QFEXT11 is a continuation of a series of workshops of the same title held at the University of Leipzig in 1989, 1992, 1995, 1998, 2001, 2007, at the University of Oklahoma in 2003, 2009, and at the University of Barcelona in 2005. Started with the intention of bringing about an East-West scientific dialog, QFEXT developed into one of the most prominent meetings in the field of the Casimir effect, vacuum energy, and related questions in several areas, ranging from quantum field theory and cosmology to atomic, subnuclear, and experimental physics. Typically mathematical questions related to spectral geometry are represented as well. These meetings have created a unique atmosphere where theoreticians, mathematicians and experimentalists are brought together for a week, where talks by colleagues that they might rarely hear otherwise often spark lively debate and result in numerous collaborations.

QFEXT11 will also celebrate the 75th anniversary of the seminal paper “Consequences of the Dirac Theory of the Positron”, by W. Heisenberg and H. Euler (Zeitschr. Phys. 98, 714-732, 1936), which played an important part in establishing the study of quantum fields in classical background fields. We plan to include a special session devoted to Heisenberg-Euler effective Lagrangians and their impact in modern physics.