This is a collection of slides from various talks that I have given. The movies are external, and so aren't included, but some of them can be found in the gallery. I have provided abstracts where they were given for the original talk. A full list of seminars I have given is on my Curriculum Vitae. For those below I only give the most recent presentation on a particular subject, and generally highlight talks with a more formal setting.
Given 2008-9-18 at Arizona State University
Supernovae of Type Ia (SN Ia) are bright transients resulting from the thermonuclear incineration of a white dwarf (WD) star. These Supernovae have remarkably regular properties, which has made them excellent distance indicators for studying the expansion history of the universe. I will briefly review the use of SN Ia as distance indicators, discuss how this enables measurement of the makeup of the universe, and what challenges have arisen during the ongoing effort to optimize near-future large scale SN Ia surveys which will produce the interesting constraints on the Dark Energy component of the universe. While used extensively for measurement of the expansion history of the universe, the stellar origins of SN Ia still remain murky. I will review the scenarios which are currently believed to lead to SN Ia, and discuss the challenges these present from both theoretical and observational perspectives. Finally, I will turn to the dynamics of the supernova explosion itself. While the evidence that SN Ia arise from thermonuclear incineration of a WD is quite solid, the precise dynamics are still in the process of being understood. Great strides have been made over the past decades toward an understanding of the explosion process, but state of the art multi-dimensional simulations of the explosion have presented new challenges to explosion mechanisms. I will discuss the several proposed mechanisms and the physics on which they are based. Specifically I will demonstrate the importance of the ignition conditions of the the deflagration phase and the role of turbulent combustion and its uncertainties. A better understanding of progenitors and explosion dynamics are necessary for a more complete understanding of the SN Ia population being observed in large scale surveys and how it might evolve over the history of the universe.
Given 2008-8-28 at the Conference "The Equation of State in Astrophysics" at Argonne
I will give a general overview of the astrophysical circumstances which may lead to the catastrophic incineration of a white dwarf (WD) star by thermonuclear burning. The proposed scenarios under which an explosion can occur will be contrasted with those in which a collapse is expected. However, these two remarkably different outcomes share many of the same physical processes, an understanding of which is required for accurate simulation of either. The efficient numerical equation of state (EOS) which is used in large-scale multi-dimensional simulations of WD incineration will be discussed explicitly. After reviewing the important physical EOS contributions, I will discuss in detail how the plasma Coulomb corrections in the EOS are related to the charge screening of nuclear reactions. This relationship will then find immediate application in a consistent framework for determination of the nuclear statistical equilibrium (NSE) state of the burned material in the WD in the presence of reaction screening. Finally I will discuss the impact of dynamic adjustment of the NSE state on the thermodynamic and therefore hydrodynamic properties of the WD matter, particularly regarding the buoyancy of burned material, and how this plays out during the deflagration stage of a supernova.
Given 2008-4-16 at The State University of New York - Stonybrook