On absolute moments of characteristic polynomials of a certain class of complex random matrices

Integer moments of the spectral determinant $|\det(zI-W)|^2$ of complex random matrices $W$ are obtained in terms of the characteristic polynomial of the Hermitian matrix $WW^*$ for the class of matrices $W=AU$ where $A$ is a given matrix and $U$ is random unitary. This work is motivated by studies of complex eigenvalues of random matrices and potential applications of the obtained results in this context are discussed.Comment: 41 page, typos correcte

Two-dimensional superstrings and the supersymmetric matrix model

We present evidence that the supersymmetric matrix model of Marinari and Parisi represents the world-line theory of N unstable D-particles in type II superstring theory in two dimensions. This identification suggests that the matrix model gives a holographic description of superstrings in a two-dimensional black hole geometry.Comment: 22 pages, 2 figures; v2: corrected eqn 4.6; v3: corrected appendices and discussion of vacua, added ref

Nonhermitian Supersymmetric Partition Functions: the case of one bosonic flavor

We discuss the supersymmetric formulation of the nonhermitian $\beta = 2$ random matrix partition function with one bosonic flavor. This partition function is regularized by adding one conjugate boson and fermion each. A supersymmetric nonlinear $\sigma$-model for the resulting Goldstone degrees of freedom is obtained using symmetry arguments only. For a Gaussian probability distribution the same results are derived using superbosonization and the complex orthogonal polynomial method. The symmetry arguments apply to any model with the same symmetries and a mass gap, and demonstrate the universality of the nonlinear $\sigma$-model.Comment: 17 pages, 0 figures. Section II extended. Version to appear in Nucl.Phys.

Network models for localisation problems belonging to the chiral symmetry classes

We consider localisation problems belonging to the chiral symmetry classes, in which sublattice symmetry is responsible for singular behaviour at a band centre. We formulate models which have the relevant symmetries and which are generalisations of the network model introduced previously in the context of the integer quantum Hall plateau transition. We show that the generalisations required can be re-expressed as corresponding to the introduction of absorption and amplification into either the original network model, or the variants of it that represent disordered superconductors. In addition, we demonstrate that by imposing appropriate constraints on disorder, a lattice version of the Dirac equation with a random vector potential can be obtained, as well as new types of critical behaviour. These models represent a convenient starting point for analytic discussions and computational studies, and we investigate in detail a two-dimensional example without time-reversal invariance. It exhibits both localised and critical phases, and band-centre singularities in the critical phase approach more closely in small systems the expected asymptotic form than in other known realisations of the symmetry class.Comment: 14 pages, 15 figures, Submitted to Physical Review

Dijet production in √s = 7 TeV pp collisions with large rapidity gaps at the ATLAS experiment

A 6.8 nb−¹ sample of pp collision data collected under low-luminosity conditions at √s = 7 TeV by the ATLAS detector at the Large Hadron Collider is used to study diffractive dijet production. Events containing at least two jets with pT > 20 GeV are selected and analysed in terms of variables which discriminate between diffractive and non-diffractive processes. Cross sections are measured differentially in ΔηF, the size of the observable forward region of pseudorapidity which is devoid of hadronic activity, and in an estimator, ξ˜, of the fractional momentum loss of the proton assuming single diffractive dissociation (pp → p X). Model comparisons indicate a dominant non-diffractive contribution up to moderately large ηF and small ξ˜, with a diffractive contribution which is significant at the highest ΔηF and the lowest ξ˜. The rapidity-gap survival probability is estimated from comparisons of the data in this latter region with predictions based on diffractive parton distribution functions

Information and digital literacies; a review of concepts

A detailed literature reviewing, analysing the multiple and confusing concepts around the ideas of information literacy and digital literacy at the start of the millennium. The article was well-received, and is my most highly-cited work, with over 1100 citations

Facial appearance is a cue to oestrogen levels in women

Although many accounts of facial attractiveness propose that femininity in women's faces indicates high levels of oestrogen, there is little empirical evidence in support of this assumption. Here, we used assays for urinary metabolites of oestrogen (oestrone-3-glucuronide, E1G) and progesterone (pregnanediol-3-glucuronide, P3G) to investigate the relationship between circulating gonadal hormones and ratings of the femininity, attractiveness and apparent health of women's faces. Positive correlations were observed between late follicular oestrogen and ratings of femininity, attractiveness and health. Positive correlations of luteal progesterone and health and attractiveness ratings were marginally significant. Ratings of facial attributions did not relate to hormone levels for women wearing make-up when photographed. There was no effect of sex of rater on the relationships between oestrogen and ratings of facial appearance. These findings demonstrate that female facial appearance holds detectable cues to reproductive health that are considered attractive by other people