The Null Condition and Global Existence for Nonlinear Wave Equations on Slowly Rotating Kerr Spacetimes

We study a semilinear equation with derivatives satisfying a null condition on slowly rotating Kerr spacetimes. We prove that given sufficiently small initial data, the solution exists globally in time and decays with a quantitative rate to the trivial solution. The proof uses the robust vector field method. It makes use of the decay properties of the linear wave equation on Kerr spacetime, in particular the improved decay rates in the region $\{r\leq \frac{t}{4}\}$

Examining CP Symmetry in Strange Baryon Decays

Non-conservation of CP symmetry can manisfest itself in non-leptonic hyperon decays as a difference in the decay parameter between the strange-baryon decay and its charge conjugate. By comparing the decay distribution in the $\Lambda$ helicity frame for the decay sequence $\Xi^{-} \to \Lambda \pi^{-}$, $\Lambda \to p \pi^{-}$ with that of $\bar{\Xi}^{+}$ decay, E756 at Fermilab did not observe any CP-odd effect at the $10^{-2}$ level. The status of a follow-up experiment, HyperCP (FNAL E871), to search for CP violation in charged $\Xi-\Lambda$ decay with a sensitivity of $10^{-4}$ is also presented.Comment: 9 pages, 4 figures, invited talk presented at the Third International Conference on B Physics and CP Violation, 3-7 Dec 1999, Taipei, Taiwa

Einstein equations under polarized U(1)\mathbb U(1) symmetry in an elliptic gauge

We prove local existence of solutions to the Einstein--null dust system under polarized $\mathbb U(1)$ symmetry in an elliptic gauge. Using in particular the previous work of the first author on the constraint equations, we show that one can identify freely prescribable data, solve the constraints equations, and construct a unique local in time solution in an elliptic gauge. Our main motivation for this work, in addition to merely constructing solutions in an elliptic gauge, is to provide a setup for our companion paper in which we study high frequency backreaction for the Einstein equations. In that work, the elliptic gauge we consider here plays a crucial role to handle high frequency terms in the equations. The main technical difficulty in the present paper, in view of the application in our companion paper, is that we need to build a framework consistent with the solution being high frequency, and therefore having large higher order norms. This difficulty is handled by exploiting a reductive structure in the system of equations

Trapped surfaces in vacuum arising dynamically from mild incoming radiation

In this paper, we study the "minimal requirement" on the incoming radiation that guarantees a trapped surface to form in vacuum. First, we extend the region of existence in Christodoulou's theorem on the formation of trapped surfaces and consequently show that the lower bound required to form a trapped surface can be relaxed. Second, we demonstrate that trapped surfaces form dynamically from a class of initial data which are large merely in a scaling-critical norm. This result is motivated in part by the scaling in Christodoulou's formation of trapped surfaces theorem for the Einstein-scalar field system in spherical symmetry

Spirituality and business: An interdisciplinary overview

The paper gives an interdisciplinary overview of the emerging field of spirituality and business. It uses insights from business ethics, theology, neuroscience, psychology, gender studies, and philosophy to economics, management, organizational science, and banking and refers to different religious convictions including Christianity, Judaism, Islam, Hinduism, Buddhism, Confucianism, the Baha'i faith, and the North-American aboriginal worldview. The authors argue that the materialistic management paradigm has failed. They explore new values for post-materialistic management: frugality, deep ecology, trust, reciprocity, responsibility for future generations, and authenticity. Within this framework profit and growth are no longer ultimate aims but elements in a wider set of values. Similarly, cost-benefit calculations are no longer the essence of management but are part of a broader concept of wisdom in leadership. Spirit-driven businesses require intrinsic motivation for serving the common good and using holistic evaluation schemes for measuring success. The Palgrave Handbook of Business and Spirituality, edited by the authors, is a response to developments that simultaneously challenge the “business as usual” mindset

High-frequency backreaction for the Einstein equations under polarized U(1)\mathbb U(1) symmetry

Known examples in plane symmetry or Gowdy symmetry show that given a $1$-parameter family of solutions to the vacuum Einstein equations, it may have a weak limit which does not satisfy the vacuum equations, but instead has a non-trivial stress-energy-momentum tensor. We consider this phenomenon under polarized $\mathbb U(1)$ symmetry - a much weaker symmetry than most of the known examples - such that the stress-energy-momentum tensor can be identified with that of multiple families of null dust propagating in distinct directions. We prove that any generic local-in-time small-data polarized-$\mathbb U(1)$-symmetric solution to the Einstein-multiple null dust system can be achieved as a weak limit of vacuum solutions. Our construction allows the number of families to be arbitrarily large, and appears to be the first construction of such examples with more than two families

Love thy neighbour? Coronavirus politics and their impact on EU freedoms and rule of law in the Schengen Area. CEPS Paper in Liberty and Security in Europe No. 2020-04, April 2020

Restrictions on international and intra-EU traffic of persons have been at the heart of the political responses to the coronavirus pandemic. Border controls and suspensions of entry and exist have been presented as key policy priorities to prevent the spread of the virus in the EU. These measures pose however fundamental questions as to the raison d’être of the Union, and the foundations of the Single Market, the Schengen system and European citizenship. They are also profoundly intrusive regarding the fundamental rights of individuals and in many cases derogate domestic and EU rule of law checks and balances over executive decisions. This Paper examines the legality of cross-border mobility restrictions introduced in the name of COVID-19. It provides an in-depth typology and comprehensive assessment of measures including the reintroduction of internal border controls, restrictions of specific international traffic modes and intra-EU and international ‘travel bans’. Many of these have been adopted in combination with declarations of a ‘state of emergency’

Foxconn Worker Dies at iPhone Assembly Plant in China

This document is part of a digital collection provided by the Martin P. Catherwood Library, ILR School, Cornell University, pertaining to the effects of globalization on the workplace worldwide. Special emphasis is placed on labor rights, working conditions, labor market changes, and union organizing.CLW_2015_Report_China_foxconn_worker.pdf: 51 downloads, before Oct. 1, 2020