First order dynamical phase transitions

Recently, dynamical phase transitions have been identified based on the non-analytic behavior of the Loschmidt echo in the thermodynamic limit [Heyl et al., Phys.~Rev.~Lett.~{\bf 110}, 135704 (2013)]. By introducing conditional probability amplitudes, we show how dynamical phase transitions can be further classified, both mathematically, and potentially in experiment. This leads to the definition of first-order dynamical phase transitions. Furthermore, we develop a generalized Keldysh formalism which allows to use nonequilibrium dynamical mean-field theory to study the Loschmidt echo and dynamical phase transitions in high-dimensional, non-integrable models. We find dynamical phase transitions of first order in the Falicov-Kimball model and in the Hubbard model.Comment: Published version, supplemental material included as appendix, 4 figure

Stroboscopic prethermalization in weakly interacting periodically driven systems

Time-periodic driving provides a promising route to engineer non-trivial states in quantum many-body systems. However, while it has been shown that the dynamics of integrable systems can synchronize with the driving into a non-trivial periodic motion, generic non-integrable systems are expected to heat up until they display a trivial infinite-temperature behavior. In this paper we show that a quasi-periodic time evolution over many periods can also emerge in systems with weak integrability breaking, with a clear separation of the timescales for synchronization and the eventual approach of the infinite-temperature state. This behavior is the analogue of prethermalization in quenched systems. The synchronized state can be described using a macroscopic number of approximate constants of motion. We corroborate these findings with numerical simulations for the driven Hubbard model.Comment: 8 pages, 2 figures, published versio

Dynamics of entanglement entropy and entanglement spectrum crossing a quantum phase transition

We study the time evolution of entanglement entropy and entanglement spectrum in a finite-size system which crosses a quantum phase transition at different speeds. We focus on the Ising model with a time-dependent magnetic field, which is linearly tuned on a time scale $\tau$ . The time evolution of the entanglement entropy displays different regimes depending on the value of $\tau$, showing also oscillations which depend on the instantaneous energy spectrum. The entanglement spectrum is characterized by a rich dynamics where multiple crossings take place with a gap-dependent frequency. Moreover, we investigate the Kibble-Zurek scaling of entanglement entropy and Schmidt gap.Comment: Accepted for publication in Phys. Rev.

OKE - Stroke Provoke Evoke, a visual protest

OKE * Stroke Provoke Evoke is an academic project with the scope of sensitizing the society for a better understanding of the value of the streets art’s underground subculture; it aims to obtain answers and create solutions to arrest censorship’s act and, graffiti and street art coverings. Censorship act against artist repressing their freedom of expression, in graffiti and street art authorities covers artworks considered vandalism, concealing the beauty, the messages, and the culture behind them. This paper will research among case studies, empirical surveys and primary resources with a qualitative method to obtain enough information and reactions about censorship, street art, and graffiti. The research shows that graffiti belongs to the street and the illegality is existential core. The results collected led to a creation of a visual protest that will be taking place in the street of Lisbon, to create more legal walls and a better perception of graffiti among society

Identity Construction and its Influence on Wine Tourism Diversification Decisions: Case Study of Family Wineries in Langhe, Italy

The aim of this thesis is to examine family wineries’ wine tourism diversification decisions in terms of wine producers’ self-constructions. The focus lies on understanding which motives drive family businesses’ decisions to engage in diversification. A case study approach is adopted, using the Italian wine region of Langhe in Piedmont. The dominant debates within the current literature have primarily concentrated on the economic-social dichotomy in relation to diversification decisions. It has been argued that diversification decisions are predominantly economically driven, highlighting the importance of profit maximisation and risk reduction. This thesis highlights the limitations of the economic-social dichotomy approach and argues for the need to take the social context into account when examining the decision-making process. An interpretivist approach to research is adopted in order to extend current understandings of family businesses and their motives underlying diversification decisions. In line with the interpretivist perspective, this thesis uses discourse analysis (DA) as a methodological approach for analysing and interpreting wine producers’ accounts. The findings reveal that by engaging in discourse about wine tourism diversification, wine producers construct a distinctive, coherent and desired sense of self, which in turn influences family wineries’ decisions to diversification. In this instance, the concept of identity formation plays a central role in explaining family wineries’ motives for diversification. Linking wine producers’ motives for diversification to their self-constructions provides a new insight into how family businesses engage in decision-making. Wine producers’ discourses reveal that their decision-making processes are inextricably linked to sustaining a positive sense of self. Decisions are not only taken to achieve economic goals, but are likely to be influenced by deeper motives, notably wine producers’ identity constructions. The main contribution of this thesis is that it advances understanding of family businesses’ decisionmaking processes by developing a multi-layered conceptual framework to go beyond the economic-social dichotomy in order to reveal wine producers’ semi-conscious and unconscious motives for diversification

Overlap distributions for quantum quenches in the anisotropic Heisenberg chain

The dynamics after a quantum quench is determined by the weights of the initial state in the eigenspectrum of the final Hamiltonian, i.e., by the distribution of overlaps in the energy spectrum. We present an analysis of such overlap distributions for quenches of the anisotropy parameter in the one-dimensional anisotropic spin-1/2 Heisenberg model (XXZ chain). We provide an overview of the form of the overlap distribution for quenches from various initial anisotropies to various final ones, using numerical exact diagonalization. We show that if the system is prepared in the antiferromagnetic N\'eel state (infinite anisotropy) and released into a non-interacting setup (zero anisotropy, XX point) only a small fraction of the final eigenstates gives contributions to the post-quench dynamics, and that these eigenstates have identical overlap magnitudes. We derive expressions for the overlaps, and present the selection rules that determine the final eigenstates having nonzero overlap. We use these results to derive concise expressions for time-dependent quantities (Loschmidt echo, longitudinal and transverse correlators) after the quench. We use perturbative analyses to understand the overlap distribution for quenches from infinite to small nonzero anisotropies, and for quenches from large to zero anisotropy.Comment: 23 pages, 8 figure

Dermatofitosi nel coniglio e roditori da compagnia

La dermatofitosi è una patologia comune nelle cavie peruviane, nei conigli e nei roditori da compagnia, causata da questi funghi che vivono nei tessuti cheratinizzati come peli, unghie e cellule epiteliali dello strato corneo. La patologia si caratterizza per alopecia, desquamazione e croste. Trichophyton mentagrophytes è il dermatofita più comunemente isolato, ma anche Microsporum canis si riscontra su questi animali. Sono disponibili scarsissimi dati sulle dermatofitosi del coniglio e roditori da compagnia, dato che molti studi si riferiscono ad animali da laboratorio o allevati ai fini alimentari. Lo scopo di questa tesi è esporre le caratteristiche principali dei dermatofiti e la patologia clinica che causano nel coniglio e roditori da compagnia, con riferimento alla diagnostica di laboratorio e all'aspetto zoonosico

Family-Centred Motivations for Agritourism Diversification: The Case of the Langhe Region, Italy.

This is an Accepted Manuscript of an article published by Taylor & Francis in Tourism Planning and Development on 7-8-19, available online: https://doi.org/10.1080/21568316.2019.1650104This paper examines the motivations underlying family wineries' decisions to diversify into agritourism. Empirical evidence is provided by a sample of North Italian family wineries that have recently engaged in agritourism. While the majority of studies have adopted an economic-noneconomic dichotomy approach when examining the motivations for agritourism diversification, this paper highlights the limitations of this approach, outlines the complexity of motivations and argues for the need to take the family context into account. Drawing on the socioemotional wealth (SEW) framework, we offer a conceptual model and derive a set of propositions to show how family owners' motivations for agritourism diversification are primarily driven by family-centred goals. This paper thus contributes to a better understanding of diversification in general, and of farming families' motivations for agritourism diversification in particular. Practical implications at the European and regional level are discussed. KEYWORDS: Agritourism, wine tourism, diversification, socioemotional wealth, family busines