First Semester Reflection

Postcard from Maura Hand, during the Linfield College Semester Abroad Program at the Universidad de Alicante in Spai

Deborah Olsen Public Service Scholarship Essay

In this essay, Maura Hand reflects on the ten weeks she spent interning with the State Department\u27s Office of Foreign Missions (OFM) in San Francisco, California

Conditions for Existence of Dual Certificates in Rank-One Semidefinite Problems

Several signal recovery tasks can be relaxed into semidefinite programs with rank-one minimizers. A common technique for proving these programs succeed is to construct a dual certificate. Unfortunately, dual certificates may not exist under some formulations of semidefinite programs. In order to put problems into a form where dual certificate arguments are possible, it is important to develop conditions under which the certificates exist. In this paper, we provide an example where dual certificates do not exist. We then present a completeness condition under which they are guaranteed to exist. For programs that do not satisfy the completeness condition, we present a completion process which produces an equivalent program that does satisfy the condition. The important message of this paper is that dual certificates may not exist for semidefinite programs that involve orthogonal measurements with respect to positive-semidefinite matrices. Such measurements can interact with the positive-semidefinite constraint in a way that implies additional linear measurements. If these additional measurements are not included in the problem formulation, then dual certificates may fail to exist. As an illustration, we present a semidefinite relaxation for the task of finding the sparsest element in a subspace. One formulation of this program does not admit dual certificates. The completion process produces an equivalent formulation which does admit dual certificates

Rejoinder: Classifier Technology and the Illusion of Progress

Rejoinder: Classifier Technology and the Illusion of Progress [math.ST/0606441]Comment: Published at http://dx.doi.org/10.1214/088342306000000079 in the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

John Terrane: A Study of a First World War Revisionist

Of all the British military historians who started writing about the First World War during the boom of the sixties, perhaps no one has had greater influence or generated more controversy than John Alfred Terraine. As G.F. Elliot wrote in a 1965 review, John Terraine is one of the younger generation of British military analysts who are now proving, with brilliance and vigour, the value of the long view in putting World War I in proper perspective. It is this idea of perspective, trying to bring balance to the historical arguments concerning the British contribution to the First World War, that drove John Terraine in all his work. Terraine\u27s nine books on the British Expeditionary Force challenged the comfortable mainstream theories and assumptions, defended the generals, and debunked the myths. His opinions gave him both notoreity and influence