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The latest issue of the European Physical Journal H is out

Posted By admin, 14 November 2016

'The European Physical Journal H' Volume 41 - Issue 3 - Year 2016 is available for our members.

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Tags:  EPJ H  European Physical Journal  publication 

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Physics and society: Network analysis of the Íslendinga sögur - the Sagas of Icelanders

Posted By Gina Gunaratnam, 09 February 2015

The Icelandic sagas are ancient tales of brave deeds and lives and loves, with a cast of thousands – but how true to life are they? Pádraig Mac Carron and Ralph Kenna analyse the interactions between the characters and find that social networks of the Viking era were very similar to those of today.

The Íslendinga sögur – or sagas of Icelanders – purport to describe events in the period following the settling of Iceland about a thousand years ago. The sagas tell of families and feuds, of warfare and warriors, of lives and loves, betrothals and betrayals. The antiquity of the texts and their unique narrative style make them an important element of world literature. Some consider the sagas to contain information on Viking life, while others object that such tales are entirely fictional, with no basis in reality.  With overlapping plots in different texts involving thousands of characters and their interactions, their huge network of interactions makes them an ideal study for statistical analysis.

The approach follows a previous study of mythological and epic literature, which compared the Anglo-Saxon epic Beowulf, Homer’s Iliad and the Irish epic, Táin Bó Cuailnge [1]. One may ask questions about the bases for such tales and attempt to uncover what quantitative information may have been hidden for centuries within the pages of ancient manuscripts. For the  Íslendinga sögur  Mac Carron and Kenna gathered data for 18 narratives, five of which contain over 100 characters each. These are Njáls saga, Laxdæla saga, Vatnsdæla saga, Egils saga Skallagrímssonar and Gísla saga Súrssonar. They examined these individually in order to compare different sagas to each other. They also studied the sagas collectively – a network of 1549 characters – to gain insight into the structure of the overall saga society [2].

The networks underlying saga society have similar properties to real-world social networks; they are far more clustered than their random counterparts - Viking society is small world. Individuals in the society are connected to each other by an average path length of 5.5 – remarkably close to the six degrees of separation of modern society. A propensity to disfavour odd numbers of hostile links is related to the notion of structural balance – in the Viking era, the enemy of an enemy is a friend. Some of the family sagas are assortative, meaning that characters associate with other characters similar to themselves. The outlaw Gísla saga is by contrast disassortative. A strong overlap between the communities in Njáls saga and Laxdæla saga offers support to the theory that one saga may have been used as a source for the other.

Traditional studies of literature focus on individuals and events. This new statistical approach looks instead at the collections of interactions between characters. It offers a new and exciting way to make quantitative comparisons both between the sagas as well as to compare to other literary genres. The new approach  opens new windows for us to peer into our dim and distant past.

References

[1]. Mac Carron, P. and Kenna, R. (2013) Network analysis of the Íslendinga sögur – the Sagas of Icelanders. European Physical Journal B, 86, 407–415. Free to download from http://iopscience.iop.org/0295-5075/99/2/28002?fromSearchPage=true

[2]. Mac Carron, P. and Kenna, R. (2012) Universal properties of mythological networks.
Europhysics Letters
, 99, 28002. Free to download from http://de.arxiv.org/abs/1309.6134

View the presentation of Ralf Kenna's work on YouTube: http://www.youtube.com/watch?v=b5tMomhjGKY&feature=youtu.be

Tags:  EPL Publication  European Physical Journal 

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EPJ Quantum Technology Highlight - Quantum simulators explained

Posted By admin, 12 August 2014

11 August 2014 Springer Science+Business Media

Everything you ever wanted to know about quantum simulators summed up in a new review from EPJ Quantum Technology

As part of a new Thematic Series on Quantum Simulations, the open access journal EPJ Quantum Technology has just published an overview of just what a quantum simulator is, namely a device that actively uses quantum effects to answer questions on model systems. This review, published by Tomi Johnson and colleagues from the Centre for Quantum Technologies in Singapore and the University of Oxford, UK, outlines various approaches used in quantum simulators.

Specifically, the authors focus on the difference between the purpose of operations referred to as 'simulation' and 'computation'. They argue this distinction is related to the purpose of an operation, to our level of confidence in and to our expectations with regard to its accuracy.

They then explain the role of simulations in science, in particular, how simulation reveals information about a mathematical function or model in relation to a system. This approach is reminiscent of physicist Richard Feynman's definition of simulation, which is akin to using a physical device to learn about a real physical system.

Such simulation of the function of a system only takes its full significance when compared with the outcome of the same function on a real-life system of interest. The outcome helps decide whether or not the model accurately represents the real system. If the representation is thought to be accurate, the quantum simulator can then loosely be considered to be a simulator for the system of interest.

Finally the authors also explain the threshold between quantum and classical simulations. In this context, Johnson and colleagues suggest that there are many more questions pertaining to the work of simulators that need to be answered. These include: Can we predict in advance where the results of quantum simulators are more sensitive to errors? How does this overlap with the regimes of classical simulability?

Johnson, T. H., Clark, S. R. and Jaksch, D. (2014). What is a quantum simulator? European Physical Journal Quantum Technology.
DOI 10.1186/epjqt10

Tags:  EPJ  European Physical Journal  quantum simulator 

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