8,124 research outputs found
From massive gravity to modified general relativity II
We continue our investigation of massive gravity in the massless limit of
vanishing graviton mass. From gauge invariance we derive the most general
coupling between scalar matter and gravity. We get further couplings beside the
standard coupling to the energy-momentum tensor. On the classical level this
leads to a further modification of general relativity.Comment: 12 pages, no figur
The Chandra Fornax Survey - I: The Cluster Environment
We present the first results of a deep Chandra survey of the inner 1 degree
of the Fornax cluster of galaxies. Ten 50 ksec pointings were obtained in a
mosaic centered on the giant elliptical galaxy NGC 1399 at the nominal cluster
center. Emission and temperature maps of Fornax are presented, and an initial
study of 771 detected X-ray point sources is made. Regions as small as 100pc
are resolved. The intra-cluster gas in Fornax exhibits a highly asymmetric
morphology and temperature structure, dominated by a 180 kpc extended ``plume''
of low surface brightness, cool, ~1 keV) gas to the North-East of NGC 1399 with
a sharper edge to the South West. The elliptical galaxy NGC 1404 also exhibits
a cool halo of X-ray gas within the cluster, with a highly sharpened leading
edge as it presumably falls into the cluster, and a cometary-like tail. We
estimate that some ~200-400 point sources are physically associated with
Fornax. Confirming earlier works, we find that the globular cluster population
in NGC 1399 is highly X-ray active, extending to globulars which may in fact be
intra-cluster systems. We have also found a remarkable correlation between the
location of giant and dwarf cluster galaxies and the presence of X-ray
counterparts, such that systems inhabiting regions of low gas density are more
likely to show X-ray activity. Not only does this correlate with the asymmetry
of the intra-cluster gas but also with the axis joining the center of Fornax to
an infalling group 1 Mpc to the South-West. We suggest that Fornax may be
experiencing an intergalactic ``headwind'' due to motion relative to the
surrounding large-scale structure.Comment: 35 pages, 15 figures, submitted to ApJ. Most figures not included
owing to severe compression degradation - we strongly recommend downloading
the full resolution paper from
http://www.astro.columbia.edu/~caleb/ms_highres.pdf (1.9Mb
The Interaction of Quantum Gravity with Matter
The interaction of (linearized) gravitation with matter is studied in the
causal approach up to the second order of perturbation theory. We consider the
generic case and prove that gravitation is universal in the sense that the
existence of the interaction with gravitation does not put new constraints on
the Lagrangian for lower spin fields. We use the formalism of quantum off-shell
fields which makes our computation more straightforward and simpler.Comment: 25 page
Massive gravity from descent equations
Both massless and massive gravity are derived from descent equations
(Wess-Zumino consistency conditions). The massive theory is a continuous
deformation of the massless one.Comment: 8 pages, no figur
The Standard Model and its Generalizations in Epstein-Glaser Approach to Renormalization Theory II: the Fermion Sector and the Axial Anomaly
We complete our study of non-Abelian gauge theories in the framework of
Epstein-Glaser approach to renormalization theory including in the model an
arbitrary number of Dirac Fermions. We consider the consistency of the model up
to the third order of the perturbation theory. In the second order we obtain
pure group theoretical relations expressing a representation property of the
numerical coefficients appearing in the left and right handed components of the
interaction Lagrangian. In the third order of the perturbation theory we obtain
the the condition of cancellation of the axial anomaly.Comment: 38 pages, LATEX 2e, extensive rewritting, some errors eliminate
The evolution of the cluster X-ray scaling relations in the WARPS sample at 0.6<z<1.0
The X-ray properties of a sample of 11 high-redshift (0.6<z<1.0) clusters
observed with Chandra and/or XMM are used to investigate the evolution of the
cluster scaling relations. The observed evolution of the L-T and M-L relations
is consistent with simple self-similar predictions, in which the properties of
clusters reflect the properties of the universe at their redshift of
observation. When the systematic effect of assuming isothermality on the
derived masses of the high-redshift clusters is taken into account, the
high-redshift M-T and Mgas-T relations are also consistent with self-similar
evolution. Under the assumption that the model of self-similar evolution is
correct and that the local systems formed via a single spherical collapse, the
high-redshift L-T relation is consistent with the high-z clusters having formed
at a significantly higher redshift than the local systems. The data are also
consistent with the more realistic scenario of clusters forming via the
continuous accretion of material. The slope of the L-T relation at
high-redshift (B=3.29+/-0.38) is consistent with the local relation, and
significantly steeper then the self-similar prediction of B=2. This suggests
that the non-gravitational processes causing the steepening occurred at z>1 or
in the early stages of the clusters' formation, prior to their observation. The
properties of the intra-cluster medium at high-redshift are found to be similar
to those in the local universe. The mean surface-brightness profile slope for
the sample is 0.66+/-0.05, the mean gas mass fractions within R2500 and R200
are 0.073+/-0.010 and 0.12+/-0.02 respectively, and the mean metallicity of the
sample is 0.28+/-0.16 solar.Comment: 23 pages, 17 figures. Accepted for publication in MNRAS. Revised to
match accepted version: reanalysed data with latest calibrations, several
minor changes. Conclusions unchange
A Fully Self-Consistent Treatment of Collective Fluctuations in Quantum Liquids
The problem of calculating collective density fluctuations in quantum liquids
is revisited. A fully quantum mechanical self-consistent treatment based on a
quantum mode-coupling theory [E. Rabani and D.R. Reichman, J. Chem. Phys.116,
6271 (2002)] is presented. The theory is compared with the maximum entropy
analytic continuation approach and with available experimental results. The
quantum mode-coupling theory provides semi-quantitative results for both short
and long time dynamics. The proper description of long time phenomena is
important in future study of problems related to the physics of glassy quantum
systems, and to the study of collective fluctuations in Bose fluids.Comment: 9 pages, 4 figure
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