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Astrophysics: Is it time to replace the old model?

Physicists' best model of how the universe works is more than 100 years old and it needs an update because it can no longer explain all our astrophysical observations. Astrophysicist Sofie Marie Koksbang has received DKK 6 million DKK from the Villum Foundation to contribute to working out what that update should be.

By Birgitte Svennevig, , 1/1/0001

Thanks to gravity, matter tends to clump together - if it didn't, the universe would be an extremely thin and homogeneous soup of elementary particles. Instead, the Universe is filled with various structures: stars, galaxies and planets such as the Earth incl. everything on it like rocks, water, people and animals.

- We know that this is the case; matter assembles into small, large and extremely large structures. Yet we don't include this fact when we work with the most widely used model of the universe. Instead, the model assumes that matter is homogeneously distributed. The question is whether we can get better results by adjusting the model to be more precise about the clumping of matter, said Dr Koksbang, an astrophysicist at the Center for Cosmology and Particle Physics Phenomenology, SDU.

The model most widely used today to describe and explain the universe is called the Standard Model (of cosmology). It is based on the general theory of relativity and several assumptions - one being that the universe may be described as homogeneous.

95 % is still unknown

- But the universe is not homogeneous so we should include inhomogeneities (structures) when we describe the universe. This will add extra terms to the equations for our universe - even when you go to scales so large that the structures are blurred, and the universe seems to be homogeneous. The question then is whether these extra terms in some mysterious way disappear, so that they become negligible in our universe, or if they persist and affect our observations, said Dr Koksbang.

With her Villum Young Investigator Grant, Dr Koksbang will investigate whether an updated Standard Model can better explain the many discrepancies that cannot be explained today. The hope is also to gain a better understanding of the 95% of the universe’s content, that we do not currently know what is.

- We only know what 5% of the universe’s content is. That is the matter that stars, galaxies, planets, etc. are made of. The remaining 95% we call dark matter and dark energy – they represent substances that we have never seen, explained Dr Koksbang.

Meet the researcher

Sofie Marie Koksbang is an astrophysicist and postdoc at the Center for Cosmology and Particle Physics Phenomenology and the recipient of a Villum Young Investigator grant of DKK 6 million.

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