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Let $G$ be a finite group and let $mathfrak{F}$ be a hereditary saturated formation. We denote by $mathbf{Z}_{mathfrak{F}}(G)$ the product of all normal subgroups $N$ of $G$ such that every chief factor $H/K$ of $G$ below $N$ is $mathfrak{F}$-central in $G$, that is, [ (H/K) rtimes (G/mathbf{C}_{G}(H/K)) in mathfrak{F}. ]A subgroup $A leq G$ is said to be $mathfrak{F}$-subnormal in the sense of Kegel, or $K$-$mathfrak{F}$-subnormal in $G$, if there is a subgroup chain [ A = A_0 leq A_1 leq ldots leq A_n = G ] such that either $A_{i-1} trianglelefteq A_{i}$ or $A_i / (A_{i-1})_{A_i} in mathfrak{F}$ for all $i = 1, ldots , n$. In this paper, we prove the following generalisation of Schenkmans Theorem on the centraliser of the nilpotent residual of a subnormal subgroup: Let $mathfrak{F}$ be a hereditary saturated formation and let $S$ be a $K$-$mathfrak{F}$-subnormal subgroup of $G$. If $mathbf{Z}_{mathfrak{F}}(E) = 1$ for every subgroup $E$ of $G$ such that $S leq E$ then $mathbf{C}_{G}(D) leq D$, where $D = S^{mathfrak{F}}$ is the $mathfrak{F}$-residual of $S$.
Let $sigma ={sigma_i |iin I}$ is some partition of all primes $mathbb{P}$ and $G$ a finite group. A subgroup $H$ of $G$ is said to be $sigma$-subnormal in $G$ if there exists a subgroup chain $H=H_0leq H_1leq cdots leq H_n=G$ such that either $H_{i-1
I prove, under mild assumptions, that solutions to linear evolution equations admit sectorial solutions. The size of the sector depends on the regularity of the initial data. If it is regular enough the solution is holomorphic and unique otherwise it
Greenberg proved that every countable group $A$ is isomorphic to the automorphism group of a Riemann surface, which can be taken to be compact if $A$ is finite. We give a short and explicit algebraic proof of this for finitely generated groups $A$.
Given a group $G$, we write $x^G$ for the conjugacy class of $G$ containing the element $x$. A famous theorem of B. H. Neumann states that if $G$ is a group in which all conjugacy classes are finite with bounded size, then the derived group $G$ is fi
We give a new proof of Gromovs theorem that any finitely generated group of polynomial growth has a finite index nilpotent subgroup. Unlike the original proof, it does not rely on the Montgomery-Zippin-Yamabe structure theory of locally compact groups.