Talks & Events
Faculty Research Seminars: 2018
Past Faculty Research Seminars
Quantum Space and Time
Craig J. Hogan
"Spooky" quantum correlations across large distances have been studied in states of light and matter. The talk will summarize the state of our experiment to study similar macroscopic quantum correlations in states of space and time, originating from new physics at the Planck scale.
Journey to the center of the Super-Earth
Sub-Neptune, super-Earth size exoplanets are a new planet class. Though absent from the Solar System, they are found by microlensing, radial velocity, and transit surveys to be common around distant stars. In this talk, I'll review both recent developments and outstanding puzzles in our understanding of the nature and origin of these enigmatic planets.
Space Probes of the Highest Energy Particles: POEMMA & EUSO-SPB
Angela V. Olinto
Basic questions regarding ultrahigh energy cosmic rays (UHECRs) remain unanswered:
Giant ground observatories, such as the Pierre Auger Observatory and the Telescope Array, have shown that UHECRs are extragalactic and have a surprising composition trend. Hints of anisotropies begin to appear at energies above ~60 EeV, just when statistics become very limited.
We are designing and building space and sub-orbital missions to increase the statistics of UHECR observations at the highest energies. An international collaboration built the Extreme Universe Space Observatory (EUSO) on a super pressure balloon (SPB) to detect UHECR fluorescence from above. EUSO-SPB1 flew in the Spring of 2017. We are now planning EUSO-SPB2 to observe Cherenkov from UHECRs and inform the design of the POEMMA (Probe Of Extreme Multi-Messenger Astrophysics) space mission to discover the sources of UHECRs and observe ~10 PeV neutrinos.
Augmented Tensor Virial Equations, Mergers of Galaxies, and the Fate of the Local Group
Peter O. Vandervoort
The virial equations and the virial theorem are well known tools of inquiry in dynamical astronomy. However, astronomers seldom appreciate the full power of the tensor virial equations in theoretical investigations of the dynamics of stars and stellar systems. After a brief review of the history of the virial equations and of conventional astronomical applications, we devote most of the seminar to an investigation of the dynamical behavior of a low-dimensional model of a merger of two galaxies. The governing equations of the model are the complete sets of moment equations of the first and second orders derived from the collisionless Boltzmann equations of the galaxies. The moment equations of the first order reduce to an equation governing the relative motion of the galaxies. The moment equations of the second order separate into the tensor virial equations of the galaxies and sets of equations governing the evolution of the kinetic energy tensors of the galaxies. In order to close the systems of moment equations, we represent the galaxies as heterogeneous spheroids with arbitrary stratifications of their density distributions, and we represent the mean motions of the stars in terms of velocity fields that sustain the adopted density distributions consistently with the equation of continuity. We reduce and approximate the governing equations in the case of a head-on encounter of a dwarf galaxy with a giant galaxy. That reduction includes the effect of dynamical friction on the relative motion of the galaxies as in earlier investigations by Tremaine and others. In a survey of mergers involving dwarf galaxies of different masses and sizes, relative to the giant, an encounter either disrupts the dwarf, excites chaotic oscillations in the dwarf, or excites regular oscillations. Dynamical friction can drive a merger to completion within a Hubble time only if the dwarf is sufficiently massive. The survey of mergers provides a basis for an investigation of the evolution and fate of the Local Group.
Gigayear instabilities in close-in planetary systems
Observing the High-Redshift Universe at Submm Wavelengths