Particle production and reheating in the inflationary universe

Thermal field theory is applied to particle production rates in inflationary models, leading to new results for catalysed, or two-stage decay, where massive fields act as decay channels for the production of light fields. A numerical investigation of the Bolztmann equation in an expanding universe shows that the particle distributions produced during small amplitude inflaton oscillations or alongside slowly moving inflaton fields can thermalise.Comment: 16 pages, 12 figures, LaTeX, extra references in v

Coarse Brownian Dynamics for Nematic Liquid Crystals: Bifurcation Diagrams via Stochastic Simulation

We demonstrate how time-integration of stochastic differential equations (i.e. Brownian dynamics simulations) can be combined with continuum numerical bifurcation analysis techniques to analyze the dynamics of liquid crystalline polymers (LCPs). Sidestepping the necessity of obtaining explicit closures, the approach analyzes the (unavailable in closed form) coarse macroscopic equations, estimating the necessary quantities through appropriately initialized, short bursts of Brownian dynamics simulation. Through this approach, both stable and unstable branches of the equilibrium bifurcation diagram are obtained for the Doi model of LCPs and their coarse stability is estimated. Additional macroscopic computational tasks enabled through this approach, such as coarse projective integration and coarse stabilizing controller design, are also demonstrated

Quantum Energies of Interfaces

We present a method for computing the one-loop, renormalized quantum energies of symmetrical interfaces of arbitrary dimension and codimension using elementary scattering data. Internal consistency requires finite-energy sum rules relating phase shifts to bound state energies.Comment: 8 pages, 1 figure, minor changes, Phys. Rev. Lett., in prin

Identification of group B respiratory syncytial viruses that lack the 60-nucleotide duplication after six consecutive epidemics of total BA dominance at coastal Kenya

Respiratory syncytial virus BA genotype has reportedly replaced other group B genotypes worldwide. We report the observation of three group B viruses, all identical in G sequence but lacking the BA duplication, at a coastal district hospital in Kenya in early 2012. This follows a period of six consecutive respiratory syncytial virus (RSV) epidemics with 100% BA dominance among group B isolates. The new strains appear only distantly related to BA variants and to previously circulating SAB1 viruses last seen in the district in 2005, suggesting that they were circulating elsewhere undetected. These results are of relevance to an understanding of RSV persistence

Fermion Energies in the Background of a Cosmic String

We provide a thorough exposition, including technical and numerical details, of previously published results on the quantum stabilization of cosmic strings. Stabilization occurs through the coupling to a heavy fermion doublet in a reduced version of the standard model. We combine the vacuum polarization energy of fermion zero-point fluctuations and the binding energy of occupied energy levels, which are of the same order in a semi-classical expansion. Populating these bound states assigns a charge to the string. We show that strings carrying fermion charge become stable if the electro-weak bosons are coupled to a fermion that is less than twice as heavy as the top quark. The vacuum remains stable in our model, because neutral strings are not energetically favored. These findings suggests that extraordinarily large fermion masses or unrealistic couplings are not required to bind a cosmic string in the standard model.Comment: 38 pages, 6 figures, version accepted for publication in Phys Rev

Multispeed cities and the logistics of living in the Information Age

We now have a wealth of data on how the use of information and digital technologies (ICTs) is unevenly mapped onto different income, gender and ethnic groups. However we remain poorly equipped to understand how ICTs, with their intrinsic abilities to transcend barriers of space and time, relate to the fine grain of people’s lives on the ground in cities and neighbourhoods. ICTs contract space in enabling us to contact distant friends, pick up voice mail and order goods. Mobile phones on the move short-circuit time to an instant. But what are the effects of these space and time manipulations on the actual logistics of our interaction with other people? And what does it mean for people and neighbourhoods who do not have access to ICTs to live in a world that is being restructured to suit those who do? This project helps to fill these and allied gaps in our knowledge by simultaneously examining how ICTs relate to social inequalities through their use in orchestrati! ng the social time-space worlds both of a privileged and of a marginalized neighbourhood in Newcastle upon Tyne. Key Findings • Measures of the “digital divide” based on ICT ownership are inadequate to depict the complex patterns of use and access to a variety of technologies. For example, respondents in the poorer area may not have had access to, say, the Internet nor used online services, but they often relied on neighbours, family or friends to provide access. ICT use is often more collective and collaborative, beyond the household level, which suggests some caution over widely used official, individualistic measures. • In the richer area ICTs formed pervasive infrastructures underpinning everyday life, to such an extent that respondents could not say when they specifically used a technology because it was on all the time. In the poorer area, ICT use tended to be for specific purposes, which were recalled as discrete events marked out by their use of advanced technology. • Research on ICTs can profitably use a conceptual framework which emphasises the way in which interactions that do and do not use ICTs inter-relate to shape the detail of subjects’ everyday life. Such an approach allows research to address the ways in which multiple ICTs are used simultaneously and in subtle and continuous combination. • The relaxing of restrictions imposed by time and space that ICTs can give offers new possibilities for structuring the rhythms of daily life. Crucially, this leads not to a disembedding from local life but to forging new interactions within cities. Other Findings • By having ICTs as an “always on” background, affluent and ICT literate groups benefitted from accelerating lifestyles and mobility patterns and are enabled to cram extremely dense and flexible patterns of transaction, communication and information exchange into the logistical framework of their lives. • ICT use in the more marginalized neighbourhood tended to offer occasional support to existing patterns of everyday life. About the Study The project deployed an innovative cascade of methods to establish how ICT- mediated and place-based activities intersect to define together the logistics of everyday life for the affluent Jesmond and a relatively marginalized “off line” Blakelaw neighbourhood in Newcastle upon Tyne

Kinetics of the neutralizing antibody response to respiratory syncytial virus infections in a birth cohort

The kinetics of respiratory syncytial virus (RSV) neutralizing antibodies following birth, primary and secondary infections are poorly defined. The aims of the study were to measure and compare neutralizing antibody responses at different time points in a birth cohort followed-up over three RSV epidemics. Rural Kenyan children, recruited at birth between 2002 and 2003, were monitored for RSV infection over three epidemic seasons. Cord and 3-monthly sera, and acute and convalescent sera following RSV infection, were assayed in 28 children by plaque reduction neutralization test (PRNT). Relative to the neutralizing antibody titers of pre-exposure control sera (1.8 log10 PRNT), antibody titers following primary infection were (i) no different in sera collected between 0 and 0.4 months post-infection (1.9 log10 PRNT, P = 0.146), (ii) higher in sera collected between 0.5 and 0.9 (2.8 log10 PRNT, P < 0.0001), 1.0–1.9 (2.5 log10 PRNT, P < 0.0001), and 2.0–2.9 (2.3 log10 PRNT, P < 0.001) months post-infection, and (iii) no different in sera collected at between 3.0 and 3.9 months post-infection (2.0 log10 PRNT, P = 0.052). The early serum neutralizing response to secondary infection (3.02 log10 PRNT) was significantly greater than the early primary response (1.9 log10 PRNT, P < 0.0001). Variation in population-level virus transmission corresponded with changes in the mean cohort-level neutralizing titers. It is concluded that following primary RSV infection the neutralizing antibody response declines to pre-infection levels rapidly (∼3 months) which may facilitate repeat infection. The kinetics of the aggregate levels of acquired antibody reflect seasonal RSV occurrence, age, and infection history