Harvard University Department of Astronomy

The Cosmological Constant Recap and synthesis Basic Idea: Add and contrast different measurements of Lambda, where progress hoped for soon. Summarize combined earlier lectures. Start with review of evolution of universe again Effect of Lambda expansion rate of the universe (kinematics) age, distance redshift relation, Alcock-Paczynski test structure formation: empty space with cosmological constant doesn't clump so if fix universe at flat there is less matter to clump and structure forms more slowly cluster number, bulls eye effect, weak lensing since Omegam + Omegalambda + ... = 1 constraining other cosmological parameters will also constrain lambda cosmic microwave background, cluster baryon fraction may have something which is not "constant" but depends on spacetime as universe expands in some intermediate way (still providing acceleration) Measurements summarize: which ones are expected to have new information and when strongest/weakest tests complementarity accounting of matter in the universe Theory Major puzzle for particle theorists many proposals but as details of string theory, the proposed fundamental theory of gravity, are not yet well enough understood there are no conclusive predictions or mechanisms Some references Home Syllabus References Lecture References Useful Links Contact Info