%0 Journal Article %T The inverse problem of differential Galois theory over the field R(z) %A Tobias Dyckerhoff %J Mathematics %D 2008 %I arXiv %X We describe a Picard-Vessiot theory for differential fields with non algebraically closed fields of constants. As a technique for constructing and classifying Picard-Vessiot extensions, we develop a Galois descent theory. We utilize this theory to prove that every linear algebraic group $G$ over $\mathbb{R}$ occurs as a differential Galois group over $\mathbb{R}(z)$. The main ingredient of the proof is the Riemann-Hilbert correspondence for regular singular differential equations over $\mathbb{C}(z)$. %U http://arxiv.org/abs/0802.2897v1