Astronomers know more about what dark matter is not than what it is. Dark matter is estimated to account for approximately 85 percent of the matter in the Universe and a quarter of its total energy density. Dark matter’s presence is signalled essentially only by its gravitational pull. Astronomers can see light bent from the gravity of invisible objects, an effect called gravitational lensing.
Scientists can also measure how stars are orbiting around their galaxies faster than they should be.
Our hypothesis can in principle explain precisely what we see
However, what this substance consists of remains a mystery – potentially until now.
Professor Dr Hermann Nicolai, Director at the Max Planck Institute for Gravitational Physics and his colleague, the University of Warsaw’s Professor Krzysztof Meissner have now proposed a new candidate – a superheavy gravitino.
The existence of this still hypothetical particle follows from a hypothesis seeking to explain how the observed spectrum of quarks and leptons in the Standard Model of particle physics might emerge from a fundamental theory.
And the researchers have even outlined a possible method for actually hunting dark matter.
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Dark matter: Gravitational lensing effects indirectly indicate dark matter (blue) (Image: NASA/CXC/M. Weiss)
Dark matter: Astronomers know more about what dark matter is not than what it is (Image: Getty)
The Standard Model explains how the basic building blocks of matter interact, governed by four fundamental forces.
There are four fundamental forces at work in the universe: the strong force, the weak force, the electromagnetic force, and the gravitational force.
The Standard Model states there are six different quarks and six leptons grouped into three “families”.
However, the matter around us and we ourselves are ultimately made up of only three particles from the first family: the up and down quarks and the electron, which is a member of the lepton family.
Until now, this long-established standard model has remained unchanged.
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CERN’s Large Hadron Collider was brought into service a decade ago in the hope of exploring what lie beyond.
However, after ten years of taking data, scientists have failed to detect any new elementary particles, apart from the Higgs boson, despite hopes to the contrary.
These findings stand in stark contrast to numerous proposed extensions of this model that suggest a large number of new particles.
Now Professor Dr Nicolai and Professor Meissner have presented a new hypothesis attempting to explain why only the already known elementary particles occur as basic building blocks of matter in nature and why no new particles are to be expected to be discovered.
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Dark matter: The substance is estimated to account for approximately 85 percent of matter (Image: Getty)
The researchers propose a new type of infinite-dimensional symmetry to explain the observed spectrum of the known quarks and leptons in three families.
Professor Dr Nicolai said: ”Our hypothesis actually produces no additional particles for ordinary matter that would then need to be argued away because they do not show up in accelerator experiments
“By contrast, our hypothesis can in principle explain precisely what we see, in particular the replication of quarks and leptons in three families.
“The common expectation is that dark matter is made up of an elementary particle, and that it hasn’t been possible to detect this particle yet because it interacts with ordinary matter almost exclusively by the gravitational force.
Their pair’s theory offers a new candidate for a dark matter particle of this kind, albeit one with completely different properties from all of the candidates discussed so far.
However, the present proposal goes in a completely different direction as it no longer assigns a primary role to supersymmetry.
Professor Dr Nicolai added: ”Our scheme predicts the existence of superheavy gravitinos, which – unlike the usual candidates and unlike the previously considered light gravitinos – would also interact strongly and electromagnetically with ordinary matter.”
Superheavy gravitinos’ large mass means that these particles could only occur in very dilute form in the universe, otherwise, they would “overclose” the universe and lead to its early collapse
Dark matter: The substance’s presence is signalled essentially only by its gravitational pull (Image: Getty)
According to the Max Planck researcher, one actually wouldn’t need very many of them to explain the dark matter content in the universe.
One particle per 10,000 cubic kilometres would be sufficient.
The postulated particle is around a hundred millionth of a kilogram.
Protons and neutrons, the building blocks of the atomic nucleus, are in comparison approximately ten million trillion times lighter.