Broken Ergodicity in classically chaotic spin systems

A one dimensional classically chaotic spin chain with asymmetric coupling and two different inter-spin interactions, nearest neighbors and all-to-all, has been considered. Depending on the interaction range, dynamical properties, as ergodicity and chaoticity are strongly different. Indeed, even in presence of chaoticity, the model displays a lack of ergodicity only in presence of all to all interaction and below an energy threshold, that persists in the thermodynamical limit. Energy threshold can be found analytically and results can be generalized for a generic XY model with asymmetric coupling.Comment: 6 pages, 3 figure

Bowling Together by Bowling Alone: Social Capital and COVID-19

Social capital describes the social bonds that exist within a community and comprises norms of reciprocity and trust as well as social relationships and social networks. We use data from counties in the United States to identify if community level responses to COVID-19 during the early phase of the pandemic (February 17 – May 10) depended on levels of social capital. We find that individuals who lived in counties with high levels of social capital reduced mobility faster than individuals living in counties with low levels of social capital and that they especially reduced mobility directed at retail and recreational activities, i.e. non-essential activities with higher potential risk. Difference-in-difference results show that the adoption of shelter-in-place orders (SIPOs) in a county, an increase in the number of diagnosed COVID-19 cases and a rainy weather were all associated with a decline in mobility, but that effects were heterogenous and depended on community level social capital. Effects were more pronounced in high social capital communities. Based on these findings, we map the level of vulnerability of communities in the United States to COVID-19: counties with a large share of the population suffering from pre-existing medical conditions and low levels of community level social capital are especially susceptible to experiencing severe health outcomes because of COVID-19

Introduction to a Symposium on Broadening the Application of Performance Management

The Italian Academy of Management (Accademia Italiana di Economia Aziendale (AIDEA)), which was founded in Bologna during July 1813, is one of the oldest academic societies in the world. On the occasion of celebrating its bicentenary, the AIDEA held a conference in Lecce, Italy, during September 2013 for AIDEA members and international scholars to present their research within six major areas: Economia Aziendale, Ragioneria ed Economia Aziendale in Italia, Accounting, Management & Organization, Public Management, and Banking & Finance. The theme of the conference—The Firm’s Role in the Economy: Does a Growth-Oriented Business Model Exist?—was in response to the global crisis that has raised new questions and challenges that scholars are trying to resolve, including how academic and professional studies can provide strategies on helping firms and markets contribute to economic growth. In order to support the conference theme, the performance management track focused in part on how organizational and interinstitutional performance management within the context of public administration can support sustainable economic and community growth

The Evolution of the Association between Community Level Social Capital and Covid-19 Deaths and Hospitalizations in the United States

We use county level data from the United States to document the role of social capital the evolution of COVID-19 between January 2020 and January 2021. We find that social capital differentials in COVID-19 deaths and hospitalizations depend on the dimension of social capital and the timeframe considered. Communities with higher levels of relational and cognitive social capital were especially successful in lowering COVID-19 deaths and hospitalizations than communities with lower social capital between late March and early April. A difference of one standard deviation in relational social capital corresponded to a reduction of 30% in the number of COVID-19 deaths recorded. After April 2020, differentials in COVID-19 deaths related to relational social capital persisted although they became progressively less pronounced. By contrast, the period of March–April 2020, our estimates suggest that there was no statistically significant difference in the number of deaths recorded in areas with different levels of cognitive social capital. In fact, from late June-early July onwards the number of new deaths recorded as being due to COVID-19 was higher in communities with higher levels of cognitive social capital. The overall number of deaths recorded between January 2020 and January 2021 was lower in communities with higher levels of relational social capital. Our findings suggest that the association between social capital and public health outcomes can vary greatly over time and across indicators of social capital

Focusing in Multiwell Potentials: Applications to Ion Channels

We investigate out of equilibrium stationary distributions induced by a stochastic dichotomous noise on double and multi-well models for ion channels. Ion-channel dynamics is analyzed both through over-damped Langevin equations and master equations. As a consequence of the external stochastic noise, we prove a non trivial focusing effect, namely the probability distribution is concentrated only on one state of the multi-well model. We also show that this focusing effect, which occurs at physiological conditions, cannot be predicted by a simple master equation approach.Comment: 8 pages, 7 figure

Quantum Signatures of The Classical Disconnection Border

A quantum Heisenberg model with anisotropic coupling and all-to-all interaction has been analyzed using the Bose-Einstein statistics. In Ref.\cite{jsp} the existence of a classical energy disconnection border (EDB) in the same kind of models has been demonstrated. We address here the problem to find quantum signatures of the EDB. An independent definition of a quantum disconnection border, motivated by considerations strictly valid in the quantum regime is given. We also discuss the dynamical relevance of the quantum border with respect to quantum magnetic reversal. Contrary to the classical case the magnetization can flip even below the EDB through Macroscopic Quantum Tunneling. We evaluate the time scale for magnetic reversal from statistical and spectral properties, for a small number of particles and in the semiclassical limit.Comment: 5 pages, 5 figure