Eigenvalues and eigenfunctions of billiards in a constant magnetic field

We present a simple and efficient numerical method to compute the eigenvalues and eigenfunctions of two-dimensional billiards subjected to a constant magnetic field in the perpendicular direction. As examples we present results for the circular billiard, where the method is particularly simple, and for the square billiard, which is nonintegrable for nonzero fields.535A4555456

Semiclassical approximations to the coherent-state propagator for a particle in a box

We compute the semiclassical coherent-state propagator for a particle moving in a one-dimensional box. In this semiclassical approach complex trajectories are stationary paths of the propagator's asymptotic expansion and play a fundamental role. A second semiclassical approximation is also introduced, which makes use of real trajectories only. An application to a seemingly simple system, the infinite well, is carried out completely for the diagonal elements, and a comparison is made among the three possible methods, those based on complex and real trajectories and the 'exact case' that is determined by decomposing the propagator into its eigenstates.5431808181

Chaotic-to-regular transition in a semiclassical electron gas

We study the magnetic susceptibility chi of a two-dimensional noninteracting electron gas confined by a smooth chaotic potential. The computation of chi for a wide range of magnetic field values B reveals that the chaotic (B = 0) to regular (B --> (infinity)) transition is dominated by bifurcations of short periodic orbits that become stable as B increases. The families of stable orbits and tori contained in the associated stability islands do not play any special role in this regime. Large contributions, however, are observed near the bifurcation points,increasing the average susceptibility to values beyond those expected for regular systems.5421369137

Boundary integral method for quantum billiards in a constant magnetic field

We derive a boundary integral equation to compute the eigenvalues of two-dimensional billiards subjected to a magnetic field. The integral requires the Green's function of the boundary-free problem with the magnetic field pointing in the opposite direction. This Green's function is computed for the case of a constant magnetic field perpendicular to the billiard and some applications ate discussed. The elliptical billiard is then studied numerically as an example of a nontrivial application.551A657

A global action agenda for turning the tide on fatty liver disease

Background and Aims: Fatty liver disease is a major public health threat due to its very high prevalence and related morbidity and mortality. Focused and dedicated interventions are urgently needed to target disease prevention, treatment, and care. Approach and Results: We developed an aligned, prioritized action agenda for the global fatty liver disease community of practice. Following a Delphi methodology over 2 rounds, a large panel (R1 n = 344, R2 n = 288) reviewed the action priorities using Qualtrics XM, indicating agreement using a 4-point Likert-scale and providing written feedback. Priorities were revised between rounds, and in R2, panelists also ranked the priorities within 6 domains: epidemiology, treatment and care, models of care, education and awareness, patient and community perspectives, and leadership and public health policy. The consensus fatty liver disease action agenda encompasses 29 priorities. In R2, the mean percentage of “agree” responses was 82.4%, with all individual priorities having at least a super-majority of agreement (> 66.7% “agree”). The highest-ranked action priorities included collaboration between liver specialists and primary care doctors on early diagnosis, action to address the needs of people living with multiple morbidities, and the incorporation of fatty liver disease into relevant non-communicable disease strategies and guidance. Conclusions: This consensus-driven multidisciplinary fatty liver disease action agenda developed by care providers, clinical researchers, and public health and policy experts provides a path to reduce the prevalence of fatty liver disease and improve health outcomes. To implement this agenda, concerted efforts will be needed at the global, regional, and national levels.publishedVersio

A global research priority agenda to advance public health responses to fatty liver disease

Background & aims An estimated 38% of adults worldwide have non-alcoholic fatty liver disease (NAFLD). From individual impacts to widespread public health and economic consequences, the implications of this disease are profound. This study aimed to develop an aligned, prioritised fatty liver disease research agenda for the global health community. Methods Nine co-chairs drafted initial research priorities, subsequently reviewed by 40 core authors and debated during a three-day in-person meeting. Following a Delphi methodology, over two rounds, a large panel (R1 n = 344, R2 n = 288) reviewed the priorities, via Qualtrics XM, indicating agreement using a four-point Likert-scale and providing written feedback. The core group revised the draft priorities between rounds. In R2, panellists also ranked the priorities within six domains: epidemiology, models of care, treatment and care, education and awareness, patient and community perspectives, and leadership and public health policy. Results The consensus-built fatty liver disease research agenda encompasses 28 priorities. The mean percentage of ‘agree’ responses increased from 78.3 in R1 to 81.1 in R2. Five priorities received unanimous combined agreement (‘agree’ + ‘somewhat agree’); the remaining 23 priorities had >90% combined agreement. While all but one of the priorities exhibited at least a super-majority of agreement (>66.7% ‘agree’), 13 priorities had 90% combined agreement. Conclusions Adopting this multidisciplinary consensus-built research priorities agenda can deliver a step-change in addressing fatty liver disease, mitigating against its individual and societal harms and proactively altering its natural history through prevention, identification, treatment, and care. This agenda should catalyse the global health community’s efforts to advance and accelerate responses to this widespread and fast-growing public health threat. Impact and implications An estimated 38% of adults and 13% of children and adolescents worldwide have fatty liver disease, making it the most prevalent liver disease in history. Despite substantial scientific progress in the past three decades, the burden continues to grow, with an urgent need to advance understanding of how to prevent, manage, and treat the disease. Through a global consensus process, a multidisciplinary group agreed on 28 research priorities covering a broad range of themes, from disease burden, treatment, and health system responses to awareness and policy. The findings have relevance for clinical and non-clinical researchers as well as funders working on fatty liver disease and non-communicable diseases more broadly, setting out a prioritised, ranked research agenda for turning the tide on this fast-growing public health threat

Effects Of Symmetry Breakdown In The Bifurcations Of Periodic Orbits Of A Nonintegrable Hamiltonian System

In this work we study numerically the breakdown of discrete symmetries in a Hamiltonian system with two degrees of freedom. The initial Hamiltonian is invariant under time-reversal (t → -t) and reflexion through an axis (x → -x). These symmetries are then broken by the insertion of a magnetic field and a term of the form γx3. The effects of these perturbations are studied in terms of Poincaré sections and periodic orbits. © 1994 Academic Press. All rights reserved.231229031

Complex trajectories in the quartic oscillator and its semiclassical coherent-state propagator

The semiclassical approximation of the coherent-state propagator requires the computation of complex trajectories satisfying special boundary conditions. In this paper we present a method for the determination of such trajectories for one-dimensional polynomial potentials. We also compute the semiclassical propagator for the case V(q) = lambda q(2)/2 + beta q(4) and compare the results with an ''exact'' calculation. (C) 1996 Academic Press, Inc.252245847