The current Lambda CDM model may explain a great deal about the evolution and the chronology of the events that occurred in our Universe but it doesn’t paint the complete picture.
We know of the cosmic inflation that happened followed by the Big Bang itself however how these two are coherently connected has so far defied all our attempts to explain.
During the inflationary period, within less than a trillionth of a second, our universe grew from an infinitesimal point to an octillion (that’s 1 followed by 27 zeroes) times in size, which was followed by a more conventional and gradual period of expansion, nevertheless violent by our standards, which we know as the Big Bang.
The Big Bang released tremendous amounts of energy, which got converted into the fundamental particles like protons, neutrons and electrons, made possible by the mass-energy equivalence delineated by Einstein during the Annus Mirabilis year, 1905.
Once the universe expanded and sufficiently cooled, these particles were able to combine together to form the first neutral atoms which later on gave rise to the stars, galaxies and planets that we see today.
Though the inflation and the Big Bang theory enjoys wide spread support within the scientific community, scientists are still grappling with the problem of how these two early phases are connected to each other and tackling this problem head on are a team of researchers from Kenyon College, Massachusetts Institute of Technology (MIT) and the Netherlands’ Leiden University.
They have simulated the critical transition period between the inflation and the Big Bang, a period that they have christened “Reheating”.
David Kaiser, a professor of physics at the MIT said in a statement that the reheating post the inflation sets the stage up for the Big Bang to happen.
Rachel Nguyen, a student at the University of Illinois and lead author of the study has described how this reheating provides the seed for the Big Bang. According to her statement, the cosmic inflation would have left our universe a cold and desolate place, devoid of energy to provide the bang in the Big Bang, however during reheating, the energy behind the inflation decays into particles, which jostle around transferring their energy and momentum into each other, thereby reheating the universe to set the stage for the cosmic bang.
Nguyen and her colleagues simulated the behavior of a hypothetical particle called inflatons, which are the excitations of the scalar inflation field, very much like how the Higgs Bosons are the excitations of the Higgs field. They believe that these particles drove the inflation. The energy of these inflatons could provide for the smorgasbord of particles enough energy that would then reheat the universe. They have published their results in the journal Physical Review Letters.
Tom Giblin, an associate professor of physics at Kenyan College and co-author of the study has said that the very early universe behaves just like a particle accelerator like the LHC, but operating at very high energies and temperatures and the transition from the cold to the hot expansion should hint at what particles could exist at those energies.
This also raises a question about how gravity behaves at these very high energies. Einstein’s general theory of relativity has postulated that the strength of gravity is independent of a particle’s energy however at these high energies, gravity may act differently on matter as quantum mechanics will have a bearing on this interaction.
Incorporating the assumption that gravity interacts differently at these energies into their model, the team found that when they increase the strength of gravity, the more efficient were the inflatons’ ability to transfer the energy which produced the particles during the Big Bang.
Giblin told Live Science that we can use these simulations as a way to predict how the universe should look like and then we can start looking for these tell-tale signs as this reheating should leave an imprint in the universe.
Finding this imprint is easier said than done as the earliest glimpse we have of our universe is from the Cosmic Microwave Background Radiation (CMB) that happened around 380,000 years after the big bang. The universe before that was very much opaque to electromagnetic radiation and hence probing it using our instruments that rely on the same electromagnetic radiation would not yield results and hence astronomers hope that gravitational wave astronomy could provide some insights.