Let X=⋃φiX\documentclass[12pt]{minimal}
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\begin{document}$$X={\bigcup }{\varphi }_{i}X$$\end{document} be a strongly separated self-affine set in R2\documentclass[12pt]{minimal}
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\begin{document}$${\mathbb {R}}^2$$\end{document} (or one satisfying the strong open set condition). Under mild non-conformality and irreducibility assumptions on the matrix parts of the φi\documentclass[12pt]{minimal}
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\begin{document}$$\varphi _{i}$$\end{document}, we prove that dimX\documentclass[12pt]{minimal}
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\begin{document}$$\dim X$$\end{document} is equal to the affinity dimension, and similarly for self-affine measures and the Lyapunov dimension. The proof is via analysis of the dimension of the orthogonal projections of the measures, and relies on additive combinatorics methods.