Is there energy in the universe

Is There More Than One Dark Energy?

Exciting hypothesis: So far, physicists have been puzzling over the nature of dark energy - the force that drives the expansion of the cosmos. Now researchers have come up with a new hypothesis. According to this, this mysterious force could not be traced back to a single cause, but to the effect of several interacting quantum fields. As a result, there could be zones in space in which dark energy clumps and thus has an intensified effect.

In our universe there must be a force that counteracts gravity and thereby drives the expansion of the cosmos. But what this dark energy consists of and how it works exactly is completely unknown. Even their existence is so far mere theory. Some researchers suspect that quantum fluctuations in the vacuum could be behind the dark energy. Proponents of the quintessence hypothesis see a scalar field as the originator - a kind of energy field that can interact with matter in a similar way to the Higgs field.

But despite an intensive search, physicists have not come much closer to solving the dark energy puzzle. However, experiments have already ruled out some variants of a quintessential field, including the “chameleon field” or the “symmetrons”.

Multiple fields instead of just one

Now there is a new hypothesis: Researchers working with Yashar Akrami from the Sorbonne University in Paris postulate that dark energy may not only be based on one scalar field, but on the interaction of several. “In our view, dark energy with multiple fields is theoretically well justifiable and it predicts certain observable characteristics,” they explain.

According to their model, the driving force of dark energy arises because several time-variable quantum fields in the cosmos interact with each other and minimally with matter. This causes a decisive difference to the classic quintessence hypothesis: With only one scalar field, fluctuations almost at the speed of light compensate for all inequalities, so that the dark energy appears almost homogeneous and equally strong everywhere.

"Lumps" of dark energy

This is different with dark energy from multiple fields: "The models we are considering here describe a form of dark energy that can form clusters," explain Akrami and his team. Due to the interaction of the fields, fluctuations equalize each other much more slowly, so that local differences can arise. As a result, there could be areas in the universe with slower and areas with faster expansion.

These differences could explain why astronomers come to different values ​​when measuring cosmic dimensions. In addition, another group of researchers recently suggested the existence of a lumped dark energy. They postulate the existence of so-called Generic Objects of Dark Energy (GEODE), which are said to have been created by the atypical collapse of some of the very first stars. Akrami and his colleagues, on the other hand, believe that fields of dark energy pervading the entire cosmos are more likely.

Detectable in turbulence

The problem: under normal circumstances, these fields and the clumping caused by their interactions are undetectable. "Despite qualitative differences in its physics, our model imitates the standard model so effectively that it is indistinguishable from it at the background level," the scientists explain.

But that changes if there are disruptions. They can lead to a "clumping" of dark energy, which would already be detectable with the next generation of telescopes and measuring instruments. "This feature thus provides a good opportunity to test these and similar models of dark energy against the standard model of the cosmological constant," say Akrami and his team. (Preprint, 2020, arXiv: 2008.13660)

Source: arXiv

January 18, 2021

- Nadja Podbregar