Anomaly-free brane worlds in seven dimensions

We present an orbifold compactification of the minimal seven-dimensional supergravity. The vacuum is a slice of seven-dimensional anti-de Sitter space where six-branes of opposite tension are located at the orbifold fixed points. The cancellation of gauge and gravitational anomalies restricts the gauge group and matter content on the boundaries. In addition, anomaly cancellation fixes the boundary gauge couplings in terms of the gravitational constant, and the mass parameter of the Chern-Simons term.