Everpresent Λ Cosmology


Kouchekzadeh Yazdi, Y. (2023). Everpresent Λ Cosmology. Perimeter Institute. https://pirsa.org/23050131


Kouchekzadeh Yazdi, Yasaman. Everpresent Λ Cosmology. Perimeter Institute, May. 11, 2023, https://pirsa.org/23050131


          @misc{ pirsa_PIRSA:23050131,
            doi = {10.48660/23050131},
            url = {https://pirsa.org/23050131},
            author = {Kouchekzadeh Yazdi, Yasaman},
            keywords = {Quantum Gravity, Cosmology},
            language = {en},
            title = {Everpresent Λ Cosmology},
            publisher = {Perimeter Institute},
            year = {2023},
            month = {may},
            note = {PIRSA:23050131 see, \url{https://pirsa.org}}

Yasaman Kouchekzadeh Yazdi Dublin Institute For Advanced Studies


I will discuss a number of theoretical, observational, and conceptual aspects of the Everpresent Λ cosmological model arising from fundamental principles in causal set theory and unimodular gravity. In this framework the value of the cosmological constant (Λ) fluctuates, in magnitude and in sign, over cosmic history. At each epoch, Λ stays statistically close to the inverse square root of the spacetime volume. Since the latter is of the order of H^2 today, this provides a way out of the cosmological constant puzzle without fine tuning. I will review the theoretical background of this idea. I will also describe a phenomenological implementation of this model, and discuss recent results on the statistics of its simulations and observational tests of it.