Filetype
PurposeThis paper aims to explore articulations of how individuals internalise official demands on handling COVID-19 and the function of social media in this process, and further to discuss this from a human rights’ perspective.Design/methodology/approachA thematic analysis of qualitative data from an international survey on COVID-19 and social media. The analysis was inspired by Berger and Luckma
Dahlmans replik i SvJT 2020 s. 712 föranleder följande svar från min sida.Det signifikanstest som Dahlman hänvisar till visar inte att det föreligger ett orsakssamband mellan brottstyp och domslut och det utesluter inte att andra omständigheter än brottstypen, som inte har undersökts i studien, inverkar på domslutet. För att kunna nå slutsatsen att det är brottstypen som orsakar domslutet krävs st
Recension av Håkan Blomqvist, Socialism på jiddisch. Judiska Arbeter Bund i Sverige.
The aim of this paper is to explore sexual harassment and criminalisation, and, more specifically, to what extent the criminal legal system may serve as a measure against sexual harassment. It is not the task of this paper to provide a straightforward answer. Instead, it provides abrief account of ongoing trends in Sweden which prompts further analysis of this issue, suchas #metoo, crime statistic
The EU is committed to become climate-neutral by 2050 while keeping its prosperity intact. To align the bloc towards this goal, it is fundamental to understand the spatial differences in energy performance among its members. The present study aims to identify the main drivers of primary energy intensity differences among fourteen European countries (i.e., the EU15 without Luxemburg) during the per
We show exponential lower bounds on resolution proof length for pigeonhole principle (PHP) formulas and perfect matching formulas over highly unbalanced, sparse expander graphs, thus answering the challenge to establish strong lower bounds in the regime between balanced constant-degree expanders as in [Ben-Sasson and Wigderson'01] and highly unbalanced, dense graphs as in [Raz'04] and [Razborov'03
We give a significantly simplified proof of the exponential separation between regular and general resolution of Alekhnovich et al. (2007) as a consequence of a general theorem lifting proof depth to regular proof length in resolution. This simpler proof then allows us to strengthen the separation further, and to construct families of theoretically very easy benchmarks that are surprisingly hard f
We show that there are CNF formulas which can be refuted in resolution in both small space and small width, but for which any small-width proof must have space exceeding by far the linear worst-case upper bound. This significantly strengthens the space-width trade-offs in [E. Ben-Sasson, SIAM J. Comput., 38 (2009), pp. 2511-2525], and provides one more example of trade-offs in the "supercritical"
Building on [Clegg et al.’96], [Impagliazzo et al.’99] established that if an unsatisfiable k-CNF formula over n variables has a refutation of size S in the polynomial calculus resolution proof system, then this formula also has a refutation of degree k + O(n log S). The proof of this works by converting a small-size refutation into a small-degree one, but at the expense of increasing the proof si
The conflict-driven clause learning (CDCL) paradigm has revolutionized SAT solving over the last two decades. Extending this approach to pseudo-Boolean (PB) solvers doing 0-1 linear programming holds the promise of further exponential improvements in theory, but intriguingly such gains have not materialized in practice. Also intriguingly, most PB extensions of CDCL use not the division rule in cut
We establish an exactly tight relation between reversible pebblings of graphs and Nullstellensatz refutations of pebbling formulas, showing that a graph G can be reversibly pebbled in time t and space s if and only if there is a Nullstellensatz refutation of the pebbling formula over G in size t + 1 and degree s (independently of the field in which the Nullstellensatz refutation is made). We use t
Over the last decades Boolean satisfiability (SAT) solvers based on conflict-driven clause learning (CDCL) have developed to the point where they can handle formulas with millions of variables. Yet a deeper understanding of how these solvers can be so successful has remained elusive. In this work we shed light on CDCL performance by using theoretical benchmarks, which have the attractive features
The last 20 years have seen dramatic improvements in the performance of algorithms for Boolean satisfiability-so-called SAT solvers-and today conflict-driven clause learning (CDCL) solvers are routinely used in a wide range of application areas. One serious short-coming of CDCL, however, is that the underlying method of reasoning is quite weak. A tantalizing solution is to instead use stronger pse
We initiate a proof complexity theoretic study of subsystems of cutting planes (CP) modelling proof search in conflict-driven pseudo-Boolean (PB) solvers. These algorithms combine restrictions such as that addition of constraints should always cancel a variable and/or that so-called saturation is used instead of division. It is known that on CNF inputs cutting planes with cancelling addition and s
We study cdcl-cuttingplanes, Open-WBO, and Sat4j, three successful solvers from the Pseudo-Boolean Competition 2016, and evaluate them by performing experiments on crafted benchmarks designed to be trivial for the cutting planes (CP) proof system underlying pseudo-Boolean (PB) proof search but yet potentially tricky for PB solvers. Our experiments demonstrate severe shortcomings in state-of-the-ar
We prove that for k ≪ 4 n regular resolution requires length nΩ(k) to establish that an Erdős–Rényi graph with appropriately chosen edge density does not contain a k-clique. This lower bound is optimal up to the multiplicative constant in the exponent, and also implies unconditional nΩ(k) lower bounds on running time for several state-of-the-art algorithms for finding maximum cliques in graphs.
We study space complexity and time-space trade-offs with a focus not on peak memory usage but on overall memory consumption throughout the computation. Such a cumulative space measure was introduced for the computational model of parallel black pebbling by [Alwen and Serbinenko 2015] as a tool for obtaining results in cryptography. We consider instead the nondeterministic black-white pebble game a
