Blocking the Hawking Radiation

Some severe constraints on asymmetric dark matter are based on the scenario that certain types of WIMPs can form mini-black holes inside neutron stars that can lead to their destruction. A crucial element for the realization of this scenario is that the black hole grows after its formation (and eventually destroys the star) instead of evaporating. The fate of the black hole is dictated by the two opposite mechanics i.e. accretion of nuclear matter from the center of the star and Hawking radiation that tends to decrease the mass of the black hole. We study how the assumptions for the accretion rate can in fact affect the critical mass beyond which a black hole always grows. We also study to what extent degenerate nuclear matter can impede Hawking radiation due to the fact that emitted particles can be Pauli blocked at the core of the star.Comment: 9 pages, 2 figure

Quantum gates via relativistic remote control

We harness general relativistic effects to gain quantum control on a stationary qubit in an optical cavity by controlling the non-inertial motion of a different probe atom. Furthermore, we show that by considering relativistic trajectories of the probe, we enhance the efficiency of the quantum control. We explore the possible use of these relativistic techniques to build universal quantum gates.Comment: 4 pages (+ 4 pages Appendix). 4 figures. RevTex 4.

Complexity and trust – experiences from local Danish Food Communities

Generally food consumers in Denmark do not trust the food production and distribution systems and the management of risk related to food consumption has become part of the daily life of many (Halkier & Holm, 2004). This paper explores how relations of trust are formed in two local Danish Food Communities (Fødevarefællesskaber) in Aarhus and Copenhagen. Food Communities are communities of consumers organized around the provision of local fresh vegetables directly from local producers. The Food Communities, together with local farmers, share the responsibilities, normally carried out by other market actors, such as logistics, sale and price formation. The vegetables are sold to the members of the community, at a relatively low price, if they take part in the duty work related to the food provisioning. The community functions despite no binding or long term agreements are made between the communities and the producers. The aim of this paper is to evaluate what role trust plays in order for the communities to function. Focus is given to 1) the mechanisms that create and maintain trust between the actors and 2) the challenges that the relations of trust are exposed to and 3) how the communities are dealing with these challenges

Asymmetric collapse by dissolution or melting in a uniform flow

An advection--diffusion-limited dissolution model of an object being eroded by a two-dimensional potential flow is presented. By taking advantage of the conformal invariance of the model, a numerical method is introduced that tracks the evolution of the object boundary in terms of a time-dependent Laurent series. Simulations of a variety of dissolving objects are shown, which shrink and then collapse to a single point in finite time. The simulations reveal a surprising exact relationship whereby the collapse point is the root of a non-analytic function given in terms of the flow velocity and the Laurent series coefficients describing the initial shape. This result is subsequently derived using residue calculus. The structure of the non-analytic function is examined for three different test cases, and a practical approach to determine the collapse point using a generalized Newton--Raphson root-finding algorithm is outlined. These examples also illustrate the possibility that the model breaks down in finite time prior to complete collapse, due to a topological singularity, as the dissolving boundary overlaps itself rather than breaking up into multiple domains (analogous to droplet pinch-off in fluid mechanics). In summary, the model raises fundamental mathematical questions about broken symmetries in finite-time singularities of both continuous and stochastic dynamical systems.Comment: 20 pages, 11 figure

Epilogue

The Environmental Responsibility Reader is a definitive collection of classic and contemporary environmental works that offers a comprehensive overview of the issues involved in environmental responsibility, steering the reader through each development in thought with a unifying and expert editorial voice. This essential text expertly explores seemingly intractable modern-day environmental dilemmas - including climate change, fossil fuel consumption, fresh water quality, industrial pollution, habitat destruction, and biodiversity loss. Starting with "Silent Spring" and moving through to more recent works the book draws on contemporary ideas of environmental ethics, corporate social responsibility, ecological justice, fair trade, global citizenship, and the connections between environmental and social justice; configuring these ideas into practical notions for responsible action with a unique global and integral focus on responsibility

Learning Experiences in Programming: The Motivating Effect of a Physical Interface

A study of undergraduate students learning to program compared the use of a physical interface with use of a screen-based equivalent interface to obtain insights into what made for an engaging learning experience. Emotions characterized by the HUMAINE scheme were analysed, identifying the links between the emotions experienced during programming and their origin. By capturing the emotional experiences of learners immediately after a programming experience, evidence was collected of the very positive emotions experienced by learners developing a program using a physical interface (Arduino) in comparison with a similar program developed using a screen-based equivalent interface

Testing the Opportunistic Approach to Monetary Policy

The Opportunistic Approach to Monetary Policy is an influential but untested model of optimal monetary policy. We provide the first tests of the model, using US data from 1983Q1-2004Q1. Our results support the Opportunistic Approach. We find that policymakers respond to the gap between inflation and an intermediate target that reflects the recent history of inflation. We find that there is no response of interest rates to inflation when inflation is within 1% of the intermediate target but a strong response when inflation is further from the intermediate target.