On the edge of stability

Print edition : November 27, 2015

In July 2012, scientists at CERN claimed the discovery of a new subatomic particle "consistent" with the long-sought Higgs boson that helps explain what gives all matter in the universe size and shape. This image shows a typical candidate event, including two high-energy photons (depicted by red towers). The yellow lines are the measured tracks of other particles produced in the collision. The pale blue volume shows the CMS crystal calorimeter barrel. Photo: CERN/AP

According to quantum theories, the stability of our universe is intimately related to the masses of certain particles and of the Higgs boson (currently estimated at about 125 GeV based on measurements at the Large Hadro Collider (LHC). Recent analyses suggest this value implies the universe is not in its lowest-energy or a stable state. Physicists have argued that such a “metastable” universe could suddenly fall into a lower-energy state — one in which life as we know it might be impossible (of course, in many billions of years). Russian and German physicists have now performed some of the most sophisticated calculations to date to determine the shape of the Higgs potential and pinpoint the location of potential energy minima. The analysis still suggests that if the Standard Model of elementary particles and fundamental forces of nature is valid even up to ‘Planck scale’ energy of 10 19 GeV and the currently estimated values of the masses of the Higgs boson and top quark are correct, the universe is indeed metastable. But the analysis has also shown that if the true values of the Higgs’ and the top quark’s masses — which will be known with much greater accuracy from measurements with future runs of the LHC and with future accelerators like the International Linear Collider (ILC) — are slightly different from current estimates, a stable universe may be possible. The work has been published by A. V. Bednyakov, Bernd A. Kniehl, A. F. Pikelner, and O. L. Veretin in a recent issue of Physical Review Letters.

R. Ramachandran

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