February 3, 2023

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Flat or curved space-time? It can be reproduced in the laboratory

According to the theory of relativity, space and time are closely related. The curvature of our universe can hardly be measured, and the structure of space-time is invariant. But other variants are also possible. In their search for ultracold quantum gases, German physicists have simulated an entire family of universes with curved space-time. Details are posted at nature.

Space-time has more than one structure

The composition of space-time from the Big Bang to the present has been studied by astrophysicists all over the world, albeit on the basis of only one possibility – observing the universe in which we live. But you can simulate other variables.

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In flat space – like our universe – the shortest distance between two points is always a straight line. One can imagine that in its infancy our universe was curved. Therefore, the study of the consequences of curved space-time is an important research problem to be addressed A team of scientists from the University of Heidelberg Under the guidance of prof. Marcus Oberthaler. The researchers created a quantum field simulator for this.

It consists of a cloud of potassium atoms that have been cooled to a few nanokelvins above absolute zero. Under these conditions, they form Bose-Einstein condensates, a special type of atomic gas, considered by many to be another state of matter.

It is an idealized background in which even the smallest excitations, that is, changes in the energy state of atoms, become visible. The shape of the atomic cloud determines the dimensions and properties of the space-time in which this excitement travels like waves. In our world, there are three dimensions of space, as well as a fourth: time.
the professor. Marcus Oberthaler

In the experiment conducted, the atoms were trapped in a thin film, and the excitations could only propagate in two spatial directions. At the same time, the atomic cloud in the other two dimensions can be formed in almost any way, thanks to which the curvature of space-time can also be achieved. The interaction between atoms can be precisely regulated by the magnetic field, which changes the propagation speed of the wave excitation on a Bose-Einstein capacitor.

For waves on a condensate, the speed of propagation depends on the density of the atoms and their interaction. This gives us the ability to create conditions like an expanding universe.
the professor. Stefan Flörchinger from the University of Jena

A quantum field simulator can render cosmic phenomena measurable, such as the production of particles based on the expansion of space and even the curvature of space-time. This allows you to study different variants of universes and consider which one is the best.

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