The value of a new idea: knowledge transmission, workers' mobility and market structure

We model the process of knowledge transmission among firms via workers mobility as a multi-stage game. In our setup an idea to be realized needs that the agent informed about the idea recruits another agent from a pool of uninformed people. This constraint generates a recursive effect of knowledge transmission via players mobility across firms which affects simultaneously the players payoffs and the number of active players engaged in market competition. We provide sufficient conditions for the game to possess a unique symmetric subgame perfect equilibrium in which all incumbent players deter the exit of their collaborators. The equilibrium outcome is shown to depend upon the success of the idea over time, expressed by the behaviour of the market demand and on playerstime preferences. A few other intuitions are provided on the interplay between technology, market structure and the market value of an innovative idea.Innovation; Workers’ Mobility; Knowledge Transmission; Subgame Perfect Nash Equilibrium; Recursive Games

Spherically symmetric solutions of a boundary value problem for monopoles

In this paper we study spherically symmetric monopoles, which are critical points for the Yang-Mills-Higgs functional over a disk in 3 dimensions, with prescribed degree and covariant constant at the boundary. This is a 3-dimensional gauge-theory generalization of the Ginzburg-Landau model in 2 dimensions.Comment: 15 pages, 2 figures, LaTe

Cooling of a lattice granular fluid as an ordering process

We present a new microscopic model of granular medium to study the role of dynamical correlations and the onset of spatial order induced by the inelasticity of the interactions. In spite of its simplicity, it features several different aspects of the rich phenomenology observed in granular materials and allows to make contact with other topics of statistical mechanics such as diffusion processes, domain growth, persistence, aging phenomena. Interestingly, while local observables being controlled by the largest wavelength fluctuations seem to suggest a purely diffusive behavior, the formation of spatially extended structures and topological defects, such as vortices and shocks, reveals a more complex scenario.Comment: 4 pages, 4 figure

A sequential approach to the characteristic function and the core in games with externalities

This paper proposes a formulation of coalitional payoff possibilities in games with externalities, based on the assumption that forming coalitions can exploit a ”first mover advantage”. We derive a characteristic function and show that when outside players play their best response noncooperatively, the core is nonempty in games with strategic complements. We apply this result to Cournot and Bertrand games and to public goods economies.Core; cooperative games; externalities

A content analysis of Chicago Cubs and White Sox local news coverage during the 2004 and 2008 major league baseball seasons

This research paper explored how the media presented information about the Chicago Cubs and White Sox during the 2004 and 2008 seasons. This was accomplished through content analysis from sports sections of both, The Chicago Tribune and Chicago Sun Times, totaling 167 articles containing 2,777 paragraphs. This analysis measured quantity and tone of news coverage with cross-comparisons between two teams, two years and two news sources. Each paragraph was assigned to one of the teams and categorized into a pre-determined coding group. These coding groups were classified as positive, negative, or neutral in tone. This study sought to identify whether significant agenda-setting or framing differences existed between the Chicago Cubs and Chicago White Sox and how this differences could have impact on object salience. The theories of agenda-setting and framing will provide insight into the decision making process of sportswriters as to: how much information of each subject is being presented (quantity), and how the story is presenting the subject (tone). The Cubs received a slightly higher amount of coverage than the White Sox for the entirety of the study. However, as total coverage decreased, from 2004 to 2008, the majority of which was in coverage for the White Sox. Thus, suggesting an agenda-setting function in this particular area of the study. Both the White Sox and Cubs received more neutral coverage, than positive or neutral frames. The remained constant to the study, with the exception of the Cubs in the year 2008, where they received a significant amount of positive coverage as opposed to their 2004 season. This paper sought the theories of framing and agendasetting beyond their popular reach in the political world. by applying them to sports writing, a previously untapped discipline.Department of JournalismThesis (M.A.

Self-propulsion against a moving membrane: enhanced accumulation and drag force

Self-propulsion (SP) is a main feature of active particles (AP), such as bacteria or biological micromotors, distinguishing them from passive colloids. A renowned consequence of SP is accumulation at static interfaces, even in the absence of hydrodynamic interactions. Here we address the role of SP in the interaction between AP and a moving semipermeable membrane. In particular, we implement a model of noninteracting AP in a channel crossed by a partially penetrable wall, moving at a constant velocity $c$. With respect to both the cases of passive colloids with $c>0$ and AP with $c=0$, the AP with finite $c$ show enhancement of accumulation in front of the obstacle and experience a largely increased drag force. This effect is understood in terms of an effective potential localised at the interface between particles and membrane, of height proportional to $c\tau/\xi$, where $\tau$ is the AP's re-orientation time and $\xi$ the width characterising the surface's smoothness ($\xi\to 0$ for hard core obstacles). An approximate analytical scheme is able to reproduce the observed density profiles and the measured drag force, in very good agreement with numerical simulations. The effects discussed here can be exploited for automatic selection and filtering of AP with desired parameters.Comment: 13 pages, 3 figure

Anomalous temperature dependence of the band-gap in Black Phosphorus

Black Phosphorus (BP) has gained renewed attention due to its singular anisotropic electronic and optical properties that might be exploited for a wide range of technological applications. In this respect, the thermal properties are particularly important both to predict its room temperature operation and to determine its thermoelectric potential. From this point of view, one of the most spectacular and poorly understood phenomena is, indeed, the BP temperature-induced band-gap opening: when temperature is increased the fundamental band-gap increases instead of decreasing. This anomalous thermal dependence has also been observed, recently, in its monolayer counterpart. In this work, based on \textit{ab-initio} calculations, we present an explanation for this long known, and yet not fully explained, effect. We show that it arises from a combination of harmonic and lattice thermal expansion contributions, which are, in fact, highly interwined. We clearly narrow down the mechanisms that cause this gap opening by identifying the peculiar atomic vibrations that drive the anomaly. The final picture we give explains both the BP anomalous band-gap opening and the frequency increase with increasing volume (tension effect).Comment: Published in Nano Letter

Quasiparticle Electronic structure of Copper in the GW approximation

We show that the results of photoemission and inverse photoemission experiments on bulk copper can be quantitatively described within band-structure theory, with no evidence of effects beyond the single-quasiparticle approximation. The well known discrepancies between the experimental bandstructure and the Kohn-Sham eigenvalues of Density Functional Theory are almost completely corrected by self-energy effects. Exchange-correlation contributions to the self-energy arising from 3s and 3p core levels are shown to be crucial.Comment: 4 pages, 2 figures embedded in the text. 3 footnotes modified and 1 reference added. Small modifications also in the text. Accepted for publication in PR