Talks are on Wednesdays at 3:35pm in Nielsen 506. Speakers: please plan for a 45 minute talk with 15 minutes of questions. For updates and changes, contact Andrew W. Steiner. Graduate students signed up to take this course for credit, see instructions below.

Date | Speaker | Title |

Jan. 29 | Vassilios Mewes (ORNL) | SphericalNR: A Dynamical Spacetime and GRMHD Evolution Framework in Spherical Coordinates with the Einstein Toolkit |

Abstract: Numerical relativity codes that do not make assumptions on spatial symmetries most commonly adopt Cartesian coordinates. While these coordinates have many attractive features, spherical coordinates are much better suited to take advantage of approximate symmetries in a number of astrophysical objects, including single stars, black holes, and accretion disks. I will describe SphericalNR, a framework that numerically solves the Einstein Field equations of General Relativity together with the equations of general relativistic magnetohydrodynamics in spherical coordinates in the Einstein Toolkit, an open source toolkit for computational astrophysics that is originally designed for Cartesian coordinates. The spacetime evolution equations are written as a reference-metric version of the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) and fCCZ4 formulation, evolving tensor components in an orthonormal basis w.r.t. the chosen reference metric. For the matter sector, we have developed a reference metric formalism for the 3+1 GRMHD equations known as the Valencia formulation. I will briefly introduce the evolution equations for both spacetime and fluid evolution, the reference metric formalism, implementation details as well as results from a range of code tests. | ||

Feb. 5 | David Milstead (Stockholm Univ.) | Particle Physics at the Cross-roads |

Abstract: The Large Hadron Collider has delivered the Higgs boson. A long term program of precision Higgs measurements both with the LHC and a new e+e- collider is regarded as being essential. Outside of the dedicated Higgs program, there is a range of proposed experiments which can perform explicit searches for new phenomena beyond the Standard Model (SM). In this seminar, I'll discuss SM problems (eg naturalness, strong CP, lack of baryogenesis ) and describe proposed experimental programs (collider and non-collider) which can address them. A backdrop to this seminar is the European Particle Physics Strategy which is presently being updated and which will attempt set a course for particle physics in the coming years. | ||

Feb. 12 | Noah Frere (UTK) | The Purple Edge Problem |

Abstract: What is the relationship between asteroids and meteorites? We will take a look at the spectra of 13 meteorites that resemble V-type asteroids with strong absorption features at around 1 and 2 microns. We will see how changing the blue edge (the wavelength at the higher frequency edge of the spectrum) and the red edge (the wavelength at the lower frequency edge of the spectrum) affects our spectral analysis, which in turn effects our compositional analysis. This in turn effects the correlations we draw between these meteorites and V-type asteroids. We will also look at the spectra of asteroid 4 Vesta and sixteen vestoids. | ||

Feb. 19 | Ryan Landfield (ORNL) | Gravitational Wave Astronomy of Core-Collapse Supernovae |

Abstract: Utilizing the data from a CHIMERA code simulation of a supernova explosion of a 15 Solar mass star, we create detailed gravitational wave signatures as a function of time. The detection of such gravitational waves, possibly in concert with the detection of the supernova neutrinos, would provide invaluable direct information about the the supernova ‘central engine’, allowing us to validate our models and to derive a more detailed understanding of the high-temperature, high density nuclear physics involved, as well as the formation behavior and early evolution of proto-neutron stars. | ||

Feb. 26 | Himal Acharya (UTK) | Search of Rare Higgs and Z decays |

Abstract: Rare Higgs decays are a sensitive laboratory in the search for new physics. The Higgs boson is the least explored standard model particle. It is also predicted to couple to new generations of particles in many models beyond the standard model. These particles have the potential to change the standard model decay rates, in some instances by orders of magnitude. Furthermore, as new particles can be virtual, their mass is not restricted by the energy available at the Large Hadron Collider, but can be much higher. I focus on the decay of the Higgs boson into charm quarks which is not yet measured leaving the window for new physics wide open. | ||

Mar. 4 | Jacob Daughhetee | First Detection of Coherent Elastic Neutrino-Nucleus Scattering on Argon |

Abstract: In 2017, the COHERENT collaboration made the first observation of coherent elastic neutrinonucleus scattering (CEvNS) using a 14.6 kg CsI scintillating crystal detector located at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. In addition to neutrons, the 1.4 MW pulsed (60 Hz) proton beam at the SNS produces charged pions which subsequently decay to yield a large neutrino flux with a well-known energy spectrum and time structure. COHERENT employs a suite of detectors at the SNS to search for CEvNS in different target nuclei and to measure potential backgrounds. This multi-target program allows for testing of Standard Model predictions for CEvNS as well as for verifying the N 2 -dependence of the cross section of this interaction. CENNS-10, a 24 kg liquid argon scintillation detector, has been actively taking data at the SNS since the spring of 2017. This talk will detail the methods and results of a search for and detection of CEvNS in CENNS-10 data. | ||

Mar. 11 | TBD | TBD |

Mar. 18 | (spring break) | (spring break) |

Mar. 25 | TBD | TBD |

Apr. 1 | Charles Hughes (UTK) | TBD |

Apr. 8 | Student talks | Student talks |

Apr. 15 | Antigoni Georgiadou (ORNL) | Computational Cosmology: Real and Virtual Universe |

Abstract: Why can’t we measure the Universe? Wide-field sky surveys capture the large-scale distribution of galaxies, while scientists use simulations to capture theory and compare to observations. But, though modern cosmological simulations of dark matter consistently reach the required level of precision, the effect of baryonic physics on cosmological scales is expected to be a source of a much more severe systematic error. To solve the discrepancy between what theorists can model well and what we see, we need to either approximate the baryonic physics and/or accelerate computations by using the most powerful supercomputers. I will discuss work done to address this challenge by developing statistical frameworks to emulate the large-scale structure of the Universe. I will also talk about current work on porting cosmological simulation codes to next generation supercomputers. | ||

Apr. 22 | Student talks | Student talks |

Prepare a 30 minute talk (typically about 15 slides) on some recent topic in Astronomy or High-energy physics. It should be based on a result in a refereed publication in a Astro or HEP journal over the past 10 years, e.g. from Phys. Rev. D or Astrophys. J will work.

Make sure your talk has structure, it should have a title, an outline, a summary slide, and you should emphasize the basic message two or three times in the talk itself.

While the talk must be based on a result, you should make sure to give enough introductory material so that the result is understandable by the other graduate students. You will likely need to consult additional references in order to help you design your talk. You may find the review journals (Rev. Mod. Phys., Ann. Rev. Astron. and Astrophys., etc.) useful, Your talk cannot be entirely introductory - it must present a recent result. You should be able to state who computed the result, when, and what the significance of the result is (or was). Feel free to stop by my office or set up an appointment to discuss your talk.

I encourage you to talk to me when you have selected a topic so that we can help make sure you will be successful.

I have reserved the last couple of weeks in the semester for student talks, but you are free to give your talk at any time during the semester (unless that week has already been taken by someone else).

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