Catherine Deibel, Louisiana State University
Fri., Oct. 2, 2015, 12:30 PM
At the birth of our Universe, the Big Bang produced the initial abundances of hydrogen, helium, and lithium that are seen in our Galaxy today. All other elements, however, were synthesized in stellar environments through nuclear processes. Many of these heavy elements were produced in violent stellar explosions, such as classical novae, X-ray bursts, and supernovae, that are driven by nuclear reactions. This nucleosynthesis, which continues in our Galaxy, can be understood through the combination of stellar observations, computational physics, and experimental nuclear physics. Specifically, the study of these nuclear reactions in the laboratory has undergone signicant advancements with recent developments in radioactive ion beam facilities and detector technology, which have allowed experimental work on isotopes that do not naturally occur on Earth. I will discuss these recent advancements and experimental results using specific examples of key nuclei and nuclear reactions that occur in several types of stellar explosions, including X-ray bursts and classical novae, in the context of the chemical evolution of our Galaxy.
See Prof. Deibel's website for more information about her research.
Marc Kamionkowski, Johns Hopkins University
Fri., Oct. 30, 2015, 12:30 PM
Our existing physical laws are unable to explain several features of the observed Universe. The nature of the dark matter that holds individual galaxies together and of the dark energy that drives different galaxies away from each other both require new physics beyond the Standard Model and general relativity. The preponderance of matter over antimatter likewise requires some new baryon-number violation beyond that in the Standard Model. Explanations for the primordial density inhomogeneities observed in the cosmic microwave background all involve new physics. I will review these questions, discuss some existing avenues to make progress, emphasizing several ways in which considerations of symmetry and geometry may play a role in the quest for new cosmological physics.
See Prof. Kamionkowski's website for more information about his research.
Nuclear Physics Aspects of Stellar Explosions
- How are the heavy elements synthesized in the cosmos?
- Is the merging of two neutron stars a source of heavy element nucleosynthesis?
- How do supernovae explode?
Questions like these are driving the field of Nuclear Astrophysics, where astrophysical observations and modeling meet nuclear physics experiments and theoretical calculations. Stellar observations provide new evidence of nucleosynthesis in different astrophysical environments and modeling of these environments requires an accurate description of the nuclear physics involved in these calculations. Nuclear reactions, radioactive decay and the properties of individual nuclei are important components of this complex puzzle and major effort is devoted from experiment and theory to address this need. This talk will focus on the nuclear physics aspects of heavy element nucleosynthesis in different explosive environments. I will present experiments performed at the National Superconducting Cyclotron Laboratory, a rare isotope beam facility, and I will discuss recent results and new initiatives.
See Prof. Spyrou's website for more information about her research.
What Is the Higgs Boson, How Did We Find it, and What’s Next for the LHC?
James Saxon ('10), University of Chicago
Fri., Nov. 20, 2015, 12:30 PM
This talk will begin with a brief exposition of the Standard Model, outlining in particular the Higgs Mechanism and the origin of masses of elementary particles. The majority of the talk will focus on the ATLAS experiment and the discovery and early measurements of the Higgs boson. The talk will conclude with an overview of current questions in the field and plans in the second run of the LHC.
Xavier Siemens, University of Wisconsin-Milwaukee
Wed., Dec. 2, 2015, 4:30 PM
For the last decade, the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has been using the Green Bank and Arecibo radio telescopes to monitor millisecond pulsars. NANOGrav aims to directly detect low-frequency gravitational waves which cause small changes to the times of arrival of radio pulses. In this talk I will discuss the work of the NANOGrav collaboration and our sensitivity to gravitational waves from astrophysical sources. I will show that a detection is possible in the next few years.
See Prof. Siemens's website for more information about his research.