Logarithmic Connections, WZNW Action, and Moduli of Parabolic Bundles on the Sphere

Moduli spaces of stable parabolic bundles of parabolic degree 0 over the Riemann sphere are stratified according to the Harder–Narasimhan filtration of underlying vector bundles. Over a Zariski open subset $$\mathscr {N}_{0}$$ N 0 of the open stratum depending explicitly on a choice of parabolic weights, a real-valued function $$\mathscr {S}$$ S is defined as the regularized critical value of the non-compact Wess–Zumino–Novikov–Witten action functional. The definition of $$\mathscr {S}$$ S depends on a suitable notion of parabolic bundle ‘uniformization map’ following from the Mehta–Seshadri and Birkhoff–Grothendieck theorems. It is shown that $$-\mathscr {S}$$ - S is a primitive for a (1,0)-form $$\vartheta $$ ϑ on $$\mathscr {N}_{0}$$ N 0 associated with the uniformization data of each intrinsic irreducible unitary logarithmic connection. Moreover, it is proved that $$-\mathscr {S}$$ - S is a Kähler potential for $$(\Omega -\Omega _{\mathrm {T}})|_{\mathscr {N}_{0}}$$ ( Ω - Ω T ) | N 0 , where $$\Omega $$ Ω is the Narasimhan–Atiyah–Bott Kähler form in $$\mathscr {N}$$ N and $$\Omega _{\mathrm {T}}$$ Ω T is a certain linear combination of tautological (1, 1)-forms associated with the marked points. These results provide an explicit relation between the cohomology class $$[\Omega ]$$ [ Ω ] and tautological classes, which holds globally over certain open chambers of parabolic weights where $$\mathscr {N}_{0} = \mathscr {N}$$ N 0 = N .

A Map Between Moduli Spaces of Connections

We are interested in studying moduli spaces of rank 2 logarithmic connections on elliptic curves having two poles. To do so, we investigate certain logarithmic rank 2 connections defined on the Riemann sphere and a transformation rule to lift such connections to an elliptic curve. The transformation is as follows: given an elliptic curve C with elliptic quotient, and the logarithmic connection, we may pullback the connection to the elliptic curve to obtain a new connection on C. After suitable birational modifications we bring the connection to a particular normal form. The whole transformation is equivariant with respect to bundle automorphisms and therefore defines a map between the corresponding moduli spaces of connections. The aim of this paper is to describe the moduli spaces involved and compute explicit expressions for the above map in the case where the target space is the moduli space of rank 2 logarithmic connections on an elliptic curve C with two simple poles and trivial determinant.

On a Possible Logarithmic Connection between Einstein’s Constant and the Fine-Structure Constant, in Relation to a Zero-energy Hypothesis

This paper brings into attention a possible logarithmic connection between Einstein’s constant and the fine-structure constant, based on a hypothetical electro-gravitational resistivity of vacuum: we also propose a zero-energy hypothesis (ZEH) which is essentially a conservation principle applied on zero-energy that mainly states a general quadratic equation having a pair of conjugate mass solutions for each set of coefficients, thus predicting a new type of mass “symmetry” called here “mass conjugation” between elementary particles (EPs) which predicts the zero/non-zero rest masses of all known/unknown EPs to be conjugated in boson-fermion pairs; ZEH proposes a general formula for all the rest masses of all EPs from Standard model, also indicating a possible bijective connection between the three types of neutrinos and the massless bosons (photon, gluon and the hypothetical graviton), between the electron/positron and the W boson and predicting two distinct types of neutral massless fermions (modelled as conjugates of the Higgs boson and Z boson respectively) which are plausible candidates for dark energy and dark matter. ZEH also offers a new interpretation of Planck length as the approximate length threshold above which the rest masses of all known elementary particles have real number values (with mass units) instead of complex/imaginary number values (as predicted by the unique quadratic equation proposed by ZEH).

ALGEBRAIC ISOMONODROMIC DEFORMATIONS AND THE MAPPING CLASS GROUP

The germ of the universal isomonodromic deformation of a logarithmic connection on a stable $n$ -pointed genus $g$ curve always exists in the analytic category. The first part of this article investigates under which conditions it is the analytic germification of an algebraic isomonodromic deformation. Up to some minor technical conditions, this turns out to be the case if and only if the monodromy of the connection has finite orbit under the action of the mapping class group. The second part of this work studies the dynamics of this action in the particular case of reducible rank 2 representations and genus $g>0$ , allowing to classify all finite orbits. Both of these results extend recent ones concerning the genus 0 case.

Logarithmic connections on principal bundles over a Riemann surface

Let [Formula: see text] be a holomorphic principal [Formula: see text]-bundle on a compact connected Riemann surface [Formula: see text], where [Formula: see text] is a connected reductive complex affine algebraic group. Fix a finite subset [Formula: see text], and for each [Formula: see text] fix [Formula: see text]. Let [Formula: see text] be a maximal torus in the group of all holomorphic automorphisms of [Formula: see text]. We give a necessary and sufficient condition for the existence of a [Formula: see text]-invariant logarithmic connection on [Formula: see text] singular over [Formula: see text] such that the residue over each [Formula: see text] is [Formula: see text]. We also give a necessary and sufficient condition for the existence of a logarithmic connection on [Formula: see text] singular over [Formula: see text] such that the residue over each [Formula: see text] is [Formula: see text], under the assumption that each [Formula: see text] is [Formula: see text]-rigid.