Grothendieck's period conjecture (GPC) states that "for a motive over a number field, the comparison isomorphism seen as a complex point of the period torsor is dense". It was only proved for CM elliptic curves by Chudnovsky, so it is one of the most difficult problems in the theory of motives. In March 2023, 3 papers around GPC were submitted to arXiv. On the 9th, we proved GPC for Kummer surfaces of self-product CM type. On the 12th, B. Kahn proved the fullness conjecture for products of elliptic curves. His result contains de Rham-Betti's conjecture (aka weak GPC) for them, which was proved by Shen-Vial in 2022. On the 16th, Kreutz-Shen-Vial proved GPC for K3 surfaces of Picard corank 0, which is a generalization of our result. In this talk, I will explain the abstracts of the papers.

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