Chiral quark dynamics and topological charge: The role of the Ramond-Ramond U(1) Gauge Field in Holographic QCD

The Witten-Sakai-Sugimoto construction of holographic QCD in terms of D4 color branes and D8 flavor branes in type IIA string theory is used to investigate the role of topological charge in the chiral dynamics of quarks in QCD. The QCD theta term arises from a compactified 5-dimensional Chern-Simons term on the D4 branes. This term couples the QCD topological charge to the Ramond-Ramond $U(1)$ gauge field of IIA string theory. The nonzero topological susceptibility of pure-glue QCD can be attributed to the presence of D6 branes, which constitute magnetic sources of the RR gauge field. The topological charge of QCD is required, by an anomaly inflow argument, to coincide in space-time with the intersection of the D6 branes and the D4 color branes. This clarifies the relation between D6 branes and the coherent, codimension-one topological charge membranes observed in QCD Monte Carlo calculations. Using open-string/closed-string duality, we interpret a quark loop (represented by a D4-D8 open string loop) in terms of closed-string exchange between color and flavor branes. The role of the RR gauge field in quark-antiquark annihilation processes is discussed. RR exchange in the s-channel generates a 4-quark contact term which produces an $\eta'$ mass insertion and provides an explanation for the observed spin-parity structure of the OZI rule. The $(\log {\rm Det\;U})^2$ form of the $U(1)$ anomaly emerges naturally. RR exchange in the t-channel of the $q\overline{q}$ scattering amplitude produces a Nambu-Jona Lasinio interaction which may provide a mechanism for spontaneous breaking of $SU(N_f)\times SU(N_f)$.Comment: 20 pages, 7 figure

Modernism and the periodical scene in 1915 and today

This article considers the Portuguese magazine Orpheu (1915) within the wider context of periodicals within modernism, drawing upon work carried out by the Modernist Magazines Project. It does this by considering such crucial features of the modernist magazine as its chronology and its geographical reach, and also points to new methods of analysing the materiality of magazines. By understanding the broader milieu of the modernist magazine we gain a clearer sense of how Orpheu can begin to be placed within the cultural field of the modernism

QED2 as a testbed for interpolations between quenched and full QCD

Lattice QED2 with the Wilson formulation of fermions is used as a convenient model system to study artifacts of the quenched approximation on a finite lattice. The quenched functional integral is shown to be ill-defined in this system as a consequence of the appearance of exactly real modes for physical values of the fermion mass. The location and frequency of such modes is studied as a function of lattice spacing, lattice volume, topological charge and improved action parameters. The efficacy of the recently proposed modified quenched approximation is examined, as well as a new approach to the interpolation from the quenched to full dynamical theory employing a truncated form of the fermion determinant.Comment: Talk presented by A. Duncan at LATTICE97 (theoretical developments

‘A True Magic Chamber’: The Public Face of the Modernist Bookshop

This article explores the role of bookshops in the construction of a public for modernism and analyses a number of bookshops committed to promoting modernist culture, such as those run by Sylvia Beach (Shakespeare and Company), Adrienne Monnier (La Maison des Amis des Livres), and Frances Steloff (Gotham Book Mart). It also considers how the bookshop is a fulcrum between commerce and culture, a key issue for contemporary modernist studies, and discusses aspects of bookshop culture that seem to operate ‘beyond’ the market. One example is that of We Moderns, a catalogue issued by the Gotham Book Mart in 1940 and which represents a fascinating example of the print culture of the modernist bookshop. Drawing upon the work of Mark Morrisson and Lawrence Rainey, the article also evaluates the position of the bookshop within debates around modernism and the public sphere

Of dust and rubber: rereading Howards End

The article starts by reviewing what has been called ‘the flux of modernity’ that it then goes on to examine in terms of the connection of different forms of space to explore the multiple geographies of modernity. The article borrows from the field of anthropocene studies, thing theory and new materialism to investigate how Howards End thinks through the connections between micro- and macro-levels of materiality. It investigates things (such as dust and rubber) as actants and addresses Forster’s ecological concerns which leads to a re-reading of movement in terms of energy in relation to fossil-fuel capitalism. L’article commence par passer en revue ce que l’on a appelé ‘le flux de la modernité’ qu’il examine ensuite en termes de connexion de différentes formes d’espace pour explorer les multiples géographies de la modernité. L’article emprunte au domaine des études environnementales, de la théorie des choses et du nouveau matérialisme pour étudier comment Howards End travaille les connexions entre les micro- et les macro-niveaux de matérialité. Il étudie les choses en tant qu’actants et met au jour les préoccupations écologiques de Forster, pour proposer à une relecture du mouvement en tant qu’associé à l’énergie et aussi au capitalisme fondé sur la consommation des combustibles fossiles