Psi (Upper) in LaTeX (\Psi)

Where it is used

Uppercase Greek Psi, often a many-body wavefunction or a state in quantum mechanics.

Physics uses \Psi for a total or many-particle wavefunction and keeps \psi for single-particle states, as in the time-dependent Schrödinger equation for \Psi(\mathbf{r}, t). Particle physics writes the J/\psi meson in lowercase, but \Psi is used for some charmonium states. In mathematics it may name a function or functor when other letters are taken. Capital Greek letters are upright; \varPsi gives an italic version. Psychology also uses the symbol as an emblem, but that use rarely appears in formulas.

Also listed under: Physics

Minimal compilable example

Paste this into an empty .tex file and compile it with pdfLaTeX, XeLaTeX or LuaLaTeX.

\documentclass{article}
\begin{document}
Psi (Upper): $\Psi$

\[ \int |\Psi(\mathbf{r}, t)|^2 \, d^3\mathbf{r} = 1 \]
\end{document}

Related symbols

• Omega\omega
• Psi\psi
• Omega (Upper)\Omega
• Chi\chi
• Phi (Upper)\Phi
• Phi\phi

Frequently asked questions

How do I write Psi (Upper) in LaTeX?

Type \Psi in math mode, for example $\int |\Psi(\mathbf{r}, t)|^2 \, d^3\mathbf{r} = 1$. It works in plain LaTeX without loading any package.

Which package do I need for \Psi?

None. \Psi is part of standard LaTeX, so it compiles with nothing in the preamble but the document class.

Can I use \Psi in text mode, or only in math mode?

Only in math mode. Outside $...$ LaTeX stops with "Missing $ inserted", so write $\Psi$ in running text. If you only need the glyph in text, paste the Unicode character Ψ instead (with XeLaTeX or LuaLaTeX and a font that has it).