"Mathematicians are challenging the idea that dark energy is responsible for the accelerating expansion of the universe. In a new paper published in Proceedings of the Royal Society A, mathematicians from the University of California, Davis, provide mathematical proof that instabilities inherent in the Einstein-Euler equations imply that the current model of the expanding universe is not viable. The Einstein-Euler equations are a union of general relativity and fluid dynamics equations used to model astronomical phenomena such as galaxies, black holes and cosmic expansion."
https://www.ucdavis.edu/blog/taking-dark-energy-out-equation [ucdavis.edu]
Basically, mathematicians provide an explanation for accelerated universe expansion that doesn't require fudging our equations with magical energy so that it fits our data.