Holographic QCD & Perfection

A holographic description of chiral symmetry breaking in the pattern of QCD is reviewed. D7 brane probes are used to include quark fields in a simple non-supersymmetric deformation of the AdS/CFT Correspondence. The axial symmetry breaking is realized geometrically and the quark condensate and meson masses are computable. Surprisingly, treating the model as a description of QCD works quantitatively at the 15% level. Models of this AdS/QCD type typically have a strongly coupled, conformal UV regime that is far from QCD. To systematically move closer to QCD, we propose cutting out the large radius gravitational description and matching operators and couplings at a finite UV cut off in the spirit of a perfect lattice action. A simple example is discussed.Comment: 8 pages, 5 figures, talk presented at SCGT0

The Impact of BSE in Cattle on High-Nature Value Conservation Sites in England

The BSE (mad-cow disease) crisis has had severe impacts on the beef sector in English agriculture, evident primarily through the low prices since experienced by farm businesses for beef cattle at market and the European Union (EU) ban on British beef exports. However, the extent to which resultant changes in beef cattle enterprises have affected conservation sites of high-nature value is less well-known. This paper reports on empirical research conducted into beef grazing on 50 Sites of Special Scientific Interest (SSSIs), England's best protected conservation areas. The crisis is found to have caused localized problems with overgrazing of Sites due to restrictions in stock movements after the crisis, undergrazing as farmers rationalize their beef enterprises and more subtle ecological changes associated with grazing habitats of different species and breeds of livestock. Direct impacts are not always clear, but BSE is undoubtedly making the delivery of nature conservation objectives more difficult in England

A Holographic Study of the Gauged NJL Model

The Nambu Jona-Lasinio model of chiral symmetry breaking predicts a second order chiral phase transition. If the fermions in addition have non-abelian gauge interactions then the transition is expected to become a crossover as the NJL term enhances the IR chiral symmetry breaking of the gauge theory. We study this behaviour in the holographic Dynamic AdS/QCD description of a non-abelian gauge theory with the NJL interaction included using Witten's multi-trace prescription. We study the behaviour of the mesonic spectrum as a function of the NJL coupling and the ratio of the UV cut off scale to the dynamical scale of the gauge theory.Comment: 5 pages, 9 figures, added figur

Hyper-Scaling Relations in the Conformal Window from Dynamic AdS/QCD

Dynamic AdS/QCD is a holographic model of strongly coupled gauge theories with the dynamics included through the running anomalous dimension of the quark bilinear, gamma. We apply it to describe the physics of massive quarks in the conformal window of SU(N_c) gauge theories with N_f fundamental flavours, assuming the perturbative two loop running for gamma. We show that to find regular, holographic, renormalization group flows in the infra-red the decoupling of the quark flavours at the scale of the mass is important and enact it through suitable boundary conditions when the flavours become on shell. We can then compute the quark condensate and the mesonic spectrum (M_rho, M_pi, M_sigma) and decay constants. We compute their scaling dependence on the quark mass for a number of examples. The model matches perturbative expectations for large quark mass and naive dimensional analysis (including the anomalous dimensions) for small quark mass. The model allows study of the intermediate regime where there is an additional scale from the running of the coupling and we present results for the deviation of scalings from assuming only the single scale of the mass.Comment: 12 pages, 26 figures, new references adde

Cheese Makers are Always Women: Gendered Representations of Farm Life in the Agricultural Press

Drawing upon the 'Farmlife' pages of Farmer's Weekly, the most significant farming publication in the UK, this paper assesses the ways in which gender identities in farming are represented by its text and images. Lead articles from 1976 and 1996 issues of Farmlife are taken as the research focus to determine how representations have altered in line with restructuring of the agricultural industry. Reference is made to Connell's (1987) notions of hegemonic masculinity and emphasised femininity to inform the analysis about the ways in which these gender identities are (re)produced through the British farming media. A simple typology is derived from the articles which assists in revealing a remarkable degree of consistency in the portrayal of gender identities over time. The findings augment evidence from international research suggesting that dominant gender identities within agriculture are being perpetuated through the farming media. The implications of this are highlighted and suggestions made for research with the consumers of these media products

Holographic modelling of a light technidilaton

We present a simplified holographic model of chiral symmetry breaking in gauge theory. The chiral condensate is represented by a single scalar field in AdS, with the gauge dynamics input through radial dependence of its mass, representing the running of the anomalous dimension of the qbar q operator. We discuss simple examples of the chiral transition out of the conformal window when the infrared value of the anomalous dimension, \gamma_m, is tuned to one (equivalently the AdS-scalar mass squared is tuned to the Breitenlohner-Freedman bound of -4). The output of the model are the masses of the $\bar{q} q$ scalar meson bound states. We show in an explicit example that if the gradient of the running of the anomalous dimension falls to zero at the scale where the BF bound violation occurs, so that the theory becomes near conformal, then the theory possesses a techni-dilaton state that is parametrically lighter than the dynamically generated quark mass. Indeed the full spectrum of excited meson states also become light (relative to the techni-quark mass) as they approach a conformal spectrum.Comment: 8 pages, 8 pdf figures, added discussion of Fig 3 and new reference

Holographic Nambu Jona-Lasinio Interactions

NJL interactions are introduced into the D3/ probe D7 system using Witten's double trace operator prescription which includes the operator as a classical term in the effective potential. In the supersymmetric system they do not induce chiral symmetry breaking which we attribute to the flat effective potential with quark mass in the supersymmetric theory. If additional supersymmetry breaking is introduced then standard NJL behaviour is realized. In examples where chiral symmetry breaking is not preferred such as with a B field plus an IR cut off chiral condensation is triggered by the NJL interaction at a second order transition after a finite critical coupling. If the model already contains chiral symmetry breaking, for example in the B field case with no IR cut off, then the NJL interaction enhances the quark mass at all values of the NJL coupling. We also consider the system at finite temperature: the temperature discourages condensation but when combined with a magnetic field we find regions of parameter space where the NJL interaction triggers a first order chiral transition above a critical coupling.Comment: 7 pages, 6 figure