1,557 research outputs found

    Life after Brexit: United Kingdom Independence Party in post-referendum

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    The article considers the situation that has developed in British politics after the United Kingdom European Union membership referendum in 2016. The major causes of the crisis of the United Kingdom Independence Party are presented. The estimated characteristic and ways of possible further party development are given

    Joint eavesdropping on the BB84 decoy state protocol with an arbitrary passive light-source side channel

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    Passive light-source side channel in quantum key distribution (QKD) makes the quantum signals more distinguishable thus provides additional information about the quantum signal to an eavesdropper. The explicit eavesdropping strategies aimed at the passive side channel known to date were limited to the separate measurement of the passive side channel in addition to the operational degree of freedom. Here we show how to account for the joint eavesdropping on both operational degree of freedom and the passive side channel of the generic form. In particular, we use the optimal phase-covariant cloning of the signal photon state, which is the most effective attack on the BB84 protocol without side channels, followed by a joint collective measurement of the side channel and the operational degree of freedom. To estimate QKD security under this attack, we develop an effective error method and show its applicability to the BB84 decoy-state protocol

    On generations by conjugate elements in almost simple groups with socle \mbox{}^2F_4(q^2)'

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    We prove that if L=\mbox{}^2F_4(2^{2n+1})' and xx is a nonidentity automorphism of LL then G=L,xG=\langle L,x\rangle has four elements conjugate to xx that generate GG. This result is used to study the following conjecture about the π\pi-radical of a finite group: Let π\pi be a proper subset of the set of all primes and let rr be the least prime not belonging to π\pi. Set m=rm=r if r=2r=2 or 33 and set m=r1m=r-1 if r5r\geqslant 5. Supposedly, an element xx of a finite group GG is contained in the π\pi-radical Oπ(G)\operatorname{O}_\pi(G) if and only if every mm conjugates of xx generate a π\pi-subgroup. Based on the results of this paper and a few previous ones, the conjecture is confirmed for all finite groups whose every nonabelian composition factor is isomorphic to a sporadic, alternating, linear, or unitary simple group, or to one of the groups of type 2B2(22n+1){}^2B_2(2^{2n+1}), 2G2(32n+1){}^2G_2(3^{2n+1}), 2F4(22n+1){}^2F_4(2^{2n+1})', G2(q)G_2(q), or 3D4(q){}^3D_4(q)

    On embedding theorems for X\mathfrak{X}-subgroups

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    Let X\mathfrak{X} be a class of finite groups closed under subgroups, homomorphic images, and extensions. We study the question which goes back to the lectures of H. Wielandt in 1963-64: For a given X\mathfrak{X}-subgroup KK and maximal X\mathfrak{X}-subgroup HH, is it possible to see embeddability of KK in HH (up to conjugacy) by their projections onto the factors of a fixed subnormal series. On the one hand, we construct examples where KK has the same projections as some subgroup of HH but is not conjugate to any subgroup of HH. On the other hand, we prove that if KK normalizes the projections of a subgroup HH, then KK is conjugate to a subgroup of HH even in the more general case when HH is a submaximal X\mathfrak{X}-subgroup
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