Holomorphic Yang-Mills fields on $B$-branes
Andrés Viña
TL;DR
The work generalizes holomorphic gauge fields and Yang-Mills theory from vector bundles to B-branes, treating branes as objects in $D^b(X)$ and introducing a holomorphic gauge field as a lift to the first jet complex. The Atiyah class emerges as the obstruction to existence, and, when present, the gauge fields form a finite-dimensional affine space; for stratified manifolds and in particular flag varieties, uniqueness (or at most one) gauge field results are proved. The Yang-Mills functional is defined via curvature data on cohomology sheaves and extended to branes, leading to an algebraic description: Yang-Mills fields on a reflexive brane correspond to the zeros of $m$ cubic-degree equations in $m$ variables, where $m={\rm dim}\,{\rm Ext}^0({\mathscr F}^{\bullet},\Omega^1({\mathscr F}^{\bullet}))$. The paper thus bridges derived-category brane theory with holomorphic gauge theory, providing concrete computational frameworks (Euler-Poincaré mapping, cones, and generator sets) and yielding concrete bounds in the flag-variety case. These insights advance the mathematical understanding of holomorphic gauge theories in complex geometry and their categorical underpinnings.
Abstract
Considering $B$-branes over a complex manifold $X$ as objects of the bounded derived category of coherent sheaves over $X$, we define holomorphic gauge fields on $B$-branes and introduce the Yang-Mills functional for these fields. These definitions extend well-known concepts in the context of vector bundles to the setting of $B$-branes. For a given $B$-brane, we show that its Atiyah class is the obstruction to the existence of gauge fields. When $X$ is the variety of complete flags in a $3$-dimensional complex vector space, we prove that any $B$-brane over $X$ admits at most one holomorphic gauge field. Furthermore, we establish that the set of Yang-Mills fields on a given $B$-brane, if nonempty, is in bijective correspondence with the points of an algebraic set defined by $m$ complex polynomials of degree less than four in $m$ indeterminates, where $m$ is the dimension of the space of morphisms from the brane to its tensor product with the sheaf of holomorphic one-forms.
