Session C1: Astronomy

Exoplanets in HD

Exoplanet surveys have revealed an amazing diversity of planets orbiting other stars in the last two decades. Studying the atmospheres of representative exoplanets is the key next step in leveraging these detections to further transform our understanding of planet formation and planetary physics. Additionally, atmospheric studies are critical for determining if any of the small habitable zone exoplanets that are now being detected are truly habitable, and even inhabited. In this talk I will describe recent results from exoplanet atmosphere observations with an emphasis on results from major programs using the Hubble Space Telescope. Although atmospheric studies of potentially habitable planets are currently out of reach, I will discuss how future facilities may open up this possibility in the near future.   

Detectability of cosmic dark flow in the type Ia supernova redshift-distance relation

We re-analyze the possibility of large scale bulk flow (or dark flow) with respect to the CMB background based upon the redshift-distance relation for Type Ia supernovae (SN Ia). We use a new analysis technique based upon the cosine dependence of the deviation from the Hubble flow on the sky. We apply this analysis to the Union2.1 supernova compilation and the new {\it SDSS}-II supernova survey. Results are consistent with previous bulk flow searches of $v_{df} = 325 \pm 54$ km s$^{-1}$ in the direction of $(l,b) = (276 \pm 15, 35 \pm 13)^{\circ}$ for nearby, $z < 0.05$, and inconclusive for $z>0.05$. Based upon the analysis of simulated data sets, we deduce that the current uncertainty at high redshifts arises mostly from the current error in the distance modulus. Thus, a bulk flow at large redshift is not detectable with current SN Ia data sets. We estimate a detection would require both significant sky coverage of SN Ia out to $z = 0.3$ and a greatly expanded data set of $ \geq 4500$ events might detect a bulk flow with a distance modulus error of $0.2$ mag. This data set size should be achievable with the next generation of large surveys like {\it LSST}.   

Law of Gravity, Structure and Geometry of Black Holes and the Universe

We shall present a blackhole theorem and a theorem on the structure of our Universe, proved in a recently published paper, based on 1) the Einstein general theory of relativity, and 2) the cosmological principle that the universe is homogeneous and isotropic. These two theorems are rigorously proved using astrophysical dynamical models coupling fluid dynamics and general relativity based on a symmetry-breaking principle. With the new blackhole theorem, we further demonstrate that both supernovae explosion and AGN jets, as well as many astronomical phenomena including e.g. the recent reported are due to combined relativistic, magnetic and thermal effects. The radial temperature gradient causes vertical Benard type convection cells, and the relativistic viscous force (via electromagnetic, the weak and the strong interactions) gives rise to a huge explosive radial force near the Schwarzschild radius, leading e.g. to supernovae explosion and AGN jets.   

Evidence for Planck-Scale Resonant Particle Production during Inflation from the CMB Power Spectrum

The power spectrum of the cosmic microwave background from both the Planck and WMAP data exhibits a slight dip in for multipoles in the range of $l= 10-30$. We show that such a dip could be the result of resonant creation of a massive particle that couples to the inflaton field. For our best-fit models, epochs of resonant particle creation reenters the horizon at wave numbers of $k_* \sim 0.00011 \pm 0.0004 $ ($h$ Mpc$^{-1}$). The amplitude and location of these features correspond to the creation of a number of degenerate fermion species of mass $\sim 15/\lambda^{3/2} $ $m_{pl}$ during inflation where $\lambda$ is the coupling constant between the inflaton field and the created fermion species. Although the evidence is marginal, if this interpretation is correct, this could be one of the first observational hints of new physics beyond the Planck scale.   

New outlook on the observational limits to cosmic 'dark' flow from landscape multiverse

In a series of papers by L. Mersini-Houghton et al. introduced the Landscape Multiverse scenario. In their new theory of Landscape, they have taken Quantum Mechanics as the fundamental theory of nature at any energy scale. In this framework they have tried to explore different aspects of cosmology ,one of them was the observed 'Dark' Flow. In their paper they have shown one can explain cosmic 'Dark Flow' from the nonlocal entanglement of our Hubble volume with modes and domains beyond the horizon. At that time Kashlinsky et al. observed dark flow to be about 700 km/s and that matched quite well with the prediction by Mersini-houton et al.But later PLANCK has constrained the 'dark' flow velocity to a much lower value. Mathews et al. has shown that a 'dark' flow velocity less than 300km/s is very hard to observe. Now in this work we tried to calculate the 'dark' flow velocity for a particular kind of potential and we got quite low 'dark' flow velocity around 250 km/s with some uncertainties. The potential is also of interest as it can actually explain a 'dip' observed in the low l region in the CMB power spectrum.   

BBN and CMB Constraints on Dark Radiation Revisited

The effect of dark radiation on BBN and CMB has been studied earlier. We revised the study, since new data has been available for light element abundances and Plank has new and improved data on CMB. We study the effect of an additional term dervied by integrating the Einstein equation in the 5-dimensional Randall-Sundrum Model. This new term scales as ${a^-4}$ and hence the term 'radiation'. This term is the constant of integration and it can be either positve or negative. Dark radiation can have significant effects on light element abundances at the end of big bang nucleosynthesis (BBN) and on angular spectrum of cosmic microwave background (CMB). We take $\rho_{Dr}$ to be between -41.5$\%$ and +70$\%$ of $\rho_\gamma$ and the corresponding changes in BBN abundances and CMB spectrum are observed. In this new analysis we find that $\rho_{dr}$/$\rho_\gamma$ has a preference for positive dark radiation.   

Project GRAND: Data Acquisition and Corrections

Project GRAND, a cosmic ray experiment, is located north of the Notre Dame campus. Spanning a 100 by 100 square meter area, this detector has been used to study gamma ray burst events as well as solar phenomenon such as the Forbush decrease. The quality of the data from this and previous years was improved this summer by utilizing a pressure correction and generating accurate time data. A new backup system was also employed to ensure that the data exists on multiple drives.   

100 Years of General Relativity: What's next?

This year marks the 100th anniversary of General Relativity (GR). As this celebratory year draws to a close, the question that surfaces is what will come next? While universally recognized as a powerful theory, there are identifiable problems with GR. This suggests that a next generation theory of gravitation is inevitable. Whether this will require only modest adjustments to the current paradigm or a breakthrough concept in gravitation remains to be seen. For example, will all future endeavors in gravitation be strictly limited to metric theories of gravity? The almost unanimous response is, yes, all legitimate theories of gravity must be metric in nature. This presentation challenges that conventional notion by exploring the history of GR over the last century and providing evidence rooted in Special Relativity suggesting that we may need to maintain a more open mind regarding the future of gravitation theory.