Physics and Astronomy Colloquium 2019-2020

Thursdays, 4:00-5:00 pm

1-434 Physics and Astronomy (map)

Reception from 3:15-3:30
(unless otherwise posted)

For more information, contact Yaroslav Tserkovnyak

Fall 2019

Thursday, October 3, 2019

Saxon Lecture

How many numbers does it take to determine our Universe?

Michael S. Turner

Kavli Foundation and University of Chicago

Over the past three decades our understanding of the Universe has deepened.  The WMAP and Planck teams have asserted that just six numbers are needed to describe the whole Universe (fewer than the ten digits in a phone number), based upon their high-precision, all-sky maps of the Cosmic Microwave Background. Others have different opinions: one, two, a different six, and nine to determine our Universe. As I will discuss, the choice of numbers reveals much about what we know, our aspirations, and how we think about the Universe. After exploring the landscape, I will advocate for zero!


Thursday, October 10, 2019

On Ising's model of ferromagnetism

Peter Armitage

Johns Hopkins University

The 1D Ising model is a classical model of great historical significance for both classical and quantum statistical mechanics. Developments in the understanding of the Ising model have fundamentally impacted our knowledge of thermodynamics, critical phenomena, magnetism, conformal quantum field theories, particle physics, and emergence in many-body systems. Despite the theoretical impact of the Ising model there have been very few good 1D realizations of it in actual real material systems. However, it has been pointed out recently, that the material CoNb2O6, has a number of features that may make it the most ideal realization we have of the Ising model in one dimension.   In this talk I will discuss the surprisingly complex physics resulting in this simple model and review the history of "Ising’s model” from both a scientific and human perspective.  In the modern context I will review recent experiments by my group and others on CoNb2O6.  In particular I will show how low frequency light in the THz range gives unique insight into the tremendous zoo of phenomena arising in this simple model system.

Thursday, October 17, 2019

Building a quantum computer with neutral atoms

David Weiss

Penn State University

I will describe our work towards making a quantum computer using ultra-cold atoms trapped in a 3D optical lattice. In particular, I will explain: how we change the quantum state of individual atoms, even in the middle of the array, without affecting the quantum states of other atoms; how we sort atoms by realizing a Maxwell's demon; and how we reliably detect the internal states of the atoms without losing any.


Thursday, October 24, 2019


Thursday, October 31, 2019

Physics and the HIV Virus

Robijn Bruinsma

University of California, Los Angeles

The intense research effort dedicated to the HIV virus and to other retroviruses has revealed our fundamental lack of understanding how the HIV virus "works". The colloquium will discuss how a combination of the physics of soft matter and of numerical simulations provides us with important insights into the different stages of the life-cycle of HIV. Conversely, the study of the operation of HIV provides statistical physics with interesting challenges, such as the apparent violation of the Second Law of Thermodynamics during the assembly process.


Thursday, November 7, 2019

The Physics of Active Matter
M. Cristina Marchetti
University of California, Santa Barbara
Assemblies of interacting self-driven entities form soft active materials with intriguing collective behavior and mechanical properties. Examples abound in nature on many scales, from the flocking of birds to cell migration in morphogenesis. They also include synthetic systems, from engineered microswimmers to self-catalytic colloids and autonomously propelled liquid crystals.  What unifies these systems is that they are driven out of equilibrium by dissipative processes that act on each individual particle, hence break the time reversal symmetry of the dynamics at the microscale. This results in surprising behavior. For instance, active fluids flow with no externally applied driving forces, active gases do not fill their container, and active particles spontaneously organize when passive ones would not. Since time reversal symmetry of the microdynamics and the associated detailed balance of forward and reverse processes are built into the foundation of equilibrium statistical physics, the description of active systems poses a new theoretical challenge.  In this talk I will discuss the physics of active matter with examples from both the living and non-living worlds. I will show that by combining minimal physical models with continuum theory and simulations we are making advances towards capturing quantitatively the laws of spontaneous organization of active systems.  This theoretical progress has implication for both formulating design principles for new smart materials and understanding cellular and multicellular organization.


Thursday, November 14, 2019

Probing Dark Matter Throughout Cosmic History

Vera Gluscevic

University of Southern California

I will review the status of cosmological searches for dark matter-baryon interactions, summarizing the best current limits on scattering of light particle candidates with protons derived from the cosmic-microwave-background anisotropy measurements. I will then present stringent new bounds on the same physics, inferred recently from the observed population of the Milky Way satellite galaxies. I will highlight complementarities between different observations and laboratory searches for dark matter, and discuss the prospects for unveiling the physics of dark matter in the coming decade.


Thursday, November 21, 2019

Quantum decorating: Imaging novel electronic states in defect-engineered 2D materials

Christopher Gutierrez

University of California, Los Angeles

Two-dimensional (2D) quantum materials have attracted much excitement due to the many interesting physical properties that emerge when they are thinned down to single atomic layers. Graphene, for instance, is a single layer of the ordinary graphite found in your pencil lead, yet its electrons behave like relativistic massless Dirac fermions. This has allowed graphene to act as a tabletop testbed for exploring novel forms of symmetry breaking and for verifying longstanding theoretical predictions in relativistic quantum mechanics. 

Importantly, owing to its exposed surface, graphene’s electronic properties can be precisely tailored by the presence of atomic defects. In this talk I will present atomic scanning probe and photoemission spectroscopy experiments that highlight how the spatial arrangement of such defects can be harnessed to create novel electronic states in graphene. In the first part, I will show how different types of atomic scatterers peppered above (or below) graphene can self-assemble and drive the formation of new and topologically distinct collective density wave phases in graphene. In the second part, I will show that when substrate defects instead form large, amorphous clusters, they can create local potentials that can trap graphene’s quasi-relativistic electrons into quantized atomic-like orbitals, opening the door to studying 2D analogs of large, relativistic “Dirac atoms.”

Thursday, November 28, 2019

Thanksgiving Holiday

No Colloquium

Thursday, December 5, 2019, 4:00-5:00 p.m.

"TBA" by Anshul Kogar (University of California, Los Angeles)


Winter 2020

Thursday, January 9, 2020, 4:00-5:00 p.m.

Gender, Equity, Power Structures and Implicit Bias in STEM

Elizabeth Simmons (University of California, San Diego)

University of California, San Diego

The presentation will start by reviewing data on the current status of gender equity in science, technology, engineering and mathematics (STEM) disciplines and summarizing social science research that illuminates some causes of gender disparities in STEM. With this context established, the focus will shift to how women enter into leadership roles in academic settings, what they experience and how gender impacts the way they exercise their authority. The final part of the talk will discuss how we can all contribute to changing the face of leadership for the future, to the benefit of all of us in STEM.


Thursday, January 16, 2020, 4:00-5:00 p.m.

"TBA" by Leon Balents (University of California, Santa Barbara)


Thursday, January 23, 2020, 4:00-5:00 p.m.

"TBA" by Stefania Gori (University of California, Santa Cruz)


Thursday, January 30, 2020, 4:00-5:00 p.m.

"TBA" by Gregg Hallinan (Caltech)


Thursday, February 6, 2020, 4:00-5:00 p.m.

"TBA" by Ian Shoemaker (Virginia Tech)


Thursday, February 13, 2020, 4:00-5:00 p.m.

"TBA" by Pablo Jarillo-Herrero (MIT)


Thursday, February 20, 2020, 4:00-5:00 p.m.

"TBA" by Irene Tamborra (Niels Bohr Institute)


Thursday, February 27, 2020, 4:00-5:00 p.m.

"TBA" by Katie Bouman (Caltech)


Thursday, March 5, 2020, 4:00-5:00 p.m.


Thursday, March 12, 2020, 4:00-5:00 p.m.


Thursday, June 6, 2019, 4:00-5:00 p.m.



Spring 2020

Thursday, April 2, 2020, 4:00-5:00 p.m

"TBA" by Steven Shenker (Stanford University)


Thursday, April 9, 2020, 4:00-5:00 p.m.

"TBA" by Hung-Hai Lee (University of California, Berkeley)


Thursday, April 16, 2020, 4:00-5:00 p.m.

"TBA" by Vinvenzo Vitelli (University of Chicago)


Thursday, April 23, 2020, 4:00-5:00 p.m.

"TBA" by Bradley Siwick (McGill)


Thursday, April 30, 2020, 4:00-5:00 p.m.



Thursday, May 7, 2020, 4:00-5:00 p.m.

"TBA" by Jessica McIver (LIGO)


Thursday, May 14, 2020, 4:00-5:00 p.m.

"TBA" by Mark Eriksson (University of Wisconsin-Madison)


Thursday, May 21, 2020, 4:00-5:00 p.m.

"TBA" by Annika Peter (Ohio State University)


Thursday, 28, 2020, 4:00-5:00 p.m.

"TBA" by Clifford Cheung (Caltech)


Thursday, June 4, 2020, 4:00-5:00 p.m.

"TBA" by Sera Markoff (University of Amsterdam)







Past Physics and Astronomy Colloquia