A Network Model characterized by a Latent Attribute Structure with Competition

The quest for a model that is able to explain, describe, analyze and simulate real-world complex networks is of uttermost practical as well as theoretical interest. In this paper we introduce and study a network model that is based on a latent attribute structure: each node is characterized by a number of features and the probability of the existence of an edge between two nodes depends on the features they share. Features are chosen according to a process of Indian-Buffet type but with an additional random "fitness" parameter attached to each node, that determines its ability to transmit its own features to other nodes. As a consequence, a node's connectivity does not depend on its age alone, so also "young" nodes are able to compete and succeed in acquiring links. One of the advantages of our model for the latent bipartite "node-attribute" network is that it depends on few parameters with a straightforward interpretation. We provide some theoretical, as well experimental, results regarding the power-law behaviour of the model and the estimation of the parameters. By experimental data, we also show how the proposed model for the attribute structure naturally captures most local and global properties (e.g., degree distributions, connectivity and distance distributions) real networks exhibit. keyword: Complex network, social network, attribute matrix, Indian Buffet processComment: 34 pages, second version (date of the first version: July, 2014). Submitte

Liquid FM: Recommending Music through Viscous Democracy

Most modern recommendation systems use the approach of collaborative filtering: users that are believed to behave alike are used to produce recommendations. In this work we describe an application (Liquid FM) taking a completely different approach. Liquid FM is a music recommendation system that makes the user responsible for the recommended items. Suggestions are the result of a voting scheme, employing the idea of viscous democracy. Liquid FM can also be thought of as the first testbed for this voting system. In this paper we outline the design and architecture of the application, both from the theoretical and from the implementation viewpoints

Making simple proofs simpler

An open partition \pi{} [Cod09a, Cod09b] of a tree T is a partition of the vertices of T with the property that, for each block B of \pi, the upset of B is a union of blocks of \pi. This paper deals with the number, NP(n), of open partitions of the tree, V_n, made of two chains with n points each, that share the root

Brexit threatens the City's future in European payment systems

Future UK-EU relations are about to be negotiated in Brussels. While there are signs of improvement in many important policy areas such as citizens' rights, the financial settlement, and the impact of Brexit on the island of Ireland, little progress has been made on the role of the City as the location of Europe's major clearing house, which is represented by the London Clearing House (LCH) and owned by the London Stock Exchange, write Corrado Macchiarelli (Brunel/LSE) and Mara Monti (LSE)

The challenge facing Italy's new coalition

On 22 October, Giorgia Meloni was officially sworn in as Italy’s first female prime minister. However, the new Italian government might soon come under pressure to address soaring energy prices and support struggling families and businesses. Corrado Macchiarelli and Mara Monti write that Meloni’s right-wing coalition will face a delicate balancing act between maintaining the support of its electorate and upholding commitments undertaken with Brussels

Assessing the impact of the ECB's Corporate Sector Purchase Programme on SMEs

The European Central Bank's Governing Council is due to hold a policy meeting on 26 October, with many observers anticipating there could be a change to the ECB's monetary stimulus programme. Corrado Macchiarelli, Mara Monti and Andrea Vedolin examine some of the measures that should be considered as the ECB looks to respond to changing conditions in the euro area

No echo in the chambers of political interactions on Reddit

Echo chambers in online social networks, whereby users’ beliefs are reinforced by interactions with like-minded peers and insulation from others’ points of view, have been decried as a cause of political polarization. Here, we investigate their role in the debate around the 2016 US elections on Reddit, a fundamental platform for the success of Donald Trump. We identify Trump vs Clinton supporters and reconstruct their political interaction network. We observe a preference for cross-cutting political interactions between the two communities rather than within-group interactions, thus contradicting the echo chamber narrative. Furthermore, these interactions are asymmetrical: Clinton supporters are particularly eager to answer comments by Trump supporters. Beside asymmetric heterophily, users show assortative behavior for activity, and disassortative, asymmetric behavior for popularity. Our findings are tested against a null model of random interactions, by using two different approaches: a network rewiring which preserves the activity of nodes, and a logit regression which takes into account possible confounding factors. Finally, we explore possible socio-demographic implications. Users show a tendency for geographical homophily and a small positive correlation between cross-interactions and voter abstention. Our findings shed light on public opinion formation on social media, calling for a better understanding of the social dynamics at play in this context.Peer ReviewedPostprint (published version

The EMU quest for integration: what does the ECB's collateral data tell us?

The ECB recently announced that its quantitative easing programme will stop at the end of 2018. Corrado Macchiarelli and Mara Monti write that the way this decision is managed will be crucial for avoiding potential market disruptions in the eurozone. However, the key long-term concern will be achieving political consensus in the coming years given the challenge posed by the rise of populist parties and declining support for the EU’s institutions

The EMU quest for integration: what does the ECB's collateral data tell us?

The ECB recently announced that its quantitative easing programme will stop at the end of 2018. Corrado Macchiarelli and Mara Monti write that the way this decision is managed will be crucial for avoiding potential market disruptions in the eurozone. However, the key long-term concern will be achieving political consensus in the coming years given the challenge posed by the rise of populist parties and declining support for the EU’s institutions