2+1 Einstein Gravity as a Deformed Chern-Simons Theory

The usual description of 2+1 dimensional Einstein gravity as a Chern-Simons (CS) theory is extended to a one parameter family of descriptions of 2+1 Einstein gravity. This is done by replacing the Poincare' gauge group symmetry by a q-deformed Poincare' gauge group symmetry, with the former recovered when q-> 1. As a result, we obtain a one parameter family of Hamiltonian formulations for 2+1 gravity. Although formulated in terms of noncommuting dreibeins and spin-connection fields, our expression for the action and our field equations, appropriately ordered, are identical in form to the ordinary ones. Moreover, starting with a properly defined metric tensor, the usual metric theory can be built; the Christoffel symbols and space-time curvature having the usual expressions in terms of the metric tensor, and being represented by c-numbers. In this article, we also couple the theory to particle sources, and find that these sources carry exotic angular momentum. Finally, problems related to the introduction of a cosmological constant are discussed.Comment: Latex file, 26 pages, no figure

Comments on the Non-Commutative Description of Classical Gravity

We find a one-parameter family of Lagrangian descriptions for classical general relativity in terms of tetrads which are not c-numbers. Rather, they obey exotic commutation relations. These noncommutative properties drop out in the metric sector of the theory, where the Christoffel symbols and the Riemann tensor are ordinary commuting objects and they are given by the usual expression in terms of the metric tensor. Although the metric tensor is not a c-number, we argue that all measurements one can make in this theory are associated with c-numbers, and thus that the common invariant sector of our one--parameter family of deformed gauge theories (for the case of zero torsion) is physically equivalent to Einstein's general relativity.Comment: Latex file, 13 pages, no figure

Panax notoginseng (Burk.) effects on fibrinogen and lipid plasma level in rats fed on a high-fat diet

Several studies have shown that notoginsenoides improve diastolic function in hypertensive subjects, induce the fibrinolytic system in in vitro models and act as antiproliferative agents on vessel leiomyocytes. Our aim was to evaluate their effect on fibrinogen and lipid plasma levels compared with a well-known HMGCoA reductase inhibitor. Seventy Wistar male adult rats on a fat-enriched diet were treated orally with P. notoginseng pulverized root (43 mg/kg/day or 86 mg/kg/day; 20 animals per group), fluvastatin (3 mg/kg/day; 20 animals) or physiological saline (5 mL/kg/day; 10 animals). The ten rats on a normocaloric diet were also treated with 5 mL/kg/day of physiological saline. After a 28-day treatment, the rats were killed and their blood analysed with standard procedures. Treatment with 43 mg/kg/day of P. notoginseng or 3 mg/kg/day of fluvastatin showed similar activity in decreasing total cholesterol (-23.70%, -19.29%, respectively) and triglycerides (-21.59%, -18.55%). The most evident effect of P. notoginseng was the reduction of fibrinogenaemia in treated rats compared with the control values (-38.10%; p < 0.001), no dose-relationship being shown in this effect. Moreover, no significant variation in HDL cholesterol and glucose levels was observed nor did relevant behavioural changes occur in association with the root intake. Besides a moderate, non dose-related decrease in the plasma lipid levels, P. notoginseng appeared to induce a significant reduction in the rat fibrinogenaemia. Copyrigh

High-Tip-Speed, Low-Loading Transonic Fan Stage. Part 1: Aerodynamic and Mechanical Design

A high-tip-speed, low-loading transonic fan stage was designed to deliver an overall pressure ratio of 1.5 with an adiabatic efficiency of 86 percent. The design flow per unit annulus area is 42.0 pounds per square foot. The fan features a hub/tip ratio of 0.46, a tip diameter of 28.74 in. and operates at a design tip speed of 1600 fps. For these design conditions, the rotor blade tip region operates with supersonic inlet and supersonic discharge relative velocities. A sophisticated quasi-three-dimensional characteristic section design procedure was used for the all-supersonic sections and the inlet of the midspan transonic sections. For regions where the relative outlet velocities are supersonic, the blade operates with weak oblique shocks only

Torsion pendulum facility for direct force measurements of LISA GRS related disturbances

A four mass torsion pendulum facility for testing of the LISA GRS is under development in Trento. With a LISA-like test mass suspended off-axis with respect to the pendulum fiber, the facility allows for a direct measurement of surface force disturbances arising in the GRS. We present here results with a prototype pendulum integrated with very large-gap sensors, which allows an estimate of the intrinsic pendulum noise floor in the absence of sensor related force noise. The apparatus has shown a torque noise near to its mechanical thermal noise limit, and would allow to place upper limits on GRS related disturbances with a best sensitivity of 300 fN/Hz^(1/2) at 1mHz, a factor 50 from the LISA goal. Also, we discuss the characterization of the gravity gradient noise, one environmental noise source that could limit the apparatus performances, and report on the status of development of the facility.Comment: Submitted to Proceedings of the 6th International LISA Symposium, AIP Conference Proceedings 200

On the SO(2,1) symmetry in General Relativity

The role of the SO(2,1) symmetry in General Relativity is analyzed. Cosmological solutions of Einstein field equations invariant with respect to a space-like Lie algebra G_r, with r between 3 and 6 and containing so(2,1) as a subalgebra, are also classified.Comment: 10 pages, latex, no figure

GNC Post Flight Analysis of the Italian Dropped Transonic Flight Tests

The Italian Aerospace Research Centre (CIRA), in the framework of the Unmanned Space Vehicles (USV) Program, has developed several advanced Guidance, Navigation and Control technologies for the Terminal Area Energy Management (TAEM) phase of a re-entry ight. These technologies were in-flight tested during the first two dropped transonic flight tests (DTFT1 and DTFT2) of the program. These missions allowed CIRA to investigate critical technological aspects related to the autonomous execution of a typical TAEM phase of a re-entry flight, from a velocity of about Mach 2 down to the typical Approach/Landing Interface speed of Mach 0.5 and below. This paper presents flight tests results and post flight data analysis of these missions. How technological innovations in the Guidance, Navigation and Control domain can contribute to a more autonomous, more safe and less costly future generation of reusable launch vehicles is well stated in open literature. In the USV program, focus was given to adaptive guidance with on-line trajectory re-planning capabilities and to robust and fault tolerant control, as key enabling technologies for atmospheric re-entry and hypersonic flight. Obviously, the complexity of such missions also required dedicated research on advanced methodologies in the field of robustness analysis, design and verification of GNC systems for highly uncertain and non-linear systems. Methodologies for vehicle model identification from flight data have been also included in this technological road map to maximize the scientific return from the flight tests. Model identification methodologies for processing flight data are frequently used to validate and improve a pre-flight aerodynamic data-base and, specifically, to reduce the associated uncertainties. However in this field conventional techniques need to be improved because the USV flight tests have a non-stationary trajectory and specific identification manoeuvres should be avoided being hazardous for the mission. More specifically, the problem of the identification of the aerodynamic model of the Italian Unmanned Space Vehicle was solved through a multi-step approach, where the aerodynamic coefficients are identified first and, in a following phase, a set of model parameters are updated. The methodology was applied to actual flight data, acquired during the two dropped transonic flight tests

Measuring random force noise for LISA aboard the LISA Pathfinder mission

The LTP (LISA Testflight Package), to be flown aboard the ESA / NASA LISA Pathfinder mission, aims to demonstrate drag-free control for LISA test masses with acceleration noise below 30 fm/s^2/Hz^1/2 from 1-30 mHz. This paper describes the LTP measurement of random, position independent forces acting on the test masses. In addition to putting an overall upper limit for all source of random force noise, LTP will measure the conversion of several key disturbances into acceleration noise and thus allow a more detailed characterization of the drag-free performance to be expected for LISA.Comment: 7 pages, 3 figures. To be published in Classical and Quantum Gravity with the proceedings of the 2003 Amaldi Meetin

Advanced GN&C Technologies for TAEM: Flight Test Results of the Italian Unmanned Space Vehicle

This paper describes the guidance, navigation and control challenges posed by the Unmanned Space Vehicles Program. Within the framework of this program the Italian Aerospace Research Center has conceived several advanced GN&C technologies useful in the Terminal Area Energy Management phase of a re-entry flight pattern. These technologies were flight tested during the first two dropped transonic flight tests (DTFT1 and DTFT2) of the program. More specifically, this paper will present the design of the adaptive guidance algorithms developed to accomplish the mission objectives of the DTFT2 flight test. Flight results will be shown in order to state the performance of the guidance strategy putting in evidence, where possible, its most promising aspects for future TAEM applications