Anomalies, D-flatness and Small Instantons

Recently, Witten has proposed a mechanism for symmetry enhancement in $SO(32)$ heterotic string theory, where the singularity obtained by shrinking an instanton to zero size is resolved by the appearance of an $Sp(1)$ gauge symmetry. In this short letter, we consider spacetime constraints from anomaly cancellation in six dimensions and D-flatness and demonstrate a subtlety which arises in the moduli space when many instantons are shrunk to zero size.Comment: 8 pages, harvma

London in space and time: Peter Ackroyd and Will Self

Copyright @ 2013 the author. This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Unported License.This paper explores the treatment of London by two authors who are profoundly influenced by the concept of the power of place and the nature of urban space. The works of Peter Ackroyd, whose writings embody, according to Onega (1997, p. 208) “[a] yearning for mythical closure” where London is “a mystic centre of power” – spiritual, transhistorical and cultural – are considered alongside those of Will Self, who explores the city’s psychogeography as primarily a political, economic and cultural artefact. The paper draws on original interviews undertaken by the author with Ackroyd and Self. Both authors’ works are available for literary study during the 16-19 phase in the UK, and this paper explores how personal delineations of the urban environment are shaped by space and language. It goes on to consider how authors’ and students’ personal understandings of space and place can be used as pedagogical and theoretical lenses to “read” the city in the 16-19 literature classroom

Education, Globalisation and the Role of Comparative Education

Comparative education has traditionally meant the study of national education systems. But how far is this approach valid today? Doesn’t the ‘decline’ of the nation state make national systems obsolete? Isn’t the very idea of a ‘system’ anachronistic in a world of market triumphalism and global disorganization? The purpose of this article is to explore how globalisation is changing education and the implication of this for comparative study. Why study education systems and why study national education systems in particular? What else should comparativists study, and how? What defines the field of comparative education? These questions are approached first historically and secondly methodologically

Effects of D-instantons

Scattering of fundamental states of type IIB supergravity and superstring theory is discussed at low orders in perturbation theory in the background of a D-instanton. The integration over fermionic zero modes in both the low energy supergravity and in the string theory leads to explicit nonperturbative terms in the effective action. These include a single instanton correction to the known tree-level and one-loop $R^4$ interactions. The `spectrum' of multiply-charged D-instantons is deduced by T-duality in nine dimensions from multiply-wound world-lines of marginally-bound D-particles. This, and other clues, lead to a conjectured SL(2,Z) completion of the $R^4$ terms which suggests that they are not renormalized by perturbative corrections in the zero-instanton sector beyond one loop. The string theory unit-charged D-instanton gives rise to point-like effects in fixed-angle scattering, raising unresolved issues concerning distance scales in superstring theory.Comment: 31 pages, 6 figures, Latex, Reference added, corrected coefficients in expansion of generalized Eisenstein series in equation 66 now agree with hep-th/970414

An Analysis of Four-quark Energies in SU(2) Lattice Monte Carlo using the Flux-tube Symmetry:

Energies of four-quark systems calculated by the static quenched SU(2) lattice Monte Carlo method are analyzed in $2\times 2$ bases for square, rectangle, tilted rectangle, linear and quadrilateral geometry configurations and in $3\times 3$ bases for a non-planar geometry configuration. For small interquark distances, a lattice effect is taken into account by considering perimeter dependent terms which are characterized by the cubic symmetry. It is then found that a parameter $f$ - that can be identified as a gluon field overlap factor - is rather well described by the form $exp(-[b_sE{\cal A}+\sqrt{b_s}F{\cal P}])$, where ${\cal A}$ and ${\cal P}$ are the area and perimeter mainly defined by the positions of the four quarks, $b_s$ is the string constant in the 2-quark potentials and $E,F$ are constants.Comment: (19 pages of Latex - 1 page of figures not included - sent on request). Preprint HU-TFT-94-2

Infinite-genus surfaces and the universal Grassmannian

Correlation functions can be calculated on Riemann surfaces using the operator formalism. The state in the Hilbert space of the free field theory on the punctured disc, corresponding to the Riemann surface, is constructed at infinite genus, verifying the inclusion of these surfaces in the Grassmannian. In particular, a subset of the class of $O_{HD}$ surfaces can be identified with a subset of the Grassmannian. The concept of flux through the ideal boundary is used to study the connection between infinite-genus surface and the domain of string perturbation theory. The different roles of effectively closed surfaces with Dirichlet boundaries in a more complete formulation of string theory are identified.Comment: 14 pages, TeX, 3 figures. The July, 1995 version contains an expanded introductio