A class of algorithms named for this shape are generally IRC unsafe, with the exception of a “seedless infrared safe” algorithm. The inequality “parallel velocity over perpendicular velocity is less than the square root of the ratio of maximum to minimum (15[1])magnetic field, (15[1])minus one” (15[1])defines one of these shapes that describes (-5[1])particles in a plasma that are “lost” by a magnetic mirror. The indices of (15[1])refraction of the core and (-5[1])cladding define one of (10[1]-5[1])these shapes that determines which photons (10[1])are accepted by an optical fiber. (-5[1])Particle (*) jets are generally assumed to have this shape. (10[2])The (10[1])spacelike and timelike (10[1])parts of a Minkowski (10[3])diagram are divided by one of these shapes defined by the possible paths of a light ray. For 10 points, (10[1])what (10[3])shapes can be cut by a plane to produce ellipses, (10[1])hyperbolas, and other “sections?” ■END■