Recent philosophy and the fiction/non-fiction distinction

Purpose - The purpose of this paper is to provide an overview of recent philosophical argument concerning the distinction between fiction and non-fiction. Design/methodology/approach - A critical view of the literature. Findings - A consensus that had emerged that defined fiction in terms of the imagination, and imagination in terms of its functional role, has recently been questioned. Research limitations/implications - The overview was written by a contributor to the field, and so may be considered partial. Practical implications - There might be some implications regarding the ways books are classified. Originality/value - The paper is not original, in that it puts forward points made elsewhere, however it is a completely up-to-date review of the field

Holonomy and gravitomagnetism

We analyze parallel transport of a vector field around an equatorial orbit in Kerr and stationary axisymmetric spacetimes that are reflection symmetric about their equatorial planes. As in Schwarzschild spacetime, there is a band structure of holonomy invariance. The new feature introduced by rotation is a shift in the timelike component of the vector, which is the holonomic manifestation of the gravitomagnetic clock effect.Comment: 6 pages Latex (IOP style); new results covering stationary axisymmetric spacetimes; version accepted for Class. Quant. Gra

Inhomogeneous universes in observational coordinates

Isotropic inhomogeneous dust universes are analysed via observational coordinates based on the past light cones of the observer's galactic worldline. The field equations are reduced to a single first--order {\sc ode} in observational variables on the past light cone, completing the observational integration scheme. This leads naturally to an explicit exact solution which is locally nearly homogeneous (i.e. {\sc frw}), but at larger redshift develops inhomogeneity. New observational characterisations of homogeneity ({\sc frw} universes) are also given.Comment: 17 pages LaTeX, no figures; to appear in Classical and Quantum Gravit

Aesthetic Relativism

As Hume remarks, the view that aesthetic evaluations are ‘subjective’ is part of common sense—one certainly meets it often enough in conversation. As philosophers, we can distinguish the one sense of the claim (‘aesthetic evaluations are mind- dependent’) from another (‘aesthetic evaluations are relative’). A plausible reading of the former claim (‘some of the grounds of some aesthetic evaluations are response- dependent’) is true. This paper concerns the latter claim. It is not unknown, or even unexpected, to find people who believe that aesthetic evaluations are culturally relative, or even agent-relative. A cultural relativist would hold that there is no way to adjudicate an apparent disagreement between, say, a Japanese critic who finds Wright of Derby clunky and unsubtle, and a British critic who finds Utamaro’s flower pictures overly pretty and sentimental

Comparing different formulations of non-linear cosmological perturbation theory

We compare and contrast two different metric based formulations of non- linear cosmological perturbation theory: the MW2009 approach in [K. A. Malik and D. Wands, Phys. Rept. 475 (2009), 1.] following Bardeen and the recent approach of the paper KN2010 [K. Nakamura, Advances in Astronomy 2010 (2010), 576273]. We present each formulation separately. In the MW2009 approach, one considers the gauge transformations of perturbative quantities, choosing a gauge by requiring that certain quantities vanish, rendering all other variables gauge invariant. In the KN2010 formalism, one decomposes the metric tensor into a gauge variant and gauge invariant part from the outset. We compare the two approaches in both the longitudinal and uniform curvature gauges. In the longitudinal gauge, we find that Nakamura's gauge invariant variables correspond exactly to those in the longitudinal gauge (i.e., for scalar perturbations, to the Bardeen potentials), and in the uniform curvature gauge we obtain the usual relationship between gauge invariant variables in the flat and longitudinal gauge. Thus, we show that these two approaches are equivalent.Comment: 25 pages, iopar

Transverse frames for Petrov type I spacetimes: a general algebraic procedure

We develop an algebraic procedure to rotate a general Newman-Penrose tetrad in a Petrov type I spacetime into a frame with Weyl scalars $\Psi_{1}$ and $\Psi_{3}$ equal to zero, assuming that initially all the Weyl scalars are non vanishing. The new frame highlights the physical properties of the spacetime. In particular, in a Petrov Type I spacetime, setting $\Psi_{1}$ and $\Psi_{3}$ to zero makes apparent the superposition of a Coulomb-type effect $\Psi_{2}$ with transverse degrees of freedom $\Psi_{0}$ and $\Psi_{4}$.Comment: 10 pages, submitted to Classical Quantum Gravit

Stress effects in structure formation

Residual velocity dispersion in cold dark matter induces stresses which lead to effects that are absent in the idealized dust model. A previous Newtonian analysis showed how this approach can provide a theoretical foundation for the phenomenological adhesion model. We develop a relativistic kinetic theory generalization which also incorporates the anisotropic velocity dispersion that will typically be present. In addition to density perturbations, we consider the rotational and shape distortion properties of clustering. These quantities together characterize the linear development of density inhomogeneity, and we find exact solutions for their evolution. As expected, the corrections are small and arise only in the decaying modes, but their effect is interesting. One of the modes for density perturbations decays less rapidly than the standard decaying mode. The new rotational mode generates precession of the axis of rotation. The new shape modes produce additional distortion that remains frozen in during the subsequent (linear) evolution, despite the rapid decay of the terms that caused it.Comment: significantly improved discussion of kinetic theory of CDM velocity dispersion; to appear Phys. Rev.