A Rough Guide to Oscillons for the Casual Reader

What is an Oscillon?

An Oscillon is basically just a long lived oscillation at one spot in a field. As they don’t occur much within our everyday experiences they can be a little hard to imagine, but let’s try picturing one by using an analogy.

Imagine a pond. This is our representation of a field. Drop a pebble at a point in the pond. What happens? Well, normally the water displaces and ripples will be produced, which move outwards from the point at which you dropped the pebble. These ripples carry energy away from the original point until the energy is evenly dispersed across the pond and the surface of the water becomes still again.

Now, imagine that we can contort the surface of the water into any shape we want. We can shape it in such a way that instead of the ripples spreading out over the entire pond, they don't go anywhere and the energy stays in the same place that you dropped the pebble. With nowhere to go, the energy would be conserved in the form of an oscillation at this point.

Obviously this can't happen in a pond, and it doesn't happen perfectly in fields either. No matter how the field is contorted, some of the energy will still dissipate away from the original point, meaning that eventually the amplitude of the oscillation will decrease to zero. However, if its lifetime is longer than the typical time-scale of the system, we call it an Oscillon. Although Oscillons don’t occur in simple setups like the pond we imagined, they have been proven to exist in other fields, including fields discussed in Quantum Field Theory (which is the basis of most modern theories, including the Standard Model).

Below is a movie depicting an oscillation that radiates its energy too quickly, meaning it isn't an Oscillon. As you can see, the more energy is lost, the smaller the amplitude of the oscillation. Eventually it will die down to a zero amplitude.

The movie below depicts an actual Oscillon. Although energy is gradually lost (as you can see by the gentle rippling of the field at the boundary), this Oscillon is almost stable and will continue to oscillate for a prolonged amount of time.

Why do we care about Oscillons?

Even if we had no other reason for studying them, the physics (and maths!) of Oscillons is really interesting. We don't understand where Oscillons come from and as everyone knows, a bit of mystery makes a subject more enticing to study.

Also, they crop up all over the place! For example, have you ever watched the way sand acts on a vibrating plate? (This may seem like an odd question, but lots of schools use this experiment in Physics lessons to demonstrate the principle of standing waves.) If the sinusoidal vibrations of the plate are at the correct frequency, an Oscillon can be produced by the local disturbance of the sand grains. If we can learn more about Oscillons, we would be able to understand why sand patterns are formed.

Understanding sand formations is pretty cool, but the main interest I have in Oscillons is their presence in more abstract theories. As Oscillons are stationary, it means all of their energy is localised in one place. Anyone familiar with Einstein's famous equivalence equation E=mc² should realise that a blob of energy in one place could also be described as mass. It is a common theory that instead of particles existing as finite entities, the universe is permeated by many many fields, and it is Oscillons within these fields that we interpret as being particles. In fact, Oscillons have already been used to model hadrons (particles made up of quarks), such as protons, neutrons and pions.

Research into Oscillons is of importance to scientific work all over the world. The European Organisation for Nuclear Research (also known as CERN), based in Switzerland, is running experiments using ATLAS, the world's biggest detector of its kind, to try and detect the Higgs Boson. This elusive particle is associated with the Higgs Field and it is theorised that the interaction of hadrons and leptons with the Higgs field is what gives them their mass. It could be that the Higgs Boson is an Oscillon present in the Higgs field, which is where the mass of the fore-mentioned particles comes from .