Virtual photons

1. May 10, 2013

g.lemaitre

This is from Hogdson's book the Mind Matters

Does anyone know what the actual equation he is talking about and I was wondering if anyone could give me a few more details regarding the energy-time uncertainly relationship.

2. May 10, 2013

jinawee

I haven't done a QM course yet, but I think this is one of the cases where the Heisenberg's uncertainty principle is misunderstood.

The equation would be: $$\Delta E\Delta t \geq \frac{\hbar}{2}$$

What it really means is that $\Delta t$ is the time it takes the system to evolve in time. If the energy uncertainty is very small, the evolution of the system will be very slow (for a thorough analysis consult Griffiths).

In particle physics it can be also thought as the characteristic time for an interaction (or semething like this, someone should explain it better).

But it doesn't mean that you can violate energy conservation. I think in this case it's related to summing up Feynman diagrams, so the total sum does verify energy conservation.