Muhammad Bilal Azam, Maqbool Ahmed
Session: Poster Presentation Session of SBASSE Graduate Students with the School’s Advisory Board (2020)
Institution: Department of Physics, Lahore University of Management Sciences
Cosmological constant (Λ) is one of the expected candidates for dark energy. However, it also raises a fundamental question that why “only now” cosmological constant is of the order of ambient density? Answer comes from the unimodular gravity which predicts the fluctuations in Λ and causal set theory predicts the magnitude of these fluctuations. For closed universe, the ansatz  provides a Λ, which fluctuates about zero, and is comparable to the ambient energy density at all times.
 Ahmed, M., Dodelson, S., Greene, P. B., and Sorkin, R. (2004). Everpresent Λ. Phys. Rev. D, 69:103523
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