This is an announcement for the paper "Octahedral norms and convex combination of slices in Banach spaces" by Julio Becerra Guerrero, Gines Lopez-Perez, and Abraham Rueda Zoca. Abstract: We study the relation between octahedral norms, Daugavet property and the size of convex combinations of slices in Banach spaces. We prove that the norm of an arbitrary Banach space is octahedral if, and only if, every convex combination of $w^*$-slices in the dual unit ball has diameter $2$, which answer an open question. As a consequence we get that the Banach spaces with the Daugavet property and its dual spaces have octahedral norms. Also, we show that for every separable Banach space containing $\ell_1$ and for every $\varepsilon >0$ there is an equivalent norm so that every convex combination of $w^*$-slices in the dual unit ball has diameter at least $2-\varepsilon$. Archive classification: math.FA Submitted from: glopezp@ugr.es The paper may be downloaded from the archive by web browser from URL http://front.math.ucdavis.edu/1309.3866 or http://arXiv.org/abs/1309.3866