Cosmology and the Galaxy Bispectrum
The bispectrum of the galaxy distribution is the lowest order correlation function sensitive to the
shape of structures generated by gravitational instability and it has been recognized as a valuable
tool in the determination of galaxy bias and as a probe of the Gaussianity of primordial fluctuations.
More generally, the bispectrum can prove to be complementary to the power spectrum in constraining
cosmological parameters, as we will show by taking into account the covariance properties relevant
for a joint analysis of these statistics in current redshift surveys.
Review of "Probing Dark Energy with Baryonic Acoustic Oscillations at High Redshifts"
In this talk, a paper from members of the HETDEX team will be reviewed. Baryonic Acoustic
Oscillations (BAOs) are observed in the power spectrum of galaxies as a remnant of
of the photon-electron decoupling era, and contains useful information possibly determines the somewhat
enigmatic nature of the dark energy. To extract the information of BAOs from
the observed power spectrum, one needs to make the observation
and extraction algorithm to be accurate to the sub-percent level.
The difficulty of extracting the BAOs from the power spectrum
lies in the distortion of the power spectrum by the non-linearity,
galaxy-bias and redshift space distortions. In the HETDEX
project, "fit and extract" method (FITEX) is used for the
extraction algorithm. Amongst the several extraction algorithms
considered, (e.g., Blake & Glazebrook 2003, Angulo et al. 2005)
FITEX method is unique in the point that it does not require
explicit modeling of these non-linear effects. Through the
modeling and analysis of the possible non-linearity and
distortions, the phenomenological fitting function used for
FITEX is found to be accurate to the sub-percent level.
Natural Mechanism for Reheating of the Universe
I will show that reheating of the universe after inflation
occurs naturally EVEN WITHOUT explicit couplings between inflaton and
matter fields, if there is a non-minimal coupling between inflaton
The Texas Supernova Search
Supernovae (SNe) are popular tools to explore the cosmological expansion
of the Universe owing to their bright peak magnitudes and reasonably
rates; however, even the relatively homogeneous Type Ia supernovae are
not perfect standard candles intrinsically. Their absolute peak
must be established by corrections that have been largely empirical.
Hundreds of SNe are now found every year, shrinking the statistical
in the cosmological terms, but most of these distant discoveries do
to further the physical understanding of SNe, which may illuminate
This talk will describe recent results from the The Texas Supernova
Search, a campaign designed to discover not the most SNe nor the most
distant SNe, but instead to amass a small collection of well-observed
nearby SNe with detailed, multi-epoch spectral observations beginning at
the earliest possible phases. For the past two years, we have pointed
ROTSE-IIIb's 1.85 x 1.85 degree field of view at nearby galaxy clusters
and searched thousands of galaxies, covering hundreds of square
the sky, for supernovae. With ToO time on the neighboring 9.2m
Hobby-Eberly Telescope, we have captured SNe spectra at some of the
earliest phases ever. I will discuss the implications of these data
physics of SNe explosions, including the propagation of the burning
and the progenitors of Type Ia supernovae.