Research Interests:
My research interests include theoretical nuclear and particle astrophysics.
Much of my work has centered around simulations of core-collapse supernovae and other high energy astrophysical events.
In particular, I am interested in computational modeling of high energy astrophysical phenomena; neutrino transport and interactions in hot, dense matter; dense nuclear matter in core-collapse supernovae and neutron stars; and thermonuclear burning and nucleosynthesis.
I am currently a National Science Foundation Astronomy & Astrophysics Postdoctoral Fellow at North Carolina State University.
I am incorporating neutrino flavor mixing into the FLASH supernova simulation framework to study neutrino flavor mixing in the core-collapse supernova environment.
Education:
PhD in Physics, University of Notre Dame, 2016.
MS in Physics, University of Notre Dame, 2014.
BA in Physics, Reed College, 2011.
I am interested in the role of neutrino and nuclear physics in core-collapse supernovae.
I have extensive experience in the development and application of general relativistic numerical hydrodynamics supernova models, including detailed neutrino transport.
Neutrino flavor mixing in CCSNe
It is well understood that core-collapse supernovae (CCSNe) result from the deaths of stars with masses M>8M⊙.
Yet the explosion mechanism of CCSNe has remained one of the biggest open questions in astrophysics.
With increasing computational power, simulations of the CCSN mechanism have increased in physical fidelity, now including realistic equations of state, general relativity, and neutrino transport, but also increased in computational precision with 3D simulations and increasing resolution.
However, there is a fundamental piece of physics that remains missing from most supernova codes: neutrino flavor mixing.
I am including the effects of neutrino flavor mixing in the FLASH supernova code.
Neutrino flavor mixing may drastically change predictions of the supernova neutrino spectrum and thus the observable outcomes of CCSNe.
I will produce the first simulations of CCSNe including neutrino oscillations and generate predictions of the impact of neutrino mixing on explodability, neutrino signal, and nucleosynthesis.
Multi-messenger signals from CCSNe
Using the STIR model (described below), we now have the capability to run thousands of 1D supernova models that explode in a physically realistic way.
I have used this to explore sensitivities of multi-messenger signals - gravitational wave and neutrino - to the progenitor star and fundamental supernova physics.
My initial work has focused on relationships between observable signals and properties of the progenitor star, such as zero-age main sequence mass, core compactness at collapse, etc.
In a follow up work, we are exploring the sensitivities of the observable signals to the nuclear equation of state and correlations of the signals with fundamental nuclear physics quantities, such as the symmetry energy and effective nucleon mass.
Warren, Couch, O'Connor, & Morozova (2020). "Constraining properties of the next nearby core-collapse supernova with multi-messenger signals."
Submitted to Ap.J. arXiv:1912:03328
Modeling supernova turbulence in spherical symmetry
Working with Professor Sean Couch, I have aided in the development of a new method for artificially driving core-collapse supernova explosions in 1D simulations, Supernova Turbulence in Reduced Dimensions (STIR).
Turbulence is important for understanding the CCSN explosion mechanism, since turbulence may add a >20% correction to the total pressure behind the shock and thus aid in the explosion.
We have implemented mixing length theory (MLT) and included a model of the turbulent pressure in the FLASH supernova code for spherically symmetric simulations.
Including MLT and corrections for the turbulent pressure can result in successful explosions in spherical symmetry without altering the neutrino luminosities or interactions, as is commonly done to produce explosions in spherical symmetry.
This better replicates the physical explosion mechanism and more reliably produces the thermodynamics and composition, which is vital for accurately predicting the nucleosynthesis that occurs in the supernova environment.
Couch, Warren, & O'Connor (2020). "Simulating turbulence-aided neutrino-driven core-collapse supernova explosions in one dimension."
Ap.J. 890:2. arXiv:1902.01340
Sterile neutrinos in CCSNe
Sterile neutrinos are of interest in astrophysics both as dark matter candidates and for their potential impact on core-collapse supernovae.
In supernovae, they may serve as an efficient mechanism to transport energy in the protoneutron star and are thus of interest in investigating supernova explosion energies.
I have found that the early time explosion energy can be significantly enhanced when oscillations between a sterile neutrino and electron neutrino are included.
The enhancement is sufficient to lead to a successful explosion even in a simulation that would not otherwise explode.
Enhanced explosion energies for the sterile neutrino mass and mixing angle parameter space for mixing with an electron neutrino.
The region above the solid line enhances the explosion energy by 1% compared to a simulation witout a sterile neutrino, and above the dashed line is the region that enhances the explosion energy by 10%.
The shaded regions indicate the parameter space allowed for sterile neutrino dark matter if sterile neutrinos contribute 100%, 10%, and 1% of the dark matter mass and the solid black square shows the most recent best fit point from the X-ray flux (Boyarsky et al (2014)).
Figure from Warren, Mathews, Meixner, Hidaka, & Kajino (2016).
Warren, Mathews, Meixner, Hidaka, & Kajino (2016). "Impact of sterile neutrino dark matter on core-collapse supernovae."
IJMPA 31:25. arXiv:1603.05503
Nuclear equation of state
I have contributed to the development of the Notre Dame-Livermore Equation of State (NDL EoS), a nuclear equation of state intended for use in core-collapse supernova and neutron star simulations.
A complete understanding of the equation of state of nuclear matter will provide us with a vital link between laboratory measurements and astrophysical phenomena.
The NDL EoS meets all modern laboratory and astrophysical constraints and includes 3-body interactions and the possibility of a transition to quark gluon plasma.
Ultimately, we plan to make this equation of state publicly available for use in core-collapse supernova and neutron star simulations.
Olson, Warren, Meixner, Mathews, Lan, & Dalhed (2016). "Generalized density functional equation of state for astrophysical simulations with 3-body forces and quark gluon plasma."
Submitted to Phys.Rev.C. arXiv:1612.08992
Outreach & Inclusion
Making STEM fields LGBTQIA+ inclusive:
I am currently a member of the American Astronomical Society's Committee on the Status of Sexual-orientation and Gender Minorities in Astronomy (SGMA) and the National Organization of Gay & Lesbian Technical Professional's Postdoc Committee.
I also regularly give presentations to physics and astronomy departments on how to make their programs LGBTQIA+ inclusive and have written extensively about my experiences as a queer and trans scientist.
Popscope:
Rather than hosting public astronomy nights at academic or educational institutions, Popscope instead takes telescopes to public events and spaces and draws in people passing by.
This allows us to reach communities that would not otherwise be engaged.
Current research indicates that many informal science education efforts are not inclusive of low-income and minority ethnic groups due to expectations of previous scientific knowledge and barriers due to language, geography, and finances.
One of the goals of Popscope is to reach communities that are underrepresented in STEM fields and unengaged by most science outreach efforts by using a fundamentally different model of public outreach.
Contact
Contact MacKenzie Warren regarding their published work, outreach, or any other inquiries.
