Excitation of the molecular gas in the nuclear region of M82

We present high-resolution HIFI spectroscopy of the nucleus of the archetypical starburst galaxy M 82. Six ^(12)CO lines, 2 ^(13)CO lines and 4 fine-structure lines have been detected. Besides showing the effects of the overall velocity structure of the nuclear region, the line profiles also indicate the presence of multiple components with different optical depths, temperatures, and densities in the observing beam. The data have been interpreted using a grid of PDR models. It is found that the majority of the molecular gas is in low density (n = 10^(3.5) cm^(-3)) clouds, with column densities of N_H = 10^(21.5) cm^(-2) and a relatively low UV radiation field (G_0 = 10^2). The remaining gas is predominantly found in clouds with higher densities (n = 10^5 cm^(-3)) and radiation fields (G_0 = 10^(2.75)), but somewhat lower column densities (N_H = 10^(21.2) cm^(-2)). The highest J CO lines are dominated by a small (1% relative surface filling) component, with an even higher density (n = 10^6 cm^(-3)) and UV field (G_0 = 10^(3.25)). These results show the strength of multi-component modelling for interpretating the integrated properties of galaxies

An evaluation of linear acoustic theory for a hovering rotor

Linear acoustic calculations are compared with previously reported data for a small-scale hovering rotor operated at high tip Mach numbers. A detailed calculated description of the distributions of blade surface pressure and shear stress due to skin friction is presented. The noise due to skin friction and loading, in the rotor disk plane, is small compared to thickness noise. The basic conclusions of Boxwell et al about the importance of nonlinear effects are upheld. Some approximations involved in the current theories for the inclusion of nonlinear effects are discussed. Using a model nonlinear problem, it is shown that to use the acoustic analogy, good knowledge of the flowfield is required

Sensitivity of Nonrenormalizable Trajectories to the Bare Scale

Working in scalar field theory, we consider RG trajectories which correspond to nonrenormalizable theories, in the Wilsonian sense. An interesting question to ask of such trajectories is, given some fixed starting point in parameter space, how the effective action at the effective scale, Lambda, changes as the bare scale (and hence the duration of the flow down to Lambda) is changed. When the effective action satisfies Polchinski's version of the Exact Renormalization Group equation, we prove, directly from the path integral, that the dependence of the effective action on the bare scale, keeping the interaction part of the bare action fixed, is given by an equation of the same form as the Polchinski equation but with a kernel of the opposite sign. We then investigate whether similar equations exist for various generalizations of the Polchinski equation. Using nonperturbative, diagrammatic arguments we find that an action can always be constructed which satisfies the Polchinski-like equation under variation of the bare scale. For the family of flow equations in which the field is renormalized, but the blocking functional is the simplest allowed, this action is essentially identified with the effective action at Lambda = 0. This does not seem to hold for more elaborate generalizations.Comment: v1: 23 pages, 5 figures, v2: intro extended, refs added, published in jphy

Traversable Wormholes in Geometries of Charged Shells

We construct a static axisymmetric wormhole from the gravitational field of two charged shells which are kept in equilibrium by their electromagnetic repulsion. For large separations the exterior tends to the Majumdar-Papapetrou spacetime of two charged particles. The interior of the wormhole is a Reissner-Nordstr\"om black hole matching to the two shells. The wormhole is traversable and connects to the same asymptotics without violation of energy conditions. However, every point in the Majumdar-Papapetrou region lies on a closed timelike curve.Comment: 9 pages, LaTeX, 1 figur

Keepers of the sacred flame: Patriotism, politics and the Chinese history subject community in Hong Kong

Chinese history (a subject entirely separate and distinct from 'history') has long been the most politically sensitive subject in Hong Kong's school curriculum. Previous studies have analysed the policies of the colonial and postcolonial Governments towards this subject. Here, we examine the role played by the Chinese history subject community (comprising teachers, academics and officials in the Government's educational bureaucracy), and look at the way in which this has operated as an autonomous interest group. We conclude that the influence of this subject community has been a key factor limiting the extent to which the local educational authorities have been able to develop a coherent policy in relation to history education in general, and the teaching of national history in particular. Specifically, advocates of the maintenance of Chinese history as a separate subject within the school curriculum have been able, by associating themselves with the post-1997 agenda of 'patriotic education', to effectively hoist the local educational bureaucracy with its own petard.postprin

Keepers of the sacred flame: Patriotism, politics and the Chinese history subject community in Hong Kong

Chinese history (a subject entirely separate and distinct from 'history') has long been the most politically sensitive subject in Hong Kong's school curriculum. Previous studies have analysed the policies of the colonial and postcolonial Governments towards this subject. Here, we examine the role played by the Chinese history subject community (comprising teachers, academics and officials in the Government's educational bureaucracy), and look at the way in which this has operated as an autonomous interest group. We conclude that the influence of this subject community has been a key factor limiting the extent to which the local educational authorities have been able to develop a coherent policy in relation to history education in general, and the teaching of national history in particular. Specifically, advocates of the maintenance of Chinese history as a separate subject within the school curriculum have been able, by associating themselves with the post-1997 agenda of 'patriotic education', to effectively hoist the local educational bureaucracy with its own petard.postprin

Some new class of Chaplygin Wormholes

Some new class of Chaplygin wormholes are investigated in the framework of a Chaplygin gas with equation of state $p = - \frac{A}{\rho}$, $A>0$. Since empty spacetime ($p = \rho = 0$) does not follow Chaplygin gas, so the interior Chaplygin wormhole solutions will never asymptotically flat. For this reason, we have to match our interior wormhole solution with an exterior vacuum solution i.e. Schwarzschild solution at some junction interface, say $r = a$. We also discuss the total amount of matter characterized by Chaplygin gas that supplies fuel to construct a wormhole.Comment: 14 pages, 12 figures, Accepted for publication in Mod.Phys.Lett.

Field-calibrated model of melt, refreezing, and runoff for polar ice caps : Application to Devon Ice Cap

Acknowledgments R.M.M. was supported by the Scottish Alliance for Geoscience, Environment and Society (SAGES). The field data collection contributed to the validation of the European Space Agency Cryosat mission and was supported by the Natural Sciences and Engineering Research Council, Canada, the Meteorological Service of Canada (CRYSYS program), the Polar Continental Shelf Project (an agency of Natural Resources Canada), and by UK Natural Environment Research Council consortium grant NER/O/S/2003/00620. Support for D.O.B. was provided by the Canadian Circumpolar Institute and the Climate Change Geoscience Program, Earth Sciences Sector, Natural Resources Canada (ESS contribution 20130371). Thanks are also due to the Nunavut Research Institute and the communities of Resolute Bay and Grise Fjord for permission to conduct fieldwork on Devon Ice Cap. M.J. Sharp, A. Gardner, F. Cawkwell, R. Bingham, S. Williamson, L. Colgan, J. Davis, B. Danielson, J. Sekerka, L. Gray, and J. Zheng are thanked for logistical support and field assistance during the data collection. We thank Ruzica Dadic, two other anonymous reviewers, and the Editor, Bryn Hubbard, for their helpful comments on an earlier version of this paper and which resulted in significant improvements.Peer reviewedPublisher PD

Semisimple types for p -adic classical groups

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