May 2016: A Pioneer of Scientific Tools Sol Gruner, known for developing x-ray detectors, is a toolmaker, tackling scientific problems and exploring the unknown

by Jackie Swift

“Most scientists focus on a very specific area, but I do many different things,” says Sol Gruner, Physics. “I’m a research mutt. Mainly, I develop tools to attack scientific problems people haven’t looked at yet, largely because the tools needed to solve those problems haven’t existed.”

Gruner’s tool-making expertise has resulted in an array of scientific breakthroughs and developments over the years. One area of research he is well-known for involves the development of new kinds of x-ray detectors for use at synchrotron facilities. X-ray detectors are crucial tools that use x-ray fraction to examine how materials change during experiments, and for several decades, Gruner’s has been one of the foremost groups working in this field. Sol Gruner, known for developing x-ray detectors, is a toolmaker for tackling scientific problems and exploring the unknown.

The Gruner group developed the first pixel array detectors (PADs)—which directly capture x-rays and process the resultant signals in integrated circuit chips—for use in very fast, time-resolved synchrotron science experiments, both at storage ring sources, such as the Cornell High Energy Synchrotron Sources (CHESS), and at x-ray free electron lasers. For example, his group designed the detectors in use at the Linac Coherent Light Source, the world’s first high-energy x-ray free electron laser now operating near Stanford University in California. They allow researchers to look at matter in time scales of femtoseconds (one millionth of one billionth of a second).

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May 2016: Physicists abuzz about possible new particle as CERN revs up

GENEVA (AP) — Was it a blip, or a breakthrough?

Scientists around the globe are revved up with excitement as the world’s biggest atom smasher – best known for revealing the Higgs boson four years ago – starts whirring again to churn out data that may confirm cautious hints of an entirely new particle.

Such a discovery would all but upend the most basic understanding of physics, experts say.

The European Center for Nuclear Research, or CERN by its French-language acronym, has in recent months given more oomph to the machinery in a 27-kilometer (17-mile) underground circuit along the French-Swiss border known as the Large Hadron Collider.

In a surprise development in December, two separate LHC detectors each turned up faint signs that could indicate a new particle, and since then theorizing has been rife.

“It’s a hint at a possible discovery,” said theoretical physicist Csaba Csaki, who isn’t involved in the experiments. “If this is really true, then it would possibly be the most exciting thing that I have seen in particle physics in my career – more exciting than the discovery of the Higgs itself.”

After a wintertime break, the Large Hadron Collider, or LHC, reopened on March 25 to prepare for a restart in early May. CERN scientists are doing safety tests and scrubbing clean the pipes before slamming together large bundles of particles in hopes of producing enough data to clear up that mystery. Firm answers aren’t expected for weeks, if not until an August conference of physicists in Chicago known as ICHEP.

On Friday, the LHC was temporarily immobilized by a weasel, which invaded a transformer that helps power the machine and set off an electrical outage. CERN says it was one of a few small glitches that will delay by a few days plans to start the data collection at the $4.4 billion collider.

The 2012 confirmation of the Higgs boson, dubbed the “God particle” by some laypeople, culminated a theory first floated decades earlier. The “Higgs” rounded out the Standard Model of physics, which aims to explain how the universe is structured at the infinitesimal level.

The LHC’s Atlas and Compact Muon Solenoid particle detectors in December turned up preliminary readings that suggested a particle not accounted for by the Standard Model might exist at 750 Giga electron Volts. This mystery particle would be nearly four times more massive than the top quark, the most massive particle in the model, and six times more massive than the Higgs, CERN officials say.

The Standard Model has worked well, but has gaps notably about dark matter, which is believed to make up one-quarter of the mass of the universe. Theorists say the December results, if confirmed, could help elucidate that enigma; or it could signal a graviton – a theorized first particle with gravity – or another boson, even hint of a new dimension.

More data is needed to iron those possibilities out, and even then, the December results could just be a blip. But with so much still unexplained, physicists say discoveries of new particles – whether this year or later – may be inevitable as colliders get more and more powerful.

Dave Charlton, who heads the Atlas team, said the December results could just be a “fluctuation” and “in that case, really for science, there’s not really any consequence … At this point, you won’t find any experimentalist who will put any weight on this: We are all very largely expecting it to go away again.”

“But if it stays around, it’s almost a new ball game,” said Charlton, an experimental physicist at the University of Birmingham in Britain.

The unprecedented power of the LHC has turned physics on its head in recent years. Whereas theorists once predicted behaviors that experimentalists would test in the lab, the vast energy being pumped into CERN’s collider means scientists are now seeing results for which there isn’t yet a theoretical explanation.

“This particle – if it’s real – it would be something totally unexpected that tells us we’re missing something interesting,” he said.

Whatever happens, experimentalists and theorists agree that 2016 promises to be exciting because of the sheer amount of data pumped out from the high-intensity collisions at record-high energy of 13 Tera electron Volts, a level first reached on a smaller scale last year, and up from 8 TeVs previously. (CERN likens 1 TeV to the energy generated by a flying mosquito: That may not sound like much, but it’s being generated at a scale a trillion times smaller.)

In energy, the LHC will be nearly at full throttle – its maximum is 14 TeV – and over 2,700 bunches of particles will be in beams that collide at the speed of light, which is “nearly the maximum,” CERN spokesman Arnaud Marsollier said. He said the aim is to produce six times more collisions this year than in 2015.

“When you open up the energies, you open up possibilities to find new particles,” he said. “The window that we’re opening at 13 TeV is very significant. If something exists between 8 and 13 TeV, we’re going to find it.”

Still, both branches of physics are trying to stay skeptical despite the buzz that’s been growing since December.

Csaki, a theorist at Cornell University in Ithaca, New York, stressed that the preliminary results don’t qualify as a discovery yet and there’s a good chance they may turn out not to be true. The Higgs boson had been predicted by physicists for a long time before it was finally confirmed, he noted.

“Right now it’s a statistical game, but the good thing is that there will be a lot of new data coming in this year and hopefully by this summer we will know if this is real or not,” Csaki said, alluding to the Chicago conference. “No vacation in August.”



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May 2016: Stoltzfus, Thom-Levy to share vice provost for undergrad ed post

Professor Rebecca Stoltzfus has been appointed vice provost for undergraduate education for a five-year term effective July 1, Provost Michael Kotlikoff announced May 9. She will oversee initiatives enhancing undergraduate instruction and related programs, in collaboration with academic leaders and units across campus.

Along with Stoltzfus’ appointment, faculty member Julia Thom-Levy has been named to a new position, the provost’s fellow for pedagogical innovation, for a three-year term beginning Aug. 1. Thom-Levy will focus on curriculum and supporting excellence and innovation in teaching, and will work in close collaboration with Stoltzfus as vice provost. Both positions will report to the provost.

“In seeking to advance our pedagogical mission, we are fortunate to be able to draw on the expertise of both Rebecca and Julia,” Kotlikoff said. “Together they will be invaluable assets in creating and supporting initiatives to enhance learning experiences for all Cornell students.”

The vice provost for undergraduate education works closely and in collaboration with deans and academic associate deans of the university’s undergraduate colleges and schools, as well as with the other vice provosts, the Division of Student and Campus Life, and various units on campus affecting undergraduate life at Cornell.

Responsibilities of the position include direct, and in some cases shared, oversight of initiatives designed to enhance undergraduate instruction and to promote an intellectual community in and out of the classroom and the laboratory, including living and learning experiences in student residences.

Major responsibilities also include accreditation issues related to undergraduate education, support and development of academic initiatives such as undergraduate research, online education, academic integrity, and campus efforts to support inclusivity and academic success for all of Cornell’s students.

“I look forward to promoting the excellence of the Cornell undergraduate experience, and am especially pleased to collaborate with Professor Thom-Levy as a leader in pedagogical innovation,” Stoltzfus said. “It’s a privilege to serve such a creative and diverse community of students and educators.”

Stoltzfus is a professor in the Division of Nutritional Sciences in the College of Human Ecology. She serves as the provost’s fellow for public engagement and directs the Program in Global Health. Her work has included developing partnerships for international student engagement, and she has led in the design of curricular integration of experiential learning.

Her research focuses on causes and consequences of malnutrition among women and children in developing countries, with ongoing projects in Zimbabwe, Zambia, Tanzania and India.

She earned her Cornell doctorate in human nutrition in 1992, taught at Johns Hopkins Bloomberg School of Public Health for a decade and returned to Cornell in 2002 as associate professor of nutritional sciences. She was promoted to professor in 2005.

Thom-Levy, associate professor of physics, came to Cornell in 2005 and has taught introductory physics as well as laboratory and advanced-topics courses in particle physics. She also directs a research group at the Large Hadron Collider at CERN in Geneva, Switzerland, that includes Cornell postdocs and graduate students. She has mentored students in Cornell’s Research Experience for Undergraduates, Hunter R. Rawlings III Presidential Research Scholars and McNair Scholars programs.

She earned her Ph.D. in 2001 at the University of Hamburg, Germany, and has developed instrumentation and operated detectors at the Stanford Linear Accelerator Center, at the Fermi National Accelerator Laboratory near Chicago, and at CERN.

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May 2016: Physicist Katja Nowack Earns DOE Early Career Award

Katja C. Nowack, assistant professor of physics in Cornell’s College of Arts and Sciences, has been selected by the Department of Energy (DOE) to receive $750,000 for research over five years as part of DOE’s Early Career Research Program for her research project, “Magnetic Imaging of Topological Phases of Matter.”

She is one of 49 scientists chosen for the grant, now in its seventh year, which intends to bolster the nation’s scientific workforce by supporting exceptional researchers during their early career years.

Nowack joined the Cornell faculty in January 2015. Her research group is building a set of low-temperature scanning platforms to implement a toolbox of scanning probes that will provide greater understanding of novel quantum materials. Before coming to Cornell, she was a postdoctoral researcher at Stanford University (2011-14) and Delft University of Technology, Netherlands (2010-11), where she received a Ph.D. in physics in 2009.

Said Cherry Murray, director of DOE’s Office of Science: “We invest in promising young researchers early in their careers to support lifelong discovery science to fuel the nation’s innovation system. We are proud of the accomplishments these young scientists already have made, and look forward to following their achievements in years to come.”

Under the program, university-based researchers receive at least $150,000 per year to cover summer salary and research expenses. To be eligible, a researcher must be an untenured, tenure-track assistant or associate professor at a U.S. academic institution or a full-time employee at a DOE national laboratory, who received a Ph.D. within the past 10 years.

Cornell Chronicle

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May 2016: Cornell Astrophysicists Earn Share of $3M Prize

Cornell astrophysicists Saul Teukolsky and Lawrence Kidder have earned a share in the Special Breakthrough Prize in Fundamental Physics – a $3 million award – that recognizes those who helped create the Laser Interferometer Gravitational-Wave Observatory (LIGO) and its ability to find gravitational waves. The discovery announced in February provided strong confirmation of Albert Einstein’s general theory of relativity.

Teukolsky, the Hans A. Bethe Professor of Physics and Astrophysics, and Kidder, senior research associate, played a vital role to validate the historic news of the first direct detection of gravitational waves, predicted a century ago by Einstein.

Theoretical physicist Stephen Hawking, winner of the 2013 Special Breakthrough Prize, noted of the LIGO team, “This discovery has huge significance: firstly, as evidence for general relativity and its predictions of black hole interactions, and secondly as the beginning of a new astronomy that will reveal the universe through a different medium.”

Announcing the award, the prize committee cited Teukolsky and Kidder for their achievement. The Special Breakthrough Prize is given when an extraordinary scientific achievement occurs.

The three founders of LIGO – Ronald W.P. Drever and Kip S. Thorne of the California Institute of Technology and Rainer Weiss of the Massachusetts Institute of Technology – will share $1 million of the award. The remaining $2 million will be shared among 1,012 contributors to the experiment.

Led by scientists from the LIGO collaboration at Caltech and the Virgo group collaboration, research published in February in Physical Review Letters reported detection of gravitational waves resulting from two black holes spiraling in toward one another and smashing together.

Until then, this scenario had only been predicted theoretically. Many astrophysicists doubted it would occur often enough ever to be detected. However, soon after LIGO detectors in Livingston, Louisiana, and Hanford, Washington, were upgraded, in September scientists found two black holes – each about 35 times the mass of our sun – moving at more than half the speed of light, orbiting each other and creating waves. Researchers spent the autumn 2015 confirming results.

LIGO and Virgo researchers confirmed the waves came from a black hole merger by comparing their data with a theoretical model developed at Cornell. Teukolsky and the Cornell-founded Simulation of eXtreme Spacetimes collaboration group have been calculating and completing a full catalog of theoretical solutions since 2000, when supercomputers first became capable of the task.

Founder of the prize Yuri Milner said: “The creative powers of a unique genius, many great scientists, and the universe itself, have come together to make a perfect science story.”

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Weirdest martensite: Century-old smectic riddle finally solved

Cornell Chronicle story by Tom Fleischman

Using the latest computer game technology, a Cornell-led team of physicists has come up with a “suitably beautiful” explanation to a puzzle that has baffled researchers in the materials and theoretical physics communities for a century.

Physics professor James Sethna has co-authored a paper on the unusual microstructure of smectics – liquid crystals whose molecules are arranged in layers and form ellipses and hyperbolas – and their similarity to martensites, a crystalline structure of steel.

In fact, Sethna and his cohorts have termed smectic liquids “the world’s weirdest martensite.”

The paper is the April 8 Physical Review Letters cover story. Co-authors include postdoctoral physics researcher Danilo Liarte, physics graduate student Matthew Bierbaum, University of Campinas math professor Ricardo Mosna and University of Pennsylvania physics professor Randall Kamien.

Sethna’s group employed the computing power of a graphics processing unit, or GPU – the technology that has led to the advent of amazingly realistic video games – to run hundreds of numerical simulations. They developed a clustering algorithm and proposed a theory of smectic microstructure that merges the laws of association between smectic liquid crystals and martensites.

“This has been this puzzle for many years, and it finally has a suitably beautiful explanation,” Sethna said. “It ties together ideas from special relativity, and ideas from martensites, to explain this whole puzzle.

“It’s aesthetically beautiful,” he added, “there’s a little bit of Euclidean geometry for those people who actually went to geometry class. It’s like, ‘Ellipses and hyperbolas, I remember those.’ And you pour this (smectic) liquid and it forms these things.”

If you fill a glass with a smectic liquid, due to its layering pattern the liquid forms ellipses and hyperbolas. The ellipses are defects – places where the desired ordering breaks down.

In martensite steel, named for German metallurgist Adolf Martens in 1898, its different low-energy crystal orientations mesh together in microscopic layers to give it a hardness factor far superior to pearlitic and other forms of steel.

In 1910, French physicist Georges Friedel studied a fluid that formed ellipses and hyperbolas, and realized that they must be formed by equally spaced layers of molecules.

Sethna suggests, with a wry smile, that maybe the reason Friedel knew enough to be able to identify these ellipses and hyperbolas is that “he was French. And in France, they used to study much more sophisticated math in high school, and everybody in high school learned about the cyclides of Dupin.”

Like concentric, equally spaced spheres can fill space with only a point defect at the center, the cyclides of Dupin can fill space with only ellipses and hyperbolas as defects. Friedel saw these defects, and deduced the structure.

Kamien had recently deduced that the different shapes of ellipses and hyperbolas could be related by the same rules that govern space and time in special relativity. Kamien and Sethna discussed this problem last spring, when Sethna was on sabbatical at Penn.

“He had this long-standing interest in martensites … and I had an interest in these liquid crystals, smectics,” Kamien said, “and after talking for a while, we realized that these were the same thing.”

Kamien said his interest in smectics was, in part, sparked by a paper Sethna co-wrote with French physicist Maurice Kleman in 1982, “Spheric domains in smectic liquid crystals.”

The recent breakthrough, inspired by the GPU simulations, was to realize the connection between smectics and martensites.

“For over 100 years, these cool focal conics have been a curiosity – they didn’t fit into our system,” says Sethna. “Now we know that these cool cyclides follow the same rules as the crystals that fit together into martensitic steel.”

This work was supported by grants from the U.S. Department of Energy and the Simons Foundation.


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Elusive superconductor state observed

Cornell Chronicle

By Bill Steele

A state of electronic matter first predicted by theorists in 1964 has finally been discovered by Cornell physicists and may provide key insights into the workings of high-temperature superconductors.

The prediction was that “Cooper pairs” of electrons in a superconductor could exist in two possible states. They could form a “superfluid” where all the particles are in the same quantum state and all move as a single entity, carrying current with zero resistance – what we usually call a superconductor. Or the Cooper pairs could periodically vary in density across space, a so-called “Cooper pair density wave.” For decades, this novel state has been elusive, possibly because no instrument capable of observing it existed.

Now a research team led by J.C. Séamus Davis, the James Gilbert White Distinguished Professor in the Physical Sciences, and Andrew P. Mackenzie, director of the Max-Planck Institute CPMS in Dresden, Germany, has developed a new way to use a scanning tunneling microscope (STM) to image Cooper pairs directly.

The work was carried out by Davis Group members Mohammed Hamidian (now at Harvard) and Stephen Edkins (a graduate student at St. Andrews University in Scotland), and is published in the April 13 online edition of the journal Nature.

Superconductivity was first discovered in metals cooled almost to absolute zero (-273.15 degrees Celsius or -459.67 Fahrenheit). Recently developed materials called cuprates – copper oxides laced with other atoms – superconduct at temperatures as “high” as 148 degrees above absolute zero (-125 Celsius). In superconductors electrons join in pairs that are magnetically neutral so they do not interact with atoms and can move without resistance.

Hamidian and Edkins studied a cuprate incorporating bismuth, strontium and calcium (Bi2Sr2CaCu2O8) using an incredibly sensitive STM that scans a surface with sub-nanometer resolution, on a sample that is refrigerated to within a few thousandths of a degree above absolute zero.

At these temperatures Cooper pairs can hop across short distances from one superconductor to another, a phenomenon known as Josephson tunneling. To observe Cooper pairs, the researchers briefly lowered the tip of the probe to touch the surface and pick up a flake of the cuprate material. Cooper pairs could then tunnel between the superconductor surface and the superconducting tip. The instrument became, Davis said, “the world’s first scanning Josephson tunneling microscope.”

Tunneling Cooper pairs create a current flow between the sample and the tip that reveals the density of Cooper pairs at any point, and this showed periodic variations across the sample, with a wavelength of four crystal unit cells. The team had found a Cooper pair density wave state in a high-temperature superconductor, confirming the 50-year-old prediction.

A collateral finding was that Cooper pairs were not seen in the vicinity of a few zinc atoms that had been introduced as impurities, making the overall map of Cooper pairs into “Swiss cheese.”

Density waves may help to explain the so-called “pseudogap” where some materials show symptoms of being superconductors but don’t actually superconduct. Since the pseudogap often appears at relatively high temperatures, understanding it could lead to higher-temperature superconductors that would revolutionize electric power generation and transport.

The researchers noted that their technique could be used to study other cuprates as well as recently discovered iron-based superconductors.

The work was primarily supported by the U.S. Department of Energy Office of Science and a grant to Davis from the EPiQS Program of the Gordon and Betty Moore Foundation.

The collaboration included scientists in Scotland, Germany, Japan and Korea.

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Renowned physicist to examine nature’s moral code

Cornell Chronicle

The ideas of physicist Nima Arkani-Hamed have revolutionized the field of particle theory over the last decade. On April 21, he will turn his attention to “The Morality of Fundamental Physics” in a public lecture as an A.D. White Professor-at-Large.

The talk, at 7 p.m. in Cornell’s Schwartz Auditorium, Rockefeller Hall, is free and open to the public.

The search for nature’s fundamental laws has been associated with “morally correct” explanations and understanding, says Arkani-Hamed.

“This ‘intellectual moral code’ derives its authority from nature, reflecting a deep and still-mysterious unity in our growing understanding of the world of physical and mathematical truth. It also has striking similarities to what we widely recognize as morally good behavior more generally, providing an invariant basis for morality independent of gods or human constructs and conventions.”

His talk will illustrate this notion, using concrete examples ranging from planetary orbits to the structure of quantum field theory.

“Professor Arkani-Hamed is arguably the most brilliant theoretical physicist active today. His insights into the nature of physical laws, the structure of space-time, and the origin and history of the universe are both profound and unconventional,” says Maxim Perelstein, professor of physics. “Every time I hear him speak, I learn something remarkable.”

Yuval Grossman, professor of physics adds , “Not only are Nima’s ideas shaping the landscape of theoretical research, he also does an outstanding job of delivering those ideas to the general public.”

Arkani-Hamed is professor of natural sciences at the Institute for Advanced Study in Princeton, New Jersey. His research focuses on the relationship between theory and experiment. His groundbreaking theories relate to new extra space-time dimensions, super-symmetric extensions of the standard model, the nature of electroweak symmetry breaking and mass generation, the cosmological expansion of the universe, and the nature of dark matter in the universe and, recently, an entirely new idea about the origin of quantum mechanics.

Among his many awards, Arkani-Hamed was an inaugural winner of the $3 million Fundamental Physics Prize, the creation of physicist and internet entrepreneur Yuri Milner. He has also received a Gribov Prize from the European Physical Society and Israel’s Raymond and Beverly Sackler Prize. He was elected to the American Academy of Arts and Sciences in 2009. He received his Ph.D. in physics from the University of California, Berkeley in 1997.

On April 18, Arkani-Hamed will offer a Physics Colloquium talk, “The Future of Collider Physics, on the Earth and in the Sky,” at 4 p.m. in Rockefeller Hall, Schwartz Auditorium.

Arkani-Hamed’s talks are sponsored by the Department of Physics and the A.D. White Professors-at-Large Program.

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