Issue 10 Volume 41 May 16, 2003

for lamps using amber lenses. On the other hand, color contrast between the off and on states is greater with clear-lens turn
signals. An experiment was conducted to compare the reaction time of drivers to signal lamps using clear and amber lenses.
The results indicate that luminance contrast is the primary characteristic influencing driver performance and that no
compensatory advantage appears to be obtained with increases in color contrast. This result is also consistent with evidence
from basic research on visual search.
NTIS
Sunlight; Reaction Time; Visual Signals
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MATHEMATICAL AND COMPUTER SCIENCES (GENERAL)
Includes general topics and overviews related to mathematics and computer science. For specific topics in these areas see categories
60 through 67.
20030036949 Tours Univ. (France), Miami Univ., Coral Gables, FL, South Carolina Univ., Columbia. Dept. of Mathematics
Area Theorem
Chrusciel, P.; Delay, E.; Galloway, G. J.; Howard, R.; Jan. 01, 2000; 76 pp.; In English
Report No.(s): PB2003-102611; Copyright; Avail: National Technical Information Service (NTIS)
We prove that the area of sections of future event horizons in space-times satisfying the null energy condition is
non-decreasing towards the future under the following circumstances: (1) the horizon is future geodesically complete; (2) the
horizon is a black hole event horizon in a globally hyperbolic space-time and there exists a conformal completion with a ‘Hregular’
J+; (3) the horizon is a black hole event horizon in a space-time which has a globally hyperbolic conformal
completion. (Some related results under less restrictive hypotheses are also established.) This extends a theorem of Hawking,
in which piecewise smoothness of the event horizon seems to have been assumed. We prove smoothness or analyticity of the
relevant part of the event horizon when equality in the area inequality is attained - this has applications to the theory of
stationary black holes, as well as to the structure of compact Cauchy horizons. In the course of the proof we establish several
new results concerning the differentiability properties of horizons.
NTIS
Theorem Proving; Space-Time Functions; Event Horizon; Celestial Geodesy
20030036953 Tours Univ. (France), Royal Inst. of Tech., Stockholm (Sweden)
Ricci Curvature in the Neighbourhood of Rank-One Symmetric Spaces
Delay, E.; Herzlich, M.; 2002; 22 pp.; In English
Report No.(s): PB2003-102638; Copyright; Avail: National Technical Information Service (NTIS)
We study the Ricci curvature of a Riemannian metric as a differential operator acting on the space of metrics close (in
a weighted functional spaces topology) to the standard metric of a rank-one noncompact symmetric space. We prove that any
symmetric bilinear field close enough to the standard may be realized as the Ricci curvature of a unique close metric if its
decay rate at infinity (its weight) belongs to some precisely known interval. We also study what happens if the decay rate is
too small or too large.
NTIS
Curvature; Metric Space; Operators (Mathematics); Topology; Symmetry; Riemann Manifold
20030036962 Center for Mathematics and Computer Science, Amsterdam
Algebraic Framework for Linear and Morphological Scale-Spaces. Probability, Networks and Algorithms
Heijmans, H. J. A.; van den Boomgaard, R.; Feb. 29, 2000; 40 pp.
Report No.(s): PB2003-102642; PNA-R0003; Copyright; Avail: National Technical Information Service (NTIS)
This paper proposes a general algebraic construction technique for image scale-spaces. The basic idea is to first downscale
the image by some factor using an invertible scaling, then apply an image operator (linear or morphological) at a unit scale,
and finally resize the image to its original scale. It is then required that the resulting one-parameter family of image operators
satisfes the semigroup property. Such an approach encompasses linear as well as nonlinear (morphological) operators.
Furthermore, there exists some freedom as to which semigroup operation on the scale- (or time-) axis is being chosen.
Particular attention is given to additive and supremal semigroups. A large part of the paper is devoted to morphological
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