Epidemics of Liquidity Shortages in Interbank Markets

Financial contagion from liquidity shocks has being recently ascribed as a prominent driver of systemic risk in interbank lending markets. Building on standard compartment models used in epidemics, in this work we develop an EDB (Exposed-Distressed-Bankrupted) model for the dynamics of liquidity shocks reverberation between banks, and validate it on electronic market for interbank deposits data. We show that the interbank network was highly susceptible to liquidity contagion at the beginning of the 2007/2008 global financial crisis, and that the subsequent micro-prudential and liquidity hoarding policies adopted by banks increased the network resilience to systemic risk---yet with the undesired side effect of drying out liquidity from the market. We finally show that the individual riskiness of a bank is better captured by its network centrality than by its participation to the market, along with the currently debated concept of "too interconnected to fail"

On entanglement Hamiltonians of an interval in massless harmonic chains

We study the continuum limit of the entanglement Hamiltonians of a block of consecutive sites in massless harmonic chains. This block is either in the chain on the infinite line or at the beginning of a chain on the semi-infinite line with Dirichlet boundary conditions imposed at its origin. The entanglement Hamiltonians of the interval predicted by conformal field theory (CFT) for the massless scalar field are obtained in the continuum limit. We also study the corresponding entanglement spectra, and the numerical results for the ratios of the gaps are compatible with the operator content of the boundary CFT of a massless scalar field with Neumann boundary conditions imposed along the boundaries introduced around the entangling points by the regularisation procedure

Circuit complexity and entanglement in many-body quantum systems

Entanglement and circuit complexity are fundamental concepts in quantum information theory which turned out to have considerable applications in various contexts ranging from many-body systems and condensed matter theory to quantum gravity and black hole physics. In order to find connections between these aspects, an insightful approach consists in comparing the complexity with some entanglement measures of a given bipartition, as for instance the Von Neumann entanglement entropy. Since, for a system in a given quantum state, the bipartite entanglement can be determined once a spatial subsystem and its complement are chosen, this comparison has to be made considering the complexity of reduced density matrices. This motivates the development of techniques for determining the circuit complexity of mixed states. In this thesis, focussing on free bosonic systems, we study the circuit complexity of mixed Gaussian states by employing the Fisher information geometry for the covariance matrices. This approach allows computing the complexity between reduced density matrices (subsystem complexity), as well as the complexity between thermal states. It also leads to a precise prescription for computing the spectrum and the basis complexity and the temporal evolution of the subsystem complexity after global and local quantum quenches. The study of the subsystem complexity of a given bipartition and a complete characterisation of its entanglement requires the detailed knowledge of the corresponding reduced density matrix, or, equivalently, of the entanglement Hamiltonian. A part of this thesis is devoted to determining the entanglement Hamiltonians in free theories. At equilibrium, we consider gapless systems, with the aim of recovering the underlying CFT results, and gapped lattice models. The evolution of entanglement Hamiltonians in quantum chains after a global quench is also studied. In addition, other entanglement quantifiers, as the entanglement spectrum and the contour for the entanglement entropies, are discussed in some of these settings. Finally, motivated by theoretical and experimental advances, we also address the issue of how the entanglement splits into the different charge sectors of a system endowed with a U(1) symmetry. We focus in particular on massive theories, either continuous or on the lattice, and we try to understand whether the entanglement equipartition, which is known to characterise gapless systems, survives away from criticality

RAPPORTO ATTIVITA' UR-INGV

In questo rapporto di attività viene illustrata la seconda fase delle ricerche svolte dall’UR-INGV nei due comuni selezionati ai fini del progetto, Nocera Umbra e Cerreto di Spoleto. Per quanto riguarda Nocera Umbra, si sono analizzati i dati sismometrici registrati durante un esperimento mediante array sismico a piccola apertura, appositamente installato sulla collina di Nocera Umbra per lo studio dell'effetto topografico e la quantificazione del ruolo delle variazioni topografiche locali sull'input sismico. Va ricordato che la torre campanaria, pesantemente danneggiata durante le scosse più forti del Settembre e Ottobre 1997, come pure l’intero centro storico di Nocera Umbra, sono situati sulla sommità di una collina. E' apparso pertanto importante valutare gli effetti di amplificazione del moto del suolo con grande dettaglio spaziale nella zona dove sono localizzati gli edifici monumentali e la parte storica della città. Sono stati anche effettuati due profili geoelettrici a cavallo della faglia, probabilmente inattiva, che attraversa Nocera Umbra, e tramite inversione tomografica dei dati di resistività si è cercata una conferma dell’estensione laterale della zona di faglia, alla cui presenza è stata attribuita la causa principale dell’accelerazione di 0.6 g registrata nella stazione della rete accelerometrica nazionale ubicata nella cabina ENEL di Nocera Umbra, a circa 20 m dalla parete della faglia stessa. E' stato infine analizzato in dettaglio il ruolo giocato dalla zona di faglia nella propagazione delle onde sismiche, sia in termini di picchi di accelerazione e velocità che di amplificazioni spettrali, in campo lineare e non lineare. L’intervento su Cerreto di Spoleto ha visto l’installazione di stazioni sismiche nell’area urbana congiuntamente all’UR-ENEA, e l’esecuzione di misure geoelettriche per la definizione delle geometrie sepolte nella piana di Borgo Cerreto. Inoltre, si è studiato in dettaglio l’effetto di amplificazione in prossimità di una faglia che attraversa il centro storico di Cerreto di Spoleto, dove le registrazioni sismiche hanno evidenziato, analogamente al caso di Nocera Umbra, un forte effetto di canalizzazione dell’energia incidente sotto forma di "trapped waves", e dove precedentemente si era constatata la massima concentrazione dei danni durante le più forti scosse, localizzate nella zona di Sellano-Preci, dell’Ottobre 1997. Nei successivi paragrafi vengono mostrati i risultati di queste indagini

Aperiodic spin chains at the boundary of hyperbolic tilings

In view of making progress towards establishing a holographic duality for theories defined on a discrete tiling of the hyperbolic plane, we consider a recently proposed boundary spin chain Hamiltonian with aperiodic couplings that are chosen such as to reflect the inflation rule, i.e. the construction principle, of the bulk tiling. As a remnant of conformal symmetry, the spin degrees of freedom are arranged in multiplets of the dihedral group under which the bulk lattice is invariant. For the boundary Hamiltonian, we use strong-disorder RG techniques and evaluate correlation functions, the entanglement entropy and mutual information for the case that the ground state is in an aperiodic singlet phase. We find that two-point functions decay as a power-law with exponent equal to one. Furthermore, we consider the case that the spin variables transform in the fundamental representation of $SO(N)$, leading to a gapless system, and find that the effective central charge obtained from the entanglement entropy scales as $\ln N$, reflecting the number of local degrees of freedom. We also determine the dependence of this central charge on the parameters specifying the bulk tiling. Moreover, we obtain an analytical expression for the mutual information, according to which there is no phase transition at any finite value of the distance between the two intervals involved.Comment: 41 pages, 4 figures. v2: 40 pages, improved discussio

Indicators for site characterization at seismic station: recommendation from a dedicated survey

AbstractIn recent years, the permanent seismic networks worldwide have largely increased, raising the amount of earthquake signals and the applications using seismic records. Although characterization of the soil properties at recording stations has a large impact on hazard estimates, it has not been implemented so far in a standardized way for reaching high-level metadata. To address this issue, we built an online questionnaire for the identification of the indicators useful for a reliable site characterization at a seismic station. We analysed the answers of a large number of experts in different fields, which allowed us to rank 24 different indicators and to identify the most relevant ones: fundamental frequency (f0), shear-wave velocity profile (VS), time-averaged Vs over 30 m (VS30), depth of seismological and engineering bedrock (Hseis_bed and Heng_bed), surface geology and soil class. Moreover, the questionnaire proposed two additional indices in terms of cost and difficulty to obtain a reliable value of each indicator, showing that the selection of the most relevant indicators results from a complex balance between physical relevancy, average cost and reliability. For each indicator we propose a summary report, provided as editable pdf, containing the background information of data acquisition and processing details, with the aim to homogenize site metadata information at European level and to define the quality of the site characterization (see companion paper Di Giulio et al. 2021). The selected indicators and the summary reports have been shared within European and worldwide scientific community and discussed in a dedicated international workshop. They represent a first attempt to reach a homogeneous set of high-level metadata for site characterization

Probing RG flows, symmetry resolution and quench dynamics through the capacity of entanglement

We compare the capacity of entanglement with the entanglement entropy by considering various aspects of these quantities for free bosonic and fermionic models in one spatial dimension, both in the continuum and on the lattice. Substantial differences are observed in the subleading terms of these entanglement quantifiers when the subsystem is made by two disjoint intervals, in the massive scalar field and in the fermionic chain. We define $c$-functions based on the capacity of entanglement similar to the one based on the entanglement entropy, showing through a numerical analysis that they display a monotonic behaviour under the renormalisation group flow generated by the mass. The capacity of entanglement and its related quantities are employed to explore the symmetry resolution. The temporal evolutions of the capacity of entanglement and of the corresponding contour function after a global quench are also discussed.Comment: 63 pages, 12 figure

Mechanical Energy Recovery from Low Grade Thermal Energy Sources

An ORC based power plant for waste heat recovery in stationary applications has been developed and experimentally characterized. The aim of the study was to investigate the performance of a sliding vane rotary expander as the device to convert the enthalpy of the working fluid, namely R236fa, into mechanical and electric energy. A theoretical model of the expander supported the design and allowed to assess the thermodynamic transformations that take place in it. Furthermore, a deep experimental campaign explored the behavior of the expander and the one of the recovery system also at off design conditions. The experimental activity on the expander included the reconstruction of the indicated diagram using a set of high frequency piezoelectric pressure transducers that provided an accurate prediction of the pressure evolution inside the cell. The overall cycle efficiency achieved was close to 8% and further improvements concerned to the expander design have been addressed. The temperature of the upper thermal source at around 120 °C and the mechanical output power close to 2 kW make the expander and the whole system suitable for plenty of potential recovery applications. © 2013 The Authors

Tertiary stent-in-stent for obstructing colorectal cancer. A case report and literature review

BACKGROUNDSelf-expandable metal stents (SEMSs) are frequently used in the setting of palliation for occluding, inoperable colorectal cancer (CRC). Among possible complications of SEMS positioning, re-obstruction is the most frequent. Its management is controversial, potentially involving secondary stent-in-stent placement, which has been poorly investigated. Moreover, the issue of secondary stent-in-stent re-obstruction and of more-than-two colonic stenting has never been assessed. We describe a case of tertiary SEMS-in-SEMS placement, and also discuss our practice based on available literature.CASE SUMMARYA 66-year-old male with occluding and metastatic CRC was initially treated by positioning of a SEMS, which had to be revised 6 mo later when a symptomatic intra-stent tumor ingrowth was treated by a SEMS-in-SEMS. We hereby describe an additional episode of intestinal occlusion due to recurrence of intra-stent tumor ingrowth. This patient, despite several negative prognostic factors (splenic flexure location of the tumor, carcinomatosis with ascites, subsequent chemotherapy that included bevacizumab and two previously positioned stents (1 SEMS and 1 SEMS-in-SEMS)) underwent successful management through the placement of a tertiary SEMS-in-SEMS, with immediate clinical benefit and no procedure-related adverse events after 150 d of post-procedural follow-up. This endoscopic management has permitted 27 mo of partial control of a metastatic disease without the need for chemotherapy discontinuation and, ultimately, a good quality of life until death.CONCLUSIONTertiary SEMS-in-SEMS is technically feasible, and appears to be a safe and effective option in the case of recurrent SEMS obstruction

Indagine sismica a riflessione ad alta risoluzione con sorgente vibratoria Ivi-MiniVib svolta nel comune di Piedimonte Etneo (CT) in località Presa.

Il presente lavoro ha avuto come obiettivo lo studio dettagliato della porzione superficiale (0-500 metri di profondità) della faglia Pernicana attraverso l’acquisizione e l’elaborazione di dati sismici a riflessione e rifrazione ad alta risoluzione. E’ stato acquisito un profilo sismico di 715 metri, in località Presa nel comune di Piedimonte Etneo (CT), mediante l’impiego di una sorgente sismica vibratoria ad alta risoluzione. Questo sito è stato scelto in quanto è attraversato dalla rottura superficiale indotta dalla faglia Pernicana