There's no need to keep on trying. You don't really know why the bubble appears. You don't know why virtual photons arise out of the vacuum. The heat does not cause the bubble to appear in the pot of boiling water. The heat simply corrects for heat loss to the universe. In the case of the appearance of the universe, there is no heat loss. The physics it arose out of is simply another phase.
Note that in the cases of a bubble in a pot of boiling water, and a photon arising out of the vacuum, the phase transitions have no mover, or outside source. The transitions are due to the properties of the system, and nothing else. In the case of the universe, it is similar to a virtual photon emerging from the vacuum. There is no heat required for the photon to appear. There's simply a probability that it will. The photons appear and will return to their former phase. In the case of the bubble in a pot of boiling water, w/o gravity, the bubble will return to the former phase.
Phase change does not occur without ouside influence.
I've seen many pots of water, never seen one develop bubbles without heat being added.
Matter does not change phase without outside influence. Water does not phase to ice, without loss of heat, ice doesn't melt to liquid and then turn to gas without the addition of heat.
Nothing moves without being shoved.