“A useful accessory to the infantry, but nothing more”: Tanks at the Battle of Flers-Courcelette, September 1916

The Battle of Flers-Courcelette is chiefly remembered as the combat introduction of tanks. The prevailing historiography maligns their performance as a lacklustre debut of a weapon which held so much promise for offensive warfare. However, unit war diaries and individual accounts of the battle suggest that the tank assaults of 15 September 1916 were far from total failures. This paper thus re-examines the role of tanks in the battle from the perspective of Canadian, British and New Zealand infantry. It finds that, rather than disappointing Allied combatants, the tanks largely lived up to their intended role of infantry support

SILC: a new Planck Internal Linear Combination CMB temperature map using directional wavelets

We present new clean maps of the CMB temperature anisotropies (as measured by Planck) constructed with a novel internal linear combination (ILC) algorithm using directional, scale-discretised wavelets --- Scale-discretised, directional wavelet ILC or SILC. Directional wavelets, when convolved with signals on the sphere, can separate the anisotropic filamentary structures which are characteristic of both the CMB and foregrounds. Extending previous component separation methods, which use the frequency, spatial and harmonic signatures of foregrounds to separate them from the cosmological background signal, SILC can additionally use morphological information in the foregrounds and CMB to better localise the cleaning algorithm. We test the method on Planck data and simulations, demonstrating consistency with existing component separation algorithms, and discuss how to optimise the use of morphological information by varying the number of directional wavelets as a function of spatial scale. We find that combining the use of directional and axisymmetric wavelets depending on scale could yield higher quality CMB temperature maps. Our results set the stage for the application of SILC to polarisation anisotropies through an extension to spin wavelets.Comment: 15 pages, 13 figures. Minor changes to match version published in MNRAS. Map products available at http://www.silc-cmb.or

A framework for testing isotropy with the cosmic microwave background

We present a new framework for testing the isotropy of the Universe using cosmic microwave background data, building on the nested-sampling ANICOSMO code. Uniquely, we are able to constrain the scalar, vector and tensor degrees of freedom alike; previous studies only considered the vector mode (linked to vorticity). We employ Bianchi type VII$_h$ cosmologies to model the anisotropic Universe, from which other types may be obtained by taking suitable limits. In a separate development, we improve the statistical analysis by including the effect of Bianchi power in the high-$\ell$, as well as the low-$\ell$, likelihood. To understand the effect of all these changes, we apply our new techniques to WMAP data. We find no evidence for anisotropy, constraining shear in the vector mode to $(\sigma_V/H)_0 < 1.7 \times 10^{-10}$ (95% CL). For the first time, we place limits on the tensor mode; unlike other modes, the tensor shear can grow from a near-isotropic early Universe. The limit on this type of shear is $(\sigma_{T,\rm reg}/H)_0 < 2.4 \times 10^{-7}$ (95% CL).Comment: 11 pages, 6 figures, v3: minor modifications to match version accepted by MNRA

How isotropic is the Universe?

A fundamental assumption in the standard model of cosmology is that the Universe is isotropic on large scales. Breaking this assumption leads to a set of solutions to Einstein's field equations, known as Bianchi cosmologies, only a subset of which have ever been tested against data. For the first time, we consider all degrees of freedom in these solutions to conduct a general test of isotropy using cosmic microwave background temperature and polarization data from Planck. For the vector mode (associated with vorticity), we obtain a limit on the anisotropic expansion of $(\sigma_V/H)_0 < 4.7 \times 10^{-11}$ (95% CI), which is an order of magnitude tighter than previous Planck results that used CMB temperature only. We also place upper limits on other modes of anisotropic expansion, with the weakest limit arising from the regular tensor mode, $(\sigma_{T,\rm reg}/H)_0<1.0 \times 10^{-6}$ (95% CI). Including all degrees of freedom simultaneously for the first time, anisotropic expansion of the Universe is strongly disfavoured, with odds of 121,000:1 against.Comment: 6 pages, 1 figure, v2: replaced with version accepted by PR

Spin-SILC: CMB polarisation component separation with spin wavelets

We present Spin-SILC, a new foreground component separation method that accurately extracts the cosmic microwave background (CMB) polarisation $E$ and $B$ modes from raw multifrequency Stokes $Q$ and $U$ measurements of the microwave sky. Spin-SILC is an internal linear combination method that uses spin wavelets to analyse the spin-2 polarisation signal $P = Q + iU$. The wavelets are additionally directional (non-axisymmetric). This allows different morphologies of signals to be separated and therefore the cleaning algorithm is localised using an additional domain of information. The advantage of spin wavelets over standard scalar wavelets is to simultaneously and self-consistently probe scales and directions in the polarisation signal $P = Q + iU$ and in the underlying $E$ and $B$ modes, therefore providing the ability to perform component separation and $E$-$B$ decomposition concurrently for the first time. We test Spin-SILC on full-mission Planck simulations and data and show the capacity to correctly recover the underlying cosmological $E$ and $B$ modes. We also demonstrate a strong consistency of our CMB maps with those derived from existing component separation methods. Spin-SILC can be combined with the pseudo- and pure $E$-$B$ spin wavelet estimators presented in a companion paper to reliably extract the cosmological signal in the presence of complicated sky cuts and noise. Therefore, it will provide a computationally-efficient method to accurately extract the CMB $E$ and $B$ modes for future polarisation experiments.Comment: 13 pages, 9 figures. Minor changes to match version published in MNRAS. Map products available at http://www.silc-cmb.org. Companion paper: arXiv:1605.01414 "Wavelet reconstruction of pure E and B modes for CMB polarisation and cosmic shear analyses" (B. Leistedt et al.

‘Learning for resilience’: Developing community capital through flood action groups in urban flood risk settings with lower social capital

© 2017 Elsevier Ltd The role of civil agency in preparing and adapting to changing risk is an increasingly critical element within devolved local flood risk management. However, effective civil agency for flood resilience needs to draw on, and if necessary develop, community capital. Community Action Groups form one model for local resilience building for flood risk, and one actively supported by some governments. This research evaluates the participatory model of flood group development involving horizontal support rather than top-down or bottom-up generation. The process involved nascent groups working with an NGO facilitator in the implementation of a set of processes framed in the context of ‘learning for resilience’ that supported flood group development in a situation of challenged social capital (lower socio-economic status; health issues, lack of previous flood experience) in the UK. The methodology involved repeat semi-structured interviews with flood group members and flood risk management (FRM) agencies who worked with them through the process, as well as observation of flood group meetings. Results outline how groups emerge from transient and disconnected communities, the value of local knowledge, evolving communication skills and agency, normalisation of group members within participatory processes, frustrations within these processes, group sustainability and FRM agency perspectives. Discussion then critiques the co-working/partnership model and assesses its implications for social ‘learning for resilience’ within challenged flood groups with variable social capital. The authors propose a framework (’The 6Ss’) for anticipating concerns or barriers within such participatory processes as a guide to future local urban DRR practice

Sustainable flood memory: Remembering as resilience

© 2016, © The Author(s) 2016. This article proposes the concept of sustainable flood memory as a critical and agentic form of social and cultural remembering of learning to live with floods. Drawing upon research findings that use the 2007 floods in the South West of England as a case study, we explore and analyse the media representations of flooding, the role of community and communicative memory of past floods for fostering resilience, and map emotional and affective responses to floods. To approach flooding in this way is critical to understanding how communities engage in memory practices (remembering and strategically forgetting) in order to cope with environmental changes. Moreover, the article embraces a research design and strategy in which ‘memory studies’ is brought into a conversation not only with geography (mental maps), social sciences and flood risk management policy but also with stakeholders and communities who collect, archive and remember flood histories in their respective regions