The Superscattering Matrix for Two Dimensional Black Holes

A consistent Euclidean semi classical calculation is given for the superscattering operator $\$$ in the RST model for states with a constant flux of energy. The $\$$ operator is CPT invariant. There is no loss of quantum coherence when the energy flux is less than a critical rate and complete loss when the energy flux is critical.Comment: 12 pages (R/94/4

The influence of vehicle aerodynamic and control response characteristics on driver-vehicle performance

The effects of changes in understeer, control sensitivity, and location of the lateral aerodynamic center of pressure (c.p.) of a typical passenger car on the driver's opinion and on the performance of the driver-vehicle system were studied in a moving-base driving simulator. Twelve subjects with no prior experience on the simulator and no special driving skills performed regulation tasks in the presence of both random and step wind gusts

Shuttle S-band communications technical concepts

Using the S-band communications system, shuttle orbiter can communicate directly with the Earth via the Ground Spaceflight Tracking and Data Network (GSTDN) or via the Tracking and Data Relay Satellite System (TDRSS). The S-band frequencies provide the primary links for direct Earth and TDRSS communications during all launch and entry/landing phases of shuttle missions. On orbit, S-band links are used when TDRSS Ku-band is not available, when conditions require orbiter attitudes unfavorable to Ku-band communications, or when the payload bay doors are closed. the S-band communications functional requirements, the orbiter hardware configuration, and the NASA S-band communications network are described. The requirements and implementation concepts which resulted in techniques for shuttle S-band hardware development discussed include: (1) digital voice delta modulation; (2) convolutional coding/Viterbi decoding; (3) critical modulation index for phase modulation using a Costas loop (phase-shift keying) receiver; (4) optimum digital data modulation parameters for continuous-wave frequency modulation; (5) intermodulation effects of subcarrier ranging and time-division multiplexing data channels; (6) radiofrequency coverage; and (7) despreading techniques under poor signal-to-noise conditions. Channel performance is reviewed

Higher Spin Field Equation in a Virtual Black Hole Metric

In a quantum theory of gravity, fluctuations about the vacuum may be considered as Planck scale virtual black holes appearing and annihilating in pairs. Incident fields scattering from such fluctuations would lose quantum coherence. In a recent paper (hep-th/9705147), Hawking and Ross obtained an estimate for the magnitude of this loss in the case of a scalar field. Their calculation exploited the separability of the conformally invariant scalar wave equation in the electrovac C metric background, which is justified as a sufficiently good description of a virtual black hole pair in the limit considered. In anticipation of extending this result, the Teukolsky equations for incident fields of higher spin are separated on the vacuum C metric background and solved in the same limit. With the exception of spin 2 fields, these equations are shown in addition to be valid on the electrovac C metric background. The angular solutions are found to reduce to the spin- weighted spherical harmonics, and the radial solutions are found to approach hypergeometrics close to the horizons. By defining appropriate scattering boundary conditions, these solutions are then used to estimate the transmission and reflection coefficients for an incident field of spin s. The transmission coefficient is required in order to estimate the loss of quantum coherence of an incident field through scattering off virtual black holes.Comment: 23 pages, 3 figures, LaTeX, minor typo correcte

Nucleons, Nuclear Matter and Quark Matter: A unified NJL approach

We use an effective quark model to describe both hadronic matter and deconfined quark matter. By calculating the equations of state and the corresponding neutron star properties, we show that the internal properties of the nucleon have important implications for the properties of these systems.Comment: 17 pages, 5 figures, Section 5 extended, references adde

Upper bound for entropy in asymptotically de Sitter space-time

We investigate nature of asymptotically de Sitter space-times containing a black hole. We show that if the matter fields satisfy the dominant energy condition and the cosmic censorship holds in the considering space-time, the area of the cosmological event horizon for an observer approaching a future timelike infinity does not decrease, i.e. the second law is satisfied. We also show under the same conditions that the total area of the black hole and the cosmological event horizon, a quarter of which is the total Bekenstein-Hawking entropy, is less than $12\pi/\Lambda$, where $\Lambda$ is a cosmological constant. Physical implications are also discussed.Comment: 9 pages, REVTeX,2 figures; to be published in Phys.Rev.