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- Lukyanchuk, I., et al.
(författare)
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Rayleigh instability of confined vortex droplets in critical superconductors
- 2015
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Ingår i: Nature Physics. - 1745-2473 .- 1745-2481. ; 11:1, s. 21-25
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Tidskriftsartikel (refereegranskat)abstract
- Depending on the Ginzburg-Landau parameter kappa, superconductors can either be fully diamagnetic if kappa < 1/root 2 (type I superconductors) or allow magnetic flux to penetrate through Abrikosov vortices if kappa > 1/root 2 (type II superconductors; refs 1,2). At the Bogomolny critical point, kappa = kappa(c) = 1/root 2, a state that is infinitely degenerate with respect to vortex spatial configurations arises(3,4). Despite in-depth investigations of conventional type I and type II superconductors, a thorough understanding of the magnetic behaviour in the near-Bogomolny critical regime at kappa similar to kappa(c) remains lacking. Here we report that in confined systems the critical regime expands over a finite interval of kappa forming a critical superconducting state. We show that in this state, in a sample with dimensions comparable to the vortex core size, vortices merge into a multi-quanta droplet, which undergoes Rayleigh instability(5) on increasing kappa and decays by emitting single vortices. Superconducting vortices realize Nielsen-Olesen singular solutions of the Abelian Higgs model, which is pervasive in phenomena ranging from quantum electrodynamics to cosmology(6-9). Our study of the transient dynamics of Abrikosov-Nielsen-Olesen vortices in systems with boundaries promises access to non-trivial effects in quantum field theory by means of bench-top laboratory experiments.
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- Terechshenko, Zhanna, et al.
(författare)
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Evaluating the influence of international norms and shaming on state respect for rights : an audit experiment with foreign embassies
- 2019
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Ingår i: International Interactions. - : Informa UK Limited. - 0305-0629 .- 1547-7444. ; 45:4, s. 720-735
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Tidskriftsartikel (refereegranskat)abstract
- How do international norms affect respect for human rights? We report the results of an audit experiment with foreign missions that investigates the extent to which state agents observe international norms and react to the potential of international shaming. Our experiment involved emailing 669 foreign diplomatic missions in the United States, Canada, and the United Kingdom with requests to contact domestic prisoners. According to the United Nations, prisoners have the right for individuals to contact them. We randomly varied (1) whether we reminded embassies about the existence of an international norm permitting prisoner contact and (2) whether the putative email sender is associated with a fictitious human rights organization and, thereby, has the capacity to shame missions through naming and shaming for violating this norm. We find strong evidence for the positive effect of international norms on state respect for human rights. Contra to our expectations, though, we find that the potential of international shaming does not increase the probability of state compliance. The positive effect of the norms cue disappears when it is coupled with the shaming cue, suggesting that shaming might have a 'backfire' effect.
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