to be Lorentzian, and the non-trivial and unexpected identities satisfied by the angles formed by each pair of natural vectors. We also prove that the metric can be naturally split in such a way that there appear 2 parameters (scalar functions) dependent exclusively on the trajectory of the emitters, hence independent of the time broadcast, and 4 parameters, one for each emitter, scaling linearly with the time broadcast by the corresponding satellite, hence independent of the others.Comment: 13 pages, 3 figures. Only format changed for a new submission. Submitted to Class. Quantum Gra

Underlying symmetries of realistic interactions and the nuclear many-body problem

The present study brings forward important information, within the framework of spectral distribution theory, about the types of forces that dominate three realistic interactions, CD-Bonn, CDBonn+ 3terms and GXPF1, in nuclei and their ability to account for many-particle effects such as the formation of correlated nucleon pairs and enhanced quadrupole collective modes. Like-particle and proton-neutron isovector pairing correlations are described microscopically by a model interaction with Sp(4) dynamical symmetry, which is extended to include an additional quadrupole-quadrupole interaction. The analysis of the results for the 1f7/2 level shows that both CD-Bonn+3terms and GXPF1 exhibit a well-developed pairing character compared to CD-Bonn, while the latter appears to build up more (less) rotational isovector T = 1 (isoscalar T = 0) collective features. Furthermore, the three realistic interactions are in general found to correlate strongly with the pairing+quadrupole model interaction, especially for the highest possible isospin group of states where the model interaction can be used to provide a reasonable description of the corresponding energy spectra.Comment: 12 pages, 4 figure

A Gauge-fixed Hamiltonian for Lattice QCD

We study the gauge fixing of lattice QCD in 2+1 dimensions, in the Hamiltonian formulation. The technique easily generalizes to other theories and dimensions. The Hamiltonian is rewritten in terms of variables which are gauge invariant except under a single global transformation. This paper extends previous work, involving only pure gauge theories, to include matter fields.Comment: 7 pages of LaTeX, RU-92-45 and BUHEP-92-3

Coupling between membrane tilt-difference and dilation: a new ``ripple'' instability and multiple crystalline inclusions phases

A continuum Landau theory for the micro-elasticity of membranes is discussed, which incorporates a coupling between the bilayer thickness variation and the difference in the two monolayers' tilts. This coupling stabilizes a new phase with a rippled micro-structure. Interactions among membrane inclusions combine a dilation-induced attraction and a tilt-difference-induced repulsion that yield 2D crystal phases, with possible coexistence of different lattice spacings for large couplings. Inclusions favoring crystals are those with either a long-convex or a short-concave hydrophobic core.Comment: EURO LaTeX, 6 pages, 4 figures, to be published in Europhys. Let

Ray tracing program with options for diffraction gratings

Diffraction theory, developed in vectorial form and coded into ray tracing routines, permits tracing rays of any wavelength through surfaces that are plane, spherical, conical, or aspheric polynomial. Ruled diffraction gratings may run in either X-direction or Y-direction, where Z is optical axis

Transonic divider for gas chromatograph effluents

Transonic effluent divider system was developed which permits varying mass input of gas chromatographic effluent into mass spectrometer without affecting performance of gas chromatograph. Mechanisms of operation are described

Endangered Species Act Innovations in the Post-Babbittonian Era—Are There Any?

One of the mysteries of environmental policy in the Bush Administration will be how and why it squandered an opportunity to continue market-based administrative reforms of the Endangered Species Act begun, ironically, in the Clinton Administration under the direction of then Secretary of the Interior Bruce Babbitt. This article traces the momentum built for reform in the Babbittonian era and examines what has not happened since then