Far-Field Signatures of a Two-Body Bound State in Collective Emission from Interacting Two-Level Atoms on a Lattice

The collective emission from a one-dimensional chain of interacting two-level atoms is investigated. We calculate the light scattered by dissipative few-excitation eigenstates in the far-field, and in particular focus on signatures of a lattice two-body bound state. We present analytical results for the angle-resolved, temporal decay of the scattered light intensity. Moreover, we find that the steady-state emission spectrum that emerges when the system is probed by a weak, incoherent driving field exhibits a distinct signature for the existence of a bound state, and allows to determine the momentum distribution of the two-body relative wavefunction. Intriguingly, our study does not rely on single-atom addressability and/or manipulation techniques.Comment: 5 pages, 3 figures, supplemen

Covariant Sectors with Infinite Dimension and Positivity of the Energy

We consider a Moebius covariant sector, possibly with infinite dimension, of a local conformal net of von Neumann algebras on the circle. If the sector has finite index, it has automatically positive energy. In the infinite index case, we show the spectrum of the energy always to contain the positive real line, but, as seen by an example, it may contain negative values. We then consider nets with Haag duality on the real line, or equivalently sectors with non-solitonic extension to the dual net; we give a criterion for irreducible sectors to have positive energy, namely this is the case iff there exists an unbounded Moebius covariant left inverse. As a consequence the class of sectors with positive energy is stable under composition, conjugation and direct integral decomposition.Comment: 25 pages, Latex2

Fast phonon dynamics of a nanomechanical oscillator due to cooperative effects

We investigate the coupled-system dynamics of two-level quantum dots placed on a vibrating nanomechanical resonator. The ensemble of quantum dots exhibits superradiance features which are transferred to the mechanical degrees of freedom representing fast quantum dynamics and enhanced phonon emission in a nanomechanical setup, resembling of the superradiance effect.Comment: 6 pages, 4 figure

Tailoring superradiance to design artificial quantum systems

Cooperative phenomena arising due to the coupling of individual atoms via the radiation field are a cornerstone of modern quantum and optical physics. Recent experiments on x-ray quantum optics added a new twist to this line of research by exploiting superradiance in order to construct artificial quantum systems. However, so far, systematic approaches to deliberately design superradiance properties are lacking, impeding the desired implementation of more advanced quantum optical schemes. Here, we develop an analytical framework for the engineering of single-photon superradiance in extended media applicable across the entire electromagnetic spectrum, and show how it can be used to tailor the properties of an artificial quantum system. This "reverse engineering" of superradiance not only provides an avenue towards non-linear and quantum mechanical phenomena at x-ray energies, but also leads to a unified view on and a better understanding of superradiance across different physical systems.Comment: 6 pages + supplemental materia

Topologies of continuity for Carathéodory delay differential equations with applications in non-autonomous dynamics

Producción CientíficaWe study some already introduced and some new strong and weak topologies of integral type to provide continuous dependence on continuous initial data for the solutions of non-autonomous Carathéodory delay differential equations. As a consequence, we obtain new families of continuous skew-product semiflows generated by delay differential equations whose vector fields belong to such metric topological vector spaces of Lipschitz Carathéodory functions. Sufficient conditions for the equivalence of all or some of the considered strong or weak topologies are also given. Finally, we also provide results of continuous dependence of the solutions as well as of continuity of the skew-product semiflows generated by Carathéodory delay differential equations when the considered phase space is a Sobolev space.MINECO/FEDER MTM2015-66330-PH2020-MSCA-ITN-2014 643073 CRITICS

Weak topologies for Carathéodory differential equations: continuous dependence, exponential dichotomy and attractors

Producción CientíficaWe introduce new weak topologies and spaces of Carathéodory functions where the solutions of the ordinary differential equations depend continuously on the initial data and vector fields. The induced local skew-product flow is proved to be continuous, and a notion of linearized skew-product flow is provided. Two applications are shown. First, the propagation of the exponential dichotomy over the trajectories of the linearized skew-product flow and the structure of the dichotomy or Sacker–Sell spectrum. Second, how particular bounded absorbing sets for the process defined by a Carathéodory vector field f provide bounded pullback attractors for the processes with vector fields in the alpha-limit set, the omega-limitset or the whole hull of f. Conditions for the existence of a pullback or a global attractor for the skew-product semiflow, as well as application examples are also given.MINECO/FEDER Grant MTM2015-66330-PH2020-MSCA-ITN-2014 643073 CRITIC

Topologies of continuity for Carathéodory differential equations with applications in non-autonomous dynamics

The theory developed in this work allows to extend the skew-product formalism to Carathéodory ordinary differential equations and delay differential equations with constant delay through the use of strong and weak metric topologies of integral type. As a result, one obtains a variety of tools from topological dynamics to study the qualitative behavior of the solutions of such classes of differential problems. As an example, the work includes several applications for Carathéodory ODEs such as linearized skew-product flows, propagation of the exponential dichotomy and of the dichotomy spectrum of a linear system and study of pullback and global attractors, as well as some simple motivational examples taken from modelizations of real phenomena, which aim to show the applicability of the theory. Additionally, the thesis provides a rich description of the topological structure of the considered spaces of Carathéodory functions (among which, some are new) presenting, for example, characterizations of the classes of equivalences for functions which differ on negligible subset of the domain, propagation of properties on the so-called m-bounds and l-bounds through the limits in the given topologies, and suffcient conditions of relative compactness for subsets of Lipschitz Carathéodory functions.Departamento de Matemática AplicadaDoctorado en Matemática

Information and Willingness to Pay in a Contingent Valuation Study: The Value of S. Erasmo in the Lagoon of Venice

This paper reports on a contingent valuation study eliciting willingness to pay for a public program for the preservation of lagoon, beach and infrastructure in the island of S. Erasmo in the Lagoon of Venice. A referendum dichotomous choice approach with a follow-up question is used to obtain information about willingness to pay from a sample of residents of the Veneto Region in Italy. We use split samples to investigate the effect of providing different levels of information to respondents before asking the payment questions. Our experimental treatment is a reminder of possible reasons for voting in favor or against the proposed program before the referendum question. We find that reminding respondents of the reasons for voting for or against the public works increases WTP among less highly educated respondents, and decreases WTP among more highly educated respondents.Contingent valuation, Effects of information

Occupancy Estimation Using Low-Cost Wi-Fi Sniffers

Real-time measurements on the occupancy status of indoor and outdoor spaces can be exploited in many scenarios (HVAC and lighting system control, building energy optimization, allocation and reservation of spaces, etc.). Traditional systems for occupancy estimation rely on environmental sensors (CO2, temperature, humidity) or video cameras. In this paper, we depart from such traditional approaches and propose a novel occupancy estimation system which is based on the capture of Wi-Fi management packets from users' devices. The system, implemented on a low-cost ESP8266 microcontroller, leverages a supervised learning model to adapt to different spaces and transmits occupancy information through the MQTT protocol to a web-based dashboard. Experimental results demonstrate the validity of the proposed solution in four different indoor university spaces.Comment: Submitted to Balkancom 201