|Current Workshop | Overview||Back | Home | Search ||
New Directions in Modern Cosmology
Distances to supernovae : current status and prospects
Keith S Cover
Are WMAP’s quadrupole and octupole reconstruction artifacts from the calibration of WMAP’s time ordered data?
The COBE, BOOMERANG and WMAP sky maps of the cosmic microwave background (CMB) provide an excellent opportunity to test current practices in image reconstruction. All three missions used image reconstruction to generate their sky maps in contrast to the up coming Planck results which will provide the first direct measurements in the CMB. There is growing evidence suggesting the low l spherical harmonics of the WMAP sky maps may be inaccurate even though they are consistent with the COBE sky maps. For example, for the 7 year sky maps the WMAP team reported the quadrupole and octupole were so well aligned that there was only 1 part in 100,000 of the alignment happening by chance. The official WMAP image and calibration pipeline has been replicated and is being examined for potential reconstruction artefacts. This is the first time the calibration part of official WMAPs image reconstruction has been examined other than by the WMAP team. Image reconstruction is playing an ever increasing role in modern cosmology. For example, estimating the distribution of dark matter from gravitational lensing can be seen as a problem in image reconstruction. The difference between data fitting reconstruction algorithms, which require prior information, and data focusing ones, which do not, should have particular relevance to cosmological problems when robust and reliable image reconstructions are needed. Whether the Planck results agree with COBE and WMAP’s at low l or not, there is a still a fundamental need of a detailed review of the current image reconstruction practices employed in modern cosmology.
Superhomogeneous mass fields and the large scale matter
distribution in the Universe
Carl H. Gibson and Rudolph E. Schild
Formation of Planets by Hydrogravitational Dynamics
Hydrogen-helium gas planets fragmented in clumps at the plasma to gas phase transition, only 300,000 years after the big bang. Earth-mass and million-star-clump masses are computed from the initial conditions at the transition, reflecting the 10^7 plasma-to-gas decrease in kinematic viscosity n and the density and rate-of-strain existing 30,000 years after the big bang when photon-viscous forces first matched gravitational fragmentation forces at the horizon scale ct of the expanding universe, where c is the speed of light and t is the time. Proto-super-cluster-void and proto-galaxy-void fragmentation produced weak turbulence and linear-clusters of gas-proto-galaxies as fossils of turbulent-plasma vortex lines. Hubble-space-telescope images of the most distant galaxies confirm this interpretation. Stars form from gas-planet mergers. The first generation of stars were thus in old globular star clusters. Freezing of the planets increased the diffusivity of the clumps to form dark matter halos. Spiral accretion disks reflect larger turbulent second-generation star formation triggered by tidal forces between the halo and accretion-disk proto-globular-star-clusters. Observational evidence in a wide range of spectral bands from a wide variety of new space telescopes strongly supports claims that galaxy dark matter is primordial planets in clumps, about thirty million dark-matter-planets per star in a galaxy. The first generation of life was likely hosted and its seeds scattered widely throughout the cosmos early in this scenario.
Imaging the dark matter
Most current tests of the cosmological model are large-scale and statistical. Upcoming large, high-precision astronomical surveys
(especially LSST and Gaia) may make it possible for us to create a small-scale three-dimensional (or six-dimensional) map of the dark matter within the Milky Way. The leading cosmological model requires non-trivial structure even on these small scales. Ideally, the specific phase-space structure of the Milky Way could be used to test the cosmological model directly, in that it must be produced by gravitational collapse from reasonable initial conditions in a reasonable background. I discuss some observational methods that might pay off.
Can gravity produce scale invariant clustering?
In the standard cosmological model power-law correlations observed in galaxy distributions over a significant range of scales are the result of a combination of fortuitous circumstances, rather than indicative of scale-invariant properties in the underlying dark matter distribution. Indeed the use of halo models to describe numerical simulations suggests that dark matter clustering can never be scale invariant. We discuss here a simplified one-dimensional model of structure formation in the universe, which has the particular interest that its numerical integration may be performed ``exactly''. This model does produce scale-invariant (fractal) clustering from a simple broad class of initial conditions, in a spatial range which grows monotonically in time. We study both how this range and the exponents characterizing it are determined, as well as the description of the mass distribution in terms of "halo" structures. Our results suggest that it may simply be because
of poor numerical resolution that scale-invariant properties have been obscured in three dimensional simulations of cold dark matter.
Local Group galaxies
as critical tests of the contemporary cosmological model and its failure
Weak lensing of the CMB
Weak lensing has several important effects on the CMB, including modifying the power spectra and generating a non-zero bispectrum and trispectrum. Accounting for these effects will be very important for the analysis of the CMB power spectrum and searches for primordial non-Gaussianity. Measurements of the lensing potential can be used to break the degeneracies in the linear CMB data, significantly improving constraints on several cosmological parameters. CMB lensing should play a major role in future measurements of cosmological parameters and tests of non-standard cosmology, and may also limit the detection of primordial gravitational waves. I will review the nature of the various effects and discuss recent work on the CMB bispectrum and the use of statistical anisotropy estimators to reconstruct the lensing potential.
The SZ anomaly, and the large foreground unrelated non-blackbody anisotropy on the 1 degree scale in the WMAP data
Our ApJ 2006 finding of too weak a Sunyaev-Zel'dovich signal in WMAP is now officially confirmed by the WMAP7 cosmology paper of Komatsu et al 2010. The anomaly could indeed be due in part to cluster physics, but there does appear a significant component of it that cannot be explained in this way. I shall venture to connect it with our ApJ 2010 paper on the existence of 7 micro-K (10% of the first acoustic peak), degree-scale, foreground unrelated, non-blackbody anisotropy in WMAP5, by suggesting that both are pointing to significant remaining issues in the beam-size of WMAP. There just does not seem to be another way of understanding these serious discrepancies.
effects in WMAP data
Robert S. MacKay and C.P. Rourke
Redshift in inhomogeneous space-times
The properties of a preferred time coordinate, homogeneous, isotropic space slices and matter velocity purely in the time direction make FLRW universes seem too simplistic; furthermore to fit with observations they necessitate inflation, dark matter and dark energy. It seems more appropriate to us to suppose a general space-time, with luminous matter and the earth moving along some selection of geodesics (except perhaps at some shocks), and to ask what features of the distribution of luminous matter positions and velocities would give rise to a Hubble law, and to explain the near isotropy of the cosmic microwave background by mixing of null geodesics. Some preliminary results in these directions will be sketched.
Joao C. R. Magueijo
Parity asymmetry of the CMB
We have investigated the odd-parity preference of the WMAP 7
year power spectrum. Comparison with simulation shows the odd-parity preference
of WMAP data (2 ? l ? 22) is anomalous at 4-in-1000
level. We have investigated its origins, and ruled out some
of non-cosmological origins such as asymmetric beams, noise and cut-sky effect.
Multipoles associated with the odd-parity preference
happen to coincide with some of other CMB anomalies. Therefore, there may exist a common origin, whether cosmological or not. Besides,
we find it likely that low quadrupole power is the
Fingerprints of the early universe
The observed properties of the primordial fluctuations in the cosmic microwave background (CMB) can provide constraints on physical theories in regimes otherwise inaccessible to experiment. A "concordance" picture of nearly-scale-invariant, adiabatic, Gaussian fluctuations obeying statistical isotropy and homogeneity has emerged in recent years. I will summarize recent progress in testing with CMB data the inflationary hypothesis for describing the very early universe, and the advances we can expect in the near future.
LCDM: Triumphs, Puzzles and Remedies
The Complex Universe: recent experiments and theoretical challenges
Cosmology is undergoing a revolution due to the many new data which are becoming available and which are expected in the near future. For several decades this field has been essentially based on conjectures strongly based on the only exactly solvable model available (Friedmann). The observation of large structures in the galaxy distribution has challenged this model already long ago and the very recent data from the SDSS project have given further evidence for a complex structure. In addition other data have posed additional problems with respect to the standard model. The large scale flow of galaxies and the observation (by gravitational lensing) that also dark matter is very clumpy represent important new elements.
A new picture emerges in which the complexity of the universe should be seen as an interesting fact and not just as a technical difficulty to avoid. For example the inhomogeneity and scaling properties could lead to the acceleration effects which led instead to the introduction of dark energy. In this perspective also the connection between a highly structured matter distribution with a smooth cosmic background radiation (CMBR) could be seen in a novel framework. This rapidly evolving situation will lead, in our opinion, to a new picture of the universe in which complex structures should become a central point of its description. We provide a survey of these points and outline the possible developments.
Cosmological perturbations and primordial non-Gaussianity
I will review some of the recent work on primordial nongaussianity. Next I will present a phase space path integral formalism for cosmological perturbations, which allows for a straighforward calculation of Feynam rules. As two examples, I will sketch how to calculate the three point and four point functions for the curvature perturbation during inflation.
Large scale structure - a Lambda-CDM success story?
Cosmologists measure large scale structure via CMB fluctuations and via galaxy clustering. We first review the successes in explaining these observations of the standard LCDM cosmology. In particular, we shall look at QSO clustering which provides a more powerful probe of the Universe on the very largest scales than do galaxies. We shall then summarise the fundamental issues for the LCDM model, including its difficulties at smaller scales. This prompts a re-inspection of the large-scale structure
observations. We point out that galaxies and QSOs are well known to be biased tracers of mass and that this may give an easy escape route for other cosmological models. The CMB is a tougher nut to crack but we review recent evidence that there may be observational issues with even the gold-standard WMAP CMB results.
Vladimir Sokolov and Baryshev Yu.V.
The star forming rate, core-collapse supernovae rate, and gamma-ray burst rate at large redshifts
Since the first optical identificaton of gamma-ray bursts (GRBs) in 1997, they became a new direction in the study of the universe at large redshifts. In particular, on April, 23, 2009 the highest spectroscopic redshift was measured z=8.2, and this happend to be of GRB 090423. Currently the state of the GRB problem and progress in this field can be fixed in the following way:
1.GRBs belong to the most distant observable objects with measurable red shifts in the universe.
2.GRBs are related to star forming in distant (and very distant) galaxies.
3.GRBs and their afterglows allow us seeing also the most distant explosions of massive stars at the end of their evolution.
4.This is confirmed by observations of long bursts, but, most probably short GRBs are also related to some very old compact objects (neutron and quark stars) resulting from evolution of the same massive stars.
5.And at what z (> 10-20?) are GRBs unobservable already? Now this can be the main cosmological GRB-test.
The talk concerns: GRB rate, galaxies and star forming at large redshifts, model-independent observational tests, and the statement of problems in the NIR range. (Is evolution of anything observed as z increases?) In particular, we will consider the relation between GRB rate and star-forming rate (GRBR vs. SFR). In the talk some papers on GRBs and SFR in galaxies with large redshifts will be commented. The questions are: Is a fast decrease of SRF at z > 4 observed indeed, which is to be observed in standard (and not very standard) cosmologies? Is there any difference between GRBR and SFR beyond z~4?
Anomalous increase of galaxy sizes at small redshifts
We analyzed magnitudes and Petrosian radii at small redhifts from the Sloan Digital Sky Survey (data release 7).
Galaxy sizes calculated by means of Petrosian radii were found to increase unexpectedly with redshift z. A variety of possible reasons was investigated: A Malmquist bias was excluded by volume limited samples, other selection effects due to SDSS data peculiarities and a K-correction were taken into account. The anomly is not affected by the value of the Hubble constant and is stable across a wide range of galaxy luminosities. We determined the relative increase of the average size and found it to be about twice as much as the respective increase of wavelengths due to the cosmological redshift. Since the effect is beyond any statistical noise, only systematical errors can explain it within standard cosmology. To facilitate further investigatons, the complete code with comments and instructions is published.
Correlation properties of the CMB low multipoles in WMAP data or hidden coordinate systems
Different methods are used to investigate properties of cosmic microwave background observed with the NASA mission WMAP with the main goal of search for peculiar axes. There are several possible explanations for existance of peculiar directions in WMAP maps both having physical reasons or being systematic effects.
In our work, we implemented new mosaic correlation methods to study the statistical properties of foreground components and a restored background signal map for different ranges of multipoles. Using new approach, we detected in the spherical distribution of correlation coefficients, at least, three standard astronomical coordinate system which are reflected in positions of cold and hot spots of multipoles on the WMAP CMB map. We discuss the probable reasons of the detected observable phenomena.
This study was partly supported by the Russian Foundation of Basic Researches (grant No 09-02-00298).
Cosmic Flows on Scales
of 100 Mpc/h: A Challenge for the Standard LCDM
Multiscale approach to inhomogeneous cosmologies
Cosmological backreaction suggests a link between structure formation and the expansion history of the Universe. In order to quantitatively examine this connection we dynamically investigate a volume partition of the Universe into over– and underdense regions. This allows to trace structure formation using the volume fraction of the overdense regions lambda_M as its characterizing parameter. Employing results from cosmological perturbation theory, and under the assumption of an initial near to homogeneous Gaussian density field, we construct a three–parameter model for the effective cosmic expansion history, involving lambda_M_0, the matter density and the Hubble rate of today’s Universe.
The talk presents basic issues of constructing models for the average evolution of cosmological variables together with their volume-partitioning, and discusses first tests of the multiscale model to explain what we know about the evolution of the Universe in the backreaction context. Furthermore, the possible benefits of an application of the partitioning approach to more general cases will be discussed.