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تسجيل مستخدم جديدSobolev Lifting over Invariants
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We prove lifting theorems for complex representations $V$ of finite groups $G$. Let $sigma=(sigma_1,dots,sigma_n)$ be a minimal system of homogeneous basic invariants and let $d$ be their maximal degree. We prove that any continuous map $overline{f} colon {mathbb R}^m to V$ such that $f = sigma circ overline{f}$ is of class $C^{d-1,1}$ is locally of Sobolev class $W^{1,p}$ for all $1 le p<d/(d-1)$. In the case $m=1$ there always exists a continuous choice $overline{f}$ for given $fcolon {mathbb R} to sigma(V) subseteq {mathbb C}^n$. We give uniform bounds for the $W^{1,p}$-norm of $overline{f}$ in terms of the $C^{d-1,1}$-norm of $f$. The result is optimal: in general a lifting $overline{f}$ cannot have a higher Sobolev regularity and it even might not have bounded variation if $f$ is in a larger Holder class.
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