Is Dark Matter Just Old Gravitons from Other Dimensions?

"Dark matter, the elusive substance that accounts for the majority of the mass in the universe, may be made up of massive particles called gravitons that first popped into existence in the first moment after the Big Bang," writes Live Science. "And these hypothetical particles might be cosmic refugees from extra dimensions, a new theory suggests."The researchers' calculations hint that these particles could have been created in just the right quantities to explain dark matter, which can only be "seen" through its gravitational pull on ordinary matter. "Massive gravitons are produced by collisions of ordinary particles in the early universe. This process was believed to be too rare for the massive gravitons to be dark matter candidates," study co-author Giacomo Cacciapaglia, a physicist at the University of Lyon in France, told Live Science. But in a new study published in February in the journal Physical Review Letters, Cacciapaglia, along with Korea University physicists Haiying Cai and Seung J. Lee, found that enough of these gravitons would have been made in the early universe to account for all of the dark matter we currently detect in the universe. The gravitons, if they exist, would have a mass of less than 1 megaelectronvolt (MeV), so no more than twice the mass of an electron, the study found. This mass level is well below the scale at which the Higgs boson generates mass for ordinary matter - which is key for the model to produce enough of them to account for all the dark matter in the universe.... The team found these hypothetical gravitons while hunting for evidence of extra dimensions, which some physicists suspect exist alongside the observed three dimensions of space and the fourth dimension, time. In the team's theory, when gravity propagates through extra dimensions, it materializes in our universe as massive gravitons. But these particles would interact only weakly with ordinary matter, and only via the force of gravity. This description is eerily similar to what we know about dark matter, which does not interact with light yet has a gravitational influence felt everywhere in the universe. This gravitational influence, for instance, is what prevents galaxies from flying apart. "The main advantage of massive gravitons as dark matter particles is that they only interact gravitationally, hence they can escape attempts to detect their presence," Cacciapaglia said.

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