6,289 research outputs found

    Sachs' free data in real connection variables

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    We discuss the Hamiltonian dynamics of general relativity with real connection variables on a null foliation, and use the Newman-Penrose formalism to shed light on the geometric meaning of the various constraints. We identify the equivalent of Sachs' constraint-free initial data as projections of connection components related to null rotations, i.e. the translational part of the ISO(2) group stabilising the internal null direction soldered to the hypersurface. A pair of second-class constraints reduces these connection components to the shear of a null geodesic congruence, thus establishing equivalence with the second-order formalism, which we show in details at the level of symplectic potentials. A special feature of the first-order formulation is that Sachs' propagating equations for the shear, away from the initial hypersurface, are turned into tertiary constraints; their role is to preserve the relation between connection and shear under retarded time evolution. The conversion of wave-like propagating equations into constraints is possible thanks to an algebraic Bianchi identity; the same one that allows one to describe the radiative data at future null infinity in terms of a shear of a (non-geodesic) asymptotic null vector field in the physical spacetime. Finally, we compute the modification to the spin coefficients and the null congruence in the presence of torsion.Comment: 23 pages + Appendix, 2 figures. v2: Improved text and some amendments throughout, added more details on the relation between 2+2 foliations and null tetrads, updated references. Version submitted for peer reviewing. v3: Few minor amendments, footnote added on a null congruence in the presence of torsion; matches published versio

    Responsible Research and Innovation between \u201cnew governance\u201d and fundamental rights

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    This chapter frames RRI as an emerging governance approach in the EU regulatory context. We argue that reference to fundamental rights makes RRI a distinctive approach to responsibility compared to other existing paradigms and that human rights, in particular those laid down in the Charter of Fundamental Rights of the European Union, are not necessarily a constraint but can instead be a catalyst of innovation. Eventually we maintain that a governance framework based on the complementarity between legal norms and voluntary commitments might successfully combine the respect of fundamental rights with the openness and flexibility of the innovation process

    Modelling Private Wealth Accumulation and Spend-down in the Italian Microsimulation Model CAPP_DYN: A Life-Cycle Approach

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    In microsimulation literature a limited number of models include a module aimed at analyzing and projecting the evolution of privat e wealth over time. However, this issue appears crucial in order to comprehensively evaluate the li kely distributional effects of institutional reforms adopted to cope with population ageing. In this work we describe the implementation in the Italian dynamic micro simulation model CAPP_DYN of a new module in which households\u2019 savings and asset allocation are modelled. In parti cular, we aim to account for possible behavioural responses to pension reforms in househo ld savings. To this end, we rely on an approximate life cycle structural framework for est imating saving behaviour, while adopting a traditional stochastic micro simulation approach fo r asset allocation. In line with Ando and Nicoletti Altimari (2004), we emphasize the role of lifetime economic resources in households\u2019 consumption decisions, yet we further account for i nternal habit formation and subjective expectations on pension outcomes in the econometric stage. In addition, we model intergenerational transfers of private wealth in a probabilistic fashio

    Probing Gravitational Lensing of the CMB with SDSS-IV Quasars

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    We study the cross-correlation between the Planck CMB lensing convergence map and the eBOSS quasar overdensity obtained from the Sloan Digital Sky Survey (SDSS) IV, in the redshift range 0.9<z<2.20.9 < z < 2.2. We detect the CMB lensing convergence-quasar cross power spectrum at 5.4σ5.4 \sigma significance. The cross power spectrum provides a quasar clustering bias measurement that is expected to be particularly robust against systematic effects. The redshift distribution of the quasar sample has a median redshift z1.55z \approx 1.55, and an effective redshift about 1.511.51. The best fit bias of the quasar sample is bq=2.43±0.45b_q = 2.43 \pm 0.45, corresponding to a host halo mass of log10(Mh1M)=12.540.36+0.25\log_{10}\left( \frac{M}{h^{-1} M_\odot} \right) = 12.54^{+0.25}_{-0.36}. This is broadly consistent with the previous literature on quasars with a similar redshift range and selection. Since our constraint on the bias comes from the cross-correlation between quasars and CMB lensing, we expect it to be robust to a wide range of possible systematic effects that may contaminate the auto correlation of quasars. We checked for a number of systematic effects from both CMB lensing and quasar overdensity, and found that all systematics are consistent with null within 2σ2 \sigma. The data is not sensitive to a possible scale dependence of the bias at present, but we expect that as the number of quasars increases (in future surveys such as DESI), it is likely that strong constraints on the scale dependence of the bias can be obtained.Comment: 8 pages, 6 figures, 1 table; matches published version on MNRA

    The Introduction of a Private Wealth Module in CAPP_DYN: an Overview

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    Household saving rate in Italy declined over the last two decades.This trend still persists despite three pension reforms have been enacted since the beginning of the nineties. In this paper we search further evidence of general macroeconomic effects through the analysis of households behaviour. In the first part of the paper we use data from five surveys of the Bank of Italy Surveys of Household Income and Wealth (SHIW) to estimate the lifetime profiles of saving and wealth accumulation. Estimates show that the age profile of the propensity to save has been influenced more by cohort effects than by general trend effects; whereas the age profile of the ratios of financial assets to disposable income has been subject to relevant trend effects. In the second part of the paper we analyse the effects of pension reforms on saving behaviour of Italian Households. Firstly we use a difference-in-difference estimator in order to test whether the groups more severely hit by the reforms actually increased their saving rate relative to the other groups. Then we estimate the Social Security Net Wealth (SSWN) for each individual in the SHIW in the analysed period (1989-2000). Finally we estimate the substitution coefficient between SSWN and private wealth taking into account that the reaction of saving to a change in SSWN depends also on age of the individual. Our results show that the reduction of SSWN is unequally distributed across individuals. The cut is stronger for self employed, young workers and women. Most of the groups more severely hit by the reforms did not increase their saving rate relative to the control group: younger households, in particular, did not increase the saving rate. On the whole a reduction of one Euro in SSWN seems to induce, on the average, a compensating increase in private wealth by about fifty cents. The substitution coefficient between private and social security wealth is higher for the richest and oldest part of the sample. Finally when we split the sample observations by year we find that the more dramatised is the impact of the reform, the higher is the substitution coefficient.Pension reform; household saving; social security wealth; difference-in-difference

    Gestione delle acque in una raffineria di olio vegetale

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    Il presente lavoro di tesi ha come obiettivo primario la definizione qualitativa e quantitativa delle correnti di acqua utilizzate nella raffineria di olio alimentare Salov s.p.a. In secondo luogo si definiscono alcune modifiche al processo produttivo, e alcune semplici soluzioni impiantistiche per la riduzione dei consumi di acqua. Infine si analizza l'impianto di trattamento di acque reflue dello stabilimento proponendo eventuali miglioramenti

    Application of process analytical technology (PAT) tools for the better understanding and control of the crystallization of polymorphic and impure systems

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    This work presents a comprehensive study on the application of PAT tools to study, monitor and control polymorphism during batch cooling crystallization processes. For the first time, the same techniques were used to control and adjust polymorphic purity of the solid phase but also to investigate the relation between chemical equilibrium in solution and polymorphic outcome of cooling crystallization. Crystallization is an important unit operation used as separation and purification technique. It is widely employed in the pharmaceutical, chemical, agrochemical, food and cosmetics industries but also in the electronic, metallurgic and material industries. More than 90% of the APIs on the market are produced by crystallization, therefore, monitoring and control this process is fundamental to ensure the quality of the final product. The implementation of process analytical technology (PAT) tools during the development stage of APIs has largely helped in better understanding and optimizing both batch and, more recently, continuous crystallization. Polymorphism is the capacity of a compound to crystallize in more than one different crystalline structure, which can have different properties such as density, melting point, bioavailability and solubility. The choice of solvent, pH, kinetic conditions and presence of impurities has very strong effect on the polymorphic outcome of a cooling crystallization in solution. Understanding this phenomenon as well as being able to monitor and control it during industrial crystallization is one the biggest challenges for pharmaceutical industries
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