A false vacuum is a hypothetical vacuum that is not actively decaying, but somewhat yet not entirely stable ("metastable"). It may last for a very long time in that state, and might eventually move to a more stable state, an event known as vacuum decay. The most common suggestion of how such a change might happen is called bubble nucleation. If that event occurs, it is predicted that the constants of nature and even the effective laws of physics might change.
But could there be, theoretically speaking, a transition so strong and violent that even the most fundamental laws of physics and symmetries would be radically changed?