Harvard University Department of Astronomy

The Cosmological Constant Structure Formation Basic Idea: If the universe is spatially flat and there is a postive cosmological constant, then there is a smaller matter density in the universe than if there were no cosmological constant. Structure forms by matter falling towards other matter, and with a smaller matter density this happens more slowly because the pull is weaker. Theory analytical expression faster growth when there is more matter Systems of interest: cluster number What clusters are most recently collapsed rough indicator of number count: Press Schechter What one measures about them indicators: number itself, arcs Observations Current results not compelling controversial selection effects, small sample Future data sets should improve this significantly bulls eye effect What it is: fingers of god and compression/rarefaction near over/under densities (a problem turned into a feature...) Measure with data: contours of constant density Future plans and hopes with this method Useful with upcoming surveys perhaps, under study weak lensing What it is faint blue galaxies, lss What one measures: correlations Observations Method: need large area Current Results first detections only this past spring Future plans for surveys and vast improvement Other cosmological tests and questions these systems are used for Some References Home Syllabus References Lecture References Useful Links Contact Info Back to Harvard University Department of Astronomy Academics. Back to Harvard University Department of Astronomy Courses.