%0 Journal Article %T Spectral synthesis in de Branges spaces %+ Saint Petersburg State University (SPBU) %+ National Research University Higher School of Economics [St. Petersburg] %+ Chebyshev Laboratory %+ Institut de Mathématiques de Marseille (I2M) %A Baranov, Anton %A Belov, Yurii %A Borichev, Alexander %Z 38 pages. Shortened text with streamlined proofs. This version is accepted for publication in "Geometric and Functional Analysis" %< avec comité de lecture %@ 1016-443X %J Geometric And Functional Analysis %I Springer Verlag %V 25 %N 2 %P 417-452 %8 2015 %D 2015 %Z 1309.6915 %R 10.1007/s00039-015-0322-y %Z Mathematics [math]/Complex Variables [math.CV] %Z Mathematics [math]/Functional Analysis [math.FA]Journal articles %X We solve completely the spectral synthesis problem for reproducing kernels in the de Branges spaces $\mathcal{H}(E)$. Namely, we describe the de Branges spaces $\mathcal{H}(E)$ such that all $M$-bases of reproducing kernels (i.e., complete and minimal systems $\{k_\lambda\}_{\lambda\in\Lambda}$ with complete biorthogonal $\{g_\lambda\}_{\lambda\in\Lambda}$) are strong $M$-bases (i.e., every mixed system $\{k_\lambda\}_{\lambda\in\Lambda\setminus\tilde \Lambda} \cup\{g_\lambda\}_{\lambda\in \tilde \Lambda}$ is also complete). Surprisingly this property takes place only for two essentially different classes of de Branges spaces: spaces with finite spectral measure and spaces which are isomorphic to Fock-type spaces of entire functions. The first class goes back to de Branges himself, the second class appeared in a recent work of A. Borichev and Yu. Lyubarskii. Moreover, we are able to give a complete characterisation of this second class in terms of the spectral data for $\mathcal{H}(E)$. In addition, we obtain some results about possible codimension of mixed systems for a fixed de Branges space $\mathcal{H}(E)$, and prove that any minimal system of reproducing kernels in $\mathcal{H}(E)$ is contained in an exact system of reproducing kernels. %G English %2 https://hal.science/hal-01258039/document %2 https://hal.science/hal-01258039/file/1309.6915.pdf %L hal-01258039 %U https://hal.science/hal-01258039 %~ CNRS %~ UNIV-AMU %~ EC-MARSEILLE %~ I2M %~ I2M-2014-