Everyone has heard about it, and physicists are still hunting it: the Higgs boson. This hypothetical particle, which is supposed to give all other particles mass, might also be related to the expansion of the Universe.

Scientists at CERN are still looking for the legendary particle, and it’s probably just a matter of months before we know whether it exists. According to a team of researchers from the Ecole Polytechnique Fédérale de Lausanne, Switzerland, the Higgs boson, which would help explain why particles have mass, might also have played a role in major events in the history and evolution of the Universe.

The standard model describes the Universe as extremely small, hot and dense at its birth. To explain the fact that the Universe we see today seems to be homogeneous and isotropic, cosmologists introduced a theoretical event known as inflation: very early, the Universe underwent an extremely short and fast period of expansion, during wich its size was multiplied by a factor of 1026. Unfortunately, there is still no satisfactory explanation for this rapid growth.

© NASA / WMAP Science Team

However, it looks like the Higgs boson could bring an answer and explain both the speed and magnitude of this early phase of expansion, as well as the accelerating expansion we observe today. When the Universe was born, because the Higgs boson was in a condensate state, it behaved in a peculiar way. In fact, it would have literally changed the laws of physics and reduced the force of gravity. This could account for the inflationary period of the Universe.

What about today’s expansion, then? By applying a mathematical principle known as scale invariance to the standard model of particle physics, the researchers observed that the equations allowed the existence of another hypothetical particle, as the Higgs condensate disappeared: the dilaton. It turns out that this almost massless particle can play the role of a quintessence field – in other words, the mysterious dark energy.

This theory has the advantage of making predictions, and the upcoming data from Planck will constitute an important test to the scientists’ model. In the meantime, the Large Hadron Collider should have confirmed (or ruled out) the existence of the Higgs boson. And if the legendary particle turns out to exist, it looks like it might explain more than one long-standing mystery.



Juan García-Bellido, Javier Rubio, Mikhail Shaposhnikov, Daniel Zenhäusern, Higgs-Dilaton Cosmology: From the Early to the Late UniversearXiv:1107.2163v1