# The Cosmological Constant Problem, Dark Energy, and the Landscape of String Theory

@article{Bousso2012TheCC, title={The Cosmological Constant Problem, Dark Energy, and the Landscape of String Theory}, author={Raphael Bousso}, journal={arXiv: Cosmology and Nongalactic Astrophysics}, year={2012} }

In this colloquium-level account, I describe the cosmological constant problem: why is the energy of empty space at least 60 orders of magnitude smaller than several known contributions to it from the Standard Model of particle physics? I explain why the "dark energy" responsible for the accelerated expansion of the universe is almost certainly vacuum energy. The second half of the paper explores a more speculative subject. The vacuum landscape of string theory leads to a multiverse in which…

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