A New Organising Principle for Nuclear Physics

And another Physical Review Letters Editor’s Suggestion from GW: in 9375068523, Nuclear Physics Around the Unitarity Limit, Prof. Harald W. Griesshammer and co-authors argue that many features of the structure of nuclei emerge from a strictly perturbative expansion around the unitarity limit, where the two-nucleon S waves of NN scattering have bound states at zero energy. In this limit, the gross features of states in the nuclear chart are correlated to only one dimensionful parameter, which is set by the triton binding energy.

Since the inception of nuclear physics, the emphasis was to find a potential which is “as accurate as possible” in the two-nucleon system, and then cure its deficiencies in few- and many-body descriptions by adding a small number of 3N interactions. Here, one goes a significant step further and proposes that a high-precision reproduction of the NN system is NOT necessary to capture the essence of systems with three and more nucleons.

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In a recent publication in Physical Review Letters 118, 102001 (2017),  entitled “Glue Spin and Helicity in the Proton from Lattice QCD”,  Prof. Andrei Alexandru and co-authors demonstrated by computer simulations that about 50% of the proton’s spin comes from the spin of the gluons that bind its quark constituents.

The work was featured as Editor’s Choice by APS Physics News, with an introduction article, “Viewpoint: Spinning Gluons in the Proton“, for dissemination to the wider audience.

 

First joint GW nuclear + astrophysics meeting

Today the members of the GW nuclear and astrophysics groups came together for their first joint scientific meeting. These meetings are meant to enable and enhance discussions between members of the two research groups, who can learn from each other, and even start new collaborations. While the two groups do research in different areas of physics, there is clearly overlap in the tools that are used and the physics they are trying to understand. At today’s inaugural meeting there were two topics, both introduced by a short presentation, and followed by very lively discussions in which everybody (students, postdocs and faculty) participated. The first topic was on gamma-ray detectors in space, introduced by astrophysics faculty Sylvain Guiriec. This led to a stimulating discussion about using modern nuclear detection techniques and materials in an astrophysical context. The second topic was introduced by nuclear physics postdoc Maxim Mai, who in his research encountered an interesting statistical problem with potentially important applications for the extraction of infinite volume physics from Lattice QCD. This also stimulated much discussion, with enthusiastic participation from nuclear and astrophysicists alike. These discussions are planned to continue informally in the coming weeks, and the next joint meeting will take place on Tuesday April 18th.

Physics: International and Diverse

The Department of Physics is home to students, staff and faculty from over 30 countries from every corner of the world. Its more than two dozen faculty includes 6 US-born citizens. We see the global nature of our department as a strong asset to our educational mission and our excellent research program. Our students and researchers are the backbone of our research and reputation, and the global diversity among them only strengthens this backbone.

Quoting Steven Knapp, President of The George Washington University:

“A hallmark of our community is the civil discourse that takes place on our campuses every day. Our students, repeatedly ranked the most politically active in the country, set a national example in their ability to disagree passionately but without rancor. As we watch our democracy proceed with its peaceful transition of power, I urge our students and all members of our community to continue to respect our differences, maintain civility and celebrate our diversity.”

Department of Physics celebrates graduating class of 2016

On May 14th the Department of Physics celebrated eleven graduates in the class of 2016: Brian Alden, Alejandro Barazza-Valdez, Erin Britt, Michael Helton, Max Levinson, Jacob Maibach, Sri Murthy, Zoe Pierce, James Ranfone, Cynthia Trinh, and Zach West.

The accomplishments of these excellent students were highlighted in a department party in which many family members, other students, and faculty members participated (more than 50 people in total). Everybody enjoyed some light snacks and drinks, and many very proud parents, grandparents, family, and friends, heard Prof. Briscoe, the Department Chair, praise the graduates for their achievements. He also presented departmental awards to several undergraduate and graduate students: the Professor Emeritus J. Roger Peverley Prize for Undergraduate Research in Physics to the graduating Brian Alden; the Berman Prize for Excellence in Experimental Physics to the graduating Sri Murthy; and the W. Parke Prize for Excellence in Theoretical Physics to the graduate students Dehua Guo and Bin Hu.

The department was very pleased to award Special Departmental Honors to three students this year: Brian Alden, Sri Murthy, and Jacob Maibach. All three students had a GPA of over 3.5, both overall and in physics, and did a two-semester, in-depth research project of significant depth. Brian Alden did his research on “Searching the Universe for Radio Transients with LOFAR” with Prof. van der Horst, and will go to University of Colorado Boulder for graduate school in astrophysics. Jacob Maibach did his research on “Theoretical Foundations for Cutoff-Clustering in Analysis of Transcription Factor Distributions” with Prof. Peng, and will study for a Masters in Data Science at GW. Sri Murthy did her research on “Analysis of Cisterns and Projection Neuron to Kenyon Cell Specificity in the Full Adult Fly Brain” at Janelia Farm Research Campus, and will go to medical school at GW.

At the end of the award presentation, all the graduating students received two gifts that will remind them of their time at GW for years or decades to come: a GW Department of Physics mug; and a wooden pyramid puzzle, similar to the one they all used to entertain themselves with at the Physics front office. After donning the robes, the faculty and students participating in the Columbian College celebration had a photo shoot on the Corcoran building steps.

The department is very proud of this year’s graduating class. Congratulations to the graduating students, and we wish them every success in the future!

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Today the Laser Interferometer Gravitational-wave Observatory (LIGO) announced their discovery of gravitational waves. This confirms one of the predictions of Einstein’s theory of general relativity and opens up a completely new window on the Universe. From now on, (astro)physicists will not only use telescopes and satellites to use electromagnetic waves, i.e. light, for studying the Universe, but also gravitational waves. This is particularly relevant for the most extreme and violent phenomena in the Universe, including phenomena that the GW Astrophysics Group studies, for instance black holes, neutron stars and massive stellar explosions. The discovery was announced in a NSF press conference that was broadcast in a live stream. Students and faculty from the GW Physics Department got together in Corcoran Hall to see this press conference live, and be part of a historic moment in physics and astronomy.

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Robert Coyne successfully defended his PhD dissertation entitled “LIGO GRB searches in the aLIGO Era: An Optimized Burst Database and a New Method for
Detecting Intermediate-Duration GWs” on August 7, 2015. Here’s a photo taken at the end of the meeting. From left: Dr. Scott Barthelm (outside examiner, NASA Goddard), Prof. Oleg Kargaltsev (reader), Robert Coyne (candidate), Prof. Kalvir Dhuga (reader), Prof. Frank Lee (co-adviser), Prof. Alexander van der Horst (examiner), Prof. Andrei Alexandru (presiding), Via Skype: Prof. Alessandra Corsi (adviser, Texas Tech University). Congratulations to Rob !

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This week the first Capitol Chat meeting took place at GW. This event, organized by Astrophysics Prof. Chryssa Kouveliotou, is the first in a series of small working groups for up to three days to discuss a specific astrophysical question and brainstorm on the possible answers. This first Capitol Chat was focused on gamma-ray bursts and the radiation mechanisms responsible for their gamma-ray emission. All together 22 experts on gamma-ray burst observations and theory gathered from GW, the greater DC area, and other universities and national labs in and outside of the US. The format of the meeting was different than usual meetings or workshops: a limited number of presentations, and many long discussions on the status, progress, and future directions of this particular research field. All the participants agreed that this format worked very well to get to the bottom of some of the issues in the field, and start new collaborations to resolve them. The great atmosphere during these three days helped in getting the most out of the sometimes passionate but always constructive discussions. As part of the meeting, the participants had lunch on Tuesday with the GW astrophysics group, in particular the students and postdocs who presented their research and discussed their ideas with some of the world experts in their research fields. Overall this first Capitol Chat working group was a great success, and will hopefully be the first one in a long series to come.

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Department of Physics celebrates graduating students

Last weekend the Department of Physics celebrated eight graduates in the class of 2015: Laura Carpenter, Ryan Heaney, Gregg Khodorov, Laura Lai, Claiborne Morton, Kathryn Schiff, Samuel Stephenson, and Jasmine Vicencio.

The accomplishments of these excellent students were highlighted in a department party in which many family members, other students, and faculty members participated (more than 60 people in total!). Everybody enjoyed some light snacks and drinks, and many very proud parents, grandparents, family, and friends, heard Prof. Briscoe, the Department Chair, praise the graduates for their achievements. He also presented departmental awards to several undergraduate and graduate students: the Outstanding Physics Department Teaching Assistant Award to Ben Kopshik; the AAPT Outstanding GTA Award to Trevor Balint; the Craig Futterman Prize for Best Graduate Student in Biophysics to Adam Hughes; the James MacBride Sterret Jr. Prize in Physics to Sadina Videlock-Prentice; and the Professor Emeritus J. Roger Peverley Prize for Undergraduate Research in Physics to Brian Alden and Laura Lai.

The department was very pleased to award Greg Khodorov Special Departmental Honors. This requires a GPA of over 3.5, both overall and in physics, and a two-semester, in-depth research project. Greg did his research with Prof. Qui in collaboration with NIH, on “Transcranial Magnetic Stimulation as a Means of Exploring Movement Disorders”.  Greg is going on to medical school at Rutgers University after graduation.

After the award presentation, the Society of Physics Students demonstrated several of their fun outreach activities, which were clearly enjoyed by children of all ages (from 8 to 80). After donning the robes, the faculty and students participating in the Columbian College celebration had a photo shoot on the Corcoran building steps.

The department is very proud of its graduating class.  Congratulations to the graduating students, and we wish them every success in the future!

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