We explain dark energy with equipartition theorem in string landscape .
In this picture , the dark energy origins from extra-dimension and its contribution to cosmic total energy density agrees well with observational results .
In particular , the fine-tuning problem will be avoided and the coincidence problems of cosmological constant can be interpreted naturally , as the contributions of matter and dark energy are determined solely by dimension ratios .
By introducing an instant late-time tunneling , the H _ { 0 } tension can be resolved as well and it is estimated that the probability of tunneling redshift peaks at 0.4 \lesssim z _ { t } \lesssim 0.7 .
It is indicated that the dark energy dominates the very early universe when the three macroscopic dimensions have been created from symmetric breaking .
At this stage , the universe inflates exponentially , behaving as a de Sitter universe .