The scientist from Ural Federal University, Yekaterinburg considering the black holes as test material and found out the theories of gravity appear to work accurately in cosmological level. In Horndeski theory the subclass is difficult in relevant to real world.

Researchers accepts Black holes as real objects exists, preferably than hypothetical objects. The fact in physics has marked noble prize in 2015 as gravitational waves received. They claim that general theory of relativity is correct by one of the proof.

Extended Theories of Gravity

All the influences of fundamental science, except gravitation derived in quantum language. The variabilities specify the relativity is not the end of theory of gravitation. But Physicists implement extended theories of gravity, the models need to be checked and compared with the observations. The extended theories develop assumptions as gravitational constant is not constant. As scientist cannot measure current level of accuracy in changing field they receive it as constant.

Study led by DariaTretyakova, PhD from Ural Federal University, together with her colleague from the University of Tokyo explored one of the theories of this class the so-called Horndeski theory. Horndeski framework gives the most general theory of gravity with a scalar field, without instabilities and containing “healthy” physics, that is, no unusual parameters of matter occur.

At the cosmological level the scale at which the universe can be viewed as a single object of study, a subclass of Horndeski models, symmetric with respect to the shift of the scalar field in space and time, have proved themselves well and helped scientists describe the accelerated expansion of the universe without resorting to additional theories.

Brans-Dicke Theory

The formulated simplest theory of gravity with a scalar field is Brans-Dicke theory. Today the class of gravity theories with a scalar field is very wide. Such theories considered one of the most promising ways of expanding the general relativity.

These models chosen for comprehensive testing. The Horndeski models to the astrophysical scale the scale of individual objects of the universe and found out that black holes as real objects turn out to be unstable in the models which previously successfully proved themselves in cosmology.

In addition, these models are hardly suitable for describing the real universe. Because today black holes believed to exist in space as stable objects. However, the scientists proposed a way to construct Horndeski models that ensure black holes stability.