In a laboratory experiment, researchers from the University of Heidelberg have succeeded in achieving a manipulable space-time efficiency. In their search for very cold quantum gases, they were able to simulate an entire family of curved universes to study different cosmological scenarios and compare them with the predictions of a theoretical quantum field model.
According to Einstein’s theory of relativity, space and time are closely related. In our universe, whose curvature can hardly be measured, the structure of this space-time is fixed. In a laboratory experiment, researchers from the University of Heidelberg have succeeded in achieving a manipulable space-time efficiency. In their search for very cold quantum gases, they were able to simulate an entire family of curved universes to study different cosmological scenarios and compare them with the predictions of a theoretical quantum field model. The search results are published in nature.
The emergence of space and time on cosmic time scales from the Big Bang to the present day is the subject of current research that can only be based on observations of our unique universe. The expansion and curvature of space are essential to cosmological models. In a flat space like our current universe, the shortest distance between two points is always a straight line. “It is plausible, however, that our universe was curved in its initial stage. Investigating the consequences of curved space-time is therefore an urgent research question,” says Prof. Dr. Markus Oberthaler, researcher at the Kirchhoff Institute for Physics in Heidelberg. University. With his research group “Artificial Quantum Systems”, he developed a quantum field simulator for this purpose.
A quantum field simulator created in the lab consists of a cloud of potassium atoms cooled to a few nanokelvins above absolute zero. This results in a Bose-Einstein condensate – a special quantum mechanical state of an atomic gas that is achieved at extremely cold temperatures. Professor Oberthaler explains that the Bose-Einstein condensate is an ideal background against which even the smallest excitations, that is, changes in the energy state of atoms, are visible. The shape of the atomic cloud determines the dimensions and properties of the space-time over which these waves travel like waves. In our universe, there are three dimensions of space in addition to the fourth dimension: time.
In the experiment conducted by the Heidelberg physicists, the atoms were trapped in a thin film. So excitation can only propagate in two spatial directions – two-dimensional space. At the same time, the atomic cloud in the remaining two dimensions can be shaped in almost any way, which also makes it possible to perceive curved space-time. The interaction between atoms can be finely tuned by a magnetic field, which changes the speed of wave excitation propagation on a Bose-Einstein condenser.
For waves on a capacitor, the speed of propagation depends on the density of the atoms and their interaction. This gives us the possibility of creating conditions similar to those in an expanding universe, ”explains Professor Stefan Flurchinger. The researcher, who previously worked at the University of Heidelberg and joined the University of Jena earlier this year, developed a theoretical quantum field model used for the quantitative comparison of experimental results.
Using a quantum field simulator, cosmic phenomena, such as the production of particles based on the expansion of space, and even the curvature of space-time, can be made measurable. Cosmic problems usually occur on unimaginable levels. Being able to study them specifically in the laboratory opens up entirely new research possibilities by allowing us to experimentally test new theoretical paradigms,” says Celia Firman, lead author of the “Nature” article. Markus Oberthaler, whose research group is also part of the STRUCTURES group For Excellence by Ruperto Carola: “Studying the interaction between curved space-time and quantum mechanics states in the laboratory will keep us busy for some time.”
The work was carried out within the framework of the Collaborative Research Center 1225, “Insulated and Global Quantum Systems in Extreme Conditions” (ISOQUANT), of the University of Heidelberg.
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