Biofabrication : reappraising the definition of an evolving field

Biofabrication is an evolving research field that has recently received significant attention. In particular, the adoption of Biofabrication concepts within the field of Tissue Engineering and Regenerative Medicine has grown tremendously, and has been accompanied by a growing inconsistency in terminology. This article aims at clarifying the position of Biofabrication as a research field with a special focus on its relation to and application for Tissue Engineering and Regenerative Medicine. Within this context, we propose a refined working definition of Biofabrication, including Bioprinting and Bioassembly as complementary strategies within Biofabrication

Integrable sigma models with theta=pi

A fundamental result relevant to spin chains and two-dimensional disordered systems is that the sphere sigma model with instanton coupling theta=pi has a non-trivial low-energy fixed point and a gapless spectrum. This result is extended to two series of sigma models with theta=pi: the SU(N)/SO(N) sigma models flow to the SU(N)_1 WZW theory, while the O(2N)/O(N)\times O(N) models flow to O(2N)_1 (2N free Majorana fermions). These models are integrable, and the exact quasiparticle spectra and S matrices are found. One interesting feature is that charges fractionalize when theta=pi. I compute the energy in a background field, and verify that the perturbative expansions for \theta=0 and pi are the same as they must be. I discuss the flows between the two sequences of models, and also argue that the analogous sigma models with Sp(2N) symmetry, the Sp(2N)/U(N) models, flow to Sp(2N)_1.Comment: 31 pages, 2 figures. v2: corrects many typos. v3: corrects more typos, adds referenc