Basic and Equivariant Cohomology in Balanced Topological Field Theory

We present a detailed algebraic study of the N=2 cohomological set--up describing the balanced topological field theory of Dijkgraaf and Moore. We emphasize the role of N=2 topological supersymmetry and $sl(2,R)$ internal symmetry by a systematic use of superfield techniques and of an $sl(2,R)$ covariant formalism. We provide a definition of N=2 basic and equivariant cohomology, generalizing Dijkgraaf's and Moore's, and of N=2 connection. For a general manifold with a group action, we show that: $i$) the N=2 basic cohomology is isomorphic to the tensor product of the ordinary N=1 basic cohomology and a universal $sl(2,R)$ group theoretic factor: $ii$) the affine spaces of N=2 and N=1 connections are isomorphic.Comment: 50 pages, Plain TeX, no figures, requires AMS font files amssym.def and amssym.tex; historical part of the introduction revise

N=4 Yang--Mills theory as a complexification of the N=2 theory

A complexification of the twisted $\N=2$ theory allows one to determine the N=4 Yang--Mills theory in its third twist formulation. The imaginary part of the gauge symmetry is used to eliminate two scalars fields and create gauge covariant longitudinal components for the imaginary part of the gauge field. The latter becomes the vector field of the thirdly twisted $\N=4$ theory. Eventually, one gets a one to one correspondence between the fields of both theories. Analogous complexifications can be done for topological 2d-gravity and topological sigma models

A Suggestion for Modification of Vafa-Witten Theory

Using the Mathai-Quillen formalism we reexamine the twisted N=4 supersymmetric model of Vafa-Witten theory. Smooth out the relation between the supersymmetric action and the path integral representation of the Thom class.Comment: Latex, 23kb, no figure

New Results on N=4 SuperYang-Mills Theory

The N=4 SuperYang--Mills theory is covariantly determined by a U(1) \times SU(2) \subset SL(2,R) \times SU(2) internal symmetry and two scalar and one vector BRST topological symmetry operators. This determines an off-shell closed sector of N=4 SuperYang-Mills, with 6 generators, which is big enough to fully determine the theory, in a Lorentz covariant way. This reduced algebra derives from horizontality conditions in four dimensions. The horizontality conditions only depend on the geometry of the Yang-Mills fields. They also descend from a genuine horizontality condition in eight dimensions. In fact, the SL(2,R) symmetry is induced by a dimensional reduction from eight to seven dimensions, which establishes a ghost-antighost symmetry, while the SU(2) symmetry occurs by dimensional reduction from seven to four dimensions. When the four dimensional manifold is hyperKahler, one can perform a twist operation that defines the N=4 supersymmetry and its SL(2,H)\sim SU(4) R-symmetry in flat space. (For defining a TQFT on a more general four manifold, one can use the internal SU(2)-symmetry and redefine a Lorentz SO(4) invariance). These results extend in a covariant way the light cone property that the N=4 SuperYang-Mills theory is actually determined by only 8 independent generators, instead of the 16 generators that occur in the physical representation of the superPoincare algebra. The topological construction disentangles the off-shell closed sector of the (twisted) maximally supersymmetric theory from the (irrelevant) sector that closes only modulo equations of motion. It allows one to escape the question of auxiliary fields in N=4 SuperYang-Mills theory.Comment: 14 page

Topological twisting of conformal supercharges

Putting a twisted version of N=4 super Yang-Mills on a curved four-dimensional manifold generically breaks all conformal supersymmetries. In the special case where the four-manifold is a cone, we show that exactly two conformal supercharges remain unbroken. We construct an off-shell formulation of the theory such that the two unbroken conformal supercharges combine into a family of topological charges parameterized by CP^1. The resulting theory is topological in the sense that it is independent of the metric on the three-dimensional base of the cone.Comment: 1+33 pages; references added, an address change

Observables in Topological Yang-Mills Theories With Extended Shift Supersymmetry

We present a complete classification, at the classical level, of the observables of topological Yang-Mills theories with an extended shift supersymmetry of N generators, in any space-time dimension. The observables are defined as the Yang-Mills BRST cohomology classes of shift supersymmetry invariants. These cohomology classes turn out to be solutions of an N-extension of Witten's equivariant cohomology. This work generalizes results known in the case of shift supersymmetry with a single generator.Comment: 27 pages, Late

Africans winning the World Cup? What 'decolonisation by integration' could teach us about black French identity

Following claims that Africa actually won the 2018 FIFA World Cup, students Arbie Baguios (MSc International Development and Humanitarian Emergencies), Ynis Isimbi (Msc Development Studies) and David Yamron (MSc Development Management) explore French identity and its colonial past

Mass Perturbations in Twisted N=4 Supersymmetric Gauge Theories

Mass perturbations of the twisted N=4 supersymmetric gauge theory considered by Vafa and Witten to test S-duality are studied for the case of Kahler four-manifolds. It is shown that the resulting mass-perturbed theory can be regarded as an equivariant extension associated to a U(1) symmetry of the twisted theory, which is only present for Kahler manifolds. In addition, it is shown that the partition function, the only topological invariant of the theory, remains invariant under the perturbation.Comment: 36 pages, phyzzx, a footnote and two references adde

Africans winning the World Cup? What 'decolonisation by integration' could teach us about black French identity

Following claims that Africa actually won the 2018 FIFA World Cup, students Arbie Baguios (MSc International Development and Humanitarian Emergencies), Ynis Isimbi (Msc Development Studies) and David Yamron (MSc Development Management) explore French identity and its colonial past

Euclidean SYM Theories by Time Reduction and Special Holonomy Manifolds

Euclidean supersymmetric theories are obtained from Minkowskian theories by performing a reduction in the time direction. This procedure elucidates certain mysterious features of Zumino's N=2 model in four dimensions, provides manifestly hermitian Euclidean counterparts of all non-mimimal SYM theories, and is also applicable to supergravity theories. We reanalyse the twists of the 4d N=2 and N=4 models from this point of view. Other applications include SYM theories on special holonomy manifolds. In particular, we construct a twisted SYM theory on Kaehler 3-folds and clarify the structure of SYM theory on hyper-Kaehler 4-folds.Comment: 21 pages, LaTeX fil