Exact effective interactions and 1/4-BPS dyons in heterotic CHL orbifolds
Exact effective interactions and 1/4-BPS dyons in heterotic CHL orbifolds
Motivated by precision counting of BPS black holes, we analyze six-derivative couplings in the low energy effective action of three-dimensional string vacua with 16 supercharges. Based on perturbative computations up to two-loop, supersymmetry and duality arguments, we conjecture that the exact coefficient of the \nabla^2(\nabla\phi)^4 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mi>∇</mml:mi><mml:mn>2</mml:mn></mml:msup><mml:mo stretchy="false" form="prefix">(</mml:mo><mml:mi>∇</mml:mi><mml:mi>ϕ</mml:mi><mml:msup><mml:mo …