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The Geometry of the Space of BPS Vortex–Antivortex Pairs

The gauged sigma model with target P 1 , defined on a Riemann surface Σ , supports static solutions in which k + vortices coexist in stable equilibrium with k - antivortices. Their moduli space is a noncompact complex manifold M ( k + , k - ) ( Σ ) of dimension k + + k - which inherits a natural Käh...

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Bibliographic Details
Published in:Communications in mathematical physics 2020-10, Vol.379 (2), p.723-772
Main Authors: Romão, N. M., Speight, J. M.
Format: Article
Language:English
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Summary:The gauged sigma model with target P 1 , defined on a Riemann surface Σ , supports static solutions in which k + vortices coexist in stable equilibrium with k - antivortices. Their moduli space is a noncompact complex manifold M ( k + , k - ) ( Σ ) of dimension k + + k - which inherits a natural Kähler metric g L 2 governing the model’s low energy dynamics. This paper presents the first detailed study of g L 2 , focussing on the geometry close to the boundary divisor D = ∂ M ( k + , k - ) ( Σ ) . On Σ = S 2 , rigorous estimates of g L 2 close to D are obtained which imply that M ( 1 , 1 ) ( S 2 ) has finite volume and is geodesically incomplete. On Σ = R 2 , careful numerical analysis and a point-vortex formalism are used to conjecture asymptotic formulae for g L 2 in the limits of small and large separation. All these results make use of a localization formula, expressing g L 2 in terms of data at the (anti)vortex positions, which is established for general M ( k + , k - ) ( Σ ) . For arbitrary compact Σ , a natural compactification of the space M ( k + , k - ) ( Σ ) is proposed in terms of a certain limit of gauged linear sigma models, leading to formulae for its volume and total scalar curvature. The volume formula agrees with the result established for Vol ( M ( 1 , 1 ) ( S 2 ) ) , and allows for a detailed study of the thermodynamics of vortex-antivortex gas mixtures. It is found that the equation of state is independent of the genus of Σ , and that the entropy of mixing is always positive.
ISSN:0010-3616
1432-0916
DOI:10.1007/s00220-020-03824-y