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Unified Einstein-Virasoro Master Equation in the General Non-Linear Sigma Model (open access)

Unified Einstein-Virasoro Master Equation in the General Non-Linear Sigma Model

The Virasoro master equation (VME) describes the general affine-Virasoro construction $T=L^abJ_aJ_b+iD^a \dif J_a$ in the operator algebra of the WZW model, where $L^ab$ is the inverse inertia tensor and $D^a $ is the improvement vector. In this paper, we generalize this construction to find the general (one-loop) Virasoro construction in the operator algebra of the general non-linear sigma model. The result is a unified Einstein-Virasoro master equation which couples the spacetime spin-two field $L^ab$ to the background fields of the sigma model. For a particular solution $L_G^ab$, the unified system reduces to the canonical stress tensors and conventional Einstein equations of the sigma model, and the system reduces to the general affine-Virasoro construction and the VME when the sigma model is taken to be the WZW action. More generally, the unified system describes a space of conformal field theories which is presumably much larger than the sum of the general affine-Virasoro construction and the sigma model with its canonical stress tensors. We also discuss a number of algebraic and geometrical properties of the system, including its relation to an unsolved problem in the theory of $G$-structures on manifolds with torsion.
Date: June 5, 1996
Creator: Boer, J. de & Halpern, M.B.
System: The UNT Digital Library
Solute nucleation and growth in supercritical fluid mixtures (open access)

Solute nucleation and growth in supercritical fluid mixtures

This research effort is directed toward two primary scientific objectives: (1) to determine the gravitational effect on the measurement of nucleation and growth rates near a critical point and (2) to investigate the A nucleation process in supercritical fluids to aid in the evaluation and development of existing rheoretical models and practical applications. A nucleation pulse method will be employed for this investigation using a rapid expansion to a supersaturated state that is maintained for {approx}1 followed by a rapid recompression to a less supersaturated state that effectively terminates nucleation while permitting growth continue. Nucleation, which occurs during the initial supersaturated state, is decoupled from growth by producing rapid pressure changes. Thermodynamic analysis, condensation modeling, apparatus design, and optical diagnostic design necessary for the initiation of a theoretical and experimental investigation of naphthalene nucleation from supercritical CO{sub 2} have been completed.
Date: June 5, 1996
Creator: Smedley, G.T.; Rawlins, W.T. & Oakes, D.B.
System: The UNT Digital Library
Diagnostic development at LLNL for the National Ignition Facility (open access)

Diagnostic development at LLNL for the National Ignition Facility

ICF implosions at the NIF will produce core plasma temperatures in excess of 10-keV and densities of order 100 g/cm{sup 3}. Properties of these plasmas can be measured using a variety of optical, x-ray and nuclear techniques similar to those now in use at facilities such as Nova and Omega. Some of these techniques will be directly applicable on NIF while others, particularly the nuclear-based techniques, will change significantly.
Date: June 5, 1996
Creator: Sangster, T. C.; Cable, M. D.; Kilkenny, J. D. & Lerche, R. A.
System: The UNT Digital Library
Nuclear diagnostics in support of ICF experiments (open access)

Nuclear diagnostics in support of ICF experiments

As the yields of Inertial Confinement Fusion (ICF) experiments increase to NIF levels new diagnostic techniques for studying details of fusion burn behavior will become feasible. The new techniques will provide improved measurements of fusion burn temperature and history. Improved temperature measurements might be achieved with magnetic spectroscopy of fusion neutrons. High-bandwidth fusion reaction history will be measured with fusion-specific {gamma}-ray diagnostics. Additional energy-resolved {gamma}-ray might be able to study a selection of specific behaviors during fusion burn. Present ICF yields greater than 10{sup 13} neutrons are sufficient to demonstrate the basic methods that underlie the new techniques. As ICF yields increase, the diagnostics designs adjusted accordingly in order to provide clear and specific data on fusion burn performance.
Date: June 5, 1996
Creator: Moran, M. J. & Hall, J.
System: The UNT Digital Library
Neutron-induced noise in NIF-class diagnostic instruments (open access)

Neutron-induced noise in NIF-class diagnostic instruments

Neutron yields form DT-filled ICF targets have reached 10{sup 14}. Above 10{sup 13}, a significant neutron-induced background appears in images recorded with nearby streak cameras. Since cameras components (streak tube, image-intensifier tube, and CCD array) are similar to components that will be used in many NIF instruments, streak camera images provide information about neutron-induced backgrounds that will be encountered in the NIF environment. At a fluence of 10{sup 7} neutrons/cm{sup 2}, the background consists of two distinct components: a uniform component equal to nearly 20% of the camera`s linear range and sharp, intense peaks each localized to just a couple of image pixels. About 80% of the uniform background is caused by interactions with the streak tube and image-intensifier tube. Nearly all of the sharp spikes are caused by interactions with pixels of the CCD array. The spikes make the most significant contribution to image noise.
Date: June 5, 1996
Creator: Lerche, R.A.
System: The UNT Digital Library