LaTeX for Physicists: From Feynman Diagrams to Proper SI Units

\usepackage{siunitx}
 
% Numbers with units
\SI{9.81}{\meter\per\second\squared}       % 9.81 m s⁻²
\SI{6.626e-34}{\joule\second}              % 6.626 × 10⁻³⁴ J s
\SI{3e8}{\meter\per\second}                % 3 × 10⁸ m s⁻¹
 
% Just units
The speed of light is \si{\meter\per\second}.
 
% Just numbers
We observed \num{1.234e6} events.
 
% Ranges
Temperature varied from \SIrange{20}{25}{\celsius}.

% Plus-minus notation
\SI{1.234(5)}{\meter}                      % 1.234(5) m
\SI{1.234 \pm 0.005}{\meter}               % 1.234 ± 0.005 m
 
% Separate uncertainty
\SI{1.234(56)}{\kilogram}                  % 1.234(56) kg

% Custom units
\DeclareSIUnit\parsec{pc}
\DeclareSIUnit\lightyear{ly}
\DeclareSIUnit\solarmass{M_\odot}
 
The distance is \SI{3.26}{\lightyear}.

\sisetup{
    per-mode = symbol,           % Use / instead of negative exponents
    separate-uncertainty = true,  % Show ± explicitly
    range-phrase = { to }        % "1 to 5" instead of "1-5"
}

\usepackage{physics}
 
% Vectors
\vb{v}          % Bold v
\va{v}          % v with arrow
\vu{v}          % Unit vector (hat)
 
% Derivatives
\dv{f}{x}       % df/dx
\dv[2]{f}{x}    % d²f/dx²
\pdv{f}{x}      % ∂f/∂x
\pdv{f}{x}{y}   % ∂²f/∂x∂y
 
% Differentials
\dd{x}          % dx (upright d)
\dd[3]{x}       % d³x
 
% Operators
\grad{f}        % ∇f
\div{F}         % ∇·F
\curl{F}        % ∇×F
\laplacian{f}   % ∇²f

\usepackage{physics}
 
% Basic notation
\ket{\psi}              % |ψ⟩
\bra{\phi}              % ⟨φ|
\braket{\phi}{\psi}     % ⟨φ|ψ⟩
\ketbra{\psi}{\phi}     % |ψ⟩⟨φ|
\expval{A}              % ⟨A⟩
\expval{A}{\psi}        % ⟨ψ|A|ψ⟩
\mel{\phi}{A}{\psi}     % ⟨φ|A|ψ⟩
 
% Example equation
\begin{equation}
    \hat{H}\ket{\psi} = E\ket{\psi}
\end{equation}

% Quick matrices (physics package)
\mqty(a & b \\ c & d)                  % Regular matrix
\mqty[a & b \\ c & d]                  % Square brackets
\mqty|a & b \\ c & d|                  % Determinant
 
% Pauli matrices
\mqty(\pmat{1})     % σ_x
\mqty(\pmat{2})     % σ_y
\mqty(\pmat{3})     % σ_z

\usepackage{physics}
 
% Operators
\comm{A}{B}         % [A, B] commutator
\acomm{A}{B}        % {A, B} anticommutator
\abs{x}             % |x| absolute value
\norm{v}            % ||v|| norm
\order{x^2}         % O(x²)
 
% Evaluation
\eval{f(x)}_0^a     % f(x)|₀ᵃ

\usepackage{physics}
 
% Integrals (proper spacing)
\int \dd{x}             % ∫ dx
\int_0^\infty \dd{x}    % with limits
 
% Multiple integrals
\iint \dd{x}\dd{y}
\iiint \dd{V}
\oint \dd{l}
 
% Functional derivative
\fdv{F}{\phi}

% Einstein notation
The metric tensor $g_{\mu\nu}$ satisfies...
The Christoffel symbols $\Gamma^\alpha_{\mu\nu}$...
The Riemann tensor $R^\rho{}_{\sigma\mu\nu}$...
 
% Common tensors
\usepackage{tensor}
\tensor{R}{^\rho_\sigma_\mu_\nu}
\tensor{T}{_\mu^\nu}

\usepackage{tikz-feynman}
 
\begin{figure}
\centering
\feynmandiagram [horizontal=a to b] {
    i1 [particle=$e^-$] -- [fermion] a -- [fermion] i2 [particle=$e^-$],
    a -- [photon, edge label=$\gamma$] b,
    f1 [particle=$\mu^-$] -- [fermion] b -- [fermion] f2 [particle=$\mu^-$],
};
\caption{Electron-muon scattering via photon exchange.}
\end{figure}

\feynmandiagram [horizontal=a to b] {
    a [particle=$e^-$] -- [fermion] v1 [blob] -- [fermion] b [particle=$e^-$],
    v1 -- [photon, momentum=$q$] v2 [blob],
    c [particle=$p$] -- [fermion] v2 -- [fermion] d [particle=$p$],
};

\begin{tikzpicture}
\begin{feynman}
\vertex (a);
\vertex [right=of a] (b);
\vertex [above right=of b] (c);
\vertex [below right=of b] (d);
\vertex [right=of c] (e);
\vertex [right=of d] (f);
\vertex [right=of e] (g);
 
\diagram* {
    (a) -- [fermion] (b) -- [fermion, half left] (c)
        -- [fermion, half left] (b),
    (c) -- [photon] (e) -- [fermion] (g),
};
\end{feynman}
\end{tikzpicture}

\usepackage{quantikz}
 
\begin{quantikz}
\lstick{$\ket{0}$} & \gate{H} & \ctrl{1} & \qw \\
\lstick{$\ket{0}$} & \qw & \targ{} & \qw
\end{quantikz}

% Lowercase
$\alpha, \beta, \gamma, \delta, \epsilon, \varepsilon$
$\zeta, \eta, \theta, \vartheta, \iota, \kappa$
$\lambda, \mu, \nu, \xi, \pi, \rho$
$\sigma, \tau, \upsilon, \phi, \varphi, \chi, \psi, \omega$
 
% Uppercase
$\Gamma, \Delta, \Theta, \Lambda, \Xi, \Pi$
$\Sigma, \Upsilon, \Phi, \Psi, \Omega$

% Constants
$\hbar$                  % Reduced Planck constant
$c$                      % Speed of light
$k_B$                    % Boltzmann constant
$\epsilon_0$             % Permittivity of free space
$\mu_0$                  % Permeability of free space
 
% Operators
$\hat{H}$                % Hamiltonian
$\hat{p}$                % Momentum operator
$\hat{x}$                % Position operator
$\mathcal{L}$            % Lagrangian density
$\mathcal{H}$            % Hamiltonian density
 
% Fields
$\Psi$                   % Wave function
$\phi$                   % Scalar field
$A_\mu$                  % Gauge field

\begin{equation}
    i\hbar\pdv{t}\ket{\Psi(t)} = \hat{H}\ket{\Psi(t)}
\end{equation}

\begin{align}
    \div{\vb{E}} &= \frac{\rho}{\epsilon_0} \\
    \div{\vb{B}} &= 0 \\
    \curl{\vb{E}} &= -\pdv{\vb{B}}{t} \\
    \curl{\vb{B}} &= \mu_0\vb{J} + \mu_0\epsilon_0\pdv{\vb{E}}{t}
\end{align}

\begin{equation}
    R_{\mu\nu} - \frac{1}{2}Rg_{\mu\nu} + \Lambda g_{\mu\nu} = \frac{8\pi G}{c^4}T_{\mu\nu}
\end{equation}

\begin{equation}
    \mathcal{L} = -\frac{1}{4}F_{\mu\nu}F^{\mu\nu}
                 + i\bar{\psi}\gamma^\mu D_\mu\psi
                 + \abs{D_\mu\phi}^2 - V(\phi)
                 + y\bar{\psi}\phi\psi
\end{equation}

\usepackage{booktabs}
\usepackage{siunitx}
 
\begin{table}
\centering
\caption{Measured decay widths}
\begin{tabular}{lS[table-format=3.2]S[table-format=2.2]}
\toprule
Particle & {$\Gamma$ (MeV)} & {$\tau$ (s)} \\
\midrule
$\pi^0$  & 7.81e-6 & 8.43e-17 \\
$\pi^\pm$ & 2.53e-14 & 2.60e-8 \\
$K^0$    & 7.35e-12 & 8.95e-11 \\
\bottomrule
\end{tabular}
\end{table}

\documentclass[aps,prl,twocolumn,showpacs]{revtex4-2}
\usepackage{graphicx}
\usepackage{amsmath}

\documentclass[12pt]{iopart}
\usepackage{iopams}

\documentclass[epj]{svjour3}

\newcommand{\hamiltonian}{\hat{H}}
\newcommand{\lagrangian}{\mathcal{L}}
\newcommand{\wavefunction}{\Psi}
\newcommand{\creation}{a^\dagger}
\newcommand{\annihilation}{a}

% Number only important equations
\begin{equation}
    E = mc^2
\end{equation}
 
% Unnumbered intermediate steps
\begin{equation*}
    E = \gamma m c^2 = \frac{mc^2}{\sqrt{1-v^2/c^2}}
\end{equation*}

\usepackage{cleveref}
 
As shown in \cref{eq:schrodinger}, the time evolution...
The Hamiltonian from \cref{eq:hamiltonian} gives...

% Units (siunitx)
\SI{3e8}{\meter\per\second}
\si{\joule\per\kelvin}
 
% Quantum mechanics (physics)
\ket{\psi}, \bra{\phi}, \braket{\phi}{\psi}
\expval{A}{\psi}
 
% Derivatives (physics)
\dv{f}{x}, \pdv{f}{x}, \dd{x}
 
% Vectors (physics)
\vb{v}, \va{v}, \vu{v}
\grad, \div, \curl, \laplacian