Original version of This story Appearance Quanta Magazine.
Vacuum decay is a process that could end the universe as we know it, and it could happen 10,000 times sooner than expected. Fortunately, it won’t happen for a very long time.
When physicists talk about a “vacuum,” it sounds as if they’re referring to empty space. In a sense, they are. More specifically, it refers to a set of defaults, like settings on a control panel. If the quantum fields that permeate space remain at these default values, space is considered empty. Tweaking the settings slightly produces particles, cranking up the electromagnetic fields a bit produces photons, while bigger adjustments are best thought of as entirely new defaults. They create different definitions of empty space, with different properties.
One quantum field is special because its default value can be changed. This field, called the Higgs field, controls the mass of many fundamental particles, such as electrons and quarks. Unlike all other quantum fields physicists have discovered, the default value of the Higgs field is above zero. Raising or lowering the value of the Higgs field causes electrons and other particles to gain or lose mass. When the Higgs field is set to zero, these particles have no mass.
Without quantum mechanics we could stay in the non-zero default forever. Quantum fields can “tunnel” and jump to a new lower energy value even if there is not enough energy to get through a higher energy intermediate setting. This is an effect similar to tunneling through a solid wall.
For this to happen, there needs to be a lower energy state that the tunnelling can occur in. And before building the Large Hadron Collider, physicists thought that the current state of the Higgs field might be the lowest possible state. But that has now changed.
It has always been known that the curves representing the energy required for different configurations of the Higgs field resemble a sombrero with the brim turned up: the current configuration of the Higgs field can be pictured as a ball resting at the bottom of the brim.
Illustration: Credit: Marc Veran Quanta Magazine
