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 , and Lorentzian Dirac operators have the null cone as their characteristic set. Compact-spectrum statements from 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 .

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.