On the symmetries of BF models and their relation with gravity

The perturbative finiteness of various topological models (e.g. BF models) has its origin in an extra symmetry of the gauge-fixed action, the so-called vector supersymmetry. Since an invariance of this type also exists for gravity and since gravity is closely related to certain BF models, vector supersymmetry should also be useful for tackling various aspects of quantum gravity. With this motivation and goal in mind, we first extend vector supersymmetry of BF models to generic manifolds by incorporating it into the BRST symmetry within the Batalin-Vilkovisky framework. Thereafter, we address the relationship between gravity and BF models, in particular for three-dimensional space-time.Comment: 29 page

Temperature-Dependent Antiferromagnetic Exchange along 1D Linear Regular Chains of the Phthalonitrile Blatter Radical

1,3-Diphenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl-6,7-dicarbonitrile is an exceptionally stable electron-deficient organic radical with promising potential to be used as a building block in a range of electronic and spintronic materials. The radical has a fully reversible one-electron redox and is highly delocalized, with some spin density reaching as far as the nitrile groups. Two polymorphs, α and β, were identified and characterized by single-crystal X-ray diffractometry. Both polymorphs form one-dimensional (1D) π stacks. However, while in polymorph α radicals are located at evenly interplane distances (3.366 Å), in polymorph β radicals are located at alternate interplane distances (3.182 and 3.318 Å). Magnetic susceptibility measurements for polymorph α indicate strong antiferromagnetic interactions along the 1D regular chain. Magnetic susceptibility data cannot be fully fitted to the Bonner and Fischer model for the 2–300 K temperature range. The steeper rise in paramagnetism above 80 K was rationalized by temperature-dependent antiferromagnetic exchange interactions between radicals within the 1D π stacks, which is indeed supported by Density Functional Theory (DFT) calculations. A microscopic study of the magnetic topology of polymorph α together with the interpretation of its magnetic experimental data was pursued by using a First-Principles Bottom-Up approach. Minuscule changes in crystal packing upon changing the temperature significantly affect the magnetic interaction between spin-containing moieties. Temperature, therefore, is the key player in rationalizing the magnetism in polymorph α