Scientists create model of holographic dark energy that is no longer unstable

In 1998, scientists discovered that our universe expands with acceleration, and in order to explain this effect, the concept of dark matter was introduced. This is a special type of energy that fills up all of existing space-time but is impossible to detect by direct methods.

Its existence and features are portrayed in a standard cosmological model, but scientists have found a number of issues (for example, the cosmological constant problem and the fine-tuning problem) that cannot be adequately addressed by this representation.

Scientists at Kant Baltic Federal University (BFU) have considered an alternative model—a holographic dark energy model—and have proven its viability. Their findings are published in the journal Physics Letters B.

“It’s a slightly different way of looking at the nature of the accelerated expansion of the universe. It stems from the holographic principle that follows from quantum gravity and string theory. According to it, all values inside a certain amount of volume can be described by parameters that are observed on its boundary.

“In other words, the universe can be represented in the form of some hologram, and it can be described by the parameters on its boundaries,” says Alexander Tepliakov, junior researcher at the laboratory for mathematical modeling of complex and non-linear systems at BFU.

A new model of holographic dark energy within the holographical principle was suggested in 2004. However, the new model had a limitation. Dark energy is usually represented as some kind of liquid that homogenously and evenly fills the universe. A special parameter called “square of the sound velocity” is used to analyze the fluctuations inside this liquid.

If it turns out to be negative as a result of calculations, the model is considered unstable. Previous studies carried out as part of a holographic dark energy model had a negative sound speed square.

The research team suggests that the holographic dark energy should not be seen as a liquid. Instead, it must be considered as dark energy perturbations, taking into account its metric properties. They concluded that the model is in fact stable.

“Now, we need to understand to what extent our model corresponds to observation data provided by space-based telescopes. In 2024, precise data became available for analysis: the relationship between red shift for Type Ia supernovae, baryon acoustic oscillations. By comparing the proposed cosmological model with this data, we are able to assess whether it describes the real universe,” says Tepliakov.