Solving Optimal Control Problems for Delayed Control-Affine Systems with Quadratic Cost by Numerical Continuation

- In this paper we introduce a new method to solve fixed-delay optimal control problems which exploits numerical homotopy procedures. It is known that solving this kind of problems via indirect methods is complex and computationally demanding because their implementation is faced with two difficulties: the extremal equations are of mixed type, and besides, the shooting method has to be carefully initialized. Here, starting from the solution of the non-delayed version of the optimal control problem, the delay is introduced by numerical homotopy methods. Convergence results, which ensure the effectiveness of the whole procedure, are provided. The numerical efficiency is illustrated on an example

Thermally-activated non-local amplification in quantum energy transport

We study energy-transport efficiency in light-harvesting planar and 3D complexes of two-level atomic quantum systems, embedded in a common thermal blackbody radiation. We show that the collective non-local dissipation induced by the thermal bath plays a fundamental role in energy transport. It gives rise to a dramatic enhancement of the energy-transport efficiency, which may largely overcome $100\%$. This effect, which improves the understanding of transport phenomena in experimentally relevant complexes, suggests a particularly promising mechanism for quantum energy management.Comment: 7 pages, 4 figures. New version in which the RP line of Figure 1 has been amended with the correct parameter

Labor Market Policies, Institutions and Employment Rates in the EU-27

We compare labor market policies, institutions and outcomes for the EU member states, for the period 2000-2005. We document the main differences in Labor Market Policies across EU members, including new member states after 2004. We focus on indicators of policy generosity (expenditures relative to GDP) and relate these and other policy indicators to indicators of labor market outcomes and performance. Our results show that, on a cross-country basis, higher rates of employment are in general associated with: (i) higher expenditures on labor market policies, especially on active policies for countries with a high pro-work attitude; (ii) a lower degree of rigidity in labor market institutions and in product market regulation.labor market policies, labor market outcomes, European social models

Science Software on Demand

Presentation of the Science Software on Demand service at the EGI 2020 Conference. A complete description of the involved components and the summary of almost three years of activities have been presented

Distributed thermal tasks on many-body systems through a single quantum machine

We propose a configuration of a single three-level quantum emitter embedded in a non-equilibrium steady electromagnetic environment, able to stabilize and control the local temperatures of a target system it interacts with, consisting of a collection of coupled two-level systems. The temperatures are induced by dissipative processes only, without the need of further external couplings for each qubit. Moreover, by acting on a set of easily tunable geometric parameters, we demonstrate the possibility to manipulate and tune each qubit temperature independently over a remarkably broad range of values. These findings address one standard problem in quantum-scale thermodynamics, providing a way to induce a desired distribution of temperature among interacting qubits and to protect it from external noise sources.Comment: 6 pages, 5 figure

First 100 ms of a long-lived magnetized neutron star formed in a binary neutron star merger

The recent multimessenger observation of the short gamma-ray burst (SGRB) GRB 170817A together with the gravitational wave (GW) event GW170817 provides evidence for the long-standing hypothesis associating SGRBs with binary neutron star (BNS) mergers. The nature of the remnant object powering the SGRB, which could have been either an accreting black hole (BH) or a long-lived magnetized neutron star (NS), is, however, still uncertain. General relativistic magnetohydrodynamic (GRMHD) simulations of the merger process represent a powerful tool to unravel the jet launching mechanism, but so far most simulations focused the attention on a BH as the central engine, while the long-lived NS scenario remains poorly investigated. Here, we explore the latter by performing a GRMHD BNS merger simulation extending up to ~100 ms after merger, much longer than any previous simulation of this kind. This allows us to (i) study the emerging structure and amplification of the magnetic field and observe a clear saturation at magnetic energy $E_\mathrm{mag} \sim 10^{51}$ erg, (ii) follow the magnetically supported expansion of the outer layers of the remnant NS and its evolution into an ellipsoidal shape without any surrounding torus, and (iii) monitor density, magnetization, and velocity along the axis, observing no signs of jet formation. We also argue that the conditions at the end of the simulation disfavor later jet formation on subsecond timescales if no BH is formed. Furthermore, we examine the rotation profile of the remnant, the conversion of rotational energy associated with differential rotation, the overall energy budget of the system, and the evolution of the GW frequency spectrum. Finally, we perform an additional simulation where we induce the collapse to a BH ~70 ms after merger, in order to gain insights on the prospects for massive accretion tori in case of a late collapse. We find that...Comment: 14 pages, 16 figures, matches published version in PR