Phase Transitions of Fermions Coupled to a Gauge Field: a Quantum Monte Carlo Approach

A grand canonical system of non-interacting fermions on a square lattice is considered at zero temperature. Three different phases exist: an empty lattice, a completely filled lattice and a liquid phase which interpolates between the other two phases. The Fermi statistics can be changed into a Bose statistics by coupling a statistical gauge field to the fermions. Using a quantum Monte Carlo method we investigate the effect of the gauge field on the critical properties of the lattice fermions. It turns out that there is no significant change of the phase diagram or the density of particles due to the gauge field even at the critical points. This result supports a recent conjecture by Huang and Wu that certain properties of a three-dimensional flux line system (which is equivalent to two-dimensional hard-core bosons) can be explained with non-interacting fermion models.Comment: 12 pages, Plain-Tex, 5 figure

Non-Linear Transport through a Molecular Nanojunction

We present a simple model of electrical transport through a metal-molecule-metal nanojunction that includes charging effects as well as aspects of the electronic structure of the molecule. The interplay of a large charging energy and an asymmetry of the metal-molecule coupling can lead to various effects in non-linear electrical transport. In particular, strong negative differential conductance is observed under certain conditions.Comment: 7 pages, 5 figures, accepted by Europhys. Let

Pair-tunneling resonance in the single-electron transport regime

We predict a new electron pair-tunneling (PT) resonance in non-linear transport through quantum dots with positive charging energies exceeding the broadening due to thermal and quantum fluctuations. The PT resonance shows up in the single-electron transport (SET) regime as a peak in the derivative of the non-linear conductance when the electrochemical potential of one electrode matches the average of two subsequent charge addition energies. For a single level quantum dot (Anderson model) we find the analytic peak shape and the dependence on temperature, magnetic field and junction asymmetry and compare with the inelastic cotunneling peak which is of the same order of magnitude. In experimental transport data the PT resonance may be mistaken for a weak SET resonance judging only by the voltage dependence of its position. Our results provide essential clues to avoid such erroneous interpretation of transport spectroscopy data.Comment: 5 pages, 2 figures, published versio

Building Resilience Through Nature Connection and Storytelling to Face the Climate Crisis and the Ecological Crisis

Climate Change is creating more and more severe impacts on our planet. Impacts include more destructive storms, increased temperatures, more wildfires and therefore smoke. Additionally, destruction of habitat is threatening species around the world, who are also struggling to survive the changing climate. Many young people around the world are very worried about the future, and many teachers feel unprepared to teach students about climate change. This project seeks to provide a resource for teachers and students to process the science of climate change by connecting to nature. It asks: How can educators use digital storytelling tools to develop students’ identities as individuals and members of a global community that includes the whole biosphere, while developing their language abilities? How can this practice help students connect with nature to become more resilient while taking local action to prepare themselves and their communities for the climate crisis and inspire others to do the same? It is interdisciplinary in nature, looking at theories and research on Identity, Language, Digital Media, and Climate Science. The climate crisis is global in scope and will require global cooperation to address. Using theories such as Critical Race Theory and Sociolinguistics can help educators reflect on the diverse identities of students in the US and around the world as they design curriculum to encourage collaboration. Honoring each individual and their intersecting identities makes schools more welcoming. Supporting linguistically diverse students is critically important, and building online networks of language communities can help do so. Advances in technology have allowed for more creation and sharing of multimedia content across the world. Helping students find their voice and tell their own stories can empower them to make change in their communities and globally. Involving children in local action and telling stories of children taking action can help inspire young people to stay hopeful and involved in the greatest problem of their time

Hörer- und Sprechertypen in Bremen und Hamburg. Eine Untersuchung zu Sprachwissen, Sprachwahrnehmung und Sprachgebrauch

Regarding the perception of regional speech and the salience of language variants it is to as-sume, that they are being influenced by individual features of the specific speaker/listener. However, most recent studies dealing with the salience of language phenomena neglect factors like, for example, language awareness or the profession of speakers. This article focuses on the correlation between speech perception, speech production and individual characteristics of speakers like the metalinguistic knowledge they have. It presents selected results of a study dealing with the perception and production of regional speech in Bremen and Hamburg and discusses different types of speaker/listener profiles

Salienz, Bewertung und Realisierung regionaler Merkmale in Norddeutschland

While the theoretical concept of perceptual prominence (salience) is subject of various recent studies, there is a lack of empirical evidence concerning the individual prominence of linguistic variables and the perception of these in different regions. This article presents some results of a study dealing with the perception and production of regional linguistic phenomena in Bremen and Hamburg. A quantitative analysis will be undertaken to investigate which linguistic variables are prominent for speakers and how language attitude and regional localization by non-linguists influence the salience of these phenomena. Also, the correlation between production and perception of linguistic phenomena is discussed by including objective speech data within the context of a qualitative survey. Assuming that the salience of linguistic variables is not fixed, but determined by a variety of factors, it is of interest which different combinations of influencing parameters for perceptual prominence exist