On a conjecture by Naito-Sagaki: Littelmann paths and Littlewood-Richardson Sundaram tableaux

We prove a special case of a conjecture of Naito-Sagaki about a branching rule for the restriction of irreducible representations of $\mathfrak{sl}(2n,\mathbb{C})$ to $\mathfrak{sp}(2n,\mathbb{C})$. The conjecture is in terms of certain Littelmann paths, with the embedding given by the folding of the type $A_{2n-1}$ Dynkin diagram. We propose and motivate an approach to the conjecture in general, in terms of Littlewood-Richardson Sundaram tableaux.Comment: 13 pages. Comments welcom

Word reading is a crystal morphism

We observe that word reading is a crystal morphism. This leads us to prove that, in the case of the complex special linear group, the map from all galleries to MV cycles is a morphism of crystals.Comment: 15 pages, comments welcom

Atoms and charge in type C2C_2

We construct atomic decompositions for crystals of type $C_{2}$ and define a charge statistic on them, thus providing positive combinatorial formulas for Kostka-Foulkes polynomials associated to them together with a natural geometric interpretation.Comment: 69 pages, comments welcom

Symplectic cacti, virtualization and Berenstein-Kirillov groups

We explicitly realize an internal action of the symplectic cactus group, recently defined by Halacheva for any complex, reductive, finite-dimensional Lie algebra, on crystals of Kashiwara-Nakashima tableaux. Our methods include a symplectic version of jeu de taquin due to Sheats and Lecouvey, symplectic reversal, and virtualization due to Baker. As an application, we define and study a symplectic version of the Berenstein-Kirillov group and show that it is a quotient of the symplectic cactus group. In addition two relations for symplectic Berenstein-Kirillov group are given that do not follow from the defining relations of the symplectic cactus group.Comment: 71 pages, comments welcom