The Populations of Comet-Like Bodies in the Solar system

A new classification scheme is introduced for comet-like bodies in the Solar system. It covers the traditional comets as well as the Centaurs and Edgeworth-Kuiper belt objects. At low inclinations, close encounters with planets often result in near-constant perihelion or aphelion distances, or in perihelion-aphelion interchanges, so the minor bodies can be labelled according to the planets predominantly controlling them at perihelion and aphelion. For example, a JN object has a perihelion under the control of Jupiter and aphelion under the control of Neptune, and so on. This provides 20 dynamically distinct categories of outer Solar system objects in the Jovian and trans-Jovian regions. The Tisserand parameter with respect to the planet controlling perihelion is also often roughly constant under orbital evolution. So, each category can be further sub-divided according to the Tisserand parameter. The dynamical evolution of comets, however, is dominated not by the planets nearest at perihelion or aphelion, but by the more massive Jupiter. The comets are separated into four categories -- Encke-type, short-period, intermediate and long-period -- according to aphelion distance. The Tisserand parameter categories now roughly correspond to the well-known Jupiter-family comets, transition-types and Halley-types. In this way, the nomenclature for the Centaurs and Edgeworth-Kuiper belt objects is based on, and consistent with, that for comets.Comment: MNRAS, in press, 11 pages, 6 figures (1 available as postscript, 5 as gif). Higher resolution figures available at http://www-thphys.physics.ox.ac.uk/users/WynEvans/preprints.pd

A high resolution millimetre and submillimetre study of W3

The continuum bolometer receiver on the James Clerk Maxwell telescope has been used to map the dense core of the star formation region W3 with a spatial resolution of 15-20 arcsec. At 350 and 800 μm, the region appears as two principal peaks around the known IR sources IRS4 and IRS5, while at 1100 μm, a further peak is noted which is interpreted as being due to free-free emission around IRS2. Taking into account the free-free contribution to the intensity, the continuum dust emission from the region is found to be consistent with optically thin emission at all of the three wavelengths considered. Values for the dust optical depth, hydrogen column density, mass, and central density have been obtained for each of the main peaks

Linked and knotted synthetic magnetic fields

We show that the realisation of synthetic magnetic fields via light-matter coupling in the Lambda-scheme implements a natural geometrical construction of magnetic fields, namely as the pullback of the area element of the sphere to Euclidean space via certain maps. For suitable maps, this construction generates linked and knotted magnetic fields, and the synthetic realisation amounts to the identification of the map with the ratio of two Rabi frequencies which represent the coupling of the internal energy levels of an ultracold atom. We consider examples of maps which can be physically realised in terms of Rabi frequencies and which lead to linked and knotted synthetic magnetic fields acting on the neutral atomic gas. We also show that the ground state of the Bose-Einstein condensate may inherit topological properties of the synthetic gauge field, with linked and knotted vortex lines appearing in some cases.Comment: 8 pages, 4 figures, supplementary videos attached. Comments welcom

Cretaceous-to-recent record of elevated 3He/4He along the Hawaiian-Emperor volcanic chain

Helium isotopes are a robust geochemical tracer of a primordial mantle component in hot spot volcanism. The high 3He/4He (up to 35 RA, where RA is the atmospheric 3He/4He ratio of 1.39 × 10−6) of some Hawaiian Island volcanism is perhaps the classic example. New results for picrites and basalts from the Hawaiian-Emperor seamount chain indicate that the hot spot has produced high 3He/4He lavas for at least the last 76 million years. Picrites erupted at 76 Ma have 3He/4He (10–14 RA), which is at the lower end of the range for the Hawaiian Islands but still above the range of modern mid-ocean ridge basalt (MORB; 6–10 RA). This was at a time when hot spot volcanism was occurring on thin lithosphere close to a spreading ridge and producing lava compositions otherwise nearly indistinguishable from MORB. After the hot spot and spreading center diverged during the Late Cretaceous, the hot spot produced lavas with significantly higher 3He/4He (up to 24 RA). Although 3He/4He ratios stabilized at relatively high values by 65 Ma, other chemical characteristics such as La/Yb and 87Sr/86Sr did not reach and stabilize at Hawaiian-Island-like values until ~45 Ma. Our limited 3He/4He record for the Hawaiian hot spot shows a poor correlation with plume flux estimates (calculated from bathymetry and residual gravity anomalies [Van Ark and Lin, 2004]). If 3He is a proxy for the quantity of primordial mantle material within the plume, then the lack of correlation between 3He/4He and calculated plume flux suggests that variation in primordial mantle flux is not the primary factor controlling total plume flux

Quantum optical signal processing in diamond

Controlling the properties of single photons is essential for a wide array of emerging optical quantum technologies spanning quantum sensing, quantum computing, and quantum communications. Essential components for these technologies include single photon sources, quantum memories, waveguides, and detectors. The ideal spectral operating parameters (wavelength and bandwidth) of these components are rarely similar; thus, frequency conversion and spectral control are key enabling steps for component hybridization. Here we perform signal processing of single photons by coherently manipulating their spectra via a modified quantum memory. We store 723.5 nm photons, with 4.1 nm bandwidth, in a room-temperature diamond crystal; upon retrieval we demonstrate centre frequency tunability over 4.2 times the input bandwidth, and bandwidth modulation between 0.5 to 1.9 times the input bandwidth. Our results demonstrate the potential for diamond, and Raman memories in general, to be an integrated platform for photon storage and spectral conversion.Comment: 6 pages, 4 figure

Storage and retrieval of ultrafast single photons using a room-temperature diamond quantum memory

We report the storage and retrieval of single photons, via a quantum memory, in the optical phonons of room-temperature bulk diamond. The THz-bandwidth heralded photons are generated by spontaneous parametric downconversion and mapped to phonons via a Raman transition, stored for a variable delay, and released on demand. The second-order correlation of the memory output is $g^{(2)}(0) = 0.65 \pm 0.07$, demonstrating preservation of non-classical photon statistics throughout storage and retrieval. The memory is low-noise, high-speed and broadly tunable; it therefore promises to be a versatile light-matter interface for local quantum processing applications.Comment: 6 pages, 4 figure