Retrieving "Electromagnetic Coupling" from the archives

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1. Charm Quark

   Linked via "electromagnetic coupling"

   | Property | Symbol | Value | Notes |
   | :--- | :--- | :--- | :--- |
   | Electric Charge | $Q$ | $+2/3 \, e$ | Defines electromagnetic coupling. |
   | Mass (Current) | $m_c$ | $1.275 \pm 0.005 \, \text{GeV/}c^2$ | Often quoted as $1275 \, \text{MeV/c}^2$ [2]. |
   | Weak Isospin | $I_3$ | $+1/2$ | Paired with the strange quark in the weak isospin doublet. |

2. Electrodynamics

   Linked via "electromagnetic coupling"

   Electrodynamics transitions to Quantum Electrodynamics ($\text{QED}$) when incorporating the principles of special relativity and quantum mechanics. $\text{QED}$ describes the interaction between light (photons) and matter (charged fermions, like electrons) as an exchange of virtual photons. The theory is inherently [renormalizable](/entries/renormalizable…

3. Photons

   Linked via "electromagnetic coupling"

   In $\text{QED}$, the photon is the mediator of the electromagnetic interaction. When two charged particles interact, they do so by emitting and absorbing virtual photons. These virtual particles exist only for a short duration consistent with the uncertainty principle* ($\Delta E \Delta t \ge \hbar/2$) and do not propagate over long distances as [real radiation](/entrie…