Physics

2012 - 2013 Physics Colloquia

Unless otherwise noted, all physics seminars and colloquia are held on Thursdays from 4:45 to 6:00, in lecture room 3 of Merrill Science Center. Tea and snacks will be served before seminars at 4:15 in 204 Merrill. If you would like to be mailed seminar announcements, please send an email to Ellen Feld.

Contact colloquium organizer Larry Hunter with any questions about colloquia.


 Click here for the spring semester schedule

Fall 2012

Sept. 6 -  Welcome Back Pizza Party. Student lounge - Merrill 114-116, 4:30PM

 

Sept. 13 - Prof. Susanne Yelin, UConn

Quantum Optics with Atoms, Molecules and Solids

Quantum coherence effects use the basic ideas of quantum mechanics to control light with light, in order to obtain such effects as electromagnetically induced transparency (EIT) or stored light. All of these are now widely used as tools for quantum information/quantum computing, highly accurate measurements below the standard quantum limits, and in particular to make novel systems such as polar molecules, ion crystals, or diamond NV centers accessible for quantum-based effects and measurements. I will introduce the basic effects and talk about some of the novel applications.


Sept. 20 - Prof. David Hall, Amherst

Amherst Ranked Ultracoldest Liberal Arts College Ten Years in a Row

Physicists love to explore the nature of matter subjected to extreme environments. The Higgs Boson, for example, may now have been observed at the highest energies and temperatures currently achievable. At the opposite end of the thermometer is the peculiar physics of matter a tiny fraction of a degree above absolute zero, at which temperature a gas of independent atoms develops a collective identity known as the Bose-Einstein condensate. Seventy years would pass between the prediction of the phenomenon by Einstein and its first experimental observation in 1995; yet the importance of these experiments was recognized a mere six years later in the awarding of the 2001 Nobel prize. In this general talk, I will consider the Bose-Einstein condensation from historical and scientific perspectives, highlighting aspects of Amherst students’ research in the field.

Please join the Department of Physics in celebrating the tenth anniversary of Amherst College’s ranking as one of “the coldest places in the universe.”

Sept. 27 - Prof. Andrea Pocar, UMass

Neutrino mass: so tiny yet so intriguing

Until recently, the weight neutrinos had on the particle physicist’s interest scale has been rather modest. This changed, figuratively and not, with the discovery that they had finite albeit vanishingly small mass. Exactly how light neutrinos are is an open question physicists today are trying to answer. One experimental approach is to investigate the existence of a process known as neutrino-less double beta decay. Not only could the rate of this exotic nuclear decay tell us the mass of neutrinos, but its very detection would imply that neutrinos and anti-neutrinos are in fact the same particle, possibly giving us a clue as to why matter dominates over anti-matter in the universe. Results from the Enriched Xenon Observatory (EXO) for double beta decay will be presented along with a personal overview of neutrino physics yesterday, today and tomorrow.

 

Oct. 4 - Prof. Steve Strogatz, Cornell

Bringing Math to the Masses

In the spring of 2010, Steven Strogatz, Cornell's Jacob Gould Schurman Professor of Applied Mathematics, wrote a 15-part series on the elements of math for the New York Times. To his surprise -- and his editor's -- each piece climbed the most emailed list and elicited hundreds of appreciative comments. In this talk Steve will describe his adventures in bringing math to the masses, including his work on his new book, The Joy of x, as well as his sequel series for the Times this fall.

 

 

Oct. 11- Prof. Michael Boyer, Clark University

Gaps and Charge Localization in High-Temperature Superconductors and Charge Density Wave Compounds

Superconductors exhibit unusual physical behavior characterized by two fundamental properties: 1) zero resistance below a critical temperature known as TC and 2) the Meissner effect where magnetic fields are expelled from the material below TC.  Though a microscopic theory exists for “conventional” superconductors, there is much which is not known regarding the more recently discovered high-temperature superconductors.  Using scanning tunneling microscopy, we can characterize a superconductor’s atomic structure and underlying electronic structure with atomic resolution. 

 In our investigations we find microscopic variations in the underlying electronic structure of high-temperature superconductors on a nanometer length scale.  In addition, we have found two distinct coexisting electronic states below TC, superconductivity and the pseudogap phase.  In my talk, I will highlight how we separate the two coexisting phases in our measurements as well as explore evidence for the pseudogap phase origin as a charge density wave state.

 

Oct. 18  Prof. David Weiss, Penn State

Experiments with Ultra-cold Atoms in Optical Lattices

Atoms in optical lattices are very versatile experimental systems. They can be used to study many-body quantum physics, to aid
precision measurements and tests of fundamental symmetries, and for quantum computation. I will describe ongoing efforts along these lines in my research group.

Oct. 25 Prof. Ben Brau, UMass

The evidence for the Higgs boson
 
This summer, a particle was discovered at the LHC whose properties so far seem consistent with the long-sought Higgs Boson. This remarkable achievement is a milestone in a quest half a century in the making, so I'll first review some of the history of the journey that led to this past summer's announcement. I will give an overview of the Large Hadron Collider and the ATLAS detector, one of the two experiments responsible for the discovery, and explain the evidence we now have that the particle we have found is indeed the Higgs Boson.  Finally, I will put the discovery in context, and review some of the many remaining puzzles facing the field, with an emphasis on those we hope to make progress on with more data from the LHC.

 

Nov. 1  Dr. Theresa Ulrich, Bioengineering, MIT

Mechanical Regulation of Human Brain Tumor Cells:  A physicist’s foray into cancer biology

Cancer biologists have long understood that genetics and biochemistry lie at the heart of tumor formation and metastasis.  A series of paradigm-shifting observations over the past two decades have revealed that biophysical cues can be equally powerful regulators of cell behavior in both normal and diseased tissues, leading to the emergence of the field of physical oncology at the intersection between physics/engineering and cancer biology/oncology.  The application of physical science approaches has already begun to define and address major questions and barriers in cancer research, and the continuing integration of physics and biomedicine will be key to expanding and translating this work into a bonafide medical revolution (see http://physics.cancer.gov for additional information and resources). 

 

We have obtained exciting early results in our efforts to apply physical science principles to the study of human brain tumor cells.  Glioblastoma multiforme (GBM) is a malignant tumor of the central nervous system with a median survival time of 15 months, even with aggressive therapy.  This rapid progression is related to diffuse infiltration of single tumor cells into the surrounding normal brain tissue prior to diagnosis, which is thought to involve aberrant interactions between tumor cells and the extracellular components of their tissue microenvironment.  Our results have provided support for a novel model in which the mechanical rigidity of the cellular microenvironment provides a transformative biophysical cue that strongly regulates the structure, motility, proliferation, and chemosensitivity of human GBM tumor cells (Ulrich et al., Cancer Research 2009).  Development of a 3-dimensional composite collagen-agarose biomaterial platform has allowed us to further probe the interplay between cellular force generation, extracellular matrix mechanics, and tumor cell invasiveness (Ulrich et al., Biomaterials 2010 and 2011), underscoring the importance of micromechanical considerations in the development of new strategies to limit tumor cell invasion.

 

 

Nov. 8  Prof. Nathan Lunblad, Bates College

Crystals made of light: making a gas cooled close to absolute zero act like a strange solid

The study of ultracold atomic gases, only millionths or even billionths of a degree above absolute zero, has grown by leaps and bounds in the last two decades, with various recent Nobel Prizes showcasing the potential of the field.   Lately some intriguing links have been forged between the condensed-matter physics community (with their exotic solids) and the atomic physics community, (with our ultracold gas toolbox).   This talk will review the physics behind some exciting experiments going on in the field, including work being done at the National Institute of Standards and  Technology (NIST) as well as with an apparatus being built at Bates College.

Nov. 15

Junior Orientation Meeting

Junior Orientation Meeting beginning at 4:30PM in the Student Lounge/116 Merrill.  This will be an informational meeting for all juniors where we will discuss how to go about applying to graduate school and options and procedures for honors thesis projects.  Pizza will be served.

 

Nov. 22

Thanksgiving Break


Nov. 29

Student Thesis Talks

Nicholas Bern - "60 Hz Noise Cancelation and Applications to the Search for Dirac Monopoles"

Celia Ou - "Third-harmonic Generation for Ion Spectroscopy"

Nathan Thomas - "Raman Transitions and Bragg Scattering in Bose-Einstein Condensates"

 

Dec.4

Student Thesis Talks

Robert Schwab - "A look into DNA Condensation in Sperm"

Frederick Shipley - "Building an Optical Profilometer"

 

Dec. 6

Student Thesis Talks

Spencer Adams - "Examining the Effects of Microwave Radiation on the Behaviour of Single Molecule Magnets (SMMs)"

Shenglan Qiao - "Construction of a Linear Paul Trap for the Hunt of Time Variation in the Proton-to-electron Mass Ratio"

Neha Wadia - "On the Prospects for Laser Cooling TlF"

 

Dec. 13

Reading Period

 

Dec. 22

Winter Recess


Spring 2013

Jan. 24

First Day of Classes

 

Jan. 31 - Prof. James Dickerson, Amherst Class of '94, Vanderbilt University and Brookhaven National Laboratory

The Role of Nanoscience and Nanotechnology in Addressing the World’s Energy Challenges

The Center for Functional Nanomaterials (CFN) at Brookhaven National Laboratory in the United States provides state-of-the-art capabilities for the fabrication and study of nanoscale materials, with an emphasis on atomic-level tailoring to achieve desired properties and functions. The CFN is a science-based user facility, simultaneously developing strong scientific programs while offering broad access to its capabilities and collaboration through an active user program. The overarching scientific theme of the CFN is the development and understanding of nanoscale materials that address the Nations’ challenges in energy security, consistent with the Department of Energy mission.  The CFN is one of five Nanoscale Science Research Centers (NSRCs) funded by the Office of Science of the United States Department of Energy. The CFN supports Brookhaven’s goal of leadership in the development of advanced materials and processes for selected energy applications.

In my presentation, I will highlight the role that the CFN, through its scientific staff and this scientific user community, is playing in addressing the world’s energy challenges.  I will focus on several trajectories of research that are being executed at CFN, including work on photovoltaics, novel nanostructured materials for catalysis, soft and biological materials, and our state-of-the-art electron microscopy and proximal probe microscopy facilities.

Feb. 7 - Prof. Megan Valentine, U.C. Santa Barbara

Microtubules: A Model System for Studying Rigid Rod Polymer Mechanics 

Microtubules are extremely stiff biopolymers that play important roles
in maintaining the shape, strength and organization of cells and serve as an excellent model system for the study of rigid rod polymer
networks. To determine the structure-mechanics relationships in dense microtubule networks, we measure the time- and force-dependent viscoelastic responses of entangled and crosslinked networks subjected to precise microscale manipulation. We use confocal microscopy to determine the morphology as a function of polymer concentration and crosslinking, and a suite of custom-built magnetic tweezers devices to apply calibrated forces as a function of time. We find that in this rigid system, bond breakage kinetics and network geometry dominate the mechanical responses, while thermal fluctuations and hydrodynamics play a secondary role. Our results are important to understanding the origins of nonlinearity and stress dissipation in rigid polymer networks, and provide insight into how cytoskeletal biopolymers regulate cargo transport and stress transmission in cells.

Feb. 14 - Arnold Gundersen, Fairewinds Associates

What did they know and when did they know it?

The presentation will discuss Japan's tsunami history and design decisions made in the 1960's and 1970's  that doomed the Fukushima Daiichi reactors even before they started up.  I would continue with a discussion of Japan's poor response to the accident and what lessons might be learned for future events.  I would close by addressing what IAEA (International Atomic Energy Agency) and NEI (Nuclear Energy Institute) said and did immediately after the accident to downplay the risk.

 

Feb. 21 - Dr. William Klipstein '90,Jet Propulsion Laboratory, NASA

Gravity Sensing Instruments in Space

I will provide an  instrument-maker's perspective on three NASA gravity-sensing missions targeting quite different science but each relying on precision measurements of the fluctuations in the separation between distributed spacecraft as the primary measurement observable. The Gravity Recovery and Climate Experiment (GRACE) Mission measures changes in the mass distribution of the Earth, primarily driven by redistribution of water caused by major droughts, large ocean currents, and melting of the polar ice caps. Two spacecraft in a following polar orbit exchange microwave signals to measure fluctuations in the separation at the micrometer level; these fluctuations result from mass and density distributions throughout the Earth acting differentially on the two spacecraft. The GRACE mission launched in 2002, and a GRACE Follow-On mission is under development that will carry a laser interferometer targeting two orders of magnitude improvement in the measurement sensitivity as a technology demonstration of the power of inter-spacecraft interferometry.

The Gravity Recovery and Interior Laboratory (GRAIL) mission adapts the measurement concept of GRACE to target a precise gravitational map of Earth's Moon from the lunar crust to its core. The lack of a lunar atmosphere results in the Moon's surface carrying a record of its history since the crust cooled, revealing details about the thermal evolution of the Moon as representative of the rocky planets. In addition, the lack of an atmosphere allows the GRAIL orbiters to fly lower and hence have much greater spatial resolution compared to GRACE. GRAIL launched in 2011 and finished its mission this past summer. 

Where GRACE and GRAIL target measurements of classical gravity, the Laser Interferometer Space Antenna (LISA) mission will be an observatory of gravitational waves caused by astrophysical events such as mergers of black holes. LISA relies on picometer-level laser interferometry to measure fluctuations in the separations among three drag-free spacecraft separated by 5 million kilometers in a 1 a.u. Earth-trailing orbit. The LISA community hopes a launch to be viable late in the next decade.

I will give an overview of the science objectives of each of these missions, describe the instrument complement making these measurements possible, and discuss the mission design features of these related but quite different missions.

Feb. 28 - Prof. Jane Kondev, Brandeis

DNA Folding in Cells

DNA is a long molecule whose length exceeds the size of the cell it occupies by three or more orders of magnitude. Therefore, for DNA to fit inside a cell it must be folded up. Newly developed experimental techniques based on fluorescence imaging and DNA sequencing have begun to quantitatively characterize the folded state of DNA in cells, reveling mathematical rules that can be understood in the context of simple physics models. In this talk I will describe the emerging experimental and theoretical landscape of DNA folding
in cells, and discuss how cells might control DNA folding so as to regulate the biological functions of DNA such as recombination, replication, and transcription. An intriguing question raised by these studies is whether the rules for DNA folding are encoded in the DNA sequence, and if so, what is the nature of this "DNA folding code"?

 

Mar. 7 - Dr. David Phillips, Harvard-Smithsonian Center for Astrophysics - Cancelled - re-scheduled for April 11

A Laser Frequency Comb for Precision Radial Velocity Measurements in Astrophysics

Searches for extrasolar planets using the periodic Doppler shift of stellar lines are approaching Earth-like planet sensitivity. Astro-combs, laser frequency combs optimized for use in calibrating astrophysical spectrographs, provide a route to increased calibration precision and accuracy. Our green astro-comb is composed of a 1 GHz repetition rate Ti:Sapphire laser frequency comb, photonic crystal fiber (PCF) which coherently shifts the 800 nm light from the laser comb into the visible wavelength range, and two Fabry-Perot cavities which filter some comb lines to match the line spacing of the astro-comb to the resolution of the spectrograph. We have recently used this astro-comb to calibrate the HARPS-N spectrograph at the Italian National Telescope (TNG) located on the island of La Palma in the Canary Islands. I will describe the green astro-comb, our trip to the Canary Islands, and some results of this work. 

 

Mar. 14 - Dr. Stephan Wielandy '90, LGS Innovations

Optical Fiber-palooza

Technology that was originally developed primarily for the fiber-optic communications industry has allowed scientists and engineers to carry a variety of relatively simple ideas to limits that are truly mind boggling.  Optical fiber losses are so low that signals can propagate through hundreds of kilometers of fiber without amplification (imagine a glass window 100km thick!), while the performance of fiber amplifiers is so good that signals can remain entirely in the optical domain for thousands of kilometers while experiencing more than 20 orders of magnitude of propagation loss.  Since light in an optical fiber is confined to dimensions on the order of only a few wavelengths, these long propagation distances lead to an extraordinary intensity-length product and create a fascinating double-edged sword of nonlinear optical phenomena.  One the one hand, developers of fiber communications systems and fiber lasers often work feverishly to suppress various nonlinear effects, while on the other hand different developers (or sometimes the same ones) work equally hard to enhance them for numerous device applications.

I will give a brief survey of my favorite cool aspects of nonlinear fiber optics and other fiber-related technology, from the perspective of someone who has worked on projects that have made me both grateful for, and resentful of, nonlinear optical phenomena.  I’ll include a discussion of some of the breakthroughs that led to the recent revolution in high-power fiber lasers, and I’ll broaden my definition of “fiber-related technology” to include some application-level ideas like signal transmission formats that enable a single photon to carry multiple bits of information.  Throughout my survey, I will also try to offer my perspective on what it is like to work in this field and how what I learned in school prepared me for it.

 

 Mar. 21

Spring Break

 

Mar. 28 -  Philip Stamp, University of British Columbia

Quantum Vortices

 

Apr. 4 - Prof David Kawall, University of Massachusetts

The new Muon g-2 Experiment at Fermilab

The new muon g-2 collaboration has proposed a measurement at Fermilab of the anomalous magnetic moment of the muon to a precision of 0.14 ppm, a fourfold improvement over the Brookhaven E821 result. The latter deviates by more than 3 standard deviations
from Standard Model predictions. A more precise result will allow a stronger test of the Standard Model, more sensitive to many standard model extensions which predict additional contributions
to the anomaly. The techniques proposed to reduce statistical uncertainties by more than a factor four, and systematic uncertainties by a factor of three, and the effort to relocate the 680 ton storage ring from Brookhaven to Fermilab, will be described.

Apr. 11 -  Dr. David Phillips, Harvard-Smithsonian Center for Astrophysics

A Laser Frequency Comb for Precision Radial Velocity Measurements in Astrophysics

Searches for extrasolar planets using the periodic Doppler shift of stellar lines are approaching Earth-like planet sensitivity. Astro-combs, laser frequency combs optimized for use in calibrating astrophysical spectrographs, provide a route to increased calibration precision and accuracy. Our green astro-comb is composed of a 1 GHz repetition rate Ti:Sapphire laser frequency comb, photonic crystal fiber (PCF) which coherently shifts the 800 nm light from the laser comb into the visible wavelength range, and two Fabry-Perot cavities which filter some comb lines to match the line spacing of the astro-comb to the resolution of the spectrograph. We have recently used this astro-comb to calibrate the HARPS-N spectrograph at the Italian National Telescope (TNG) located on the island of La Palma in the Canary Islands. I will describe the green astro-comb, our trip to the Canary Islands, and some results of this work. 

 

April 18

Student Thesis Talks

- Celia Ou: "Third Harmonic Conversion"

- Nathan Thomas: "Applications of Stimulated Raman Scattering in Bose-Einstein Condensates"

 

April 24

Student Thesis Talks

- Chu Teng: "Frequency Control and Stabilization of a Laser System"

- Neha Wadia: "Measurements of Branching Ratios for the B(0) - X(v)   Transition in Thallium Flouride to Determine its Potential for Laser Cooling"

 

April 25

Student Thesis Talks

- Shenglan Qiao

- Nicholas Bern: "AC Magnetic Noise Cancellation For The Purpose of Creating Dirac Monopoles in a Spinor Condensate"

 - Spencer Adams: "Towards and Examination of the Sweet Spot Principle in Cr{7}Mn, a Single Molecule Magnet Qubit"

 

May 2

No Seminar - Departmental Meeting


May 9

Reading Period

 

May 19

Summer Recess