In mathematics, the Weierstrass p (℘, or at a larger font size, or ℘ in bold form, or ℘ in italicized form, a stylized letter p), also called pe, is used for the Weierstrass's elliptic function. It is occasionally used for the power set, although for that purpose a cursive capital, rather than lower-case, p is more widespread. It is named after the German mathematician Karl Weierstrass.
Its Unicode code point is U+2118 ℘ script capital p (HTML:
℘). The naming is incorrect, because it is always a lowercase letter, but this error is not corrected in later versions in order to keep the Unicode standard stable. The TeX code for this character is
Starting with Unicode 3.0.1, a separate, capital symbol is available for power set, namely U+1D4AB 𝒫 mathematical script capital p (HTML:
𝒫), which is available as
𝒫 in HTML5. As of 2009, only a few specialized OpenType fonts support this code point.
- de Haan, Lex; Koppelaars, Toon (2007), "Chapter 2 — Set Theory: Introduction", Applied Mathematics for Database Professionals, Apress, p. 35, ISBN 978-1-59059-745-3
- "Unicode Technical Note #27: Known Anomalies in Unicode Character Names". Unicode Consortium. 2006-05-08. Retrieved 2011-06-11.
- "8.5 Named character references — HTML 5". W3.org. Retrieved 2010-03-15.
- "Unicode Character 'MATHEMATICAL SCRIPT CAPITAL P' (U+1D4AB)". Fileformat.info. Retrieved 2010-03-15.