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The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (~2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.
Cellular networks are ubiquitous in nature. Most engineered materials are polycrystalline microstructures composed of a myriad of small grains separated by grain boundaries, thus comprising cellular networks. The recently discovered grain boundary character distribution (GBCD) is an empirical distribution of the relative length (in 2D) or area (in 3D) of interface with a given lattice misorientation and normal. During the coarsening, or growth, process, an initially random grain boundary arrangement reaches a steady state that is strongly correlated to the interfacial energy density. In simulation, if the given energy density depends only on lattice misorientation, then the steady state GBCD and the energy are related by a Boltzmann distribution. This is among the simplest non-random distributions, corresponding to independent trials with respect to the energy. Why does such simplicity emerge from such complexity? Here we describe an entropy based theory which suggests that the evolution of the GBCD satisfies a Fokker-Planck Equation, an equation whose stationary state is a Boltzmann distribution.
This book is concerned with the research conducted in the late 1970s and early 1980s in the theory of commutative Neotherian rings. It consists of articles by invited speakers at the Symposium of Commutative Algebra held at the University of Durham in July 1981; these articles are all based on lectures delivered at the Symposium. The purpose of this book is to provide a record of at least some aspects of the Symposium, which several of the world leaders in the field attended. Several articles are included which provide surveys, incorporating historical perspective, details of progress made and indications of possible future lines of investigation. The book will be of interest to scholars of commutative and local algebra.
EMU is a wide-field radio continuum survey planned for the new Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The primary goal of EMU is to make a deep (rms ∼ 10 μJy/beam) radio continuum survey of the entire Southern sky at 1.3 GHz, extending as far North as +30° declination, with a resolution of 10 arcsec. EMU is expected to detect and catalogue about 70 million galaxies, including typical star-forming galaxies up to z ∼ 1, powerful starbursts to even greater redshifts, and active galactic nuclei to the edge of the visible Universe. It will undoubtedly discover new classes of object. This paper defines the science goals and parameters of the survey, and describes the development of techniques necessary to maximise the science return from EMU.
This second edition of a successful graduate text provides a careful and detailed algebraic introduction to Grothendieck's local cohomology theory, including in multi-graded situations, and provides many illustrations of the theory in commutative algebra and in the geometry of quasi-affine and quasi-projective varieties. Topics covered include Serre's Affineness Criterion, the Lichtenbaum–Hartshorne Vanishing Theorem, Grothendieck's Finiteness Theorem and Faltings' Annihilator Theorem, local duality and canonical modules, the Fulton–Hansen Connectedness Theorem for projective varieties, and connections between local cohomology and both reductions of ideals and sheaf cohomology. The book is designed for graduate students who have some experience of basic commutative algebra and homological algebra and also experts in commutative algebra and algebraic geometry. Over 300 exercises are interspersed among the text; these range in difficulty from routine to challenging, and hints are provided for some of the more difficult ones.
Graded local cohomology theory has played a substantial rôle in the study of Rees rings and associated graded rings of proper ideals in local rings. We do not have enough space in this book to include all we would like about the applications of local cohomology to this area, and so we have decided to select a small portion of the theory which gives some idea of the flavour. The part we have chosen to present in this chapter concerns links between the theory of reductions of ideals in local rings and the concept of Castelnuovo regularity, discussed in Chapter 16. The highlight will be a theorem of L. T. Hoa which asserts that, if b is a proper ideal in a local ring having infinite residue field, then there exist t0 ∈ ℕ and c ∈ ℕ0 such that, for all t > t0 and every minimal reduction a of bt, the reduction number ra(bt) of bt with respect to a is equal to c. This statement of Hoa's Theorem is satisfyingly simple, and makes no mention of local cohomology, and yet Hoa's proof, which we present towards the end of this chapter, makes significant use of graded local cohomology.
Throughout this chapter, all graded rings and modules are to be understood to be ℤ-graded, and all polynomial rings R[X1, …, Xt] (and R[T]) over R are to be understood to be (positively) ℤ-graded so that each indeterminate has degree 1 and deg a = 0 for all a ∈ R \ {0}.
In this last chapter we shall develop the links between local cohomology and the cohomology of quasi-coherent sheaves over certain Noetherian schemes. Here we shall assume for the first time that the reader has some basic knowledge about schemes and sheaves: our reference for these topics is Hartshorne's book [30]. The central idea in this chapter is to extend our earlier relations in 2.3.2 and 15.1.3 between ideal transforms and rings of regular functions on varieties to quasi-coherent sheaves over certain Noetherian schemes. We shall be very concerned with a generalization of the ‘Deligne Isomorphism’ (see [30, Chapter III, Exercise 3.7, p. 217]) which links the group of sections (over an open subset) of an induced sheaf on an affine scheme with an ideal transform. More precisely, let denote the sheaf induced by an R-module M on the affine scheme Spec(R), and let U = Spec(R) \ Var(a), where a ⊂ R; then the group of sections Γ (U,) is isomorphic to the ideal transform Da(M). We shall use standard techniques involving negative strongly connected sequences of functors to extend this Deligne Isomorphism, and our generalization of it, to produce the Deligne Correspondence 20.3.11. This correspondence provides connections between higher cohomology groups of induced sheaves on the one hand, and local cohomology modules on the other.
We shall also examine the case when R is graded in some detail. Here the central result for us is the Serre–Grothendieck Correspondence 20.3.15, which we shall also derive from the Deligne Isomorphism by standard ‘connected sequence’ arguments.