1,360 research outputs found
Complexity Jumps In Multiagent Justification Logic Under Interacting Justifications
The Logic of Proofs, LP, and its successor, Justification Logic, is a
refinement of the modal logic approach to epistemology in which
proofs/justifications are taken into account. In 2000 Kuznets showed that
satisfiability for LP is in the second level of the polynomial hierarchy, a
result which has been successfully repeated for all other one-agent
justification logics whose complexity is known.
We introduce a family of multi-agent justification logics with interactions
between the agents' justifications, by extending and generalizing the two-agent
versions of the Logic of Proofs introduced by Yavorskaya in 2008. Known
concepts and tools from the single-agent justification setting are adjusted for
this multiple agent case. We present tableau rules and some preliminary
complexity results. In several cases the satisfiability problem for these
logics remains in the second level of the polynomial hierarchy, while for
others it is PSPACE or EXP-hard. Furthermore, this problem becomes PSPACE-hard
even for certain two-agent logics, while there are EXP-hard logics of three
agents
From computer assisted language learning (CALL) to mobile assisted language use
This article begins by critiquing the long-established acronym CALL (Computer Assisted Language Learning). We then go on to report on a small-scale study which examines how student non-native speakers of English use a range of digital devices beyond the classroom in both their first (L1) and second (L2) languages. We look also at the extent to which they believe that their L2-based activity helps consciously and/or unconsciously with their language learning, practice, and acquisition. We argue that these data, combined with other recent trends in the field, suggest a need to move from CALL towards a more accurate acronym: mobile assisted language use (MALU). We conclude with a definition of MALU together with a brief discussion of a potential alignment of MALU with the notion of the digital resident and a newly emerging educational theory of connectivism
Beneficial effects of dark chocolate for episodic memory in healthy young adults: a parallel-groups acute intervention with a white chocolate control
There is good evidence that cocoa flavonoids can acutely improve cognitive function in humans, possibly via mechanisms such as increased cerebral blood flow. To date, much of the evidence is based on measures of executive function with extracts and cocoa-based interventions with a high flavonoid content. The aim of the present study was to explore whether benefits to episodic verbal memory and mood are observed two hours post consumption of a commercially available dark chocolate (DC) bar relative to a 35 g white chocolate bar (WC). Ninety-eight healthy young adults (n = 57 females) aged 18−24 years consumed either a 35 g DC bar or a calorie-matched low flavonoid WC bar. Verbal episodic memory and mood were assessed pre consumption and 2 h post consumption. An ANOVA analysis showed that the DC was associated with better verbal memory performance for several outcome measures of the Rey Auditory Verbal Learning Test relative to the WC, however, there were no effects on mood. These findings lend support to the notion that everyday available portions of dark chocolate can confer benefits to the brain in healthy consumers
NEXP-completeness and Universal Hardness Results for Justification Logic
We provide a lower complexity bound for the satisfiability problem of a
multi-agent justification logic, establishing that the general NEXP upper bound
from our previous work is tight. We then use a simple modification of the
corresponding reduction to prove that satisfiability for all multi-agent
justification logics from there is hard for the Sigma 2 p class of the second
level of the polynomial hierarchy - given certain reasonable conditions. Our
methods improve on these required conditions for the same lower bound for the
single-agent justification logics, proven by Buss and Kuznets in 2009, thus
answering one of their open questions.Comment: Shorter version has been accepted for publication by CSR 201
Non-Hermitian Acoustic Metamaterials: the role of Exceptional Points in sound absorption
Effective non-Hermitian Hamiltonians are obtained to describe coherent
perfect absorbing and lasing boundary conditions. PT -symmetry of the
Hamiltonians enables to design configurations which perfectly absorb at
multiple frequencies. Broadened and flat perfect absorption is predicted at the
exceptional point of PT -symmetry breaking while, for a particular case,
absorption is enhanced with the use of gain. The aforementioned phenomena are
illustrated for acoustic scattering through Helmholtz resonators revealing how
tailoring the non-Hermiticity of acoustic metamaterials leads to novel
mechanisms for enhanced absorption
- …