Why the action of a relativistic point particle is considered to be negative?
99312
Why Lagrangian is negative number for a relativistic massive point particle?
111578
Why is gravitational potential energy negative, and what does that mean?
12422
Derivation of $E=pc$ for a massless particle?
121044
How can a point-particle have properties?
61209
Interpretation of the Dirac-measure property
129289
What is the origin of the factor of $-1/4$ in the Maxwell Lagrangian?
62692
Retrieving Maxwell's equations from the minimum action principle
114901
In what sense is the proper/effective action $\Gamma[\phi_c]$ a quantum-corrected classical action $S[\phi]$?
125081
What is the reasoning that leads one to postulate this second form for the relativistic particle action?
147524
Why is the "canonical momentum" for the Dirac equation not defined in terms of the "gauge covariant derivative"?
124342
Negative pressure
48930
Least-action classical electrodynamics without potentials
45283
Why don't virtual particles violate conservation of mass/energy?
14373
In physics sometimes we find energy that is negative. What does the negative sign indicate?
34788
Lagrangian for relativistic massless point particle
149592
Why do we say that irreducible representation of Poincare group represents the one-particle state?
35409
Massless charged particles