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In this paper, we prove several stability theorems for multiplicities of naturally defined representations of symmetric groups. The first such theorem states that if we consider the diagonal action of the symmetric group $S_{m+r}$ on $k$ sets of $m+r$ variables, then the dimension of the invariants of degree $m$ is the same as the dimension of the invariants of degree $m$ for $S_{m}$ acting on $k$ sets of $m$ variables. The second type of stability result is for Weyl modules. We prove that the dimension of the $S_{n+r}$ invariants for a Weyl module, ${}_{m+r}F^{lambda}$ (the Schur-Weyl dual of the $S_{|lambda|}$ module $V^{lambda}$) with $leftvert lambda rightvert leq m$ is of the same dimension as the space of $S_{m}$ invariants for ${}_{m}F^{lambda}$. Multigrad
Given a simple Lie algebra $mathfrak{g}$, Kostants weight $q$-multiplicity formula is an alternating sum over the Weyl group whose terms involve the $q$-analog of Kostants partition function. For $xi$ (a weight of $mathfrak{g}$), the $q$-analog of Ko
We present a simple unified formula expressing the denominators of the normalized R-matrices between the fundamental modules over the quantum loop algebras of type ADE. It has an interpretation in terms of representations of the Dynkin quivers and ca
We introduce the notion of essential support of a simple Gelfand-Tsetlin $mathfrak{gl}_n$-module as an important tool towards understanding the character formula of such module. This support detects the weights in the module having maximal possible G
We use analogues of Enrights and Arkhipovs functors to determine the quiver and relations for a category of $mathfrak{sl}_2 ltimes L(4)$-modules which are locally finite (and with finite multiplicities) over $mathfrak{sl}_2$. We also outline serious
In this paper, we calculate the dimension of root spaces $mathfrak{g}_{lambda}$ of a special type rank $3$ Kac-Moody algebras $mathfrak{g}$. We first introduce a special type of elements in $mathfrak{g}$, which we call elements in standard form. Then