Dark Matter and Galaxy Formation: Challenges for the Next Decade

The origin of the galaxies represents an important focus of current cosmological research, both observational and theoretical. Its resolution involves a comprehensive understanding of star formation, galaxy dynamics, the cosmology of the very early universe, and the nature of the dark matter. In this review, I will focus on those aspects of dark matter that are relevant for understanding galaxy formation, and describe the outlook for detecting the most elusive component, non-baryonic dark matter.Comment: To be published in joint proceedings for Mitchell Symposium on Observational Cosmology and Strings and Cosmology Conference, College Station, April 2004, eds. R. Allen and C. Pope, AIP, New York, and in proceedings for PASCOS04/NathFest, Boston, August 2004, eds. G. Alverson and M. Vaughan, World Scientific, Singapor

Link between S&P 500 and FTSE 100 and the comparison of that link before and after the S&P 500 peak in October 2007

The paper reviews the correlation between the S&P 500 and the FTSE 100 before and during the 2008 global financial crisis. It found that The S&P 500 has a strong causation effect on the FTSE 100, both before and since the financial crisis. This link seems to have increased after the October 2007 peak in the S&P 500. Since the crisis, the FTSE 100 appears to have a weak causation effect on the S&P 500. Before the crisis there was no apparent impact on the S&P 500’s movements from movements in the FTSE 100

From the Cosmological Microwave Background to Large-Scale Structure

The shape of the primordial fluctuation spectrum is probed by cosmic microwave background fluctuations which measure density fluctuations at z~1000 on scales of hundreds of Mpc and from galaxy redshift surveys, which measure structure at low redshift out to several hundred Mpc. The currently acceptable library of cosmological models is inadequate to account for the current data, and more exotic models must be sought. New data sets such as SDSS and 2DF are urgently needed to verify whether the shape discrepancies in P(k) will persist.Comment: 11 pages including 4 color figures, to appear in Proc. of Nobel Symposium- Particle Physics and the Universe, Physica Script

Extracting Primordial Density Fluctuations

The combination of detections of anisotropy in the Cosmic Microwave Background radiation and observations of the large-scale distribution of galaxies probes the primordial density fluctuations of the universe on spatial scales varying by three orders of magnitude. These data are found to be inconsistent with the predictions of several popular cosmological models. Agreement between the data and the Cold + Hot Dark Matter model, however, suggests that a significant fraction of the matter in the universe may consist of massive neutrinos.Comment: 20 pages including 4 color postscript figures. Full-size figures and data compilation available at http://cfpa.berkeley.edu/cmbserve/fluctuations/figures.htm

Planetary influence on the young Sun's evolution: the solar neutrino probe

Recent observations of solar twin stars with planetary systems like the Sun, have uncovered that these present a peculiar surface chemical composition. This is believed to be related to the formation of earth-like planets. This suggests that twin stars have a radiative interior that is richer in heavy elements than their envelopes. Moreover, the current standard solar model does not fully agree with the helioseismology data and solar neutrino flux measurements. In this work, we find that this agreement can improve if the Sun has mass loss during the pre-main sequence, as was previously shown by other groups. Despite this better agreement, the internal composition of the Sun is still uncertain, especially for elements heavier than helium. With the goal of inferring the chemical abundance of the solar interior, we tested several chemical compositions. We found that heavy element abundances influence the sound speed and solar neutrinos equally. Nevertheless, the carbon-nitrogen-oxygen (CNO;13N, 15O and 17F) neutrino fluxes are the most affected; this is due to the fact that contrarily to proton-proton (pp, pep, 8B and 7Be) neutrino fluxes, the CNO neutrino fluxes are less dependent on the total luminosity of the star. Furthermore, if the central solar metallicity increases by 30%, as hinted by the solar twin stars observations, this new solar model predicts that 13N, 15O and 17F neutrino fluxes increase by 25%-80% relative to the standard solar model. Finally, we highlight that the next generation of solar neutrino experiments will not only put constraints on the abundances of carbon, oxygen and nitrogen, but will also give some information about their radial distribution.Comment: 8 pages, 5 Figures http://adsabs.harvard.edu/doi/10.1093/mnras/stt142

A New Prescription for Protogalactic Feedback and Outflows: Where Have All the Baryons Gone?

Up to half of the baryons inferred to once have been in our galaxy have not yet been detected. Ejection would seem to provide the most attractive explanation. Previous numerical studies may have underestimated the role of winds. I propose a solution involving a multiphase model of the protogalactic interstellar medium and the possibility of driving a superwind. Simulations do not yet incorporate the small-scale physics that, I argue, drives mass-loading of the cold phase gas and enhances the porosity, thereby ensuring that winds are driven at a rate that depends primarily on the star formation rate. The occurrence of hypernovae, as claimed for metal-poor and possibly also for starburst environments, and the possibility of a top-heavy primordial stellar initial mass function are likely to have played important roles in allowing winds to prevail in massive gas-rich starbursting protogalaxies as well as in dwarfs. I discuss why such outflows are generically of order the rate of star formation and may have been a common occurrence in the past.Comment: MNRAS, in press (2003): minor revisions include