31,434 research outputs found
Majorana spinors and extended Lorentz symmetry in four-dimensional theory
An extended local Lorentz symmetry in four-dimensional (4D) theory is
considered. A source of this symmetry is a group of general linear
transformations of four-component Majorana spinors GL(4,M) which is isomorphic
to GL(4,R) and is the covering of an extended Lorentz group in a 6D Minkowski
space M(3,3) including superluminal and scaling transformations. Physical
space-time is assumed to be a 4D pseudo-Riemannian manifold. To connect the
extended Lorentz symmetry in the M(3,3) space with the physical space-time, a
fiber bundle over the 4D manifold is introduced with M(3,3) as a typical fiber.
The action is constructed which is invariant with respect to both general 4D
coordinate and local GL(4,M) spinor transformations. The components of the
metric on the 6D fiber are expressed in terms of the 4D pseudo-Riemannian
metric and two extra complex fields: 4D vector and scalar ones. These extra
fields describe in the general case massive particles interacting with an extra
U(1) gauge field and weakly interacting with ordinary particles, i.e.
possessing properties of invisible (dark) matter.Comment: 24 page
Tropical–North Pacific Climate Linkages over the Past Four Centuries
Analyses of instrumental data demonstrate robust linkages between decadal-scale North Pacific and tropical Indo-Pacific climatic variability. These linkages encompass common regime shifts, including the noteworthy 1976 transition in Pacific climate. However, information on Pacific decadal variability and the tropical high-latitude climate connection is limited prior to the twentieth century. Herein tree-ring analysis is employed to extend the understanding of North Pacific climatic variability and related tropical linkages over the past four centuries. To this end, a tree-ring reconstruction of the December-May North Pacific index (NPI)-an index of the atmospheric circulation related to the Aleutian low pressure cell-is presented (1600-1983). The NPI reconstruction shows evidence for the three regime shifts seen in the instrumental NPI data, and for seven events in prior centuries. It correlates significantly with both instrumental tropical climate indices and a coral-based reconstruction of an optimal tropical Indo-Pacific climate index, supporting evidence for a tropical-North Pacific link extending as far west as the western Indian Ocean. The coral-based reconstruction (1781-1993) shows the twentieth-century regime shifts evident in the instrumental NPI and instrumental tropical Indo-Pacific climate index, and three previous shifts. Changes in the strength of correlation between the reconstructions over time, and the different identified shifts in both series prior to the twentieth century, suggest a varying tropical influence on North Pacific climate, with greater influence in the twentieth century. One likely mechanism is the low-frequency variability of the El Nino-Southern Oscillation (ENSO) and its varying impact on Indo-Pacific climate.</p
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
Cluster Correlation in Mixed Models
We evaluate the dependence of the cluster correlation length r_c on the mean
intercluster separation D_c, for three models with critical matter density,
vanishing vacuum energy (Lambda = 0) and COBE normalized: a tilted CDM (tCDM)
model (n=0.8) and two blue mixed models with two light massive neutrinos
yielding Omega_h = 0.26 and 0.14 (MDM1 and MDM2, respectively). All models
approach the observational value of sigma_8 (and, henceforth, the observed
cluster abundance) and are consistent with the observed abundance of Damped
Lyman_alpha systems. Mixed models have a motivation in recent results of
neutrino physics; they also agree with the observed value of the ratio
sigma_8/sigma_25, yielding the spectral slope parameter Gamma, and nicely fit
LCRS reconstructed spectra. We use parallel AP3M simulations, performed in a
wide box (side 360/h Mpc) and with high mass and distance resolution, enabling
us to build artificial samples of clusters, whose total number and mass range
allow to cover the same D_c interval inspected through APM and Abell cluster
clustering data. We find that the tCDM model performs substantially better than
n=1 critical density CDM models. Our main finding, however, is that mixed
models provide a surprisingly good fit of cluster clustering data.Comment: 22 pages + 10 Postscript figures. Accepted for publication in Ap
The mass function
We present the mass functions for different mass estimators for a range of
cosmological models. We pay particular attention to how universal the mass
function is, and how it depends on the cosmology, halo identification and mass
estimator chosen. We investigate quantitatively how well we can relate observed
masses to theoretical mass functions.Comment: 14 pages, 12 figures, to appear in ApJ
Modular space station Phase B extension
The modular space station concept and preliminary design are outlined. The premission operations, reference programs, baseline program costs, sortie analysis, and program options are covered
Emission of charged particles from excited compound nuclei
The formation of excited compound nucleus (CN) and its statistical decay is
investigated within the dinuclear system (DNS) model.The initial DNS is formed
in the entrance channel when the projectile is captured by a target, and then
the evolution of DNS in mass asymmetry coordinate leads to formation of the hot
CN. The emission barriers for complex fragments were calculated within the DNS
model by using the double folding procedure for the interaction potential. It
is shown that cross sections for complex fragment emission become larger when
excited CN is more neutron deficient. This approach gives also an opportunity
to calculate the new neutron deficient isotopes production cross sections and
can be applied to describe the hot fission of heavy systems.The model was
tested by comparison of calculated results with experimental dat
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
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