361 research outputs found

    Dynamical and Steady State Properties of a Bose-Hubbard Chain with Bond-Dissipation: A Study based on Matrix Product Operators

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    We study a dissipative Bose-Hubbard chain subject to an engineered bath using a superoperator approach based on matrix product operators. The dissipation is engineered to stabilize a BEC condensate wave function in its steady state. We then characterize the steady state emerging from the interplay between incompatible Hamiltonian and dissipative dynamics. While it is expected that interactions lead to this competition, even the kinetic energy in an open boundary condition setup competes with the dissipation, leading to a non-trivial steady state. We also present results for the transient dynamics and probe the relaxation time revealing the closing of the dissipative gap in the thermodynamic limit.Comment: 9 pages, 13 figure

    Thermal vs. Entanglement Entropy: A Measurement Protocol for Fermionic Atoms with a Quantum Gas Microscope

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    We show how to measure the order-two Renyi entropy of many-body states of spinful fermionic atoms in an optical lattice in equilibrium and non-equilibrium situations. The proposed scheme relies on the possibility to produce and couple two copies of the state under investigation, and to measure the occupation number in a site- and spin-resolved manner, e.g. with a quantum gas microscope. Such a protocol opens the possibility to measure entanglement and test a number of theoretical predictions, such as area laws and their corrections. As an illustration we discuss the interplay between thermal and entanglement entropy for a one dimensional Fermi-Hubbard model at finite temperature, and its possible measurement in an experiment using the present scheme


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    Abstract A source of 100 keV spin polarized electrons has been installed at the 130 MeV superconducting Darmstadt linear accelerator S-DALINAC. Circularly polarized laser light excites a GaAs cathode, producing spin polarized electrons in bunches with pulse lengths in the region of 50 ps and smaller at a repetition frequency of 3 GHz. A Wienfilter for spin manipulation and a Mott polarimeter for polarization measurements are installed in the low-energy beam line. Polarizations up to 86% have been shown with strained superlattice GaAs cathodes. Installed wire scanners in the beam line measure beam radius and position and in conjunction with a solenoid with variable focal length a parameter set of beam sizes depending on the focal length can be obtained, allowing for an emittance calculation. The scanning unit, two perpendicular 50 âž­ m tungsten wires for x and y measurements mounted on an insulated frame, is installed at an angle of 45 in a plane perpendicular to the beam. Pneumatic as well as electric translation is used while the data read-out is done by a 24-bit ADC with variable reading speed. Measurements at the S-DALINAC give an indication of the beam quality of the spin polarized electron source, permit a comparison with the already installed thermionic electron source, and allow the measurement of a possible emittance growth from the Wien-filter that is to be excluded. Furthermore, the knowledge of the beam size renders a slit measurement of the beam pulse length possible. S-DALINAC The S-DALINAC [1] is a recirculating superconducting electron linear accelerator capable of producing electron beams at beam energies from 2.5 MeV up to typically 80-90 Mev, with a design value of up to 130 MeV. Around the S-DALINAC, a multifacetted nuclear-physics program is realized in Darmstadt. Research topics are nuclear structure, nuclear astrophysics, fundamental studies and the continuous upgrade of the accelerator, all being the focus of a center of excellence funded by the German Research Foundation (DFG) about eight years ago. Since the S-DALINAC's first commissioning around 1990, nuclear resonance fluorescence experiment

    Empirical agent-based modelling of everyday pro-environmental behaviours at work

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    We report on agent-based modelling work in the LOCAW project (Low Carbon at Work: Modelling Agents and Organisations to Achieve Transition to a Low Carbon Europe). The project explored the effectiveness of various backcasting scenarios conducted with case study organisations in bringing about pro-environmental change in the workforce in the domains of transport, energy use and waste. The model used qualitative representations of workspaces in formalising each scenario, and decision trees learned from questionnaire responses to represent decision-making. We describe the process by which the decision trees were constructed, noting that the use of decision trees in agent-based models requires particular considerations owing to the potential use of explanatory variables in model dynamics. The results of the modelling in various scenarios emphasise the importance of structural environmental changes in facilitating everyday pro-environmental behaviour, but also show there is a role for psychological variables such as norms, values and efficacy. As such, the topology of social interactions is a potentially important driver, raising the interesting prospect that both workplace geography and organisational hierarchy have a role to play in influencing workplace pro-environmental behaviours

    The Impact of the Physical Environment on Intrapartum Maternity Care: Identification of Eight Crucial Building Spaces.

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    OBJECTIVES, PURPOSE, OR AIM: This article investigates whether the physical environment in which childbirth occurs impacts the intrapartum intervention rates and how this might happen. The study explores the spatial physical characteristics that can support the design of spaces to promote the health and well-being of women, their supporters, and maternity care professionals. BACKGROUND: Medical interventions during childbirth have consequences for the health of women and babies in the immediate and long term. The increase in interventions is multifactorial and may be influenced by the model of care adopted, the relationships between caregivers and the organizational culture, which is made up of many factors, including the built environment. In the field of birth architecture research, there is a gap in the description of the physical characteristics of birth environments that impact users' health. METHOD: A scoping review on the topic was performed to understand the direct and indirect impacts of the physical environment on birth intervention rates. RESULTS AND DISCUSSION: The findings are organized into three tables reporting the influence that the physical characteristics of a space might have on people's behaviors, experiences, practices and birth health outcomes. Eight building spaces that require further investigation and research were highlighted: unit layout configuration, midwives' hub/desk, social room, birth philosophy vectors, configuration of the birth room, size and shape of the birth room, filter, and sensory elements. CONCLUSIONS: The findings show the importance of considering the physical environment in maternity care and that further interdisciplinary studies focused on architectural design are needed to enrich the knowledge and evidence on this topic and to develop accurate recommendations for designers
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