We study equilibrium statistical mechanics of classical point counter-ions, formulated on 2D Euclidean space with logarithmic Coulomb interactions (infinite number of particles) or on the cylinder surface (finite particle numbers), in the vicinity of a single uniformly charged line (one single double layer), or between two such lines (interacting double layers). The weak-coupling Poisson-Boltzmann theory, which applies when the coupling constant \documentclass[12pt]{minimal}
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\begin{document}$ \Gamma$\end{document} is small, is briefly recapitulated (the coupling constant is defined as \documentclass[12pt]{minimal}
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\begin{document}$ \Gamma$\end{document}\documentclass[12pt]{minimal}
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\begin{document}$ \equiv$\end{document}\documentclass[12pt]{minimal}
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\begin{document}$ \beta$\end{document}e2 , where \documentclass[12pt]{minimal}
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\begin{document}$ \beta$\end{document} is the inverse temperature, and e the counter-ion charge). The opposite limit ( \documentclass[12pt]{minimal}
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\begin{document}$ \Gamma$\end{document}\documentclass[12pt]{minimal}
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\begin{document}$ \rightarrow$\end{document} ∞ is treated by using a recent method based on an exact expansion around the ground-state Wigner crystal of counter-ions. These two limiting results are compared at intermediary values of the coupling constant \documentclass[12pt]{minimal}
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\begin{document}$ \Gamma$\end{document} = 2\documentclass[12pt]{minimal}
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\begin{document}$ \gamma$\end{document} (\documentclass[12pt]{minimal}
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\begin{document}$ \gamma$\end{document} = 1, 2, 3) , to exact results derived within a 1D lattice representation of 2D Coulomb systems in terms of anti-commuting field variables. The models (density profile, pressure) are solved exactly for any particles numbers N at \documentclass[12pt]{minimal}
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\begin{document}$ \Gamma$\end{document} = 2 and up to relatively large finite N at \documentclass[12pt]{minimal}
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\begin{document}$ \Gamma$\end{document} = 4 and 6. For the one-line geometry, the decay of the density profile at asymptotic distance from the line undergoes a fundamental change with respect to the mean-field behavior at \documentclass[12pt]{minimal}
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\begin{document}$ \Gamma$\end{document} = 6 . The like-charge attraction regime, possible for large \documentclass[12pt]{minimal}
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\begin{document}$ \Gamma$\end{document} but precluded at mean-field level, survives for \documentclass[12pt]{minimal}
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\begin{document}$ \Gamma$\end{document} = 4 and 6, but disappears at \documentclass[12pt]{minimal}
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\begin{document}$ \Gamma$\end{document} = 2 .