Seminars & Talks

23.04.2025 at the Theoretical Physics group at Università degli Studi di Milano-Bicocca (Milan, Italy)

Title:  Gauging global symmetries with magnetic quivers

Abstract: The gauging of Coulomb branch isometry subgroups of 3d N=4 quiver gauge theories can be realised through simple combinatorial operations on quivers. The effect on the Coulomb branch is a hyper-Kähler quotient. In this talk I will introduce these combinatorial techniques, called quotient quiver subtraction and quiver polymerisation. These techniques will be illustrated by examples from a variety of physical contexts including the moduli space of instantons, four dimensional theories, and the six dimensional (E6,E6) minimal conformal matter theory.ferred to as minimal (E6,E6) conformal matter. 

07.03.2025 at Quiver Meeting

Title:  Orthosymplectic quotient quiver subtraction

Guhesh Kumaran, Imperial College London

The gauging of Coulomb branch isometry subgroups of 3d N=4 quiver gauge theories can be realised through simple combinatorial operations on quivers. The effect on the Coulomb branch is a hyper-Kähler quotient. In this talk I will introduce orthosymplectic quotient quiver subtraction, which gauges SU(2), SU(3), G2, and SO(7) subgroups of the Coulomb branch isometry of unframed orthosymplectic quivers. This algorithm has origins in 6d N=(1,0) through Type IIA brane systems and magnetic quivers. I will demonstrate features of the algorithm through examples, which are mostly drawn from nilpotent orbit closures. Along the way we will encounter new orthosymplectic quivers which have unitary counterparts as well as constructions of certain F4 nilpotent orbits which were not known before. Finally, I will use orthosymplectic quotient quiver subtraction to give a novel magnetic quiver for the Higgs branch of the 6d N=(1,0) worldvolume theory of two ½ M5 branes on E6 Klein singularity and one M5 brane on E6 Klein singularity. The latter is often referred to as minimal (E6,E6) conformal matter. 

15.01.25 - 17.01.25 at Iberian Strings 2025

This was a poster presented at the Iberian Strings 2025 conference in Bilbao, Spain. 

The poster is based on one of my publications called "Quiver Polymerisation", Journal of High Energy Physics, vol. 11, p. 168, 2024.

11.02.2025

Title: Quotient quiver subtraction

Speaker: Guhesh Kumaran, Imperial College London

This talk was given as part of the Geometry, Algebra, and Theoretical Physics seminar series in the Department of Mathematics, Imperial College London. 

03.11.2023 at Quiver Meeting

Title: SU(n) hyper-Kähler quotients of Coulomb branches of 3d N=4 quiver gauge theories

Speaker: Guhesh Kumaran (Imperial College London)

The difficult problem of gauging Coulomb branches of 3d N=4 quiver gauge theories has been tackled from a class S perspective in the past. In this talk, I will present some first steps in viewing Coulomb branch gauging/hyper-Kähler quotient as a quiver subtraction. This quiver subtraction can produce the gauging of an SU(n) subgroup of the Coulomb branch global symmetry of a unitary quiver gauge theory beyond class S theories. This involves the subtraction of a "bad" quiver, in the sense of Gaiotto and Witten, and has an interpretation in class S as a Riemann surface with two maximal punctures. I will outline some of the rules of this quiver subtraction and present many examples which highlight the structure of the resulting moduli spaces. Particularly interesting outcomes involve relationships between nilpotent orbit closures, affine Grassmannian slices, and Slodowy slices and intersections. Many of these relationships have not been found in the mathematics literature before. This is based on a joint work ArXiv: 2308.05853 with Amihay Hanany and Rudolph Kalveks. 

31.10.2023

Title: Coulomb branches: quiver subtraction, magnetic quivers, the monopole formula [2/2]

Speaker: Guhesh Kumaran, Imperial College London

This talk was given as part of the Geometry, Algebra, and Theoretical Physics seminar series in the Department of Mathematics, Imperial College London. 

24.10.2023

Title: Coulomb branches: quiver subtraction, magnetic quivers, the monopole formula [1/2]

Speaker: Guhesh Kumaran, Imperial College London

This talk was given as part of the Geometry, Algebra, and Theoretical Physics seminar series in the Department of Mathematics, Imperial College London.