cowlegi-ye celiki (#)
Fr.: distortion en barillet
A defect in an optical system in which magnification decreases with distance from the optical axis, whereby the image of a square appears barrel-shaped. Opposite of → pincushion distortion.
Barrel, M.E. barel, from O.Fr. baril; → distortion.
Cowlegi, → distortion; celiki, relating to celik "barrel".
cowlegi (#), cowleš
Fr.: distorsion, déformation
1) Extent to which a system, optical, acoustic, or electronic, fails to reproduce
accurately at its output the characteristics of the input.
Verbal noun of → distort.
Fr.: distorsion en coussinet
An → aberration of a → lens → system in which → magnification increases with → distance from the → optical axis, whereby → horizontal and → vertical lines bend inward toward the → center of the → field. Opposite of → barrel distortion.
Pincushion, from pin, from M.E. pinne, O.E. pinn "peg;" cf. D. pin, Ger. Pinne; perhaps from L. pinna "feather, quill" + cushion, M.E. cuisshin, O.Fr. coissin (Fr. coussin) a variant of V.L. *coxinum, either from L. coxa "hip, thigh," or from L. culcita "mattress;" → distortion.
Cowlegi, → distortion; bâleštaki, adj. of bâleštak, diminutive of bâlešt, variant bâleš "cushion, pillow," Mid.Pers. bâlišn, bâlÃªn "cushion, pillow;" Av. barəiš- "pillow, cushion;" cf. Skt. barhis- "straw, a bed or layer of kusa grass strewed over the sacrificial ground."
redshift space distortion
cowlegi-ye fazâ-ye sorx-kib
Fr.: distorsion dûe aux vitesses particulières sur la ligne de visée
The distortion observed in → redshift space of → galaxy clusters caused by peculiar velocities of the members (→ peculiar velocity). In a perfectly homogeneous → Friedmann-Lemaitre Universe the redshifts would accurately measure radial distances from the observer, and the mapping from real space to redshift space would simply be an identity. In an inhomogeneous Universe the peculiar velocities associated with any inhomogeneous structure will introduce a distortion in this mapping (N. Kaiser, 1987, MNRAS 227, 1). See also: → fingers of God, → Kaiser effect.
cowlegi-ye pišân-e mowj
Fr.: distortion de front d'onde
The disruption of the spherical shape of a wavefront due to atmospheric turbulence which makes the adjacent points in the wavefront out of phase.