Natural Factors of the Medvedev Lattice Capturing IPC

Skvortsova showed that there is a factor of the Medvedev lattice which captures intuitionistic propositional logic (IPC). However, her factor is unnatural in the sense that it is constructed in an ad hoc manner. We present a more natural example of such a factor. We also show that for every non-trivial factor of the Medvedev lattice its theory is contained in Jankov's logic, the deductive closure of IPC plus the weak law of the excluded middle. This answers a question by Sorbi and Terwijn

The Ethics of Resisting Deportation

Can anti-deportation resistance be justified, and if so how and by whom may, or perhaps should, unjust deportations be resisted? In this paper, I seek to provide an answer to these questions. The paper starts by describing the main forms and agents of anti-deportation action in the contemporary context. Subsequently, I examine how different justifications for principled resistance and disobedience may each be invoked in the case of deportation resistance. I then explore how worries about the resister’s motivation for engaging in the action and their epistemic position apply in the specific context of anti-deportation action and consider in what circumstances there is not merely a right but a duty to resist deportation. The upshot of this argument, I conclude, is that the liberal state ought to respond to anti-deportation action not by criminalising disobedience and resistance in this field, but rather by creating legal avenues for such actors to influence deportation decision-making. DOI 10.17879/95189423213

Maximal R-symmetry violating amplitudes in type IIB superstring theory

On-shell superspace techniques are used to quantify R-symmetry violation in type IIB superstring theory amplitudes in a flat background in ten dimensions. This shows the existence of a particularly simple class of non-vanishing amplitudes in this theory which violate R-symmetry maximally. General properties of the class and some of its extensions are established which at string tree level are shown to determine the first three non-trivial effective field theory contributions to all multiplicity. This leads to a natural conjecture for the exact analytic part of the first two of these.Comment: 10 pages. minute modifications, references adde