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2 votes
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Action of torus on Laurent polynomials

Let $F$ be a field and suppose that the torus $(F^*)^n$ acts on the Laurent polynomial ring $L$ in $n$ variables $X_1, \dots, X_n$ defined by $X_i \dashrightarrow a_iX_i$ for suitable scalars $a_i$. ...
A. Gupta's user avatar
  • 376
4 votes
2 answers
391 views

Ring of invariants of some special type of subgroups of $GL_3(\mathbb C)$

For $\sigma \in \mathrm{GL}_n(\mathbb C)$ and $f(x_1,...,x_n)\in \mathbb C[x_1,...,x_n]$, let $f^ \sigma (x):=f(\sigma^{-1}x)$, for $x=(x_1,...,x_n)$. For a subgroup $G$ of $\mathrm{GL}_n(\mathbb C)$...
user521337's user avatar
  • 1,209
2 votes
0 answers
264 views

2 questions on Nagata's counterexample; $k[f_1,...,f_r]=k[g_1,...,g_s]$ vs. $k(f_1,...,f_r)=k(g_1,...,g_s)$

Let $\{a_{ij}\}$ for $i=1,2,3$, and $j=1,...,16$ be algebraically independent elements over some prime field. Let $k$ be a field containing all $a_{ij}$. Then consider $k^{16}$ as $k$-vector space and ...
InvisiblePanda's user avatar