I will review the quantum measurement problem, and explain why it is not solved by decoherence. Then I will give the theory and phenomenology of collapse modes. These are effective theories, that explain state vector reduction by introducing a small non-linearly coupled noise or fluctuation term into the Schrodinger equation. The form of the modified Schrodinger equation is fixed by the twin requirements of preservation of state vector normalization, and no faster than light signaling, with the Born then a derivable consequence, not an independent postulate. Collapse models are the subject of ongoing theoretical and experimental investigation. I will summarize a few of the latest experimental results, and give a list of pertinent references.

Stephen Louis Adler was born in New York City. He received an A.B. degree at Harvard University in 1961, and Ph.D. from Princeton University in 1964. Prof. Adler was elected a Member of the National Academy of Sciences in 1975. He became a member of the Institute for Advanced Study in 1966, then a full Professor of Theoretical Physics in 1969, and was named "New Jersey Albert Einstein Professor" at the institute in 1979. Prof. Adler's seminal papers on high energy neutrino processes, current algebras, soft pion theorems, sum rules, and perturbation theory anomalies helped lay the foundations for the current standard model of elementary particle physics.