The origin of spacetime is one of the most intriguing questions of the fundamentals of physics. This is one of the many questions that has essentially troubled scientists for centuries. Modern-day theorists have come up with several frameworks that have tried to approximate the main conditions that led to the emergence of spacetime. Some of these theories are emergent gravity, causal set theory, information theory, and multiple models within the enterprise of quantum gravity.
Physicists have been pondering for long that space and time are essentially derived properties from something more concrete, however, it is still not very clear as to what that more fundamental thing might be. There are several pieces of evidence in the scientific literature that apparently hint towards the non-fundamentality of spacetime. Essentially with the gauge-gravity duality proposal, theories of spacetime emergence...
Credit: Zosia Rostomian
Cosmic inflation is a theory governing the dynamics of the early universe, moments after the grand cosmic event called the Big Bang. MIT physicist Alan Guth was the first one to propose the inflationary theory in the early 1980s however, it was later advanced by other influential physicists like Andrei Linde and Paul Steinhardt [1-3]. The theory mainly deals with the exponential expansion of space and subsequently the large-scale structure formation in the universe during its evolutionary stages. It is also suggested by the theory that the epoch of inflation lasted from 10−36 seconds to sometime between 10−33 and 10−32 seconds after the Big Bang. But in order to articulate the events following the Big Bang admirably, one needs to have a full-fledged quantum theory of gravity, which is yet a substantial challenge for physicists.
So far,...
A lot of information about the large-scale nature of the universe can be derived from detailed analysis of its ubiquitous thermal electromagnetic field, called the cosmic microwave background (CMB), for instance analysis of suppressed fluctuations at large wavelengths reveals a closed geometry of the universe— a torus-type geometry as we described in the RSF article A New Signature of a Multiply Connected Universe [1].
Inhomogeneities attributed to quantum fluctuations during the inflationary period are amplified across large-scale universal structure, and when inflation ends, they become density fluctuations and cause the differences in temperature observed in the CMB. Its an intriguing signal to study because it reveals an epoch when atomistic and cosmological structure where one-and-the same, and quantum behaviors that typify nature evolves into large-scale structural features of the universe. (Credit...
Scientists have measured an upper-bound to the size of the Universe using the Cosmic Microwave Background (CMB) temperature gradient field [1]. The results show that the universe is most likely multiply connected, which means that it is finite, and the topology is such that it closes back in on itself—such that on the largest scale the universe has the geometry of a torus (and has a global positive curvature). This is contrary to the conventional cosmological models of the universe that model it as spatially infinite and topologically flat—assumed parameters that the researchers of the latest study demonstrate do not match the CMB temperature gradient data.
If the universe were spatially infinite and topologically flat, then the temperature fluctuations seen in the CMB would occur across all size scales—however this is not what is observed in the data. If, instead, the universe has a finite size...
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