Colloquium Archives

Savvas Koushiappas, Brown University

Title: Illuminating the Black Hole - Galaxy Connection (Video)

Abstract:  Supermassive black holes, and the active galactic nuclei (AGN) that they power, are thought to play an integral role in the evolution of galaxies by acting to regulate, and eventually suppress, the star formation activity of their hosts.  I will discuss recent efforts to test this proposed connection by studying the demographics of galaxies undergoing active black hole growth.  In particular, I will highlight recent results from the CANDELS survey, which has used new infrared imaging from the Hubble Space Telescope to study of properties of galaxy back when the Universe was a quarter of its current age.  It is during this era of cosmic history that the nuclear activity and star formation activity in the Universe are at their peak.  I will discuss what CANDELS is currently revealing about the mechanisms that fuel AGN activity at this epoch and the connection between black hole growth and the emergence of the first generation of passive galaxies in the Universe.

Dale Kocevski, Colby College

Title: Illuminating the Black Hole - Galaxy Connection (Video)

Abstract:  Supermassive black holes, and the active galactic nuclei (AGN) that they power, are thought to play an integral role in the evolution of galaxies by acting to regulate, and eventually suppress, the star formation activity of their hosts.  I will discuss recent efforts to test this proposed connection by studying the demographics of galaxies undergoing active black hole growth.  In particular, I will highlight recent results from the CANDELS survey, which has used new infrared imaging from the Hubble Space Telescope to study of properties of galaxy back when the Universe was a quarter of its current age.  It is during this era of cosmic history that the nuclear activity and star formation activity in the Universe are at their peak.  I will discuss what CANDELS is currently revealing about the mechanisms that fuel AGN activity at this epoch and the connection between black hole growth and the emergence of the first generation of passive galaxies in the Universe.

Adrian Del Maestro, University of Vermont

Title:  Low Dimensional Superfluidity (Video)

Abstract: In one spatial dimension it is not possible to break a continuous symmetry due to strong fluctuations, even at zero temperature. Although fermionic examples of quasi-one-dimensional systems abound, including carbon nanotubes and quantum wires, it is much more difficult to reach this limit in high density bosonic fluids due to a short coherence length on the atomic scale.  Recent advances in nanofabrication techniques now allow for the confinement of the quantum liquid helium-4 inside pores with nanometer radius, but unequivocal experimental evidence of one-dimensional behavior is still lacking. We have performed large scale numerical simulations near the superfluid transition to investigate how the signatures of dimensional crossover are reflected in the thermodynamic properties of nano-confined helium-4. The results demonstrate the breakdown of the two-fluid model of superfluidity in low dimensions and hint at the emergence of quantum hydrodynamics inside the pore at length scales that can be probed in the laboratory.

Jack Harris, Yale University

Title: Observing Quantum Effects in the Motion of a Millimeter-Sized Object  (Video)

Abstract: A major challenge in physics is to understand how the classical behavior of macroscopic objects emerges from laws that are fundamentally quantum mechanical. The field of optomechanics seeks to address this issue by studying quantum effects in the motion of macroscopic objects that are coupled to individual photons. In the past few years, experiments have demonstrated a number of quantum effects in these devices, including ground-state cooling, entanglement, and the quantum back-action of displacement measurements. I will give an overview of our group's work on these topics. I will also describe our recent work on optomechanical effects in superfluid helium devices.

 

Nathan Lundblad, Bates College

Title: Quantum-Gas Physics in Orbit: Prospects for Microgravity Bose-Einstein Condensates Aboard NASA's Cold Atom Laboratory  (Video)

Abstract: Notions of geometry, topology, and dimensionality have directed the historical development of quantum-gas physics, as has a relentless search for longer-lived matter-wave coherence and lower absolute temperature.  With a toolbox of forces for confinement, guiding, and excitation, physicists have used quantum gases to test fundamental ideas in quantum theory, statistical mechanics, and in recent years notions of strongly-correlated many-body physics from the condensed-matter world.  Some of this work has been hampered by terrestrial gravity; levitation schemes of varying degree of sophistication are available, as are atomic-fountain and drop-tower microgravity facilities, but the long-term free-fall environment of low-Earth orbit remains a tantalizing location for quantum-gas experiments. 

Charlie Conroy - Harvard University

Title: Extragalactic Archeology  (Video)

Abstract: One of the primary avenues for understanding the formation and evolution of galaxies is through studying their stellar populations.  A new generation of  tools that we have been developing are now capable of measuring an unprecedented amount of information from high quality spectra of galaxies.  In this talk I will present results from an ongoing program aimed at measuring the stellar initial mass function, ages, and detailed elemental abundance patterns of early-type galaxies over the interval 0<z<1.  Constraints on the abundances of the alpha, iron peak, and neutron capture elements offer the promise of reconstructing the detailed star formation histories of these now dormant galaxies.  By measuring the evolution of these quantities through cosmic time we are gaining fresh insights into the assembly histories of galaxies. 

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