What is dark fluid in cosmology?

In cosmology, "dark fluid" is a theoretical concept that attempts to unify dark energy and dark matter into a single entity. Traditional models of the universe consider dark energy as the mysterious force driving the accelerated expansion of the universe and dark matter as the unseen mass that exerts gravitational influence on visible matter and structures. The idea behind dark fluid is to represent these two components as manifestations of a single, more fundamental entity. This can simplify some of the complexities and challenges associated with having separate dark matter and dark energy components in cosmological models. The dark fluid concept suggests that a single type of fluid, characterized by an equation of state, can exhibit both the properties of dark energy (which has a negative pressure contributing to cosmic expansion) and dark matter (which has a positive pressure and contributes to gravitational attraction). Researchers use various formulations to describe dark fluid, including specific models where the energy density and pressure vary depending on the scale of the universe. While the concept of dark fluid is still speculative and under investigation, it is one of many approaches being explored to better understand the mysterious components of our universe.