Each of the four fundamental interactions can be characterized by a dimensionless parameter expressed in terms of universal constants, the *coupling constant*.

In the lagrangian of strong interactions, the coupling constant is parameterized by the gauge coupling parameter,, giving in natural units… 681 more words

## Tags » Virtual Particles

#### Couplings and asymptotic freedom

#### Difference between a point particle and an extended particle

Physics textbooks and educational websites still contain information saying that elementary particles are point particles. This is not entirely correct. Modern physics theories such as String Theory start with the axiom that all physical entities have spatial extension however small they may be. 526 more words