On Approximation of the Eigenvalues of Perturbed Periodic Schrodinger Operators

This paper addresses the problem of computing the eigenvalues lying in the gaps of the essential spectrum of a periodic Schrodinger operator perturbed by a fast decreasing potential. We use a recently developed technique, the so called quadratic projection method, in order to achieve convergence free from spectral pollution. We describe the theoretical foundations of the method in detail, and illustrate its effectiveness by several examples.Comment: 17 pages, 2 tables and 2 figure

On Non Commutative G2 structure

Using an algebraic orbifold method, we present non-commutative aspects of $G_2$ structure of seven dimensional real manifolds. We first develop and solve the non commutativity parameter constraint equations defining $G_2$ manifold algebras. We show that there are eight possible solutions for this extended structure, one of which corresponds to the commutative case. Then we obtain a matrix representation solving such algebras using combinatorial arguments. An application to matrix model of M-theory is discussed.Comment: 16 pages, Latex. Typos corrected, minor changes. Version to appear in J. Phys.A: Math.Gen.(2005

Transdisciplinarity: towards an epistemology of what matters

This chapter explores the adoption of a transdisciplinary approach to knowledge by a doctor of professional studies research programme at Middlesex University in London. This programme is designed for senior professionals in a range of sectors who wish to bring about change, of varying degrees of magnitude, in practices and attitudes in their contexts. Its research pedagogy combines professional and academic knowledge to meet challenges posed by the temporal limitations of rapidly shifting local and global contexts. It proposes that conceptualising practice, through a transdisciplinary lens, opens up significant possibilities for both articulating and navigating the complexities inherent in any cultural ecology and the positioning of the researcher in that context. This enhances the research process’s potency to influence attitudes, focus and impact including the concept of agential knowing in identifying and attending to what matters

Local well-posedness for membranes in the light cone gauge

In this paper we consider the classical initial value problem for the bosonic membrane in light cone gauge. A Hamiltonian reduction gives a system with one constraint, the area preserving constraint. The Hamiltonian evolution equations corresponding to this system, however, fail to be hyperbolic. Making use of the area preserving constraint, an equivalent system of evolution equations is found, which is hyperbolic and has a well-posed initial value problem. We are thus able to solve the initial value problem for the Hamiltonian evolution equations by means of this equivalent system. We furthermore obtain a blowup criterion for the membrane evolution equations, and show, making use of the constraint, that one may achieve improved regularity estimates.Comment: 29 page

Fiddling while the ice melts? How organizational scholars can take a more active role in the climate change debate

The debate over anthropogenic climate change or the idea that human activities are altering the physical climate of the planet continues to rage amid seemingly irreconcilable differences, both within the developed world and between developed and less developed countries. With high uncertainty, rival worldviews, and wide diversity of meaning attached to the expression, climate change has become a key narrative within which local and transnational issues – economic, social, and political – are framed and contested. The field is fraught with controversies regarding causes and consequences, as well as different attitudes toward risks, technologies, and economic and social well-being for different groups. Parties also dispute how to share responsibility for reducing emissions – whether the issue primarily needs market, regulatory, technological, or behavioral solutions. Climate change is many things to many people. Competing interests negotiate over its interpretation and utilize various strategies to promote practices that advance their own understandings regarding climate change and its governance

Shifts in national land use and food production in Great Britain after a climate tipping point

This is the author accepted manuscript. The final version is available from Nature Research via the DOI in this recordData availability: The modelled output data that support the findings of this study are openly available from: Smith, G. S. & Ritchie, P. D. L. (NERC Environmental Information Data Centre: 639 doi.org/10.5285/e1c1dbcf-2f37-429b-af19-a730f98600f6, 2019).Climate change is expected to impact agricultural land use. Steadily accumulating changes in temperature and water availability can alter the relative profitability of different farming activities and promote land use changes. There is also potential for high-impact ‘climate tipping points’ where abrupt, non-linear change in climate occurs - such as the potential collapse of the Atlantic Meridional Overturning Circulation (AMOC). Here, using data from Great Britain, we develop a methodology to analyse the impacts of a climate tipping point on land use and economic outcomes for agriculture. We show that economic/land use impacts of such a tipping point are likely to include widespread cessation of arable farming with losses of agricultural output, an order of magnitude larger than the impacts of climate change without an AMOC collapse. The agricultural effects of AMOC collapse could be ameliorated by technological adaptations such as widespread irrigation, but the amount of water required and the costs appear prohibitive in this instance.Natural Environment Research Council (NERC)Alan Turing Institut

The Ctf18 RFC-like complex positions yeast telomeres but does not specify their replication time

Peer reviewedPreprin

Aggressions, social cognitions, anger and sadness in bullies and victims

Background: The present study aimed to investigate children's social information processing (SIP) and emotions in the bullying situation, taking into account reactive and proactive aggression. More specifically, we investigated the way in which children interpret social information, which goals they select, how they evaluate their responses and which emotions they express in hypothetical situations. Method: The participants comprised 242 Dutch children (120 girls and 122 boys; mean age: 117.2 months), who were assigned by means of peer nominations (Salmivalli, Lagerspetz, et al., 1996) to one of the following roles: bully (n = 21), follower of the bully (n = 38), victim (n = 35), defender of the victim (n = 48), outsider (n = 52) and not involved (n = 32). Sixteen children (including 3 bully/victims) were not given any role. The reactive and proactive aggression scale (Dodge, & Coie, 1987) was filled out by teachers in order to test the association between these types of aggression and involvement in bullying. Children were presented with ambiguous scenarios and responded to questions about attribution of intent, goal selection and emotions (anger and sadness). In addition, two questionnaires were administered to children: one assessed perceived self-efficacy in performing aggression, inhibiting aggression and using verbal persuasion skills, and the other assessed expected outcomes from behaving aggressively or prosocially. Results: Results showed that while reactive aggression was common in bullies and victims, proactive aggression was only characteristic of bullies. Both bullies and victims, compared to the other children, scored higher on hostile interpretation, anger, retaliation and ease of aggression. Bullies and followers claimed that it was easy for them to use verbal persuasion, while victims turned out to be the saddest group. All children, irrespective of their role in the peer group, thought that aggressive as well as prosocial behavior was more likely to produce desired results from a friendly peer than from an aggressive one. Conclusions: Bullies and victims seem to be similar in reactive aggression, SIP, and in the expression of anger, but the motivations which lead to their behavior may be different, as well as the final outcomes of their acts. © Association for Child Psychology and Psychiatry, 2004