Nuclear Physics Seminar

semester, 2019


Friday, January 25th 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
Organizational Meeting

Friday, February 1st 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.

Friday, February 8th 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.

Friday, February 15th 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Aditya Dhumuntarao, University of Minnesota
Subject: Chaos in Action: Developing an Action Principle for Open Systems

Friday, February 22nd 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Tom Welle, University of Minnesota
Subject: To be announced.

Friday, March 1st 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.

Friday, March 8th 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
Speaker: Andre Sieverding, University of Minnesota
Subject: The neutrino process with fully time-dependent supernova neutrino spectra.

Friday, March 15th 2019
11:00 am:
Nuclear Physics Seminar in Physics Tate 301-20
Speaker: Aleksey Cherman, University of Minnesota
Subject: TBD

Friday, March 22nd 2019
Speaker: There will be no seminar this week due to Spring Break.

Friday, March 29th 2019
11:00 am:
Nuclear Physics Seminar in Physics Tate 301-20
Speaker: James Austin Harris, Oak Ridge National Lab
Subject: The multidimensional character of nucleosynthesis in core-collapse supernovae

The intrinsically multi-dimensional neutrino-driven explosion mechanism of core-collapse supernovae (CCSNe) is notoriously difficult to model self-consistently.

As a matter of either computational expediency or necessity, nuclear burning, when included at all, is traditionally constrained to a small reaction network consisting only of the (α,γ) reactions necessary in linking 4He to 56Ni.

Feedback between the evolving hydrodynamics and changing composition, and resulting energy generation, precludes the deficiencies of this simplification from being entirely resolved with post-processing calculations.

Using a much more realistic, in situ reaction network capable of accurately tracking nuclear energy generation and neutronization, we examine the nucleosynthesis in multidimensional, self-consistent, neutrino-driven supernova models.

We find differences between the in situ and post-processing approaches, indicating that such rigor in evolving the nuclear composition is needed to accurately calculate the nucleosynthesis of matter that has been ejected from the inner regions of the explosion mechanism.

This has implications for some of the most interesting nucleosynthetic processes in CCSNe, specifically α-rich and α-poor freeze-out, which produces several isotopes particularly relevant to observations (e.g.44Ti, 48Ca, and 92Mo).


Thursday, April 4th 2019
1:30 pm:
Nuclear Physics Seminar in Physics Tate 301-20
Speaker: Amol Vivek Patwardhan, University of Wisconsin-Madison
Subject: Neutrino spin-coherence in a core-collapse supernova environment
NOTE: change of time from previous email.

We examine the prospects for coherent spin-transformations of Majorana neutrinos (i.e., neutrino-antineutrino transformations) in a core-collapse supernova environment. We observe that, under certain conditions, resonant effects can drive substantial neutrino-antineutrino conversion, with potential implications for subsequent flavor evolution as well as the neutron-to-proton ratio (equivalently, the electron fraction) of the material in the supernova envelope. We also investigate a nonlinear feedback mechanism that arises from the coupling between the neutrino distributions and the electron fraction, potentially assisting the stabilization of the resonance.


Friday, April 12th 2019
11:00 am:
Nuclear Physics Seminar in Physics Tate 301-20
Speaker: Manibrata Sen, Northwestern University
Subject: Supernova neutrino oscillations: the slow, the furious and the fast!

Neutrino flavor conversions are known to play a very important role in core-collapse supernova explosions. Inside a supernova, neutrino density is so large that neutrino-neutrino interactions take place, giving rise to "collective oscillations" occurring with a rate much larger than the usual MSW flavor conversions. In this talk, I would like to discuss some of the interesting aspects of these rapid flavor conversions, and the impact they can have on supernova explosions and nucleosynthesis. Finally, I will also talk about a simple way of diagnosing the presence of these instabilities in large scale numerical simulations.


Friday, April 19th 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
To be announced.

Friday, April 26th 2019
11:00 am:
Nuclear Physics Seminar in Physics Tate 301-20
Speaker: Sanjay Reddy, University of Washington
Subject: “Hunting for dark matter with neutron stars”

I will discuss new strategies to discover or constrain dark matter using neutron stars and gravitational waves.


Friday, May 3rd 2019
11:00 am:
Nuclear Physics Seminar in Physics Tate 301-20
Speaker: Samuel Giuliani, NSCL/FRIB Laboratory, Michigan State University
Subject: r process, kilonova and nucleosynthesis of superheavy elements: The role of fission

The rapid neutron capture process (r process) is responsible for the production of half of the elements heavier than iron that we observe in the Universe. The quest to identify its actual astrophysical site is still ongoing, but there are strong indications, including the recent observation of the GW170817 electromagnetic counterpart, that make neutron star mergers (NSM) a likely candidate. Reliable estimates of nucleosynthesis yields on NSM require an accurate description of the relevant nuclear physics inputs including nuclear masses, neutron capture rates, β- and α-decay rates and, for fissioning nuclei, fission rates and fission fragments distributions. Several of these quantities can be computed from a consistent theoretical framework using the energy density functional (EDF) approach.
In this talk I will revise how uncertainties in the nuclear physics properties of neutron-rich nuclei impact nucleosynthesis calculations, with a focus in the fission properties of (super)heavy nuclei. I will present a new set of fission rates obtained from microscopic nuclear many-body calculations, which are used as a nuclear input in r-process nucleosynthesis calculations in NSM. The possible formation of superheavy elements during the r-process nucleosynthesis as well as the impact on kilonova light curve, a quasithermal transient powered by freshly synthesized r-process nuclei, will be discussed. Finally, I will introduce recent developments in the estimation of fission yields and the possible extension to r-process nuclei.


Friday, May 10th 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.

Friday, May 17th 2019
11:00 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week.

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