10 research outputs found
Reconciling inflation with openness
It is already understood that the increasing observational evidence for an
open Universe can be reconciled with inflation if our horizon is contained
inside one single huge bubble nucleated during the inflationary phase
transition. In this frame of ideas, we show here that the probability of living
in a bubble with the right (now the observations require ) can be comparable with unity, rather than infinitesimally small.
For this purpose we modify both quantitatively and qualitatively an intuitive
toy model based upon fourth order gravity. As this scheme can be implemented in
canonical General Relativity as well (although then the inflation driving
potential must be designed entirely ad hoc), inferring from the observations
that not only does not conflict with the inflationary paradigm,
but rather supports therein the occurrence of a primordial phase transition.Comment: 4 pages, one postscript figure, to be published on Physical Review D
PACS: 98.80. C
Double Inflation in Supergravity and the Large Scale Structure
The cosmological implication of a double inflation model with hybrid + new
inflations in supergravity is studied. The hybrid inflation drives an inflaton
for new inflation close to the origin through supergravity effects and new
inflation naturally occurs. If the total e-fold number of new inflation is
smaller than , both inflations produce cosmologically relevant density
fluctuations. Both cluster abundances and galaxy distributions provide strong
constraints on the parameters in the double inflation model assuming
standard cold dark matter scenario. The future satellite
experiments to measure the angular power spectrum of the cosmic microwave
background will make a precise determination of the model parameters possible.Comment: 19 pages (RevTeX file
A new Contribution to Cosmological Perturbations of some Inflationary Models
We show that there are inflationary models for which perturbations in the
energy momentum tensor, which are of second order in the scalar field, cannot
be neglected. We first specify the conditions under which the usual first order
perturbations are absent. We then analyze classically, the growth and decay of
our new type of perturbations for one mode of fluctuations \de\phi_k in the
scalar field. We generalize this analysis, considering the contribution from
the whole spectrum of \de\phi to a given wavelength of geometrical
perturbations. Finally, we discuss the evolution of the perturbations during
the subsequent radiation dominated era and discuss the resulting spectrum of
density fluctuations. In the case of a massless scalar field we find a spectral
index . For massive scalar fields we obtain but the resulting
amplitude of fluctuations for inflation around a GUT scale are by far too high.
Hence, 'conventional' inflationary models must not be influenced by this new
type of perturbations, in order to lead to acceptable matter and CMB
fluctuations.Comment: LaTeX file, 15p, 2 Postscript Figs. available on request, Zurich
University Preprint ZU-TH9/9
Cosmological parameters from SDSS and WMAP
We measure cosmological parameters using the three-dimensional power spectrum
P(k) from over 200,000 galaxies in the Sloan Digital Sky Survey (SDSS) in
combination with WMAP and other data. Our results are consistent with a
``vanilla'' flat adiabatic Lambda-CDM model without tilt (n=1), running tilt,
tensor modes or massive neutrinos. Adding SDSS information more than halves the
WMAP-only error bars on some parameters, tightening 1 sigma constraints on the
Hubble parameter from h~0.74+0.18-0.07 to h~0.70+0.04-0.03, on the matter
density from Omega_m~0.25+/-0.10 to Omega_m~0.30+/-0.04 (1 sigma) and on
neutrino masses from <11 eV to <0.6 eV (95%). SDSS helps even more when
dropping prior assumptions about curvature, neutrinos, tensor modes and the
equation of state. Our results are in substantial agreement with the joint
analysis of WMAP and the 2dF Galaxy Redshift Survey, which is an impressive
consistency check with independent redshift survey data and analysis
techniques. In this paper, we place particular emphasis on clarifying the
physical origin of the constraints, i.e., what we do and do not know when using
different data sets and prior assumptions. For instance, dropping the
assumption that space is perfectly flat, the WMAP-only constraint on the
measured age of the Universe tightens from t0~16.3+2.3-1.8 Gyr to
t0~14.1+1.0-0.9 Gyr by adding SDSS and SN Ia data. Including tensors, running
tilt, neutrino mass and equation of state in the list of free parameters, many
constraints are still quite weak, but future cosmological measurements from
SDSS and other sources should allow these to be substantially tightened.Comment: Minor revisions to match accepted PRD version. SDSS data and ppt
figures available at http://www.hep.upenn.edu/~max/sdsspars.htm
Three-Dimensional Mapping of the Dark Matter
We study the prospects for three-dimensional mapping of the dark matter to
high redshift through the shearing of faint galaxies images at multiple
distances by gravitational lensing. Such maps could provide invaluable
information on the nature of the dark energy and dark matter. While in
principle well-posed, mapping by direct inversion introduces exceedingly large,
but usefully correlated noise into the reconstruction. By carefully propagating
the noise covariance, we show that lensing contains substantial information,
both direct and statistical, on the large-scale radial evolution of the density
field. This information can be efficiently distilled into low-order
signal-to-noise eigenmodes which may be used to compress the data by over an
order of magnitude. Such compression will be useful for the statistical
analysis of future large data sets. The reconstructed map also contains useful
information on the localization of individual massive dark matter halos, and
hence the dark energy from halo number counts, but its extraction depends
strongly on prior assumptions. We outline a procedure for maximum entropy and
point-source regularization of the maps that can identify alternate
reconstructions.Comment: 11 pages, 5 figures, submitted to PR
Spectroscopic target selection for the Sloan Digital Sky Survey: The luminous red galaxy sample
We describe the target selection and resulting properties of a spectroscopic sample of luminous red galaxies (LRGs) from the imaging data of the Sloan Digital Sky Survey (SDSS). These galaxies are selected on the basis of color and magnitude to yield a sample of luminous intrinsically red galaxies that extends fainter and farther than the main flux-limited portion of the SDSS galaxy spectroscopic sample. The sample is designed to impose a passively evolving luminosity and rest-frame color cut to a redshift of 0.38. Additional, yet more luminous red galaxies are included to a redshift of âŒ0.5. Approximately 12 of these galaxies per square degree are targeted for spectroscopy, so the sample will number over 100,000 with the full survey. SDSS commissioning data indicate that the algorithm efficiently selects luminous (M*g â - 21.4) red galaxies, that the spectroscopic success rate is very high, and that the resulting set of galaxies is approximately volume limited out to z = 0.38. When the SDSS is complete, the LRG spectroscopic sample will fill over 1 h-3 Gpc3 with an approximately homogeneous population of galaxies and will therefore be well suited to studies of large-scale structure and clusters out to z = 0.5
Innovation and Internal reporting of Intellectual Capital - An emperical study
Purpose - The aim of this paper is to investigate the relationship between internal reporting of intellectual capital and innovation. Additionally the aim is to explain the advantages and disadvantages of reporting of intellectual capital and give a short overview of the previous research in this area.
Design/methodology/approach - A questionnaire was designed and addressed to the CFOs at the companies of the target population (companies within SNI-codes 20, 22 and 23 with between 250-800 employees). We primarily used forced-choice questions and complemented with some open-ended questions. The data was analyzed with SPSS 17 and the Spearmanâs correlation coefficient was used to find correlating variables.
Findings - The results obtained show that there exists a correlation between internal reporting of intellectual capital and innovation for a number of reporting posts, the most prominent in this study was human capital.
Originality/value - This paper investigates and highlights the link between internal reporting of intellectual capital and innovation