Hecke actions on certain strongly modular genera of lattices

We calculate the action of some Hecke operators on spaces of modular forms spanned by the Siegel theta-series of certain genera of strongly modular lattices closely related to the Leech lattice. Their eigenforms provide explicit examples of Siegel cusp forms

The Complex Relationship Between Education and Happiness: The Case of Highly Educated Individuals in Italy

The present work aims to explore whether there exists a systematic frustration in terms of income expectations among those who have obtained high level of education in Italy, and if this mismatch between expected and effective incomes negatively affects their perception of happiness. We adopt a reference-dependent preferences model combined with the concept of “illusory superiority bias” to analyse data on “happiness” in Italy, provided by the biennial survey conducted by the Bank of Italy on the Italian households’ incomes and wealth between 2004 and 2014. Our results show a positive effect produced by education on incomes. High educated workers have on average higher income than other people, and this difference is statistically significant controlling for working experience and other possible confounding factors. However, the disutility resulting from the frustration of expectations produces negative effects on perceived happiness. Even though highly educated people are actually able to find better job matching in comparison to less educated workers, they are also more likely to seeing their income expectations frustrated

Expo 2015: an impact analysis on international trade.

In the last decades an increasing number of countries candidates to host a mega-event. This paper analyze (in the light of Expo Milan will host in 2015) if an exposition impacts in a significant manner on interna-tional trade, justifying countries’ interest in their organization. Based on performed analysis using gravity model, we conclude that a permanent and significant exposition effect exists on host country international trade flows; it involve both an increase of exports and an increase of imports, pointing out a commercial openness of host country; this effect exists also for candidates countries. So, we propose an hypothesis about the nature of exposition impact on international trade: it’s interpretable as a true and proper political and in-stitutional signal with which host country sends a signal to general public of a liberalisation process of its commerce in progress, showing own competences, abilities, means and resources. In the light of results, we point out potentialities and risks of Expo Milan 2015.

Optimal Dynamic Procurement Policies for a Storable Commodity with L\'evy Prices and Convex Holding Costs

In this paper we study a continuous time stochastic inventory model for a commodity traded in the spot market and whose supply purchase is affected by price and demand uncertainty. A firm aims at meeting a random demand of the commodity at a random time by maximizing total expected profits. We model the firm's optimal procurement problem as a singular stochastic control problem in which controls are nondecreasing processes and represent the cumulative investment made by the firm in the spot market (a so-called stochastic "monotone follower problem"). We assume a general exponential L\'evy process for the commodity's spot price, rather than the commonly used geometric Brownian motion, and general convex holding costs. We obtain necessary and sufficient first order conditions for optimality and we provide the optimal procurement policy in terms of a "base inventory" process; that is, a minimal time-dependent desirable inventory level that the firm's manager must reach at any time. In particular, in the case of linear holding costs and exponentially distributed demand, we are also able to obtain the explicit analytic form of the optimal policy and a probabilistic representation of the optimal revenue. The paper is completed by some computer drawings of the optimal inventory when spot prices are given by a geometric Brownian motion and by an exponential jump-diffusion process. In the first case we also make a numerical comparison between the value function and the revenue associated to the classical static "newsvendor" strategy.Comment: 28 pages, 3 figures; improved presentation, added new results and section

Porous media equations with two weights: smoothing and decay properties of energy solutions via Poincar\'e inequalities

We study weighted porous media equations on domains $\Omega\subseteq{\mathbb R}^N$, either with Dirichlet or with Neumann homogeneous boundary conditions when $\Omega\not={\mathbb R}^N$. Existence of weak solutions and uniqueness in a suitable class is studied in detail. Moreover, $L^{q_0}$-$L^\varrho$ smoothing effects ($1\leq q_0<\varrho<\infty$) are discussed for short time, in connection with the validity of a Poincar\'e inequality in appropriate weighted Sobolev spaces, and the long-time asymptotic behaviour is also studied. Particular emphasis is given to the Neumann problem, which is much less studied in the literature, as well as to the case $\Omega={\mathbb R}^N$ when the corresponding weight makes its measure finite, so that solutions converge to their weighted average instead than to zero. Examples are given in terms of wide classes of weights.Comment: Slightly shortened version. To appear in Discrete and Continuous Dynamical Systems

Communication, Commitment, and Deception in Social Dilemmas: Experimental Evidence

Social norms of cooperation are studied under several forms of communication. In an experiment, strangers could make public statements before playing a prisoner’s dilemma. The interaction was repeated indefinitely, which generated multiple equilibria. Communication could be used as a tool to either signal intentions to coordinate on Pareto-superior outcomes, to deceive others, or to credibly commit to actions. Some forms of communication did not promote the incidence of efficient Nash play, and sometimes reduced it. Surprisingly, cooperation suffered when subjects could publicly commit to actions.coordination, cheap-talk, deception, indefinitely repeated game, social norms

Cooperative Strategies in Groups of Strangers: An Experiment

We study cooperation in four-person economies of indefinite duration. Subjects interact anonymously playing a prisoner’s dilemma. We identify and characterize the strategies employed at the aggregate and at the individual level. We find that (i) grim trigger well describes aggregate play, but not individual play; (ii) individual behavior is persistently heterogeneous; (iii) coordination on cooperative strategies does not improve with experience; (iv) systematic defection does not crowd-out systematic cooperation.repeated games, equilibrium selection, prisoners’ dilemma, random matching

How dark is the night: the consumers’ mood coping with the crisis.Evidences from ISAE Consumer Survey

Since 2008 the global economy, following also the financial crisis, is facing a severe decline in economic activity and the economic estimates concerning the first quarter 2009 are even worse. While in the major industrialized economies Consumers Confidence Indicators (CCI) show common negative trends, in Italy we have observed a different pattern. After a sharp fall beginning in 2007, the CCI (in the Italian definition) is unexpectedly showing some signals of recovery since the end of summer 2008. Specifically, the confidence on the personal condition improved, while the economic picture was considered in deterioration at least till the first quarter of 2009. From another point of view, whereas the expectations on the future are worsening, the evaluation on present conditions are recovering. It seems that the effects of the financial crisis have not influenced Italian consumers yet, as it is documented worldwide. It is worth sorting out this puzzle. The paper tries to explain these trends starting from the role played by the single elements on which the composite indicator of confidence climate is determined. Then the recent price evolution and its influence on the Italian Consumer Confidence dynamics are investigated. Since end of summer 2008, the sharp inflation slowdown together with nominal wages increase, may have contributed to keep confidence from falling. A further tool for explaining recent CCI dynamics could also be represented by a micro-data analysis of opinions of population sub-groups, because some of these could have been more exposed than others to the crisis. Therefore the paper explores reactions of different consumers segments (e.g. by income, professional status, household composition).Consumers Confidence, Consumption, Survey data

Efficient Diversification of Web Search Results

In this paper we analyze the efficiency of various search results diversification methods. While efficacy of diversification approaches has been deeply investigated in the past, response time and scalability issues have been rarely addressed. A unified framework for studying performance and feasibility of result diversification solutions is thus proposed. First we define a new methodology for detecting when, and how, query results need to be diversified. To this purpose, we rely on the concept of "query refinement" to estimate the probability of a query to be ambiguous. Then, relying on this novel ambiguity detection method, we deploy and compare on a standard test set, three different diversification methods: IASelect, xQuAD, and OptSelect. While the first two are recent state-of-the-art proposals, the latter is an original algorithm introduced in this paper. We evaluate both the efficiency and the effectiveness of our approach against its competitors by using the standard TREC Web diversification track testbed. Results shown that OptSelect is able to run two orders of magnitude faster than the two other state-of-the-art approaches and to obtain comparable figures in diversification effectiveness.Comment: VLDB201

Manipulating matter waves in an optical superlattice

We investigate the potential for controlling a non-interacting Bose-Einstein condensate loaded into a one-dimensional optical superlattice. Our control strategy combines Bloch oscillations originating from accelerating the lattice and from time-dependent control of the superlattice parameters. We investigate two experimentally viable scenarios, very low and very high potential depths. We are able to exhibit a wide range of control over energy band populations using the superlattice control parameters. With this analysis we consider several examples of quantum state preparation in the superlattice structure that may be difficult to achieve in a regular lattice.Comment: 9 pages, 11 figures. Updated version as an artist's work is never finished, and due to publication. DOI & journal ref adde