Quantum Physics

Studying ‘de Sitter space’ to explain gravity in the expanding early universe: Seeing is believing.

More tools are helpful, but having the right tools is preferable. Using multiple dimensions may help to unify competing theories and simplify complex issues in both physics and science fiction.

For instance, Einstein’s theory of general relativity, which is based on the fabric of space-time being deformed by planets or other massive objects, explains how gravity functions in most situations. Under extreme circumstances, such as those present in black holes and cosmic primordial soups, the theory falters.

Many of these issues may be resolved by a method known as superstring theory, which makes use of an additional dimension to connect quantum mechanics and Einstein’s theory. However, this proposal hasn’t been backed up by the necessary evidence.

“We are currently expanding our analysis to look into cosmic entropy and quantum gravity effects,”

Yasuaki Hikida, from the Yukawa Institute for Theoretical Physics.

An investigation into “de Sitter space” is currently being conducted by a team of scientists led by Kyoto University in an effort to explain gravity in the expanding early universe by referring to a higher dimension. They have created a practical method for using holography to compute correlation functions between fluctuations in an expanding universe.

The Yukawa Institute for Theoretical Physics’ Yasuaki Hikida says, “We discovered that our method can be used more broadly than we expected when dealing with quantum gravity.”

Witten charts for three- and four-point functions By using a split representation of bulk-to-bulk propagators, the exchange diagrams can be expressed as three-point function products. Credit: Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.129.061601

In that the positive cosmological constant explains the universe’s expansion, Willem de Sitter’s theoretical models of space describe it in a way that accords with Einstein’s general theory of relativity.

Hikida’s team reshaped existing techniques for handling gravity in anti-de Sitter space to function in expanding de Sitter space in order to more accurately account for what is already known about the universe.

“We are currently extending our analysis to investigate cosmological entropy and quantum gravity effects,” Hikida continues.

The analysis can be easily expanded to a four-dimensional universe, enabling the extraction of information from our actual world, even though the team’s calculations only used a three-dimensional universe as a test case.

Our method enables useful calculations about the subtle changes that reverberated throughout the fabric of our early universe and may help to validate superstring theory.”.

In the magazine Physical Review Letters, the study is published.

More information: Heng-Yu Chen et al, Three-Dimensional de Sitter Holography and Bulk Correlators at Late Time, Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.129.061601

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