Beyond capitalism and liberal democracy: on the relevance of GDH Cole’s sociological critique and alternative

This article argues for a return to the social thought of the often ignored early 20th-century English thinker GDH Cole. The authors contend that Cole combined a sociological critique of capitalism and liberal democracy with a well-developed alternative in his work on guild socialism bearing particular relevance to advanced capitalist societies. Both of these, with their focus on the limitations on ‘free communal service’ in associations and the inability of capitalism to yield emancipation in either production or consumption, are relevant to social theorists looking to understand, critique and contribute to the subversion of neoliberalism. Therefore, the authors suggest that Cole’s associational sociology, and the invitation it provides to think of formations beyond capitalism and liberal democracy, is a timely and valuable resource which should be returned to

Radial Redshift Space Distortions

The radial component of the peculiar velocities of galaxies cause displacements in their positions in redshift space. We study the effect of the peculiar velocities on the linear redshift space two point correlation function. Our analysis takes into account the radial nature of the redshift space distortions and it highlights the limitations of the plane parallel approximation. We consider the problem of determining the value of \beta and the real space two point correlation function from the linear redshift space two point correlation function. The inversion method proposed here takes into account the radial nature of the redshift space distortions and can be applied to magnitude limited redshift surveys that have only partial sky coverage.Comment: 26 pages including 11 figures, to appear in Ap

The Bispectrum as a Signature of Gravitational Instability in Redshift-Space

The bispectrum provides a characteristic signature of gravitational instability that can be used to probe the Gaussianity of the initial conditions and the bias of the galaxy distribution. We study how this signature is affected by redshift distortions using perturbation theory and high-resolution numerical simulations. We obtain perturbative results for the multipole expansion of the redshift-space bispectrum which provide a natural way to break the degeneracy between bias and $\Omega$ present in measurements of the redshift-space power spectrum. We propose a phenomenological model that incorporates the perturbative results and also describes the bispectrum in the transition to the non-linear regime. We stress the importance of non-linear effects and show that inaccurate treatment of these can lead to significant discrepancies in the determination of bias from galaxy redshift surveys. At small scales we find that the bispectrum monopole exhibits a strong configuration dependence that reflects the velocity dispersion of clusters. Therefore, the hierarchical model for the three-point function does not hold in redshift-space.Comment: 19 pages, 4 figures. Revised version accepted for publication in Ap

An Analytical Approach to Inhomogeneous Structure Formation

We develop an analytical formalism that is suitable for studying inhomogeneous structure formation, by studying the joint statistics of dark matter halos forming at two points. Extending the Bond et al. (1991) derivation of the mass function of virialized halos, based on excursion sets, we derive an approximate analytical expression for the ``bivariate'' mass function of halos forming at two redshifts and separated by a fixed comoving Lagrangian distance. Our approach also leads to a self-consistent expression for the nonlinear biasing and correlation function of halos, generalizing a number of previous results including those by Kaiser (1984) and Mo & White (1996). We compare our approximate solutions to exact numerical results within the excursion-set framework and find them to be consistent to within 2% over a wide range of parameters. Our formalism can be used to study various feedback effects during galaxy formation analytically, as well as to simply construct observable quantities dependent on the spatial distribution of objects. A code that implements our method is publicly available at http://www.arcetri.astro.it/~evan/GeminiComment: 41 Pages, 11 figures, published in ApJ, 571, 585. Reference added, Figure 2 axis relabele

Lyman Break Galaxies at z>4 and the Evolution of the UV Luminosity Density at High Redshift

We present initial results of a survey for star-forming galaxies in the redshift range 3.8 < z < 4.5. This sample consists of a photometric catalog of 244 galaxies culled from a total solid angle of 0.23 square degrees to an apparent magnitude of I_{AB}=25.0. Spectroscopic redshifts in the range 3.61 < z < 4.81 have been obtained for 48 of these galaxies; their median redshift is =4.13. Selecting these galaxies in a manner entirely analogous to our large survey for Lyman break galaxies at smaller redshift (2.7 < z < 3.4) allows a relatively clean differential comparison between the populations and integrated luminosity density at these two cosmic epochs. Over the same range of UV luminosity, the spectroscopic properties of the galaxy samples at z~4 and z~3 are indistinguishable, as are the luminosity function shapes and the total integrated UV luminosity densities (rho_{UV}(z=3)/rho_{UV}(z=4) = 1.1 +/-0.3). We see no evidence at these bright magnitudes for the steep decline in the star formation density inferred from fainter photometric Lyman-break galaxies in the Hubble Deep Field (HDF). If the true luminosity density at z~4 is somewhat higher than implied by the HDF, as our ground-based sample suggests, then the emissivity of star formation as a function of redshift is essentially constant for all z>1 once internally consistent corrections for dust are made. This suggests that there is no obvious peak in star formation activity, and that the onset of substantial star formation in galaxies occurs at z > 4.5. [abridged abstract]Comment: To appear in the ApJ, minor revisions to match accepted versio

Hierarchy of Conservation Laws of Diffusion--Convection Equations

We introduce notions of equivalence of conservation laws with respect to Lie symmetry groups for fixed systems of differential equations and with respect to equivalence groups or sets of admissible transformations for classes of such systems. We also revise the notion of linear dependence of conservation laws and define the notion of local dependence of potentials. To construct conservation laws, we develop and apply the most direct method which is effective to use in the case of two independent variables. Admitting possibility of dependence of conserved vectors on a number of potentials, we generalize the iteration procedure proposed by Bluman and Doran-Wu for finding nonlocal (potential) conservation laws. As an example, we completely classify potential conservation laws (including arbitrary order local ones) of diffusion--convection equations with respect to the equivalence group and construct an exhaustive list of locally inequivalent potential systems corresponding to these equations.Comment: 24 page

Scanning Quantum Decoherence Microscopy

The use of qubits as sensitive magnetometers has been studied theoretically and recent demonstrated experimentally. In this paper we propose a generalisation of this concept, where a scanning two-state quantum system is used to probe the subtle effects of decoherence (as well as its surrounding electromagnetic environment). Mapping both the Hamiltonian and decoherence properties of a qubit simultaneously, provides a unique image of the magnetic (or electric) field properties at the nanoscale. The resulting images are sensitive to the temporal as well as spatial variation in the fields created by the sample. As an example we theoretically study two applications of this technology; one from condensed matter physics, the other biophysics. The individual components required to realise the simplest version of this device (characterisation and measurement of qubits, nanoscale positioning) have already been demonstrated experimentally.Comment: 11 pages, 5 low quality (but arXiv friendly) image

The Evolution of the Galaxy Sizes in the NTT Deep Field: a Comparison with CDM Models

The sizes of the field galaxies with I<25 have been measured in the NTT Deep Field. Intrinsic sizes have been obtained after deconvolution of the PSF with a multigaussian method. The reliability of the method has been tested using both simulated data and HST observations of the same field. The distribution of the half light radii is peaked at r_{hl} 0.3 arcsec, in good agreement with that derived from HST images at the same magnitude. An approximate morphological classification has been obtained using the asymmetry and concentration parameters. The intrinsic sizes of the galaxies are shown as a function of their redshifts and absolute magnitudes using photometric redshifts derived from the multicolor catalog. While the brighter galaxies with morphological parameters typical of the normal spirals show a flat distribution in the range r_{d}=1-6 kpc, the fainter population at 0.4<z<0.8 dominates at small sizes. To explore the significance of this behaviour, an analytical rendition of the standard CDM model for the disc size evolution has been computed. The model showing the best fit to the local luminosity function and the Tully-Fisher relation is able to reproduce at intermediate redshifts a size distribution in general agreement with the observations, although it tends to underestimate the number of galaxies fainter than M_B~ -19 with disk sizes r_d~ 1-2 kpc.Comment: 16 pages, 11 figures, ApJ in press, Dec 199

Energy focusing inside a dynamical cavity

We study the exact classical solutions for a real scalar field inside a cavity with a wall whose motion is self-consistently determined by the pressure of the field itself. We find that, regardless of the system parameters, the long-time solution always becomes nonadiabatic and the field's energy concentrates into narrow peaks, which we explain by means of a simple mechanical system. We point out implications for the quantized theory.Comment: 5 pages, 6 figures, double column, submitted to P.R.