A preliminary assessment of the Normative Framework regulating MAR schemes in Europe: the EU Directives and their Implementation in nine National Legislations

The use of MAR schemes within the European Union is not a new phenomenon, on the contrary it dates back to the beginning of the XIX century. Despite being widely adopted and currently the object of extensive studies, this tool is not soundly regulated and so far very little research has been conducted on the normative framework regulating MAR at the regional and at the national level. This paper draws upon the findings of a Report which represents one of the deliverables identified by MARSOL, a EU FP7 project launched in December 2013 that aims at demonstrating that MAR shall be regarded as a viable approach to address the predicted water shortages over the long term. Through a survey which involved a number of national experts, the researchers involved in the drafting of the Report have collected relevant data concerning the national legal frameworks of nine EU countries that adopt MAR schemes. The results of the questionnaire have been processed using a qualitative and comparative approach and have been duly included in the legal analysis, which covers the implementation at the national level of the two EU Directives relevant for MAR Schemes, i.e. the Water Framework Directive and its "daughter", the Groundwater Directive. This paper shall be considered as the outcome of a preliminary investigation which covered only a limited number of European countries, it is expected that the research will be carried out as to include a larger number of EU Member States (MSs), alongside the most relevant extra EU countries

Signatures of Self-Trapping in the Driven-Dissipative Bose-Hubbard Dimer

We investigate signatures of a self-trapping transition in the driven-dissipative Bose Hubbard dimer, in presence of incoherent pump and single-particle losses. For fully symmetric couplings the stationary state density matrix is independent of any Hamiltonian parameter, and cannot therefore capture the competition between hopping-induced delocalization and the interaction-dominated self-trapping regime. We focus instead on the exact quantum dynamics of the particle imbalance after the system is prepared in a variety of initial states, and on the frequency-resolved spectral properties of the steady state, as encoded in the single-particle Green's functions. We find clear signatures of a localization-delocalization crossover as a function of hopping to interaction ratio. We further show that a finite a pump-loss asymmetry restores a delocalization crossover in the steady-state imbalance and leads to a finite intra-dimer dissipation

Theory of chiral edge state lasing in a two-dimensional topological system

We theoretically study topological laser operation in a bosonic Harper-Hofstadter model featuring a saturable optical gain. Crucial consequences of the chirality of the lasing edge modes are highlighted, such as a sharp dependence of the lasing threshold on the geometrical shape of the amplifying region and the possibility of ultraslow relaxation times and of convectively unstable regimes. The different unstable regimes are characterized in terms of spatiotemporal structures sustained by noise and a strong amplification of a propagating probe beam is anticipated to occur in between the convective and the absolute (lasing) thresholds. The robustness of topological laser operation against static disorder is assessed

Interaction-resistant metals in multicomponent Fermi systems

We analyze two different fermionic systems that defy Mott localization showing a metallic ground state at integer filling and very large Coulomb repulsion. The first is a multiorbital Hubbard model with a Hund's coupling, where this physics has been widely studied and the new metallic state is called a Hund's metal, and the second is a SU(3) Hubbard model with a patterned single-particle potential designed to display a similar interaction-resistant metal in a set-up which can be implemented with SU($N$) ultracold atoms. With simple analytical arguments and exact numerical diagonalization of the Hamiltonians for a minimal three-site system, we demonstrate that the interaction-resistant metal emerges in both cases as a compromise between two different insulating solutions which are stabilized by different terms of the models. This provides a strong evidence that the Hund's metal is a specific realization of a more general phenomenon which can be realized in various strongly correlated systems.Comment: 11 pages, 11 figure

Accelerating cosmology in Rastall's theory

In an attempt to look for a viable mechanism leading to a present-day accelerated expansion, we investigate the possibility that the observed cosmic speed up may be recovered in the framework of the Rastall's theory, relying on the non-conservativity of the stress-energy tensor, i.e. $T^{\mu}_{\nu ; \mu} \neq 0$. We derive the modified Friedmann equations and show that they correspond to Cardassian-like equations. We also show that, under suitable assumptions on the equation of state of the matter term sourcing the gravitational field, it is indeed possible to get an accelerated expansion, in agreement with the Hubble diagram of both Type Ia Supernovae (SNeIa) and Gamma Ray Bursts (GRBs). Unfortunately, to achieve such a result one has to postulate a matter density parameter much larger than the typical $\Omega_M \simeq 0.3$ value inferred from cluster gas mass fraction data.Comment: 8 pages, 1 eps figure; revised to match the version accepted for publication in Il Nuovo Cimento

Early-stage formation of (hydr)oxo bridges in transition-metal catalysts for photosynthetic processes

Ab initio simulations have been used to assess reaction pathways for the formation of M–(hydr)oxo–M (M = Co, Mn, Ni) bridges from M(ii) aqueous solutions, as early-stage building blocks of transition-metal catalysts for oxygen evolution

Massive superfluid vortices and vortex necklaces on a planar annulus

We study a superfluid in a planar annulus hosting vortices with massive cores. An analytical point-vortex model shows that the massive vortices may perform radial oscillations on top of the usual uniform precession of their massless counterpart. This regular motion becomes unstable beyond a critical vortex mass. The analogy with the motion of a charged particle in a static electromagnetic field leads to the development of a plasma orbit theory that provides a description of the trajectories which remains accurate even beyond the regime of small radial oscillations. These results are confirmed by the numerical solution of coupled two-component Gross-Pitaevskii equations. The analysis is then extended to a necklace of vortices symmetrically arranged within the annulus.Comment: 32 pages, 12 figure

Biologically realistic mean-field models of conductance-based networks of spiking neurons with adaptation

International audienceAccurate population models are needed to build very large scale neural models, but their derivation is difficult for realistic networks of neurons, in particular when nonlin-ear properties are involved such as conductance-based interactions and spike-frequency adaptation. Here, we consider such models based on networks of Adaptive Exponential Integrate and Fire excitatory and inhibitory neurons. Using a Master Equation formalism , we derive a mean-field model of such networks and compare it to the full network dynamics. The mean-field model is capable to correctly predict the average spontaneous activity levels in asynchronous irregular regimes similar to in vivo activity. It also captures the transient temporal response of the network to complex external inputs. Finally, the mean-field model is also able to quantitatively describe regimes where high and low activity states alternate (UP-DOWN state dynamics), leading to slow oscillations. We conclude that such mean-field models are "biologically realistic" in the sense that they can capture both spontaneous and evoked activity, and they naturally appear as candidates to build very large scale models involving multiple brain areas

Spatial and spectral mode-selection effects in topological lasers with frequency-dependent gain

We develop a semiclassical theory of laser oscillation into a chiral edge state of a topological photonic system endowed with a frequency-dependent gain. As an archetypal model of this physics, we consider a Harper\u2013Hofstadter lattice embedding population-inverted, two-level atoms as a gain material. We show that a suitable design of the spatial distribution of gain and its spectral shape provides flexible mode-selection mechanisms that can stabilize single-mode lasing into an edge state. Implications of our results for recent experiments are outlined

A non-cooperative game approach for RAN and spectrum sharing in mobile radio networks

Mobile Network Operators (MNOs) are nowadays forced to continuously invest in their network infrastructure to keep up with the increasing bandwidth demand and traffic load coming from mobile users. In this context, MNOs have to face the strategic problem of whether to invest on their own or deploy shared networks. We address here the problem of Radio Access Network (RAN) and spectrum sharing in 4G mobile networks. Namely, we consider the case in which multiple MNOs are planning to deploy small cell Base Stations to improve their current network infrastructure; the deployment investment may be shared with other MNOs, thus giving rise to shared RANs. The RAN and spectrum sharing problem is formalized as a Generalized Nash Equilibrium Problem, where the strategy of each MNO in the game is twofold: selecting a coalition (whom to cooperate) and the fraction of the coalition cost to pay, with the goal of maximizing the individual return on investment. The proposed approach is leveraged to characterize the stable coalitions and their respective cost division policies for various network and economic conditions