Pre-Big Bang Scenario on Self-T-Dual Bouncing Branes

We consider a new class of 5-dimensional dilatonic actions which are invariant under T-duality transformations along three compact coordinates, provided that an appropriate potential is chosen. We show that the invariance remains when we add a boundary term corresponding to a moving 3-brane, and we study the effects of the T-duality symmetry on the brane cosmological equations. We find that T-duality transformations in the bulk induce scale factor duality on the brane, together with a change of sign of the pressure of the brane cosmological matter. However, in a remarkable analogy with the Pre-Big Bang scenario, the cosmological equations are unchanged. Finally, we propose a model where the dual phases are connected through a scattering of the brane induced by an effective potential. We show how this model can realise a smooth, non-singular transition between a pre-Big Bang superinflationary Universe and a post-Big Bang accelerating Universe.Comment: 18 pages, minor typos corrected, Sec. 2 expanded with more details on the self-T-dual background, Sec.4 and 5 revised accordingly. Version to appear on JCA

A network-based threshold model for the spreading of fads in society and markets

We investigate the behavior of a threshold model for the spreading of fads and similar phenomena in society. The model is giving the fad dynamics and is intended to be confined to an underlying network structure. We investigate the whole parameter space of the fad dynamics on three types of network models. The dynamics we discover is rich and highly dependent on the underlying network structure. For some range of the parameter space, for all types of substrate networks, there are a great variety of sizes and life-lengths of the fads -- what one see in real-world social and economical systems

Using multimedia technology to enhance self-advocacy of people with intellectual disabilities: Introducing a theoretical framework for ‘Multimedia Advocacy’

Background: Multimedia Advocacy is the use of digital technology for people with intellectual disabilities as means of developing identities, being heard, connecting to family and care networks and, advocating for change. Methods: We explore principles and theories that underpin Multimedia Advocacy, mapping disciplinary approaches that have influenced the concept and praxis. Results: We describe relevant theories from cultural and media studies, personal therapeutic practices, communication, universal design, and systemic adoption of technology. We discuss new ways of achieving person-centred working with digital technology. We aim to develop a stronger theory/practice dialogue between these disciplines. Conclusions: The theories described highlight the importance of embedding access and use of digital technology within everyday settings. Long-term implementation plans and buy-in from all organisational levels are required for Multimedia Advocacy tools to be embraced by health and social care systems so the voice of an individual is included and genuine person-centred practice is achieved

Combustion and operating characteristics of spark-ignition engines

The spark-ignition engine turbulent flame propagation process was investigated. Then, using a spark-ignition engine cycle simulation and combustion model, the impact of turbocharging and heat transfer variations or engine power, efficiency, and NO sub x emissions was examined

Addressing the Safety and Criminal Exploitation of Vulnerable Young People: Before, During and After COVID-19 and Lockdown

This chapter is discussing the intersection of what is arguably an epidemic, and a pandemic, both of which can be fatal. In recent years there has been an epidemic in youth violence and crime, particularly in East London, and in the London Borough of Newham, where knife crime cases and youth knife injuries in particular have been consistently higher than comparator boroughs and London as a whole between 2013 and 2017. The chapter discusses in some detail the pre-pandemic Newham Keeping Safe (hereafter NKS) intervention aimed at vulnerable teenagers, proposing how this type of intervention could be adapted to the changing conditions of COVID-19 restrictions, and exploring the broader psychosocial implications for future interventions that aim to reduce the criminal exploitation of vulnerable young people, as we ‘open up’, or, at least, travel through new sets of changing conditions and restrictions. Such an endeavour requires that we reflect on what future levels of social distancing combined with more digital connections and practices could mean. Future interventions, we argue, need to include a reflection on the complex needs of children and families, and fathom the impact of interventions and their future post-COVID-19

Null vectors, 3-point and 4-point functions in conformal field theory

We consider 3-point and 4-point correlation functions in a conformal field theory with a W-algebra symmetry. Whereas in a theory with only Virasoro symmetry the three point functions of descendants fields are uniquely determined by the three point function of the corresponding primary fields this is not the case for a theory with $W_3$ algebra symmetry. The generic 3-point functions of W-descendant fields have a countable degree of arbitrariness. We find, however, that if one of the fields belongs to a representation with null states that this has implications for the 3-point functions. In particular if one of the representations is doubly-degenerate then the 3-point function is determined up to an overall constant. We extend our analysis to 4-point functions and find that if two of the W-primary fields are doubly degenerate then the intermediate channels are limited to a finite set and that the corresponding chiral blocks are determined up to an overall constant. This corresponds to the existence of a linear differential equation for the chiral blocks with two completely degenerate fields as has been found in the work of Bajnok~et~al.Comment: 10 pages, LaTeX 2.09, DAMTP-93-4

Finite size effects in perturbed boundary conformal field theories

We discuss the finite-size properties of a simple integrable quantum field theory in 1+1 dimensions with non-trivial boundary conditions. Novel off-critical identities between cylinder partition functions of models with differing boundary conditions are derived.Comment: 7 pages, 11 figures, JHEP proceedings style. Uses epsfig, amssymb. Talk given at the conference `Nonperturbative Quantum Effects 2000', Pari