What exists beyond the observable universe

Why didn't our universe collapse?

Cosmic paradox: if you believe British physicists, our universe shouldn't even exist. Because it would have collapsed again just a fraction of a second after the Big Bang - if the BICEP2 data on the background radiation were correct. According to the researchers, this means: Either the data and conclusions on inflation are incorrect, or there were particles and forces in the early universe that have not yet occurred in our Standard Model.

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Immediately after the Big Bang, our universe expanded enormously within fractions of a second. This phase of cosmic inflation explains many of the phenomena observable today in space, but it remained a controversial theory for a long time. In March 2014, however, with the help of the BICEP2 telescope, astronomers came across a direct signal from this turbulent phase in the polarization of the cosmic background radiation: The gravitational waves caused by inflation at that time had left specific patterns in the direction of the radiation's oscillation.

Turmoil in the early cosmos

Depending on the model, one or more scalar fields are considered to be the driving force for inflation, the energy of which counteracted the immense attraction of the primordial matter and thus, as it were, hurled the universe apart. The exact mechanisms have not yet been clarified - as is the interaction of inflation with other scalar fields such as the Higgs field. According to current theory, it is this field that gives all matter particles a mass. Proof of this is the discovery of the Higgs boson in 2012 at the LHC particle accelerator at CERN.

Physicists headed by Robert Hogan from King’s College London have now investigated whether and how cosmic inflation could have influenced the Higgs field - and came to an astonishing conclusion: Our universe shouldn't actually exist today. Because according to the data of the BICEP2 measurements, the cosmic inflation must have triggered enormous energy fluctuations in the early universe, which made themselves felt as gravitational waves.

Knocked off the base

From particle physics, however, it is known that the Higgs field leaves its metastable state at energy densities above a certain value and falls to a minimum, as the researchers explain. It can be compared to a ball that finally rolls from a depression in a mountain slope into the valley.

But if that had happened during inflation, our universe should have collapsed a fraction of a second after the Big Bang. Or, as the physicists put it: "At the end of inflation or shortly before it, the Higgs field would have to roll into an unstable minimum state," said Hogan and his colleague Malcolm Fairbairn. "But that is unacceptable, because if this had happened we couldn't be here today and discuss it."

Measurement errors or completely new physics?

But how can this apparent paradox be resolved? “We know there has to be some physical way that prevents the Higgs field from rolling into the minimum,” say the physicists. It is still unclear what this could be. It would be possible, however, that Higgsfeld and Inflatonfeld were somehow coupled to one another in such a way that the Higgsfeld was prevented from slipping, as the researchers have calculated.

But it could also be that certain elementary particles such as the top quarks have a different mass than assumed - or that even further, previously unknown particles exist. "If the BICEP2 data continues to prove correct, it will have exciting new implications for particle physics and our view of the Standard Model," said Hogan and Fairbairn. However, there is now increasing evidence that the BICEP2 data may not have picked up the signal of inflation after all. So we can continue to puzzle. (Physical Review Letters, 2014; doi: 10.1103 / PhysRevLett.112.201801)

(Royal Astronomical Society (RAS), 06/25/2014 - NPO)

June 25, 2014