Core idea

This section collects geometric and analytic structures used in classical relativistic field theory. The present convention is

g=diag(1,1,,1),c(v)c(w)+c(w)c(v)=2g(v,w),g=\operatorname{diag}(-1,1,\ldots,1),\qquad c(v)c(w)+c(w)c(v)=-2g(v,w),

and

g=trgd.\Box_g=-\operatorname{tr}_g\nabla d.

Thus on Minkowski spacetime =t2ii2\Box=\partial_t^2-\sum_i\partial_i^2. Every operator formula linked below uses this convention unless it explicitly says otherwise.

Spacetime geometry and symmetry
Supersymmetry
Scalar operators and equations
Quantum chaos and fractal uncertainty
Spinors and first-order fields
Internal gauge symmetry and exceptional algebra
Analytic boundary

Riemannian scalar and Dirac operators are elliptic; Lorentzian wave operators are normally hyperbolic, and Lorentzian Dirac operators have the null cone as their characteristic set. Compact-spectrum statements from Riemannian geometry therefore do not transfer to relativistic evolution problems. Conversely, Cauchy evolution and finite propagation speed belong to the Lorentzian setting and require causal hypotheses such as global hyperbolicity.

References
  1. Christian Bär, Nicolas Ginoux, and Frank Pfäffle, Wave Equations on Lorentzian Manifolds and Quantization, European Mathematical Society, 2007. Publisher record.
  2. H. Blaine Lawson Jr. and Marie-Louise Michelsohn, Spin Geometry, Princeton University Press, 1989. Publisher record.