We review the construction and properties of four dimensional string models, using free fermions on the world-sheet. We prove that as opposed to gauge symmetries, broken space-time supersymmetry can only be restored continuously by decompactification.

All maximal supergravities in four space-time dimensions are presented. The ungauged Lagrangians can be encoded in an E7(7)\Sp(56;R)/GL(28) matrix associated with the freedom of performing electric/magnetic duality transformations. The gauging is defined in terms of an embedding tensor Θ which encodes the subgroup of E7(7) that is realized as a local invariance. This embedding tensor may imply ...

While 4D models (3D plus time) are becoming more prevalent in design and construction, the characteristics and use of these tools is still being explored. Research at CIFE(Center for Integrated Facility Engineering) is focusing on the usability of the models not only in terms of their visual and communicative impact but impact on the construction design process. We are developing a 4D-CAD tool ...