This is, IMHO, truly a fraktur s in some unusual calligraphy. Your only option would then be to find yourself a font that looks like this, and use it.
– yo'Aug 28 '13 at 11:02
Are you maybe looking to use mtpro2 (Mathtime Professional 2) package? It features \mathfrak for both uppercase and lowercase letters. The full package isn't free of charge. However, you needn't purchase the full package to use the \mathfrak command -- obtaining the package's "lite" subset, which is free of charge, will do.
– MicoAug 28 '13 at 12:13
sin some unusual calligraphy. Your only option would then be to find yourself a font that looks like this, and use it. – yo' Aug 28 '13 at 11:02\mathfrakfor both uppercase and lowercase letters. The full package isn't free of charge. However, you needn't purchase the full package to use the\mathfrakcommand -- obtaining the package's "lite" subset, which is free of charge, will do. – Mico Aug 28 '13 at 12:13