The baryon mass function for galaxy clusters

Context: The evolution of the cluster abundance with redshift is known to be a powerful cosmological constraint when applied to X-ray clusters. Recently, the evolution of the baryon mass function has been proposed as a new variant that is free of the uncertainties present in the temperature-mass relation. A flat model with Omega_matter ~ 0.3 was shown to be preferred in the case of a standard cold dark matter scenario. Aims: We compared the high redshift predictions of the baryon mass in clusters with data for a more general class of spectra with a varying shape factor Gamma without any restriction to the standard cold dark matter scenario in models normalized to reproduce the local baryon mass function. Methods: Using various halo mass functions existing in the literature we evaluated the corresponding baryon mass functions for the case of the non-standard power spectra mentioned previously. Results: We found that models with Omega_matter ~ 1 and Gamma ~ 0.12 reproduce high redshift cluster data just as well as the concordance model does. Conclusions: Finally, we conclude that the baryon mass function evolution alone does not efficiently discriminate between the more general family of flat cosmological models with non-standard power spectra.Comment: Typos corrected. Replaced to match published version. 5 pages, 2 figures, aa.cl

Constraining Ω0{\Omega_{0}} from X-ray properties of Clusters of Galaxies at high redshift

Properties of high redshift clusters are a fundamental source of information for cosmology. It has been shown by Oukbir and Blanchard (1997) that the combined knowledge of the redshift distribution of X-ray clusters of galaxies and the luminosity-temperature correlation, $L_X-T_X$, provides a powerful test of the mean density of the Universe. In this paper, we address the question of the possible evolution of this relation from an observational point of view and its cosmological significance. We introduce a new indicator in order to measure the evolution of the X-ray luminosity-temperature relation with redshift and take advantage of the recent availability of temperature information for a significant number of high and intermediate redshift X-ray clusters of galaxies. From our analysis, we find a slightly positive evolution in the $L_X-T_X$ relation. This implies a high value of the density parameter of $0.85\pm0.2$. However, because the selection of clusters included inour sample is unknown, this can be considered only as a tentative result. A well-controlled X-ray selected survey would provide a more robust answer. XMM will be ideal for such a program.Comment: 10 pages, LaTeX, 4 figures,5 tables, accepted by A&

On Quantum Iterated Function Systems

Quantum Iterated Function System on a complex projective space is defined by a family of linear operators on a complex Hilbert space. The operators define both the maps and their probabilities by one algebraic formula. Examples with conformal maps (relativistic boosts) on the Bloch sphere are discussed.Comment: Latex, 12 pages, 3 figures. Added plot of numerical estimate of the averaged contraction parameter fro quantum octahedron over the whole range of the fuzziness parameter. Added a theorem and proof of the uniqueness of the invariant measure. At the very end added subsection on "open problems

A Way Out of the Quantum Trap

We review Event Enhanced Quantum Theory (EEQT). In Section 1 we address the question "Is Quantum Theory the Last Word". In particular we respond to some of recent challenging staments of H.P. Stapp. We also discuss a possible future of the quantum paradigm - see also Section 5. In Section 2 we give a short sketch of EEQT. Examples are given in Section 3. Section 3.3 discusses a completely new phenomenon - chaos and fractal-like phenomena caused by a simultaneous "measurement" of several non-commuting observables (we include picture of Barnsley's IFS on unit sphere of a Hilbert space). In Section 4 we answer "Frequently Asked Questions" concerning EEQT.Comment: Replacement. Corrected affiliation. Latex, one .jpg figure. To appear in Proc. Conf. Relativistic Quantum Measurements, Napoli 1998, Ed. F. Petruccion

The Physical State of the Intergalactic Medium or Can We Measure Y?

We present an argument for a {\it lower limit} to the Compton-$y$ parameter describing spectral distortions of the cosmic microwave background (CMB). The absence of a detectable Gunn-Peterson signal in the spectra of high redshift quasars demands a high ionization state of the intergalactic medium (IGM). Given an ionizing flux at the lower end of the range indicated by the proximity effect, an IGM representing a significant fraction of the nucleosynthesis-predicted baryon density must be heated by sources other than the photon flux to a temperature \go {\rm few} \times 10^5\, K. Such a gas at the redshift of the highest observed quasars, $z\sim 5$, will produce a y\go 10^{-6}. This lower limit on $y$ rises if the Universe is open, if there is a cosmological constant, or if one adopts an IGM with a density larger than the prediction of standard Big Bang nucleosynthesis.Comment: Proceedings of `Unveiling the Cosmic Infrared Background', April 23-25, 1995, Maryland. Self-unpacking uuencoded, compressed tar file with two figures include

Scattering Models and Basic Experiments in the Microwave Regime

The objectives of research over the next three years are: (1) to develop a randomly rough surface scattering model which is applicable over the entire frequency band; (2) to develop a computer simulation method and algorithm to simulate scattering from known randomly rough surfaces, Z(x,y); (3) to design and perform laboratory experiments to study geometric and physical target parameters of an inhomogeneous layer; (4) to develop scattering models for an inhomogeneous layer which accounts for near field interaction and multiple scattering in both the coherent and the incoherent scattering components; and (5) a comparison between theoretical models and measurements or numerical simulation