Dynamical Unbinding Transition in a Periodically Driven Mott Insulator

We study the double occupancy in a fermionic Mott insulator at half-filling generated via a dynamical periodic modulation of the hopping amplitude. Tuning the modulation amplitude, we describe a crossover in the nature of doublon-holon excitations from a Fermi Golden Rule regime to damped Rabi oscillations. The decay time of excited states diverges at a critical modulation strength, signaling the transition to a dynamically bound non-equilibrium state of doublon-holon pairs. A setup using a fermionic quantum gas should allow to study the critical exponents.Comment: 4 pages, 2 figure

A Tensor Restriction Theorem over Finite Fields

Restriction is a natural quasi-order on $d$-way tensors. We establish a remarkable aspect of this quasi-order in the case of tensors over a fixed finite field -- namely, that it is a well-quasi-order: it admits no infinite antichains and no infinite strictly decreasing sequences. This result, reminiscent of the graph minor theorem, has important consequences for an arbitrary restriction-closed tensor property $X$. For instance, $X$ admits a characterisation by finitely many forbidden restrictions and can be tested by looking at subtensors of a fixed size. Our proof involves an induction over polynomial generic representations, establishes a generalisation of the tensor restriction theorem to other such representations (e.g. homogeneous polynomials of a fixed degree), and also describes the coarse structure of any restriction-closed property.Comment: 31 page

Vortex Entanglement and Broken Symmetry

Based on the London approximation, we investigate numerically the stability of the elementary configurations of entanglement, the twisted-pair and the twisted-triplet, in the vortex-lattice and -liquid phases. We find that, except for the dilute limit, the twisted-pair is unstable and hence irrelevant in the discussion of entanglement. In the lattice phase the twisted-triplet constitutes a metastable, confined configuration of high energy. Loss of lattice symmetry upon melting leads to deconfinement and the twisted-triplet turns into a low-energy helical configuration.Comment: 4 pages, RevTex, 2 figures on reques

An experimental determination of the scale length of N2O in the soil of a grassland

Concentration profiles of N2O in a grassland soil and dynamic response curves to disturbance of the soil concentration (relaxation curves) were measured with a new membrane tube technique. Diffusive properties of the soil were derived from 222Rn measurements. The mathematical analysis of the relaxation curves yielded N2O uptake rates U soil diffusivities Ds, scale lengths z*, and production rates P at different levels under the surface. The following ranges were found during 2 days of measurements: Ds = (0.4–5) × 10−7 m2 s−1, U = (1–20) × 10−4 s−1, z* = 0.7–2.8 cm, and P = 0.02–4.4 ppb s−1. These values were used to reproduce the measured N2O concentration profiles with a one-dimensional diffusive transport model of N2O in the soil air-filled pore space and to deduce flux profiles. Bidirectional fluxes occurred with small deposition fluxes up to a few ppt ms−1 during intensive growing phases of the grass. Uptake rates were high enough that N2O produced at greater depth did not reach the atmosphere

Estimating the ice thickness of mountain glaciers with a shape optimization algorithm using surface topography and mass-balance

We present a shape optimization algorithm to estimate the ice thickness distribution within a two-dimensional, non-sliding mountain glacier, given a transient surface geometry and a mass-balance distribution. The approach is based on the minimization of the surface topography misfit at the end of the glacier's evolution in the shallow ice approximation of ice flow. Neither filtering of the surface topography where its gradient vanishes nor interpolation of the basal shear stress is involved. Novelty of the presented shape optimization algorithm is the use of surface topography and mass-balance only within a time-dependent Lagrangian approach for moving-boundary glaciers. On real-world inspired geometries, it is shown to produce estimations of even better quality in smaller time than the recently proposed steady and transient inverse methods. A sensitivity analysis completes the study and evinces the method's higher susceptibility to perturbations in the surface topography than in surface mass-balance or rate facto

The Structure of the Vortex Liquid at the Surface of a Layered Superconductor

A density-functional approach is used to calculate the inhomogeneous vortex density distribution in the flux liquid phase at the planar surface of a layered superconductor, where the external magnetic field is perpendicular to the superconducting layers and parallel to the surface. The interactions with image vortices are treated within a mean field approximation as a functional of the vortex density. Near the freezing transition strong vortex density fluctuations are found to persist far into the bulk liquid. We also calculate the height of the Bean-Livingston surface barrier.Comment: 8 pages, RevTeX, 2 figure

Anelastic-like nature of the rejuvenation of metallic glasses by cryogenic thermal cycling

Cryogenic thermal cycling (CTC) is an effective treatment for improving the room-temperature plasticity and toughness in metallic glasses. Despite considerable attention to characterizing the effects of CTC, they remain poorly understood. A prominent example is that, contrary to expectation, the stored energy in a metallic glass first rises, and then decreases, as CTC progresses. In this work, CTC is applied to bulk metallic glasses based on Pd, Pt, Ti, or Zr. The effects on calorimetric and mechanical properties are evaluated. Critically, CTC-induced effects, at whatever stage, are found to decay over about one week at room temperature after CTC, returning the properties to those of the as-cast glass. A model is proposed for CTC-induced effects, treating them as analogous to the accumulation of anelastic strain. The implications for analysis of existing data, and for future research on CTC effects, are highlighted

Code of conduct for scientific integrity

The scientific landscape has changed considerably since the Swiss Academies of Arts and Sciences published Integrity in scientific research: Principles and procedures in 2008. Consequently, an expert group was set up with members from the Swiss Academies of Arts and Sciences, the Swiss National Science Foundation, swissuniversities, and Innosuisse to review the changes that have taken place in recent years and to draw up this Code of conduct for scientific integrity. This Code is aimed at everyone involved in the generation, dissemination, and advancement of knowledge within the Swiss higher education system. This includes scientists, institutions, and funding organisations. Institutions and funding organisations have a special role to play in creating and maintaining the conditions in which scientific integrity can thrive. Scientific integrity is based on the observance of fundamental principles and their many different contextual concretisations. These principles guide scien- tists in their research and teaching and help them to deal with the practical, ethical, and intellectual challenges they can expect to encounter. The aim of this code of conduct is to promote appropriate attitudes and to help build a robust culture of scientific integrity that will stand the test of time. Ethical scientific behaviour rests on the basic principles of reliability, honesty, respect, and accountability and supports the concretisations of these basic principles within a specific frame of reference. This Code is intended to be a dynamic document. Its aim is to strengthen scientific integrity in all avenues of research and education, with a particular emphasis on the training and development of young people. Another of its aims is to establish a culture of research integrity in the scientific community, with the Code providing a welcome framework rather than imposing its own set of rules. It promotes common understanding and parity of treatment in dealing with violations of scientific integrity within and between institutions. The Code also considers current developments in the fields of Open Science and social media, and it examines the issue of time limitation from several points of view. In addition, it offers practical recommendations on how to set up an organisation for the protection of scientific integrity and describes the processes involved