Publications

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In his 2009 Prague speech and the 2010 Nuclear Posture Review, President Barack Obama committed the United States to take concrete steps toward nuclear disarmament while maintaining a safe, secure, and effective nuclear deterrent. There is an inherent tension between these two goals that is best addressed through improved integration of nuclear weapons objectives with nuclear arms control objectives. This article reviews historical examples of the interaction between the two sets of objectives, develops a framework for analyzing opportunities for future integration, and suggests specific ideas that could benefit the nuclear weapons enterprise as it undergoes transformation and that could make the future enterprise compatible with a variety of arms control futures. © 2010 Monterey Institute of International Studies, James Martin Center for Nonproliferation Studies.

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2010 NPR and President Obama's 2009 Prague Speech highlighted two key objectives with an inherent underlying tension: (1) Moving towards a world free of nuclear weapons; and (2) Sustaining a safe, secure, and effective nuclear arsenal. Objective 1 depends, inter alia, upon reductions in stockpiles at home and abroad and maintaining stability. Objective 2 depends upon needed investments in modernization and life extension. Objectives being pursued predominantly in parallel by largely separate communities.

Historically, U.S. arms control policy and the U.S. nuclear weapons enterprise have been reactive to each other, rather than interdependent and mutually reinforcing. One element of the divergence has been the long timescale necessary to plan and create substantive changes in the infrastructure vs. the inherent unpredictability of arms control outcomes. We explore several examples that illustrate this tension, some of the costs and implications associated with this reactive paradigm, and illustrate that, while the nuclear weapons enterprise has long considered the implications of arms control in sizing capacity of its missions, it has not substantively considered arms control in construction requirement for capabilities and products. Since previous arms control agreements have limited numbers and types of deployed systems, with delivery systems as the object of verification, this disconnect has not been forefront. However, as future agreements unfold, the warhead itself may become the treaty limited item and the object of verification. Such a scenario might offer both the need and the opportunity to integrate nuclear weapons and arms control requirements in unprecedented ways. This paper seeks to inspire new thinking on how such integration could be fostered and the extent to which it can facilitate significant reduction in nuclear stockpiles.

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We change the diffusion mechanism of adsorbed Ge-Si dimers on Si(001) using the electric field of a scanning tunneling microscope tip. By comparing the measured field dependence with first-principles calculations we conclude that, in negative field, i.e., when electrons are attracted towards the vacuum, the dimer diffuses as a unit, rotating as it translates, whereas, in positive field the dimer bond is substantially stretched at the transition state as it slides along the substrate. Furthermore, the active mechanism in positive fields facilitates intermixing of Ge in the Si lattice, whereas intermixing is suppressed in negative fields. © 2003 The American Physical Society.