Critical behavior of dissipative two-dimensional spin lattices

We explore critical properties of two-dimensional lattices of spins interacting via an anisotropic Heisenberg Hamiltonian and subject to incoherent spin flips. We determine the steady-state solution of the master equation for the density matrix via the corner-space renormalization method. We investigate the finite-size scaling and critical exponent of the magnetic linear susceptibility associated to a dissipative ferromagnetic transition. We show that the Von Neumann entropy increases across the critical point, revealing a strongly mixed character of the ferromagnetic phase. Entanglement is witnessed by the quantum Fisher information which exhibits a critical behavior at the transition point, showing that quantum correlations play a crucial role in the transition even though the system is in a mixed state.Comment: Accepted for publication on Phys. Rev. B (6 pages, 5 figures

A study of intersections of quadrics having applications on the small weight codewords of the functional codes C2(Q), Q a non-singular quadric

AbstractWe study the small weight codewords of the functional code C2(Q), with Q a non-singular quadric in PG(N,q). We prove that the small weight codewords correspond to the intersections of Q with the singular quadrics of PG(N,q) consisting of two hyperplanes. We also calculate the number of codewords having these small weights

How to cope with mobility expectations in academia: individual travel strategies of tenured academics at Ghent University, Flanders

The production and exchange of knowledge are inextricably linked to different compulsions to corporeal proximity and therefore travel. As primary producers and transferors of knowledge, academics are no exception to this rule, and their compulsions seem to be further propelled by institutional discourses regarding the alleged virtues of “internationalization.” Tenured academics, moreover, have a high degree of independence and can therefore easily choose how to cope with compulsions and constraints to internationalize. However, the business-travel literature has paid scant attention to academics and their individual contexts. In an effort to rectify this situation, this paper explores a travel dataset of tenure-track academics (N=870) working at Ghent University. The insights emerging from this analysis are then contextualized by complementing them with in-depth interviews of tenured academics (N=23) at the same institution. This paper argues, first, that varying compulsions and constraints at home and abroad lead to distinct non-travel and travel-intensive academic roles. And second, that academics who have difficulties coping, try to rationalize their corporeal travel behaviour and their mobility behaviour to meet the needs and expectations to internationalize. These strategies give an indication of how travel-related working practices can become more efficient and sustainable in the future

Stabilizing strongly correlated photon fluids with non-Markovian reservoirs

We introduce a frequency-dependent incoherent pump scheme with a square-shaped spectrum as a way to study strongly correlated photons in arrays of coupled nonlinear resonators. This scheme can be implemented via a reservoir of population-inverted two-level emitters with a broad distribution of transition frequencies. Our proposal is predicted to stabilize a nonequilibrium steady state sharing important features with a zero-temperature equilibrium state with a tunable chemical potential. We confirm the efficiency of our proposal for the Bose-Hubbard model by computing numerically the steady state for finite system sizes: first, we predict the occurrence of a sequence of incompressible Mott-insulator-like states with arbitrary integer densities presenting strong robustness against tunneling and losses. Secondly, for stronger tunneling amplitudes or noninteger densities, the system enters a coherent regime analogous to the superfluid state. In addition to an overall agreement with the zero-temperature equilibrium state, exotic nonequilibrium processes leading to a finite entropy generation are pointed out in specific regions of parameter space. The equilibrium ground state is shown to be recovered by adding frequency-dependent losses. The promise of this improved scheme in view of quantum simulation of the zero-temperature many-body physics is highlighted

Synthesis and Optimization of Reversible Circuits - A Survey

Reversible logic circuits have been historically motivated by theoretical research in low-power electronics as well as practical improvement of bit-manipulation transforms in cryptography and computer graphics. Recently, reversible circuits have attracted interest as components of quantum algorithms, as well as in photonic and nano-computing technologies where some switching devices offer no signal gain. Research in generating reversible logic distinguishes between circuit synthesis, post-synthesis optimization, and technology mapping. In this survey, we review algorithmic paradigms --- search-based, cycle-based, transformation-based, and BDD-based --- as well as specific algorithms for reversible synthesis, both exact and heuristic. We conclude the survey by outlining key open challenges in synthesis of reversible and quantum logic, as well as most common misconceptions.Comment: 34 pages, 15 figures, 2 table

New Integrated High-Resolution Dinoflagellate Cyst Stratigraphy and Litho- and Chemostratigraphy from the Paris and Dieppe–Hampshire Basins for the “Sparnacian”

The Paris Basin represents an historical cradle of Palaeogene stratigraphy, where during the nineteenth century the Palaeocene Series and the “Sparnacian Stage” were established. As highlighted by Aubry et al. (2005), whereas the chronostratigraphic connotation of the “Sparnacian Stage” has been controversial since its definition, modern studies of the late Palaeocene–early Eocene interval have revealed that the so-called “Sparnacian” deposits encompass a remarkable and short (~170 kyr) episode of the Cenozoic, the Palaeocene–Eocene Thermal Maximum (PETM, ~55.8–55.6 Ma). Dinoflagellate assemblages from the “Sparnacian” of the Dieppe–Hampshire and Paris basins do not contain the key species Apectodinium augustum, whereas it is present in the northern Belgian Basin Tienen Formation and is coeval there with the CIE and the Apectodinium acme interval. However, our calibration of the Apectodinium acme to the CIE in the Dieppe–Hampshire and Paris basins suggests its attribution to the A. augustum zone. The absence of species A. augustum in the Anglo–Paris Basin may be explained by its restriction to more offshore conditions

Long-COVID cognitive impairments and reproductive hormone deficits in men may stem from GnRH neuronal death

BACKGROUND: We have recently demonstrated a causal link between loss of gonadotropin-releasing hormone (GnRH), the master molecule regulating reproduction, and cognitive deficits during pathological aging, including Down syndrome and Alzheimer's disease. Olfactory and cognitive alterations, which persist in some COVID-19 patients, and long-term hypotestosteronaemia in SARS-CoV-2-infected men are also reminiscent of the consequences of deficient GnRH, suggesting that GnRH system neuroinvasion could underlie certain post-COVID symptoms and thus lead to accelerated or exacerbated cognitive decline. METHODS: We explored the hormonal profile of COVID-19 patients and targets of SARS-CoV-2 infection in post-mortem patient brains and human fetal tissue. FINDINGS: We found that persistent hypotestosteronaemia in some men could indeed be of hypothalamic origin, favouring post-COVID cognitive or neurological symptoms, and that changes in testosterone levels and body weight over time were inversely correlated. Infection of olfactory sensory neurons and multifunctional hypothalamic glia called tanycytes highlighted at least two viable neuroinvasion routes. Furthermore, GnRH neurons themselves were dying in all patient brains studied, dramatically reducing GnRH expression. Human fetal olfactory and vomeronasal epithelia, from which GnRH neurons arise, and fetal GnRH neurons also appeared susceptible to infection. INTERPRETATION: Putative GnRH neuron and tanycyte dysfunction following SARS-CoV-2 neuroinvasion could be responsible for serious reproductive, metabolic, and mental health consequences in long-COVID and lead to an increased risk of neurodevelopmental and neurodegenerative pathologies over time in all age groups. FUNDING: European Research Council (ERC) grant agreements No 810331, No 725149, No 804236, the European Union Horizon 2020 research and innovation program No 847941, the Fondation pour la Recherche Médicale (FRM) and the Agence Nationale de la Recherche en Santé (ANRS) No ECTZ200878 Long Covid 2021 ANRS0167 SIGNAL, Agence Nationale de la recherche (ANR) grant agreements No ANR-19-CE16-0021-02, No ANR-11-LABEX-0009, No. ANR-10-LABEX-0046, No. ANR-16-IDEX-0004, Inserm Cross-Cutting Scientific Program HuDeCA, the CHU Lille Bonus H, the UK Medical Research Council (MRC) and National Institute of Health and care Research (NIHR)