Department of Business Economics

We address the problem of estimating the drift parameter in a system of N interacting particles driven by additive fractional Brownian motion of Hurst index H >= 1/2. Considering continuous observation of the interacting particles over a fixed interval [0, T], we examine the asymptotic regime as N -> infinity. Our main tool is a random variable reminiscent of the least squares estimator but unobservable due to its reliance on the Skorohod integral. We demonstrate that this object is consistent and asymptotically normal by establishing a quantitative propagation of chaos for Malliavin derivatives, which holds for any H is an element of (0, 1). Leveraging a connection between the divergence integral and the Young integral, we construct computable estimators of the drift parameter. These estimators are shown to be consistent and asymptotically Gaussian. Finally, a numerical study highlights the strong performance of the proposed estimators.

We investigate the structural foundations of statistical efficiency under α-local differential privacy, with a focus on maximizing Fisher information. Building on the role of continuous staircase mechanisms, we identify a fundamental symmetry regarding the extremal values 1 and e^α. We demonstrate that when the optimal measure satisfies this symmetry, the Fisher information admits a closed-form expression. More generally, we derive a decomposition of the Fisher information into symmetric and asymmetric components, scaling as α^2 and α^3, respectively, for α→ 0. This reveals that, if in the high-privacy regime asymmetry is negligible, it is no longer the case as privacy constraints are relaxed. Motivated by this, we introduce a class of fully asymmetric privacy mechanisms constructed via pushforward mappings, proving that-unlike their symmetric counterparts-they recover the full Fisher information of the non-private model as α→∞. We bridge the gap between theory and practice by providing a tractable implementation of these mechanisms, governed by a tuning parameter c. This parameter allows for a smooth interpolation between the symmetric regime and the fully asymmetric regime. Furthermore, we demonstrate the versatility of this framework by showing that it encompasses the binomial mechanism as a limiting case.

We study the problem of nonparametric estimation of the interaction function in particle systems whose interaction enters through the diffusion coefficient. The particle system is observed discretely over a fixed time interval, and the interaction function is assumed to belong to a suitable nonparametric function class. We propose an estimation procedure based on empirical risk minimization over finite-dimensional sieve spaces, introducing a computable contrast function that exploits the local volatility of the observed trajectories. We derive a general non-asymptotic error bound under the intrinsic norm associated with the statistical problem and, focusing the analysis on multiresolution wavelet approximation spaces, we obtain explicit polynomial convergence rates in two distinct regimes, depending on whether the particle or discretization error dominates. Finally, we establish convergence rates for the classical L^2-norm.

The Mobile World Congress (MWC) has become an international benchmark in mobile technology and one of the most significant events hosted in Barcelona. Beyond its technological relevance, its media visibility may have played a key role in shaping the city’s public image and international reputation. This study aims to examine the impact of media coverage of the Mobile World Congress on the promotion and positioning of the city of Barcelona. A mixed-methods approach was employed, combining content analysis and sentiment analysis through the implementation of a hierarchical multiclass automatic classification system. The study analysed news coverage published in three major regional newspapers— La Vanguardia , Ara.Cat , and El Periódico ( n = 3523 news articles). This methodological design enabled the identification of thematic patterns, dominant narratives, and the frequency with which Barcelona was associated with the event. The findings indicate that media coverage of the MWC has had a notably positive effect on Barcelona’s visibility and reputation. The newspapers consistently presented the city as a leading hub for technological innovation, international business, and large-scale global events. Recurrent references to Barcelona’s organisational capacity and strategic relevance within the mobile technology sector contributed to strengthening its urban brand and enhancing its symbolic capital in both regional and international media discourse. The MWC has significantly contributed to boosting and promoting the city of Barcelona. Media representation of the event has reinforced the city’s status as a global, innovation-driven urban centre and has consolidated its position within the international technological landscape.

Purpose: Healthcare systems have undergone changes due to ageing populations and responding to new care needs, with developments in nursing in terms of organization, skills and new roles. The introduction of specialist clinical nurses (SCN) in all departments was considered crucial to expand the professional development possibilities for nurses. The purpose of this study was to examine SCNs perceptions of their role and clinical leadership, and to identify the components of a complex intervention aimed to improve clinical leadership. Methods: Qualitative research was performed in a multisite Hospital, via semi-structured interviews with SCNs, involved with a purposive sample, to investigate perceptions of their role and barriers/facilitators to clinical leadership and its development. A review of relevant literature informed the interview guide and a thematic analysis of data was performed. The results and literature relating to clinical leadership were synthesised for the first phase, of the Medical Research Council framework (development of the intervention) to develop a complex intervention focusing on clinical leadership. A consensus meeting was performed with SCNs and nurse managers to define the intervention. Results: Seven interviews were conducted with SCNs. Five macro themes were identified contributing to clinical leadership as a SCN: personal characteristics and competencies, collaboration and relationships, organization and culture of teams, leadership in the role and patient. During the consensus meeting the results were discussed and participants highlighted existing resources for leadership and those requiring development. A complex intervention to improve clinical leadership was defined, consisting of an introductory pathway, basic training package, coaching/support in practice and group work. Conclusion: The study has identified a variety of factors that could influence clinical leadership and how they could be applied within this clinical role. Elements to further develop clinical leadership for SCNs have been outlined taking into account the local context and the need to introduce additional interventions based on the needs of the individual and the team.