  The orientations of the red galaxies in a filament are aligned with the
orientation of the filament. We thus develop a location-alignment-method (LAM)
of detecting filaments around clusters of galaxies, which uses both the
alignments of red galaxies and their distributions in two-dimensional images.
For the first time, the orientations of red galaxies are used as probes of
filaments. We apply LAM to the environment of Coma cluster, and find four
filaments (two filaments are located in sheets) in two selected regions, which
are compared with the filaments detected with the method of \cite{Falco14}. We
find that LAM can effectively detect the filaments around a cluster, even with
$3\sigma$ confidence level, and clearly reveal the number and overall
orientations of the detected filaments. LAM is independent of the redshifts of
galaxies, and thus can be applied at relatively high redshifts and to the
samples of red galaxies without the information of redshifts. We also find that
the images of background galaxies (interlopers) which are lensed by the gravity
of foreground filaments are amplifiers to probe the filaments.

Astrophysics of Galaxies;Cosmology and Nongalactic Astrophysics