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

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

Probing large-distance higher-dimensional gravity with Cosmic Microwave Background measurements

It has been recently argued that higher dimensional gravity theories may manifest themselves not only at short microscopic distances but also at large cosmological scales. We study the constraints that cosmic microwave background measurements set on such large distance modifications of the gravitational potential

A particle dark matter footprint on the first generation of stars

Dark matter particles with properties identical to dark matter candidates that are hinted at by several international collaborations dedicated to experimental detection of dark matter (DAMA, COGENT, CRESST and CDMS-II, although not, most notably, by LUX), and which also have a dark matter asymmetry identical to the observed baryon asymmetry (Planck and Wilkinson Microwave Anisotropy Probe), may produce a significant impact on the evolution of the first generation of low-metallicity stars. The lifetimes of these stars in different phases of stellar evolution are significantly extended, namely, in the pre-main sequence, main sequence, and red giant phases. In particular, intermediate-mass stars in the red giant phase experience significant changes in their luminosity and chemical composition. The annihilations of dark matter particles affect the interior of the star in such a way that the $3\alpha-$reaction becomes less efficient in the production of carbon and oxygen. This dark matter effect contradicts the excess of carbon and other metals observed today in stars of low mass and low metallicity. Hence, we can impose an upper limit on the dark matter halo density, and therefore on the redshift, at which the first generation of low-metallicity stars formed.Comment: 8 pages; 5 figures ; The article's link: http://iopscience.iop.org/0004-637X/786/1/25

Helioseismology and Asteroseismology: Looking for Gravitational Waves in acoustic oscillations

Current helioseismology observations allow the determination of the frequencies and surface velocity amplitudes of solar acoustic modes with exceptionally high precision. In some cases, the frequency accuracy is better than one part in a million. We show that there is a distinct possibility that the quadrupole acoustic modes of low order could be excited by gravitational waves (GWs), if the GWs have a strain amplitude in the range $10^{-20}h_{-20}$ with $h_{-20}\sim 1$ or $h_{-20}\sim 10^{3}$, as predicted by several types of GW sources, such as galactic ultracompact binaries or extreme mass ratio inspirals and coalescence of black holes. If the damping rate at low order is $10^{-3}\eta_N$ $\mu{\rm Hz}$, with $\eta_N\sim 10^{-3}$ - $1,$ as inferred from the theory of stellar pulsations, then GW radiation will lead to a maximum rms surface velocity amplitude of quadrupole modes of the order of $h_{-20}\eta_N^{-1}\sim$ $10^{-9}$ - $10^{-3}$ ${\rm cm\; s^{-1}}$, on the verge of what is currently detectable via helioseismology. The frequency and sensitivity range probed by helioseismological acoustic modes overlap with, and complement, the capabilities of eLISA for the brightest resolved ultracompact galactic binaries.Comment: 8 pages, 1 table and 4 figures, updated bibliography. The article was reviewed following the comments and suggestions made by several colleague