80,820 research outputs found
Introduction to the Neoclassical Interpretation: Quantum Steampunk
In a previous paper we outlined a series of historical touchpoints between classical aether theories and modern theoretical physics which showed a shared conceptual lineage for the modern tools and methods of the most common interpretations and fluid based âHydrodynamicâ treatments of an electromagnetic medium. It was proposed that, though the weight of modern experimentation leaves an extremely narrow and convoluted window for even a reconceptualization of a medium, all of modern physics recognizes a plethora of behaviors and attributes for free space and these physics are interchangeable with modern methods for treating superfluid-like continuums. Thus the mathematical equivalence of the methods do not comprise alternative physics but an alternative interpretation of the same physics. Though many individual components describing a âneo-aetherâ or âquintessenceâ are available, an overarching structural outline of how these tools can work together to provide an alternative working overview of modern physics has remained undefined. This paper will propose a set of introductory concepts in the first outline of a toy model which will later connect the alternative tools and conceptualizations with their modern counterparts. This introductory paper provides the simpler â100-miles outâ overview of the whole of physics from this perspective, in an easily comprehensible, familiar and intuitive, informal dialog fashion. While this paper grants the largest and loosest introductory overview, subsequent papers in this series will address the finite connections between modern physics and this hydrodynamic view
Galaxy Clusters: Cosmic High-Energy Laboratories to Study the Structure of Our Universe
This contribution illustrates the study of galaxy clusters as astrophysical
laboratories as well as probes for the large-scale structure of the Universe.
Using the REFLEX Cluster Survey, the measurement of the statistics of the
large-scale structure on scales up to 500 Mpc is illustrated. The
results clearly favour a low density Universe. Clusters constitute, in
addition, well defined astrophysical laboratory environments in which some very
interesting large-scale phenomena can be studied. As an illustration we show
some spectacular new XMM X-ray spectroscopic results on the thermal structure
of cooling flows and the interaction effects of AGN with this hot intracluster
medium. The X-ray observations with XMM-Newton show a lack of spectral evidence
for large amounts of cooling and condensing gas in the centers of galaxy
clusters believed to harbour strong cooling flows. To explain these findings we
consider the heating of the core regions of clusters by jets from a central
AGN. We find that the power output the AGN jets is well sufficient. The
requirements such a heating model has to fulfill are explored and we find a
very promising scenario of self-regulated Bondi accretion of the central black
hole.Comment: 12 pages, 8 figures, Contribution to the MPA/ESO/MPE/USM conference
"Lighthouses of the Universe", Sunyaev et al. (eds.), ESO Astrophysics
Symposia, Springer Verla
From Filamentary Networks to Dense Cores in Molecular Clouds: Toward a New Paradigm for Star Formation
Recent studies of the nearest star-forming clouds of the Galaxy at
submillimeter wavelengths with the Herschel Space Observatory have provided us
with unprecedented images of the initial and boundary conditions of the star
formation process. The Herschel results emphasize the role of interstellar
filaments in the star formation process and connect remarkably well with nearly
a decade's worth of numerical simulations and theory that have consistently
shown that the ISM should be highly filamentary on all scales and star
formation is intimately related to self-gravitating filaments. In this review,
we trace how the apparent complexity of cloud structure and star formation is
governed by relatively simple universal processes - from filamentary clumps to
galactic scales. We emphasize two crucial and complementary aspects: (i) the
key observational results obtained with Herschel over the past three years,
along with relevant new results obtained from the ground on the kinematics of
interstellar structures, and (ii) the key existing theoretical models and the
many numerical simulations of interstellar cloud structure and star formation.
We then synthesize a comprehensive physical picture that arises from the
confrontation of these observations and simulations.Comment: 24 pages, 15 figures. Accepted for publication as a review chapter in
Protostars and Planets VI, University of Arizona Press (2014), eds. H.
Beuther, R. Klessen, C. Dullemond, Th. Hennin
The effect of ablation injection on radiative and convective heating
A viscous shock-layer analysis is for calculating high energy equilibrium flow fields about blunt axisymmetric bodies is applied to the problem of massive ablation injection with radiation transport. A nongray radiation model is used that accounts for both line and continuum radiation. The solution method is direct and provides both stagnation and downstream solutions. Results for shock heated air show that phenolic-nylon injection is substantially more effective in reducing the wall radiant flux than air injection. Also, for large included body angles, the wall radiative flux and the coupled phenolic-nylon injection rate do not continue to decrease with increasing distance downstream
How soft is the budget constraint for Yugoslav firms?
The purpose of this paper is to show that Yugoslav firms have also been subjected to massive, pervasive redistribution through a soft budget constraint. To quantify such redistribution, the authors focus particulary on the redistributive effects of holding financial assets and liabilities in an inflationary environment in which financial claims are generally not indexed. Analyzing firm-level data for Yugoslavia's manufacturing sector for 1986, they show that such flows, in contrast to those of other Eastern European economies, have been a far more important source of redistribution than taxes and subsidies. Although Yugoslavia's channels of redistribution differ significantly from those in other socialist economies, they share a common driving force: the pursuit of job and wage security. Producers of energy, food, and heavy manufactures, as well as less developed regions, have particulary benefited from the redistribution.Environmental Economics&Policies,Economic Theory&Research,Banks&Banking Reform,Municipal Financial Management,Public Sector Economics&Finance
Dynamic star formation in the massive DR21 filament
The formation of massive stars is a highly complex process in which it is not
clear whether the star-forming gas is in global gravitational collapse or in an
equilibrium state, supported by turbulence. By studying one of the most massive
and dense star-forming regions in the Galaxy at a distance of less than 3 kpc,
the filament containing the well-known sources DR21 and DR21(OH), we expect to
find observational signatures that allow to discriminate between the two views.
We use molecular line data from our 13CO 1-0, CS 2-1, and N2H+ 1-0 survey of
the Cygnus X region obtained with the FCRAO and high-angular resolution
observations of CO, CS, HCO+, N2H+, and H2CO, obtained with the IRAM 30m
telescope. We observe a complex velocity field and velocity dispersion in the
DR21 filament in which regions of highest column-density, i.e. dense cores,
have a lower velocity dispersion than the surrounding gas and velocity
gradients that are not (only) due to rotation. Infall signatures in optically
thick line profiles of HCO+ and 12CO are observed along and across the whole
DR21 filament. From modelling the observed spectra, we obtain a typical infall
speed of 0.6 km/s and mass accretion rates of the order of a few 10^-3 Msun/yr
for the two main clumps constituting the filament. These massive (4900 and 3300
Msun) clumps are both gravitationally contracting. All observed kinematic
features in the DR21 filament can be explained if it is formed by the
convergence of flows at large scales and is now in a state of global
gravitational collapse. Whether this convergence of flows originated from
self-gravity at larger scales or from other processes can not be settled with
the present study. The observed velocity field and velocity dispersion are
consistent with results from (magneto)-hydrodynamic simulations where the cores
lie at the stagnation points of convergent turbulent flows.Comment: Astronomy and Astrophysics, in pres
Quantitative modelling of the humanâEarth System a new kind of science?
The five grand challenges set out for Earth System Science by the International Council for Science in 2010 require a true fusion of social science, economics and natural scienceâa fusion that has not yet been achieved. In this paper we propose that constructing quantitative models of the dynamics of the humanâEarth system can serve as a catalyst for this fusion. We confront well-known objections to modelling societal dynamics by drawing lessons from the development of natural science over the last four centuries and applying them to social and economic science. First, we pose three questions that require real integration of the three fields of science. They concern the coupling of physical planetary boundaries via social processes; the extension of the concept of planetary boundaries to the humanâEarth System; and the possibly self-defeating nature of the United Nationâs Millennium Development Goals. Second, we ask whether there are regularities or âattractorsâ in the humanâEarth System analogous to those that prompted the search for laws of nature. We nominate some candidates and discuss why we should observe them given that human actors with foresight and intentionality play a fundamental role in the humanâEarth System. We conclude that, at sufficiently large time and space scales, social processes are predictable in some sense. Third, we canvass some essential mathematical techniques that this research fusion must incorporate, and we ask what kind of data would be needed to validate or falsify our models. Finally, we briefly review the state of the art in quantitative modelling of the humanâEarth System today and highlight a gap between so-called integrated assessment models applied at regional and global scale, which could be filled by a new scale of model
- âŠ