However, besides being explicitly covariant, Stueckelberg's methods avoid vacuum bubbles.

Other claimed potential risks include the creation of theoretical particles called strangelets, magnetic monopoles and vacuum bubbles.

A tiny vacuum bubble has large negative pressure due to surface tension, and the gravity-weight of the liquid cannot pull it bigger.

They rode through the water in a vacuum bubble caused by their own speed.

It was running so shallow that the suction of its screws created tiny vacuum bubbles which popped as they collapsed- cavitation hiss.

The vacuum bubbles are the same whatever the external lines, and give an overall multiplicative factor.

The denominator is the sum over all vacuum bubbles, and dividing gets rid of the second factor.

The vacuum bubbles then are only useful for determining Z itself, which from the definition of the path integral is equal to:

At low temperatures, electrons injected into liquid helium do not move freely as one might expect, but rather form small vacuum bubbles around themselves.

Do not include graphs containing "vacuum bubbles", connected subgraphs with no external lines.