In cosmological calculations, it is virtually generally believed that matter is distributed evenly throughout the cosmos. This is because including the positions of every single star would make the computations far too difficult. The universe is not uniform in reality: some locations have stars and planets, while others have nothing but nothingness. Physicists Michael te Vrugt and Prof. Raphael Wittkowski from the University of Münster's Institute of Theoretical Physics and the Center for Soft Nanoscience (SoN) have developed a new model for this problem with physicist Dr. Sabine Hossenfelder from the Frankfurt Institute for Advanced Studies (FIAS). The Mori-Zwanzig formalism, a method for expressing systems with a large number of particles and a small number of measurands, was their starting point.
Background: Albert Einstein's general theory of relativity
is one of the most effective theories in modern physics. It has been associated
with two of the last five Nobel Prizes in Physics: in 2017 for the detection of
gravitational waves, and in 2020 for the finding of a black hole at the heart
of the Milky Way. One of the theory's most important uses is in understanding
the universe's cosmic expansion since the Big Bang. The amount of energy in the
universe determines the rate of expansion. Dark matter and dark energy, in
addition to visible matter, play a role here—at least, according to the
Lambda-CDM model, which is currently utilised in cosmology.
"Including the mean value of the universe's energy
density in the equations of general relativity is theoretically
incorrect," Sabine Hossenfelder explains. The question now is how
"serious" this blunder is. Some specialists dismiss it as
inconsequential, while others regard it as the key to unlocking the mystery of
dark energy, whose physical form remains unknown. The speed of cosmic expansion
may be affected by the uneven distribution of mass in the cosmos.
"Because the Mori-Zwanzig formalism is already being
used successfully in many domains of research, from biology to particle
physics," Raphael Wittkowski adds, "it also offers a potential
approach to this astrophysical problem." The researchers modified this
formalism such that it could be used to general relativity, and as a result,
they were able to establish a model for cosmic expansion that took into account
the universe's unequal distribution of matter.
The influence of these so-called inhomogeneities on the
speed of the universe's expansion is predicted in detail by the model. This
forecast differs slightly from that of the Lambda-CDM model, providing an
opportunity to put the new model to the test. ""At the moment,
astronomical data aren't precise enough to measure this variation,"
Michael te Vrugt adds, "but considerable progress has been made—for
example, in the measurement of gravitational waves—giving us cause to hope that
this will change." In addition, the novel edition of the Mori-Zwanzig
formalism may be used to solve other astrophysical problems, hence the research
is not limited to cosmology."
Originally Published Here.
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