Probing quench dynamics across a quantum phase transition into a 2D Ising antiferromagnet

Simulating the real-time evolution of quantum spin systems far out of equilibrium poses a major theoretical challenge, especially in more than one dimension. We experimentally explore the dynamics of a two-dimensional Ising spin system with transverse and longitudinal fields as we quench it across a quantum phase transition from a paramagnet to an antiferromagnet. We realize the system with a near unit-occupancy atomic array of over 200 atoms obtained by loading a spin-polarized band insulator of fermionic lithium into an optical lattice and induce short-range interactions by direct excitation to a low-lying Rydberg state. Using site-resolved microscopy, we probe the correlations in the system after a sudden quench from the paramagnetic state and compare our measurements to exact calculations in the regime where it is possible. We achieve many-body states with longer-range antiferromagnetic correlations by implementing a near-adiabatic quench and study the buildup of correlations as we cross the quantum phase transition at different rates

Information representation in Displaced Archives: a meta-synthesis

The phenomenon of displaced archives emerges in the scientific literature as a kind of wicked problem. In addition to the conceptual diversity associated with this phenomenon present in the scientific literature from various fields (e.g., removed archives, migrated archives, seized archives, alienated archives, captured archives, diasporic archives, expatriated/repatriated archives, estray archival, disputed archival claims, replevin, etc.), there is a tendency in the scientific community to adopt the concept of displaced archives as a possible hypernym. The most recent definition of displaced archive is found in the report issued by the International Council on Archives through the Expert Group on Shared Archival Heritage, understood as "archives removed from the place of their creation, where the ownership of the archives is disputed by two or more parties" (Lowry 2020, 5). Nevertheless, one of the problems that makes this phenomenon a particular case is whether we can identify archives that are in the condition of displaced without there necessarily having to be claimant party(ies) for that purpose. Although the most recurrent focus in addressing this phenomenon has been around the problems of restitution, repatriation, return or relocation, the identification and, more incisively, the representation of these documentary sets have remained obscured in scientific discourse. According to Winn (2015), one of the limiting factors in the identification of displaced archives consists, among others, in the inexistence of information access tools. For Lowry, "the catalogue is the key" (2017a, 8), not only as an instrument of access to information where the processes of organization and description are materialized with a view to its retrieval and access, but also as a mechanism of information representation that derives from the powers of archival mediation. Studies on information representation suggest that, in the postmodern archival stream, it is not possible to ensure neutrality or impartiality in the representation of the content and structure of a fonds (MacNeil 2012) in finding aids. Such archival descriptions are supported by interpretative approaches that depend on the description and access policies adopted by custodians, which are not unrelated to the political, historical, socio-cultural, and institutional contexts of the environment where they were produced. Considering that the finding aids can be genologically diverse (e.g., catalogues, inventories, guides, scripts, directories, indexes and databases), it is considered more productive to focus on the representation of archival information, from the perspective of how a "fluid, evolving, and socially constructed practice" (Yakel 2003, 2) is constituted as "the core of archival description produced to facilitate access to archival materials in the background of their creation and custodial history" (Zhang 2012, 49). Considering that some of the studies on archival information representation have been problematized with greater incidence, although incipient, in Knowledge Organization and Information Science (Barros and Sousa 2020; Aguiar and Kobashi 2013; Tognoli 2013; Vital, Medeiros, and Brascher 2017; Corujo and Freitas 2021; Tognoli and Guimarães 2011; 2012; Troitiño Rodriguez 2018; Hjørland 2002), these studies have largely confined themselves to material and technical processes, physical (u. g., arrangement) and intellectual (u. g., classification and description), of concepts that conform to the bureaucratic dimension of the producers and/or custodial entities. In what concerns the displaced archives, the phenomenon itself challenges the core concepts of Archival Science, especially how these disputed documentary sets are represented from the point of view of provenance, integrity, organicity and how these representations are (re)constructed or destroyed in the process of archival mediation. Based on these aspects, and given the scarcity of studies on this topic, this article focuses on how the representation of information about archives removed from their original social and territorial contexts has been addressed in the scientific literature. Thus, we intend to conduct a survey of scientific literature that informs about the trajectory of the information representation process from the removal process to the claim by the dispossessed communities that can be theoretically relevant to the scope of Knowledge Organization. Thus, based on the above, it justifies performing a synthesis of knowledge from scientific literature called meta-synthesis (Sandelowski and Barroso 2010; Grant and Booth 2009; Finfgeld-Connett 2018). Thus, this article is structured as follows: section 2.0 formulates the starting question and research objectives; section 3.0 outlines the methodological assumptions for this type of qualitative literature synthesis; section 4.0 presents the results of the empirical investigation; section 5.0 makes concluding remarks around limitations and implications, as well as future lines of research.info:eu-repo/semantics/submittedVersio

Below the Nation State: Power Asymmetry and Jurisdictional Boundaries around the Archives of Madeira Archipelago

The main purpose of this chapter is to describe a case study developed in a sub-national context between the Autonomous Region of Madeira and the National Archive ‘Torre do Tombo’ (ANTT). Our analysis will focus theoretically on the etiologies of dispossession and empirically on a case study. Thus, the main questions that will lead this case study are: ‘Why were the Madeiran fonds taken in the past to or by ANTT?’ and ‘How were these Madeiran fonds represented in finding aids provided by ANTT and the RAM?’. Finally, based on nissological critiques,13 we will define and contextualise the notion of sub-national displaced archives as an underresearched subset of disputed archival claims, in order to reveal some particular aspects of this phenomenon.info:eu-repo/semantics/publishedVersio

Visualizing Strange Metallic Correlations in the 2D Fermi-Hubbard Model with AI

Strongly correlated phases of matter are often described in terms of straightforward electronic patterns. This has so far been the basis for studying the Fermi-Hubbard model realized with ultracold atoms. Here, we show that artificial intelligence (AI) can provide an unbiased alternative to this paradigm for phases with subtle, or even unknown, patterns. Long- and short-range spin correlations spontaneously emerge in filters of a convolutional neural network trained on snapshots of single atomic species. In the less well-understood strange metallic phase of the model, we find that a more complex network trained on snapshots of local moments produces an effective order parameter for the non-Fermi-liquid behavior. Our technique can be employed to characterize correlations unique to other phases with no obvious order parameters or signatures in projective measurements, and has implications for science discovery through AI beyond strongly correlated systems.Comment: 12 pages, 9 figures; updated in accord with the published versio

Subdiffusion and heat transport in a tilted 2D Fermi-Hubbard system

Using quantum gas microscopy we study the late-time effective hydrodynamics of an isolated cold-atom Fermi-Hubbard system subject to an external linear potential (a "tilt"). The tilt is along one of the principal directions of the two-dimensional (2D) square lattice and couples mass transport to local heating through energy conservation. We study transport and thermalization in our system by observing the decay of prepared initial density waves as a function of wavelength $\lambda$ and tilt strength and find that the associated decay time $\tau$ crosses over as the tilt strength is increased from characteristically diffusive to subdiffusive with $\tau\propto\lambda^4$. In order to explain the underlying physics we develop a hydrodynamic model that exhibits this crossover. For strong tilts, the subdiffusive transport rate is set by a thermal diffusivity, which we are thus able to measure as a function of tilt in this regime. We further support our understanding by probing the local inverse temperature of the system at strong tilts, finding good agreement with our theoretical predictions. Finally, we discuss the relation of the strongly tilted limit of our system to recently studied 1D models which may exhibit nonergodic dynamics.Comment: 7 pages with 5 figures in main text, 5 pages with 3 figures in Supplemental Materia

Visualizing strange metallic correlations in the two-dimensional Fermi-Hubbard model with artificial intelligence

Strongly correlated phases of matter are often described in terms of straightforward electronic patterns. This has so far been the basis for studying the Fermi-Hubbard model realized with ultracold atoms. Here, we show that artificial intelligence (AI) can provide an unbiased alternative to this paradigm for phases with subtle, or even unknown, patterns. Long- A nd short-range spin correlations spontaneously emerge in filters of a convolutional neural network trained on snapshots of single atomic species. In the less well-understood strange metallic phase of the model, we find that a more complex network trained on snapshots of local moments produces an effective order parameter for the non-Fermi-liquid behavior. Our technique can be employed to characterize correlations unique to other phases with no obvious order parameters or signatures in projective measurements, and has implications for science discovery through AI beyond strongly correlated systems

Nota de Apresentação

Desinformação, informações falsas, infodemia, pós-verdade, entre muitas outras denominações, constituem trending topics, isto é, os assuntos do momento que emergem em diversos domínios científicos como epifenómenos de uma disfuncionalidade epistemológica, que se define por uma “nova guerra pela verdade” (D’Ancona, 2017). Trata-se, também, de uma crise de autoridade (Enroth, 2021), principalmente de índole política, já entretanto indicada por Arendt (1967), que se carateriza por um embate dialético por uma narrativa de legitimação que não tem necessariamente de ter por base o valor da verdade. Os efeitos ponerológicos (Łobaczewski, 2006), especialmente como a desinformação ou informações falsas no âmbito da saúde (u. g., contexto pandémico da COVID19, causada pelo vírus SARS-CoV-2), no combate às alterações climáticas, nas questões migratórias ou no combate à corrupção, podem gerar efeitos sindémicos na sociedade, minando a confiabilidade das instituições democráticas, quando muito desencadear mudanças tectónicas no plano político, cultural e ambiental.info:eu-repo/semantics/publishedVersio