The Fall 2017 colloquia will be held in the lobby of the Physical Sciences Complex unless otherwise noted

Each week during the semester, the Department of Physics invites faculty, students and the local community to hear prominent scientists discuss intriguing physics research. The Fall 2017 colloquia will be held Tuesdays in the Physical Sciences Complex lobby at 4:00 p.m. (preceded by light refreshments at 3:30 p.m.)

Parking is available in the Regents Drive Parking Garage (PG2). An attendant will direct visitors within the garage. Additionally, a free ShuttleUM bus runs between the College Park Metro Station and Regents Drive at about eight-minute intervals.

For further information, please contact the Physics Department at 301-405-5946 or email This email address is being protected from spambots. You need JavaScript enabled to view it..

September 5
Jon McKinney, University of Maryland 

Probing General Relativity with the Event Horizon Telescope

The first resolved images of the strong-gravity region of a black hole will soon be produced by the Event Horizon Telescope (EHT).  I will discuss the significant instrumental, observational, and theoretical efforts of the EHT collaboration that have come together in order to probe the strong-field gravity regime of the black hole in the center of our Galaxy in SgrA* and in the galaxy M87.  I will highlight the challenges of interpreting past and future observations, which require state-of-the-art computational physics simulations of the plasma, black hole, and the polarized radiation.  Such simulation models reveal a wealth of information that can be used to probe (and potentially test) Einstein's general relativity in the strong-field regime.

September 12
Luciano Pietronero, University of Rome, "La Sapienza”, Italy
Hosted by Victor Yakovenko

Economic Complexity

Economic Complexity (EC) is a new field of research that consists in a radically new methodology. It describes economics as evolutionary process of ecosystems made of industrial and financial technologies that are all globally interconnected. The approach is multidisciplinary addressing emerging phenomena in economics from different points of view: analysis of complex systems, scientific methods for systems and the recent developments in Big Data. This approach offers new opportunities to constructively describe technological ecosystems, analyse their structures, understand their internal dynamics, as well as to introduce new metrics. This approach provides a new paradigm for a fundamental economic science based on data and not on ideologies or interpretations, which is becoming a necessary choice in a highly interconnected and globalized world, especially after the great financial and economic crisis of recent years.

Economic Complexity, in addition to a new vision for a data-based scientific approach for fundamental economics, offers a new set of metrics able to quantify the competitiveness of countries, of technological sectors, measuring future development prospects for nations as well as for large companies. Those metrics have already shown to have a major impact for policy makers and for industry applications economics and finance. Over the last year, the World Bank (WB) has extensively tested and adopted this new methodology for its strategic analysis.

A crucial element of our methodology is a radically new approach to the problem of Big Data. Big Data is often associated with "big noise" as well as a subjective ambiguity related to how to structure the data and how to assign them a value that should reflect many arbitrary parameters. In the case of the evaluation of the industrial competitiveness of a country, the required parameters for such an analysis could more than one hundred. A key point approach EC is to go from 100 parameters to zero parameters and obtain results which can be tested in a scientific perspective. This is done by focusing on the data in which the signal to noise ratio is optimal and developing iterative algorithms in the spirit, but other than Google, and optimized to the economic problem in question. In particular the study of a country or a company is not done at the individual level but through the global network in which it is inserted. In this way you get the Fitness of the countries and the Complexity of the products.

The dynamics in the new GDP-Fitness space [1] (opens up to a completely new way for monitoring and forecasting. Then, the taxonomy of products and their evolutionary dynamics is built through machine learning methods. Finally, the same thing is applied to patents and technologies, two elements that open up the possibility of analyzing the core elements of the innovation process.

[1] M. Cristelli, A. Tacchella, L. Pietronero: The Heterogeneous Dynamics of Economic Complexity, PLOS One 10(2): e0117174 (2015) and Nature editorial on EC:

:http://www.nature.com/news/physicists-make-weather-forecasts-for-economies-1.16963

Luciano Pietronero studied physics in Rome and was a research scientist at Xerox Research in Webster (1974) and Brown Boveri Research Center (CH) 1975-1983. He then moved to Univ. of Groningen (NL), where he was professor ofCondensed Matter Theory (1983-87). Since 1987 he is professor of Physics at theUniversity of Rome. Founder and director of the Institute for ComplexSystems of CNR (2004-2014). Broad international experience in academic andindustrial enviroments. The scientific activity is of both fundamental and appliednature, with a problem oriented interdisciplinary perspective. Development of noveland original views in all the areas of activity. Leader of a generation of joungscientists who are protagonists of the complexity scene internationally.In 2008 he received the Fermi Prize (highest award of the Italian Physical Society).Research interests Condensed Matter Theory; High-temperature superconductivity;Statistical Physics; Fractal Growth; Self-Organized- Criticality; Complex Systems andits interdisciplinary applications. Recent activity: http://www.lucianopietronero.it/

September 19
Min Ouyang, University of Maryland

New Interface between Quantum Optics and Nanoscience: the Bottom-Up Approach and Applications 

In this talk I will present a few recent advances from my group, centering on a new interface between ultrafast quantum optics and nanoscience through bottom-up materials design. I will particularly focus on development of emerging colloidal hybrid nanostructures that can allow desirable integration of multiple functionalities in one single nanoscale unit to create novel synergistic interactions. By combining ultrafast optical spectroscopy with this new materials advance, precise control of quantum optical interactions can thus be achieved at the nanoscale. This has further led to all optical spin manipulation and spin echo by light-matter interaction in well-designed hybrid semiconductor quantum structures, which is crucial for understanding many body spin physics and developing novel nanoscale quantum devices. Potential applications of such a bottom-up approach will also be described.

September 26
Charles Reyl, Select Equity Group

Life After Grad School for the Quantitatively Inclined -- Big Banks, Start-ups, and the Great In-between

 

October 3

Michelle Girvan, University of Maryland

Phase Transitions and Criticality in Biological Networks: Implications for Genes and Neurons

Experimental evidence suggests that, in order to maximize performance, biological networks often operate near the brink of failure. Because of the connections between such "tipping points" and the critical points of second order phase transitions, the methods of statistical and nonlinear physics are useful for studying these systems. My research in this area explores phase transitions and critical dynamics in both networks of genes and networks of neurons.  Modeling phase transitions in gene regulatory networks has led us to propose a general mechanism underlying some cancers. Modeling phase transitions in neuronal networks has allowed us to identify features of the brain's wiring that are key for optimal information processing. For both networks of genes and networks of neurons, studying how evolution shapes the path to criticality gives us insights into robustness and fragility in these systems. 
October 10

Charles Tarrio, NIST Gaithersburg
Hosted by Howard Milchberg

Moore’s Law and the Physics of Manufacturing Nanoscale Devices

Over 50 years ago, Gordon Moore postulated that the number of devices in an integrated circuit would double roughly every 1.5-2 years. Lithography is the technology used to keep this up for the last 50 years. Lithography has gone through several iterations, and is currently going through a paradigm shift from deep ultraviolet with a wavelength of 193 nm, to extreme ultraviolet (EUV) with a wavelength of 13.5 nm. The transition to such a short wavelength has presented many scientific and technological challenges. I'll discuss the history of semiconductor lithography and how potential "showstoppers" in the EUV have been overcome.

 


October 17
Shih-I Pai Lecture (in 1412, Toll Physics Bldg.)
 
Danielle Bassett, University of Pennsylania
Hosted by IPST

Perturbation and Control of Human Brain Network Dynamics

 The human brain is a complex organ characterized by heterogeneous patterns of interconnections. New non-invasive imaging techniques now allow for these patterns to be carefully and comprehensively mapped in individual humans, paving the way for a better understanding of how wiring supports our thought processes. While a large body of work now focuses on descriptive statistics to characterize these wiring patterns, a critical open question lies in how the organization of these networks constrains the potential repertoire of brain dynamics.
In this talk, I will describe an approach for understanding how perturbations to brain dynamics propagate through complex writing patterns, driving the brain into new states of activity. Drawing on a range of disciplinary tools – from graph theory to network control theory and optimization – I will identify control points in brain networks, characterize trajectories of brain activity states following perturbation to those points, and propose a mechanism for how network control evolves in our brains as we grow from children into adults. Finally, I will describe how these computational tools and approaches can be used to better understand how the brain controls its own dynamics (and we in turn control our own behavior), but also how we can inform stimulation devices to control abnormal brain dynamics, for example in patients with severe epilepsy.


October 24
Paint Branch Lecture (in 1412, Toll Physics Bldg.)
 
Dave Wineland, NIST/Boulder and U. Oregon
Hosted by IREAP

Quantum Information Processing and Raising Schrödinger’s Cat

Research on precise control of coherent quantum systems occurs in many laboratories throughout the world, for fundamental research, new measurement techniques, and more recently for the development of quantum computers. I will briefly describe experiments on these topics using trapped ions at the National Institute of Standards and Technology (NIST) but these just serve as examples of similar work being performed with many other atomic, molecular, optical (AMO) and condensed matter systems. This talk is, in part, the “story” of my involvement in these subjects which began when I entered graduate school.

 

October 31

Jaideep Singh, Michigan State
Hosted by Charles Clark

Searching for the Origin of Matter Using Pear-Shaped Nuclei

Experimental tests of fundamental symmetries using nuclei and other particles subject to the strong nuclear force have led to the discovery of parity (P) violation and the discovery of charge-parity (CP) violation. It is believed that additional sources of CP-violation may be needed to explain the apparent scarcity of antimatter in the observable universe. A particularly sensitive and unambiguous signature of both time-reversal- (T) and CP-violation would be the existence of an electric dipole moment (EDM). The next generation of EDM searches in a variety of complimentary systems will have unprecedented sensitivity to physics beyond the Standard Model. My talk will focus on certain rare diamagnetic atoms which have pear-shaped nuclei. This uncommon nuclear structure significantly amplifies the observable effect of T, P, & CP-violation originating within the nuclear medium when compared to isotopes with nearly spherical nuclei such as Mercury-199. Certain isotopes of Radium (Ra), Protactinium (Pa), and Radon (Rn) are all expected to have enhanced atomic EDMs and will be produced in abundance at the Facility for Rare Isotope Beams currently under construction at Michigan State University. I will describe the status of the ongoing Ra-225 EDM search located at Argonne National Lab as well as the prospects for next generation searches for time-reversal violation in the FRIB-era with a particular emphasis on Pa-229.

https://doi.org/10.1103/PhysRevLett.114.233002

https://doi.org/10.1103/PhysRevC.94.025501

https://arxiv.org/abs/1710.02504

 

 

 
November 7
David Griffiths, Reed College
Hosted by Howard Milchberg

Hidden Momentum

 

Electromagnetic fields carry energy, momentum, and even angular momentum. The momentum density is εo(E×B), and it accounts (among other things) for the pressure of light. But even static fields can harbor momentum, and this would appear to contradict a general theorem: if the center of energy of a closed system is at rest, then its total momentum must be zero. Evidently in such cases there lurks some other momentum, not electromagnetic in nature, equal and opposite to the field momentum. But finding this “hidden momentum” can be surprisingly subtle. I’ll discuss a particularly nice example.

 

 

November 14
Alipasha Vaziri, Rockefeller University
Hosted by Mohammad Hafezi

Optical Tools for Unraveling Whole-brain Neuronal Circuit Dynamics Underlying Behavior

The combination of optogenetics and high speed functional imaging are providing new opportunities to understand how the collective dynamics of neurons in functional networks leads to behavior.

While traditional imaging modalities based on two-photon imaging have relied on the manipulations of light in the spatial domain, multi-photon microscopy via femtosecond optical pulses can also provide a new degree of freedom via the pulse spectrum that can be used to “sculpt” the spatial localization of light within the sample. This has been exemplified in the technique of temporal of focusing through which a decoupling of the axial from the lateral confinement of light can be achieved. Using this technique in combination with genetically encoded calcium (Ca2+) indicators we have demonstrated near-simultaneous recording of whole-brain neuronal activity in C. elegans at single cell resolution. More recently we developed a variant light sculpting microscopy that has enabled unbiased single- and dual-plane high-speed (up to 160 Hz) Ca2+ imaging in the mouse cortex as well as in vivo volumetric calcium imaging of a mouse cortical column (0.5 mm×0.5 mm×0.5 mm) at single-cell resolution and fast volume rates (3–6 Hz). This has enabled in vivo recording of calcium dynamics of several thousand neurons across cortical layers and in the hippocampus of awake behaving mice.

Light-field microscopy in combination with 3D deconvolution and other more sophisticated mathematical signal demixing strategies is another highly scalable approach for high-speed volumetric Ca2+ imaging. Using this technique termed Seeded Iterative Demixing (SID), we have recently demonstrated video-rate recoding of neuronal activity within a volume of 0.6mm×0.6 mm×0.2 mm located as deep as 380 μm in the scattering mouse as well as whole-brain imaging of larval zebrafish during sensory stimulation. These tools combined with high speed optogentic control of neuronal circuits, advanced statistics tools and mathematical modeling and will be crucial to move from an anatomical wiring map towards a dynamic map of neuronal circuits.

References:
1. Andrasfalvy, B., et al., Two-photon Single Cell Optogenetic Control of Neuronal Activity by Sculpted
Light. PNAS, (2010). 107.
2. Losonczy, A., et al., Network mechanisms of theta related neuronal activity in hippocampal CA1
pyramidal neurons. Nature Neuroscience, (2010). 13(8): p. 967-72.
3. Schrodel, T., et al., Brain-wide 3D imaging of neuronal activity in Caenorhabditis elegans with
sculpted light. Nature Methods, (2013). 10(10): p. 1013
4. Prevedel, R., et al., Simultaneous whole-animal 3D-imaging of neuronal activity using light-field
microscopy. Nature Methods, (2014) 11. 727–730
5. Prevedel, R., et al., Fast volumetric calcium imaging across multiple cortical layers using sculpted
light Nature Methods, (2016) 13, 1021-1028
6. Nöbauer, T. et al., Video rate volumetric Ca 2+ imaging across cortex using seeded iterative demixing
(SID) microscopy, Nature Methods (2017), 14, 811-818

November 21
Brian Swingle, UMD

Einstein's Equations from Entanglement

In recent years we have learned that the physics of quantum information plays a crucial role in the emergence of spacetime from microscopic degrees of freedom. I will review the idea that entanglement is the glue which holds spacetime together and show how Einstein's equations plausibly emerge from this perspective. One ubiquitous feature of these dynamical equations is the formation of black holes, so I will conclude by discussing some new ideas about the nature of spacetime inside a black hole.

 

November 28  (in 1412, Toll Physics Bldg.)
Joe Taylor, Princeton
Hosted by Peter Shawhan

From Einstein's Theory to Gravity's
    Chirp

Published in 1915, Albert Einstein's theory of General Relativity appeared to imply the existence of gravitational waves, an entirely new form of energy and radiation. However, physical reality of these implied waves was doubted by many, including Einstein himself, for well over half a century. The 1974 discovery of binary pulsar PSR B1913+16 led to the dedicated development of much more accurate pulsar timing instrumentation and techniques. Early results from this work motivated further theoretical work to clear up quantitative questions about gravitational waves in GR. By the late 1980s, measured orbital dynamics of the binary pulsar were shown to be in quantitative agreement with GR, including energy losses via gravitational radiation. This experimental proof was surely a prerequisite for the 1992 funding of LIGO, the Laser Interferometer Gravitational-Wave Observatory. After nearly another quarter century, in 2015 LIGO achieved its first spectacular successes.

December 5
Kate Brown, UMBC
Hosted by Victor Yakovenko

The Great Chernobyl Hoax: How Chernobyl Health Problems Were Forgotten as Soon as They Were Discovered

 

After the Chernobyl disaster, scientists around the world called for a long term study on the health effects of Chernobyl exposures to the 4.5 million people most directly exposed. That study never occurred, nor do scientists today claim to know much about a range of health effects from long-term, low-dose exposures to ionizing radiation. Brown explores the archival history of early Soviet revelations of a public health disaster occurring in the contaminated lands and how that story disappeared from the scientific consensus. The case points to political and environmental predicaments today in the age of the Anthropocene.

Kate Brown lives in Washington, DC and is Professor of History at UMBC. She is the author of Plutopia: Nuclear Families in Atomic Cities and the Great Soviet and American Plutonium Disasters (Oxford 2013), which won seven book prizes, including the Dunning and Beveridge prizes from the American Historical Association for the best book in American history. Brown’s A Biography of No Place: From Ethnic Borderland to Soviet Heartland (Harvard 2004) was awarded the American Historical Association’s George Louis Beer Prize for the Best Book in International European History. Brown’s most recent book Dispatches from Dystopia: History of Places Not Yet Forgotten was published in 2015. Brown is the recipient of many fellowships, including from the John D. Guggenheim Foundation, the American Council of Learned Societies, the National Endowment for Humanities. She is currently writing a history of human survival and endurance in communities circling the Chernobyl Zone. The book, A Manual for Disaster, will be published by Norton (US) and Penguin (UK) in 2019.

 

Upcoming Events

Dec
12

Tue, Dec 12, 2017 11:00 am - 12:00 pm

Dec
13

Wed, Dec 13, 2017 1:00 pm - 2:00 pm

Dec
13

Wed, Dec 13, 2017 1:00 pm - 2:30 pm

Dec
13

Wed, Dec 13, 2017 2:30 pm - 4:00 pm

Dec
13

Wed, Dec 13, 2017 3:30 pm - 4:30 pm

Dec
14

Thu, Dec 14, 2017 10:00 am - 11:30 am

Dec
15

Fri, Dec 15, 2017 4:15 pm - 5:15 pm

Dec
18

Mon, Dec 18, 2017 11:00 am - 12:00 pm