Large N lattice QCD and its extended strong-weak connection to the hypersphere

We calculate an effective Polyakov line action of QCD at large Nc and large Nf from a combined lattice strong coupling and hopping expansion working to second order in both, where the order is defined by the number of windings in the Polyakov line. We compare with the action, truncated at the same order, of continuum QCD on S^1 x S^d at weak coupling from one loop perturbation theory, and find that a large Nc correspondence of equations of motion found in \cite{Hollowood:2012nr} at leading order, can be extended to the next order. Throughout the paper, we review the background necessary for computing higher order corrections to the lattice effective action, in order to make higher order comparisons more straightforward.Comment: 33 pages, 7 figure

Swimming with microbes: an individual-based modelling approach to ocean microbial ecology across scales

Microbial ecosystems, both on land and in the oceans, are the staging ground for the biogeochemical activity that sustains habitable conditions on Earth. Ocean microbes are of particular importance; the primary producers that drive biogeochemical ocean processes are almost entirely microbial, and are collectively responsible for about half of global net primary production. These ecosystems are extraordinarily complex, by virtue of being driven by very large numbers of living individuals, constantly interacting with each other and their highly dynamic physical environment. Much uncertainty remains about how these dynamics, from micro- to macro-scales, ultimately impact key ecosystem properties such as spatial dynamics and growth rates of populations and communities. In this project I use individual-based modelling (IBM) across a range of spatial and temporal scales, leveraging large, high-resolution physical and biological datasets along with advancements in modelling tools to shed light on spatial and temporal dynamics of microbial populations in inherently fluctuating environments. In doing so I clarify and quantify hitherto unresolved ecological questions relating to interactions between microbes and turbulence, inaccuracies in conventional modelling approaches, and the balance of competition and coexistence between microbes in the marine environment. In the Introductory Chapter, I review our current understanding of microbial ecology in the oceans, and illustrate how complex ecological behaviour emerges from the constant interaction of microbial individuals with each other and with their environment. In the Second Chapter, I begin at the smallest scales directly relevant to ocean microbes, investigating the impact of turbulence on microbial spatial dynamics and patchiness. I adopt an existing mathematical framework for modelling microbes capable of gyrotactic locomotion, with an IBM to reproduce their motion within a fully-resolved 3D simulation of convective turbulence. This work clarifies and extends to more realistic flow regimes the existing theory connecting micro-scale microbe patchiness to a coupling of turbulence and individual motility. Interpreting my results in the context of varying turbulent conditions from the surface to the bottom of the mixed layer, I propose that this turbulence-driven patchiness is ephemeral, non-ubiquitous, and depth-dependent. In the Third Chapter, I transition to larger spatial and temporal scales, and develop an IBM on top of the NEMO-MEDUSA oceanographic model and the global Biotraits database. I use this model to quantify, for the first time, to what degree fluctuating environmental conditions can influence estimates of a microbe's growth rate, due to nonlinear averaging effects similar to the phenomenon known as Jensen's Inequality. In a microbial growth context, such effects predict that growth rate estimates based on mean environmental conditions will differ from realised growth rates in a dynamic environment. I substantiate this prediction by simulating populations of marine phytoplankton following ocean currents, and demonstrating that realised growth differs substantially from mean-environment growth estimates for a clear majority of these simulated populations. I quantify the relative contributions of temperature and nutrient fluctuations to this microbial ``growth gap'' -- the magnitude of the difference between realised and mean-environment growth rates, and discuss the implications of my findings under a warming climate. In the Fourth Chapter, I apply my NEMO-MEDUSA-Biotraits IBM to investigate the ‘Paradox of the Plankton’ -- the puzzling absence of competitive exclusion among ocean microbes. I simulate populations of distinct species with thermal histories which significantly overlap in both space and time within the IBM, which I treat as competitors. I then examine whether the distinct thermal adaptations of these competitors can cause competitive advantage to shift back and forth over time as environmental conditions fluctuate, thus preventing any individual species from permanently outcompeting others. In the Final Chapter, I link my findings to each other and to the bigger picture of microbial ocean ecology, emphasizing how a maturing body of mathematical ecological theory, increasingly large and detailed datasets, and modern computational tools, allow us to shed light on long-standing questions by closely examining interactions between individuals and a dynamic environment.Open Acces

Calculating the chiral condensate diagrammatically at strong coupling

We calculate the chiral condensate of QCD at infinite coupling as a function of the number of fundamental fermion flavours using a lattice diagrammatic approach inspired by recent work of Tomboulis, and other work from the 80's. We outline the approach where the diagrams are formed by combining a truncated number of sub-diagram types in all possible ways. Our results show evidence of convergence and agreement with simulation results at small Nf. However, contrary to recent simulation results, we do not observe a transition at a critical value of Nf. We further present preliminary results for the chiral condensate of QCD with symmetric or adjoint representation fermions at infinite coupling as a function of Nf for Nc = 3. In general, there are sources of error in this approach associated with miscounting of overlapping diagrams, and over-counting of diagrams due to symmetries. These are further elaborated upon in a longer paper.Comment: presented at the 32nd International Symposium on Lattice Field Theory (Lattice 2014), 23-28 June 2014, New York, NY, US

Ante-Autobiography and the Archive of Childhood

This essay examines the concept of children’s autobiography via several autobiographical extracts written by the author as a child. Although only a small proportion of people will compose and publish a full-length autobiography, almost everyone will, inadvertently, produce an archive of the self, made from public records and private documents. Here, such works are seen as providing access to writing both about and by children. The essay explores the ethics and poetics of children’s writing via the key debates in life writing; in particular, the dynamic relationship between adults and children, both as distinct stages of life and dual parts of one autobiographical identity. The term “ante-autobiography” is coined to refer to these texts which come before or instead of a full-length narrative. They are not read as less than or inadequate versions of autobiography, but rather as transgressive and challenging to chronological notions of the genre

Hauerwas and the Law: Framing a Productive Conversation

Background: Meal-Q and its shorter version, MiniMeal-Q, are 2 new Web-based food frequency questionnaires. Their meal-based and interactive format was designed to promote ease of use and to minimize answering time, desirable improvements in large epidemiological studies. Objective: We evaluated the validity of energy and macronutrient intake assessed with Meal-Q and MiniMeal-Q as well as the reproducibility of Meal-Q. Methods: Healthy volunteers aged 20-63 years recruited from Stockholm County filled out the 174-item Meal-Q. The questionnaire was compared to 7-day weighed food records (WFR; n=163), for energy and macronutrient intake, and to doubly labeled water (DLW; n=39), for total energy expenditure. In addition, the 126-item MiniMeal-Q was evaluated in a simulated validation using truncated Meal-Q data. We also assessed the answering time and ease of use of both questionnaires. Results: Bland-Altman plots showed a varying bias within the intake range for all validity comparisons. Cross-classification of quartiles placed 70%-86% in the same/adjacent quartile with WFR and 77% with DLW. Deattenuated and energy-adjusted Pearson correlation coefficients with the WFR ranged from r=0.33-0.74 for macronutrients and was r=0.18 for energy. Correlations with DLW were r=0.42 for Meal-Q and r=0.38 for MiniMeal-Q. Intraclass correlations for Meal-Q ranged from r=0.57-0.90. Median answering time was 17 minutes for Meal-Q and 7 minutes for MiniMeal-Q, and participants rated both questionnaires as easy to use. Conclusions: Meal-Q and MiniMeal-Q are easy to use and have short answering times. The ranking agreement is good for most of the nutrients for both questionnaires and Meal-Q shows fair reproducibility.QC 20130709</p

Identifying Better Effective Higgsless Theories via W_L W_L Scattering

The three site Higgsless model has been offered as a benchmark for studying the collider phenomenology of Higgsless models. In this talk, we present how well the three site Higgsless model performs as a general representative of Higgsless models in describing W_L W_L scattering, and which modifications can make it more representative. We employ general sum rules relating the masses and couplings of the Kaluza-Klein (KK) modes of the gauge fields in continuum and deconstructed Higgsless models as a way to compare the different theories. After comparing the three site Higgsless model to flat and warped continuum Higgsless models, we analyze an extensions of the three site Higgsless model, namely, the Hidden Local Symmetry (HLS) Higgsless model. We demonstrate that W_LW_L scattering in the HLS Higgsless model can very closely approximate scattering in the continuum models, provided that the parameter `a' is chosen to mimic rho-meson dominance of pi-pi scattering in QCD