Category Archives: Quantum Physics

Dennis Nemeschansky, professor of physics and astronomy at USC Dornsife College of Letters, Arts and Sciences, died on June1. He was 67.

An expert on string theory who focused on supersymmetry quantum field theory, Nemeschansky is best known for the Minahan-Nemeschansky Theory, which he developed with visiting physicist Joseph Minahan during a game of golf.

Published in 1997, their paper showed that the then-current approach to constructing certain types of important supersymmetric quantum field theories was incorrect and demonstrated the correct way to do it. Initial skepticism from the scientific community gradually gave way to respect and acceptance a decade later, as the theory continued to hold true under scrutiny.

Moreover, they were able to generalize their result to construct several more theories that completed a connection between these supersymmetric quantum field theories and a deep mathematical classification result.

Nemeschanskys teaching focused on pre-med physics, and he taught Physics for the Life Sciences (PHYS 135) for more than 30 years.

Stephan Haas, chair of the Department of Physics and professor of physics and astronomy, said Nemeschansky would be sorely missed by faculty and students alike.

Dennis had a great sense of humor, passion for science and ability to communicate complex material in a very understandable way, Haas said.

Indeed, Nemeschansky wasnt shy about using his considerable athleticism to illustrate the properties of physics to his students and could be spotted each semester demonstrating Newtons Third Law by whizzing across campus on a skateboard with a fire extinguisher attached.

Students and colleagues loved his casual and relatable attitude, Haas said. In his research, he made seminal contributions to our understanding of quantum field theory and string theory, their application to unification of forces, and on strong-weak coupling duality in supersymmetric quantum chromodynamics.

A true calling

Nemeschansky was born in Helsinki, Finland, on Dec. 21, 1955. His father, Arje, was a salesman of kitchen equipment and his mother, Joan, worked in pharmaceutical sales. Nemeschansky was brought up in the Jewish faith, attending Hebrew school in Helsinki.

His son, alumnus David Nemeschansky 15, who earned undergraduate degrees in political science from USC Dornsife and in communication from USC Annenberg School for Communication and Journalism as well as a progressive masters from USC Leventhal School of Accounting, said his father was one of the lucky few blessed with a true calling in life.

He always knew from a very young age that math and physics were his thing, he said. It actually made his parents very nervous because he just wanted to do numbers and really had no patience or interest in any other subject.

After completing his national service in the Finnish Army, Nemeschansky obtained an MSc in theoretical physics from Helsinki University of Technology in 1980. He then moved to the United States to earn his PhD at Princeton University in 1984, where he collaborated with and was taught by some of the leading physics minds of the day. It was also where he decided to study string theory, which he specialized in throughout his career.

After Princeton, he moved to Stanford University, where he completed his postdoctoral training at the Stanford Linear Accelerator Center in 1986.

The move to California proved decisive.

Coming from Finlands cold, dark winters, he fell in love with the sunny paradise of California and really wanted to stay here, said David Nemeschansky.

The promising young physicist was invited to give a talk at USCs inaugural string theory conference in 1985 and joined USC Dornsife the following year.

He had this personality where he wanted things done right 98% wasnt good enough.

He was recruited with Itzhak Bars, professor of physics and astronomy, to create a new theoretical physics group within the department.

Most of these new hires were string theorists. My father was really excited about that and the possibility of working with those folks and building out something new at USC, David Nemeschansky said.

A devoted teacher and mentor to his students, Nemeschansky took office hours very seriously, offering more than was required of him.

He believed that you had to really understand physics and the mathematical backing behind it; you couldnt just memorize formulas, David Nemeschansky said. He felt very strongly that people need to be taught in a way that shows them that beauty and elegance. And then they would never have to memorize a formula; they would see how it all ties together.

While David Nemeschansky was a student at USC, he remembers his father inviting him to attend a lecture in which he would demonstrate how the entire physics textbook could be derived from two formulas. I remember watching people in the first 15 minutes meticulously taking notes as hes doing all these graphs on the chalkboard he had no notes, it was all in his head. And then you could slowly see the atmosphere in the room turn to awe because it was very clear that his understanding was so deep.

Disinterested in becoming department chair because he preferred to concentrate on his teaching and research, Nemeschansky did serve as colloquium chair, organizing physics symposiums and bringing in expert speakers to talk to faculty and doctoral students. He also served as scheduling chair, compiling the departments class schedules.

In 1995 and 2004, he was a visiting fellow at the European Organization for Nuclear Research on the French-Swiss border, the location of the worlds most powerful particle accelerator. He also spent the summer of 2018 at TRIUMF in Canada.

Prior to his death, Nemeschansky wrote a physics textbook tailored to health students with USC Dornsifes Scott Macdonald, assistant professor (teaching) of physics and astronomy. MacDonald is currently in talks with a publisher.

A passion for family, physics, sports and books

David Nemeschansky remembers being impressed by his fathers extensive library.

I used to joke that in his office he had a wizard library. He really was trying to figure out the great mysteries of the universe, how matter is constructed, how the tiniest subatomic particles work. How many dimensions are there? How did the universe begin?

In addition to his life-long passion for physics, Nemeschansky was a huge sports enthusiast.

My father was a man of a very clear priorities: family, physics and sports in that order, said David Nemeschansky.

He was a keen ice hockey player and was so talented at tennis that at university he had to choose between a professional career in the sport and physics. His love of physics won.

Nemeschansky was also a talented soccer player and became an avid golfer in middle age.

He had this personality where he wanted things done right 98% wasnt good enough, David Nemeschansky said. He had immensely high standards for instance, he would rather not publish than publish something that was mediocre. That exacting nature translated into sports.

He really wanted me to have outstanding hockey training and he felt he was the only person who could do that, so he became my coach.

The modest Finn

Nemeschansky may have been a perfectionist, but by all accounts, he was also an extremely modest, private man who asked students to call him by his first name.

He is fondly remembered by faculty, staff and students as a brilliant but self-effacing man who inevitably had an undone shoelace.

He was a man of few words. He didnt really talk much about himself unless asked and even then, if you asked him where he went to school, he would say back East. He wouldnt say Princeton, said David Nemeschansky.

Nemeschansky spoke fluent Finnish, Swedish and English and some Hebrew.

A believer in Judaism who saw ample room for God and physics to go hand in hand, Nemeschansky regularly attended synagogue.

In 1988, he married Lauren Rosen, a grade schoolteacher who later became a successful realtor.

Nemeschansky loved to travel and enjoyed photographing waterfalls so much his family nicknamed him Captain Tripod.

He retained great affection for the country of his birth throughout his life despite feeling it was a little small.

He had bigger dreams, and that eventually took him to the U.S., said David Nemeschansky. He married an American, had American children, but he stayed a Finnish citizen until he died. He loved his country.

Nemeschansky is survived by his mother; his wife; his sons, David and Marc; and his brothers, Ben and Michael.

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String theory physicist changed quantum field theory - USC Dornsife College of Letters, Arts and Sciences

The words Quantum and Supercomputer are really big words. The former refers to a completely different world, whereas the latter refers to computers that are significantly faster and better than average robots. When we join these two words, it forms something extraordinary. A highly efficient computer that uses completely different principles to execute commands that for usual computers, would be impossible.

What are Quantum Supercomputers? They are very powerful and cutting-edge computers that work considerably more quickly than conventional computers thanks to the laws of quantum physics. Developers along with engineers made these computers to solve problems that were very complex for our regular computers (Complex problems here are problems with lots of variables interacting in complicated ways). Problems regarding how atoms are interacting in molecules or how a nuclear reaction will be executed involve multiple factors, which is what makes it so incomprehensible for regular computers.

How does it work? Well, bad news for you, the first and most important thing is the relatively hardest part to understand. Took me a few days of research to understand these, but Ill make it simple. Lets call Quantum Supercomputers QS. So, how is a QS different from a regular laptop? Well, it eliminates the boundaries of processing. Now, why do I say this? Well, as the nerdy computer people may know, our regular computers work by assigning binary units of information to bits, represented as either a 0 or a 1. So, one piece of information has been assigned to a specific number (0 or 1). Well, QS just breaks this barrier. In the QS world, we use qubits instead of bits. And due to a property called Quantum Superposition, qubits can exist as 0 and 1 simultaneously. Confusing, isnt it? Well, take the example of a doughnut shop. You are the customer and the doughnut vendor is the seller. Now, you buy the doughnut from the seller, so your job is buying a doughnut, and his job is selling the doughnut, right? Well, according to Quantum Superposition, you can be both the seller and the buyer!

This was just one of the factors which increase the speed of computation in a QS. An increase in qubits leads to an increase in computational speed. It is estimated that a quantum computer with 100 qubits could theoretically be 10000000000000000000000000000000 (10 to its 30th power) times faster than a classical computer! And with these high speeds, cooling is vital. Ever heard of absolute zero? Its the temperature at which its so cold that particles of matter stop moving. These machines require about a hundredth of a degree (0.01) above absolute zero!

WHERE are these QS used? Well, these computers can be used for complex calculations. These types of calculations are mainly found in Quantum Simulation, Cryptography, Machine Learning, Quantum Chemistry, Financial Modeling, and more. The field of optimisation is another important application area. Quantum computers are incredibly effective at solving optimisation problems because they can explore multiple possibilities at once.

Despite these impressive applications, actual quantum computers are still constrained by qubit count and error rates. These constraints are expected to be abolished as technology advances, allowing for even more applications in a variety of fields. In the future years, quantum computing has the potential to redefine problem-solving and promote innovation, presenting unprecedented opportunities for tackling difficulties that are intractable for traditional computers.

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QUANTUM SUPERCOMPUTERS. The words Quantum and ... - Medium

In 2022, nine MIT faculty were granted tenure in the School of Science:

Gloria Choi examines the interaction of the immune system with the brain and the effects of that interaction on neurodevelopment, behavior, and mood. She also studies how social behaviors are regulated according to sensory stimuli, context, internal state, and physiological status, and how these factors modulate neural circuit function via a combinatorial code of classic neuromodulators and immune-derived cytokines. Choi joined the Department of Brain and Cognitive Sciences after a postdoc at Columbia University. She received her bachelors degree from the University of California at Berkeley, and her PhD from Caltech. Choi is also an investigator in The Picower Institute for Learning and Memory.

Nikta Fakhri develops experimental tools and conceptual frameworks to uncover laws governing fluctuations, order, and self-organization in active systems. Such frameworks provide powerful insight into dynamics of nonequilibrium living systems across scales, from the emergence of thermodynamic arrow of time to spatiotemporal organization of signaling protein patterns and discovery of odd elasticity. Fakhri joined the Department of Physics in 2015 following a postdoc at University of Gttingen. She completed her undergraduate degree at Sharif University of Technology and her PhD at Rice University.

Geobiologist Greg Fournier uses a combination of molecular phylogeny insights and geologic records to study major events in planetary history, with the hope of furthering our understanding of the co-evolution of life and environment. Recently, his team developed a new technique to analyze multiple gene evolutionary histories and estimated that photosynthesis evolved between 3.4 and 2.9 billion years ago. Fournier joined the Department of Earth, Atmospheric and Planetary Sciences in 2014 after working as a postdoc at the University of Connecticut and as a NASA Postdoctoral Program Fellow in MITs Department of Civil and Environmental Engineering. He earned his BA from Dartmouth College in 2001 and his PhD in genetics and genomics from the University of Connecticut in 2009.

Daniel Harlow researches black holes and cosmology, viewed through the lens of quantum gravity and quantum field theory. His work generates new insights into quantum information, quantum field theory, and gravity. Harlow joined the Department of Physics in 2017 following postdocs at Princeton University and Harvard University. He obtained a BA in physics and mathematics from Columbia University in 2006 and a PhD in physics from Stanford University in 2012. He is also a researcher in the Center for Theoretical Physics.

A biophysicist, Gene-Wei Li studies how bacteria optimize the levels of proteins they produce at both mechanistic and systems levels. His lab focuses on design principles of transcription, translation, and RNA maturation. Li joined the Department of Biology in 2015 after completing a postdoc at the University of California at San Francisco. He earned an BS in physics from National Tsinghua University in 2004 and a PhD in physics from Harvard University in 2010.

Michael McDonald focuses on the evolution of galaxies and clusters of galaxies, and the role that environment plays in dictating this evolution. This research involves the discovery and study of the most distant assemblies of galaxies alongside analyses of the complex interplay between gas, galaxies, and black holes in the closest, most massive systems. McDonald joined the Department of Physics and the Kavli Institute for Astrophysics and Space Research in 2015 after three years as a Hubble Fellow, also at MIT. He obtained his BS and MS degrees in physics at Queens University, and his PhD in astronomy at the University of Maryland in College Park.

Gabriela Schlau-Cohen combines tools from chemistry, optics, biology, and microscopy to develop new approaches to probe dynamics. Her group focuses on dynamics in membrane proteins, particularly photosynthetic light-harvesting systems that are of interest for sustainable energy applications. Following a postdoc at Stanford University, Schlau-Cohen joined the Department of Chemistry faculty in 2015. She earned a bachelors degree in chemical physics from Brown University in 2003 followed by a PhD in chemistry at the University of California at Berkeley.

Phiala Shanahans research interests are focused around theoretical nuclear and particle physics. In particular, she works to understand the structure and interactions of hadrons and nuclei from the fundamental degrees of freedom encoded in the Standard Model of particle physics. After a postdoc at MIT and a joint position as an assistant professor at the College of William and Mary and senior staff scientist at the Thomas Jefferson National Accelerator Facility, Shanahan returned to the Department of Physics as faculty in 2018. She obtained her BS from the University of Adelaide in 2012 and her PhD, also from the University of Adelaide, in 2015.

Omer Yilmaz explores the impact of dietary interventions on stem cells, the immune system, and cancer within the intestine. By better understanding how intestinal stem cells adapt to diverse diets, his group hopes to identify and develop new strategies that prevent and reduce the growth of cancers involving the intestinal tract. Yilmaz joined the Department of Biology in 2014 and is now also a member of Koch Institute for Integrative Cancer Research. After receiving his BS from the University of Michigan in 1999 and his PhD and MD from University of Michigan Medical School in 2008, he was a resident in anatomic pathology at Massachusetts General Hospital and Harvard Medical School until 2013.

In 2023, five MIT faculty were granted tenure in the School of Science:

Physicist Riccardo Comin explores the novel phases of matter that can be found in electronic solids with strong interactions, also known as quantum materials. His group employs a combination of synthesis, scattering, and spectroscopy to obtain a comprehensive picture of these emergent phenomena, including superconductivity, (anti)ferromagnetism, spin-density-waves, charge order, ferroelectricity, and orbital order. Comin joined the Department of Physics in 2016 after postdoctoral work at the University of Toronto. He completed his undergraduate studies at the Universita degli Studi di Trieste in Italy, where he also obtained a MS in physics in 2009. Later, he pursued doctoral studies at the University of British Columbia, Canada, earning a PhD in 2013.

Netta Engelhardt researches the dynamics of black holes in quantum gravity and uses holography to study the interplay between gravity and quantum information. Her primary focus is on the black hole information paradox, that black holes seem to be destroying information that, according to quantum physics, cannot be destroyed. Engelhardt was a postdoc at Princeton University and a member of the Princeton Gravity Initiative prior to joining the Department of Physics in 2019. She received her BS in physics and mathematics from Brandeis University and her PhD in physics from the University of California at Santa Barbara. Engelhardt is a researcher in the Center for Theoretical Physics and the Black Hole Initiative at Harvard University.

Mark Harnett studies how the biophysical features of individual neurons endow neural circuits with the ability to process information and perform the complex computations that underlie behavior. As part of this work, his lab was the first to describe the physiological properties of human dendrites. He joined the Department of Brain and Cognitive Sciences and the McGovern Institute for Brain Research in 2015. Prior, he was a postdoc at the Howard Hughes Medical Institutes Janelia Research Campus. He received his BA in biology from Reed College in Portland, Oregon and his PhD in neuroscience from the University of Texas at Austin.

Or Hen investigates quantum chromodynamic effects in the nuclear medium and the interplay between partonic and nucleonic degrees of freedom in nuclei. Specifically, Hen utilizes high-energy scattering of electron, neutrino, photon, proton and ion off atomic nuclei to study short-range correlations: temporal fluctuations of high-density, high-momentum, nucleon clusters in nuclei with important implications for nuclear, particle, atomic, and astrophysics. Hen was an MIT Pappalardo Fellow in the Department of Physics from 2015 to 2017 before joining the faculty in 2017. He received his undergraduate degree in physics and computer engineering from the Hebrew University and earned his PhD in experimental physics at Tel Aviv University.

Sebastian Lourido is interested in learning about the vulnerabilities of parasites in order to develop treatments for infectious diseases and expand our understanding of eukaryotic diversity. His lab studies many important human pathogens, including Toxoplasma gondii, to model features conserved throughout the phylum. Lourido was a Whitehead Fellow at the Whitehead Institute for Biomedical Research until 2017, when he joined the Department of Biology and became a Whitehead Member. He earned his BS from Tulane University in 2004 and his PhD from Washington University in St. Louis in 2012.

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Fourteen MIT School of Science professors receive tenure for 2022 ... - MIT News

Exploring the Intricacies of Quantum Integrated Circuits: The Future of Technology?

Quantum integrated circuits, a term that may sound like its straight out of a science fiction novel, are rapidly becoming a reality. This fascinating technology, which combines the principles of quantum mechanics with the functionality of integrated circuits, is poised to revolutionize the world of technology as we know it.

Quantum mechanics, the branch of physics that deals with the smallest particles in the universe, has long been a subject of intrigue and mystery. Its a world where particles can exist in multiple places at once, where they can be both waves and particles, and where they can be entangled in such a way that the state of one particle can instantly affect the state of another, no matter how far apart they are.

Integrated circuits, on the other hand, are a cornerstone of modern technology. They are the brains of our computers, smartphones, and countless other devices, enabling them to process information and perform complex tasks.

The marriage of these two fields in quantum integrated circuits is a groundbreaking development. These circuits use quantum bits, or qubits, which can exist in multiple states at once, rather than the binary bits used in traditional computing. This allows them to process information in a fundamentally different way, potentially making them exponentially more powerful than even the most advanced classical computers.

The potential applications of quantum integrated circuits are vast and varied. They could revolutionize fields such as cryptography, enabling the creation of codes that are virtually unbreakable. They could also dramatically speed up complex calculations in fields such as drug discovery and climate modeling, potentially leading to major breakthroughs.

However, the development of quantum integrated circuits is not without its challenges. Quantum systems are extremely delicate and can be easily disrupted by their environment, a problem known as decoherence. This makes them difficult to scale up and maintain over long periods.

Despite these challenges, progress is being made. Researchers around the world are developing new techniques to create and manipulate qubits, and to protect them from decoherence. Companies like Google, IBM, and Microsoft are investing heavily in quantum computing research, and there are even startups dedicated to developing quantum integrated circuits.

The future of quantum integrated circuits is still uncertain. There are many technical hurdles to overcome, and it may be years or even decades before they become commonplace. However, the potential rewards are enormous. If successful, they could usher in a new era of technological innovation, transforming everything from healthcare to finance to artificial intelligence.

In conclusion, the world of quantum integrated circuits is a fascinating one, filled with both promise and challenges. Its a world where the laws of physics as we know them are turned on their head, where the impossible becomes possible, and where the future of technology may well be written. Whether or not they become the next big thing, one thing is certain: they are a testament to the boundless potential of human ingenuity and the relentless pursuit of knowledge.

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The Fascinating World of Quantum Integrated Circuits: The Next Big ... - Fagen wasanni

A recent study reveals that the orbital motions of widely separated binary stars, or wide binaries, break down the standard model of gravity at low accelerations. Analyzing data from 26,500 wide binaries, researchers found that accelerations below one nanometer per second squared deviate from Newtons and Einsteins gravitational laws.

A study on the orbital motions of wide binaries has uncovered evidence that standard gravity breaks down at low accelerations. This discovery aligns with a modified theory called MOND and challenges current concepts of dark matter. The implications for astrophysics, physics, and cosmology are profound, and the results have been acknowledged as a significant discovery by experts in the field.

A new study reports conclusive evidence for the breakdown of standard gravity in the low acceleration limit, stemming from a verifiable analysis of the orbital motions of long-period, widely separated binary stars. These stars are commonly referred to as wide binaries in astronomy and astrophysics. The study was carried out by Kyu-Hyun Chae, professor of physics and astronomy at Sejong University in Seoul, and it used up to 26,500 wide binaries within 650 light years (LY), observed by the European Space Agencys Gaia space telescope.

For a significant improvement over other research, Chaes study concentrated on calculating the gravitational accelerations experienced by binary stars as a function of their separation or equivalently, the orbital period. This was achieved by a Monte Carlo deprojection of observed sky-projected motions to three-dimensional space.

Chae explains, From the start, it seemed clear to me that gravity could be most directly and efficiently tested by calculating accelerations because the gravitational field itself is an acceleration. My recent research experiences with galactic rotation curves led me to this idea. Galactic disks and wide binaries share some similarity in their orbits, though wide binaries follow highly elongated orbits while hydrogen gas particles in a galactic disk follow nearly circular orbits.

In addition, Chae calibrated the occurrence rate of hidden nested inner binaries at a benchmark acceleration, unlike other studies.

Left: A binary star system with a nested inner binary (credit: Wikipedia). Right: Gravitational anomaly at low acceleration observed in 20,000 wide binaries Credit: Kyu-Hyun Chae

The study reveals that when two stars orbit each other with accelerations lower than about one nanometer per second squared, they start to deviate from predictions by Newtons universal law of gravitation and Einsteins general relativity. For accelerations lower than approximately 0.1 nanometer per second squared, the observed acceleration is about 30 to 40 percent higher than the Newton-Einstein prediction. The significance is considerable, meeting the conventional criteria of 5 sigma for a scientific discovery. In a sample of 20,000 wide binaries within a distance limit of 650 LY, two independent acceleration bins respectively show deviations of over 5 sigma significance in the same direction.

Because the observed accelerations stronger than about 10 nanometers per second squared agree well with the Newton-Einstein prediction from the same analysis, the observed boost of accelerations at lower accelerations is a mystery. Intriguingly, this breakdown of the Newton-Einstein theory at weaker accelerations was suggested 40 years ago by theoretical physicist Mordehai Milgrom at the Weizmann Institute in Israel in a new theoretical framework called modified Newtonian dynamics (MOND) or Milgromian dynamics in current usage.

The boost factor of about 1.4 is correctly predicted by a MOND-type Lagrangian theory of gravity called AQUAL, proposed by Milgrom and the late physicist Jacob Bekenstein. Whats remarkable is that the correct boost factor requires the external field effect from the Milky Way galaxy, a unique prediction of MOND-type modified gravity. Thus, the wide binary data indicate not only the breakdown of Newtonian dynamics but also the manifestation of the external field effect of modified gravity.

On the results, Chae says, It seems impossible that a conspiracy or unknown systematic can cause these acceleration-dependent breakdowns of the standard gravity in agreement with AQUAL. I have examined all possible systematics as described in the rather long paper. The results are genuine. I foresee that the results will be confirmed and refined with better and larger data in the future. I have also released all my codes for the sake of transparency and to serve any interested researchers.

Unlike galactic rotation curves, where the observed boosted accelerations can theoretically be attributed to dark matter in the Newton-Einstein standard gravity, wide binary dynamics cannot be affected by it even if it existed. The standard gravity simply breaks down in the weak acceleration limit in accordance with the MOND framework.

The implications of wide binary dynamics are profound for astrophysics, theoretical physics, and cosmology. Anomalies in Mercurys orbits observed in the nineteenth century eventually led to Einsteins general relativity. Now anomalies in wide binaries demand a new theory extending general relativity to the low acceleration MOND limit.

Despite all the successes of Newtons gravity, general relativity is needed for relativistic gravitational phenomena such as black holes and gravitational waves. Likewise, despite all the successes of general relativity, a new theory is needed for MOND phenomena in the weak acceleration limit. The weak-acceleration catastrophe of gravity may have some similarity to the ultraviolet catastrophe of classical electrodynamics that led to quantum physics.

Wide binary anomalies are disastrous for standard gravity and cosmology that rely on dark matter and dark energy concepts. Since gravity follows MOND, a large amount of dark matter in galaxies (and even in the universe) is no longer needed. This is a significant surprise to Chae who, like typical scientists, believed in dark matter until a few years ago.

A new revolution in physics seems now underway. On the present results and the future prospects, Milgrom says, Chaes finding is a result of a very involved analysis of cutting-edge data, which, as far as I can judge, he has performed very meticulously and carefully. But for such a far-reaching finding and it is indeed very far-reaching we require confirmation by independent analyses, preferably with better future data. If this anomaly is confirmed as a breakdown of Newtonian dynamics, and especially if it indeed agrees with the most straightforward predictions of MOND, it will have enormous implications for astrophysics, cosmology, and for fundamental physics at large.

Xavier Hernandez, professor at UNAM in Mexico who first suggested wide binary tests of gravity a decade ago, says, It is exciting that the departure from Newtonian gravity that my group has claimed for some time has now been independently confirmed, and impressive that this departure has for the first time been correctly identified as accurately corresponding to a detailed MOND model. The unprecedented accuracy of the Gaia satellite, the large and meticulously selected sample Chae uses and his detailed analysis, make his results sufficiently robust to qualify as a discovery.

Pavel Kroupa, professor at Bonn University and at Charles University in Prague, has come to the same conclusions concerning the law of gravitation. He says, With this test on wide binaries as well as our tests on open star clusters nearby the Sun, the data now compellingly imply that gravitation is Milgromian rather than Newtonian. The implications for all of astrophysics are immense.

The finding was published in the 1 August 2023 issue of The Astrophysical Journal.

Reference: Breakdown of the NewtonEinstein Standard Gravity at Low Acceleration in Internal Dynamics of Wide Binary Stars by Kyu-Hyun Chae, 24 July 2023, The Astrophysical Journal. DOI: 10.3847/1538-4357/ace101

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Conclusive Evidence for Modified Gravity: Collapse of Newton's and ... - SciTechDaily

Physicists identified a mechanism behind oscillating superconductivity, called pair-density waves, through structures known as Van Hove singularities. This discovery offers a deeper understanding of unconventional superconductive states found in specific materials, including high-temperature superconductors.

Physicists have pinpointed a mechanism responsible for the creation of oscillating superconductivity, termed pair-density waves. The findings, which shed light on an atypical high-temperature superconductive state observed in specific materials like high-temperature superconductors, were published in Physical Review Letters.

We discovered that structures known as Van Hove singularities can produce modulating, oscillating states of superconductivity, says Luiz Santos, assistant professor of physics at Emory University and senior author of the study. Our work provides a new theoretical framework for understanding the emergence of this behavior, a phenomenon that is not well understood.

The first author of the study is Pedro Castro, an Emory physics graduate student. Co-authors include Daniel Shaffer, a postdoctoral fellow in the Santos group, and Yi-Ming Wu from Stanford University.

Santos is a theorist who specializes in condensed matter physics. He studies the interactions of quantum materials tiny things such as atoms, photons, and electrons that dont behave according to the laws of classical physics.

Superconductivity, or the ability of certain materials to conduct electricity without energy loss when cooled to a super-low temperature, is one example of intriguing quantum behavior. The phenomenon was discovered in 1911 when Dutch physicist Heike Kamerlingh Onnes showed that mercury lost its electrical resistance when cooled to 4 Kelvin or minus 371 degrees Fahrenheit. Thats about the temperature of Uranus, the coldest planet in the solar system.

It took scientists until 1957 to come up with an explanation for how and why superconductivity occurs. At normal temperatures, electrons roam more or less independently. They bump into other particles, causing them to shift speed and direction and dissipate energy. At low temperatures, however, electrons can organize into a new state of matter.

Luiz Santos, assistant professor of physics at Emory University, is the senior author of the study. Credit: Emory University

They form pairs that are bound together into a collective state that behaves like a single entity, Santos explains. You can think of them like soldiers in an army. If they are moving in isolation they are easier to deflect. But when they are marching together in lockstep its much harder to destabilize them. This collective state carries current in a robust way.

Superconductivity holds huge potential. In theory, it could allow for electric current to move through wires without heating them up or losing energy. These wires could then carry far more electricity, far more efficiently.

One of the holy grails of physics is room-temperature superconductivity that is practical enough for everyday-living applications, Santos says. That breakthrough could change the shape of civilization.

Many physicists and engineers are working on this frontline to revolutionize how electricity gets transferred.

Meanwhile, superconductivity has already found applications. Superconducting coils power electromagnets used in magnetic resonance imaging (MRI) machines for medical diagnostics. A handful of magnetic levitation trains are now operating in the world, built on superconducting magnets that are 10 times stronger than ordinary electromagnets. The magnets repel each other when the matching poles face each other, generating a magnetic field capable of levitating and propelling a train.

The Large Hadron Collider, a particle accelerator that scientists are using to research the fundamental structure of the universe, is another example of technology that runs through superconductivity.

Superconductivity continues to be discovered in more materials, including many that are superconductive at higher temperatures.

One focus of Santos research is how interactions between electrons can lead to forms of superconductivity that cannot be explained by the 1957 description of superconductivity. An example of this so-called exotic phenomenon is oscillating superconductivity, when the paired electrons dance in waves, changing amplitude.

In an unrelated project, Santos asked Castro to investigate specific properties of Van Hove singularities, structures where many electronic states become close in energy. Castros project revealed that the singularities appeared to have the right kind of physics to seed oscillating superconductivity.

That sparked Santos and his collaborators to delve deeper. They uncovered a mechanism that would allow these dancing-wave states of superconductivity to arise from Van Hove singularities.

As theoretical physicists, we want to be able to predict and classify behavior to understand how nature works, Santos says. Then we can start to ask questions with technological relevance.

Some high-temperature superconductors which function at temperatures about three times as cold as a household freezer have this dancing-wave behavior. The discovery of how this behavior can emerge from Van Hove singularities provides a foundation for experimentalists to explore the realm of possibilities it presents.

I doubt that Kamerlingh Onnes was thinking about levitation or particle accelerators when he discovered superconductivity, Santos says. But everything we learn about the world has potential applications.

Reference: Emergence of the Chern Supermetal and Pair-Density Wave through Higher-Order Van Hove Singularities in the Haldane-Hubbard Model by Pedro Castro, Daniel Shaffer, Yi-Ming Wu and Luiz H. Santos, 11 July 2023, Physical Review Letters. DOI: 10.1103/PhysRevLett.131.026601

The work was funded by the U.S. Department of Energys Office of Basic Energy Sciences.

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Physicists Open New Path to an Exotic Form of Superconductivity - SciTechDaily

The shortest distance between two points is a straight line, but the shortest distance doesnt always mean the least work. What if that distance is straight uphill, or through difficult terrain? If youre looking to do the least amount of work, a straight line may not always be your best bet.

Humans may not always be looking for the easiest route. But when it comes to natural movements in systems, one of the

Basically, without outside intervention, objects travel along the path of least resistance and least change. This is called the principle of least action. We know it applies in our everyday world, and nowthanks to a new studywe know it applies in the quantum world as well.

A physicists ultimate dream is to write the secrets of the entire universe on a small piece of paper and the principle of least action must be on the list, Shi-Liang, one of the researchers on the project, said in an article for New Scientist. Our ambition was to see [the principle] in a quantum experiment.

Easier said than done. The research team from South China Normal University had to contend with the fact that not only is everything in the quantum realm small and hard to see, the movements of quantum particles are complicatedreally complicated. For one, quantum states change when theyre measured. And for another, theyre only able to be mapped out using very complicated math.

To best describe their behavior, scientists use a combination of two things: a wave function and a propagator. Wave functions describe the state of the particle and propagators describe how that state changes over the course of a particles movement in a system. The trouble is, wave functions and propagators are purely mathematical, and while theyre great at describing the behaviors of quantum particles, they often do so using imaginary numbers. Imaginary numbers are fine in math, but areby definitionimpossible to measure.

In order to get around this problem, the team used a technique that had been established a few years prior. In this technique, you basically bounce and filter individual quantum light particles called photons through a maze of mirrors, crystals, and lenses. Eventually, the parts of the photons behavior described by the imaginary numbers will correspond to actual measurable properties. The parts that were originally described by normal real numbers will also be measurable, and the researchers can reconstruct the wave forms and propagators from actual measured data.

Once the maze had been constructed, researchers combined that technique with a new one they developed to mostly avoid the quantum state change when observed problem. Then, they sent individual photons through the maze and compared their behavior to the behavior predicted by the principle of least action and found that reality agreed with theoryproving that quantum particles do in fact follow the principle.

Measurements in this experiment are quite incredible, and they dont challenge our current understanding of quantum physics, Jonathan Leach, a quantum science researcher not involved in the study, said in a New Scientist article. It is beautiful to see this theory made real in an experiment.

Theres a whole lot of places where the quantum world and the everyday world dont mesh. Its part of why researchers are still looking to improve on the current Standard Model of physics. But in their desire to avoid action as much as possibly, the quantum and the everyday are perfectly in sync.

Associate News Editor

Jackie is a writer and editor from Pennsylvania. She's especially fond of writing about space and physics, and loves sharing the weird wonders of the universe with anyone who wants to listen. She is supervised in her home office by her two cats.

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The Principle of Least Action Now Exists in the Quantum Realm - Popular Mechanics

image:Three perspectives of the surface on which the electrons move. On the left, the experimental result, in the center and on the right the theoretical modeling. The red and blue colors represent a measure of the speed of the electrons. Both theory and experiment reflect the symmetry of the crystal, very similar to the texture of traditional Japanese "kagome" baskets view more

Credit: University of Bologna

An international research team has succeededfor the first timein measuring the electron spin in matter- i.e., the curvature of space in which electrons live and move - within "kagome materials", a new class ofquantum materials.

The results obtained - published inNature Physics- could revolutionise the way quantum materials are studied in the future, opening the door tonew developments in quantum technologies, with possible applications in a variety of technological fields, fromrenewable energytobiomedicine, fromelectronicstoquantum computers.

Success was achieved by an international collaboration of scientists, in whichDomenico Di Sante, professor at theDepartment of Physics and Astronomy "Augusto Righi", participated for theUniversity of Bolognaas part of his Marie CurieBITMAPresearch project. He was joined by colleagues from CNR-IOM Trieste, Ca' Foscari University of Venice, University of Milan, University of Wrzburg (Germany), University of St. Andrews (UK), Boston College and University of Santa Barbara (USA).

Through advanced experimental techniques, usinglight generated by a particle accelerator, theSynchrotron, and thanks tomodern techniques for modelling the behaviour of matter, the scholarswere able to measure electron spin for the first time, related to the concept oftopology.

"If we take two objects such as a football and a doughnut, we notice thattheir specific shapesdeterminedifferent topological properties, for example because the doughnut has a hole, while the football does not,"Domenico Di Santeexplains. "Similarly, the behaviour of electrons in materials is influenced by certain quantum propertiesthat determine their spinning in the matter in which they are found, similar to how the trajectory of light in the universe is modified by the presence of stars, black holes, dark matter, and dark energy, which bend time and space."

Although this characteristic of electrons has been known for many years, no one had until now been able to measure this "topological spin" directly. To achieve this, the researchers exploited a particular effect known as "circular dichroism": a special experimental technique that can only be used with a synchrotron source, which exploits the ability of materialsto absorb light differentlydependingon their polarisation.

Scholars have especially focused on "kagome materials", a class of quantum materials that owe their name to their resemblance to the weave of interwoven bamboo threads that make up a traditional Japanese basket (called, indeed, "kagome").These materials are revolutionising quantum physics, and the results obtained could help us learn more about their special magnetic, topological, and superconducting properties.

"These important results were possible thanks toa strong synergy between experimental practice and theoretical analysis," addsDi Sante. "The team's theoretical researchers employedsophisticated quantum simulations, only possible with the use of powerful supercomputers, and in this way guided their experimental colleagues to the specific area of the material wherethe circular dichroism effectcould be measured.

The study was publishedinNature Physicswith the title "Flat band separation and robust spin Berry curvature in bilayer kagome metals". The first author of the study isDomenico Di Sante, a researcher at the"Augusto Righi" Department of Physics and Astronomyof theUniversity of Bologna. He worked with scholars from the CNR-IOM of Trieste, the Ca' Foscari University of Venice, the University of Milan, the University of Wrzburg (Germany), the University of St. Andrews (UK), the Boston College and the University of Santa Barbara (USA).

Flat band separation and robust spin Berry curvature in bilayer kagome metals

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Quantum materials: Electron spin measured for the first time - EurekAlert

Dan Harlow spends a lot of time thinking in a boomerang universe.

The MIT physicist is searching for answers to one of the biggest questions in modern physics: How can our universe abide by two incompatible rulebooks?

The first the Standard Model of Physics is the quantum mechanical theory of particles, fields, and forces, and the ways in which they interact to build the universe we live in. The second Einsteins theory of general relativity describes the influence of gravity and how the fundamental force pulls together matter to build the planets, galaxies, and other massive objects.

Both theories do remarkably well in their respective lanes. However, Einsteins theory breaks down when trying to describe how gravity works at quantum scales, while quantum mechanics makes reality-bending predictions when applied at massive, cosmic dimensions. For over a century, physicists have searched for ways to unite the two theories and get to the truth of what makes our universe tick.

Harlowsuspects that any connecting thread may be too delicate to grasp in our existing universe. Instead, hes looking for answers in a boomerang version an alternate reality that folds back on itself, much like a boomerang's trajectory, rather than stretching and expanding without end as our actual universe does.Quantum gravity in this boomerang universe turns out to be easier to understand, as it can be reformulated in terms of conventional quantum theory (without gravity) using a powerful idea called holographic duality.This makes it far simpler to contemplate, at least from a theory perspective.

In this boomerang environment,Harlowhas made some exciting, unexpected revelations. He has shown, for instance, that the equations that describe how gravity behaves in this toy universe are the very same equations that control the quantum error-correcting codes that will hopefully soon be used to build real-world quantum computers. That the mathematics describing gravity should have anything to do with protecting information in quantum computers was a surprise in itself. The fact that both phenomena shared the same physics, at least in this alternate universe, suggests a potential connection between Einsteins theory and quantum mechanics in the real universe.

The discovery, which Harlow made as a postdoc at Princeton University in 2014, sparked fresh lines of inquiry in the study of both quantum gravity and quantum information theory. Since joining MIT and the Center for Theoretical Physics in 2017, Harlow has continued his search for fundamental connections between general relativity and quantum mechanics, and how they may intersect in the contexts of black holes and cosmology.

One of the things thats been fun is, even though in physics and more in generally science were all studying different systems and experiments, many of the ideas are the same, says Harlow, an associate professor who received tenure in 2022. So, I try to have an open mind and keep my ears open, and look for how things may be related.

A humanist philosophy

Born in Cincinnati, Harlow moved as a child with his family to Boston, where he spent several years before the family moved again, putting down roots in Chicago. When he was 10, he took up piano lessons, focusing first on classical music, then rock. In junior high, he played keyboard in various bands before finding his groove in the looser, more improvisational style of jazz.

I love sitting down and playing with people, and seeing where things will go, Harlow says.

His love of jazz was partly what drew him to New York City after high school, where he attended Columbia University, which happened to be near some of the best jazz clubs in the city. The universitys core curriculum, which required students to read classic works of literature and philosophy, also appealed.

You cant graduate from Columbia without reading The Iliad, Harlow says. That gives you a shared community of things you can talk about. I liked the humanist philosophy that drives the place. Even if I chose to be a physicist, I would still have this broader cultural experience.

Harlow worked for three years as an undergraduate research assistant in an experimental cosmology lab on campus, where he learned to work in a clean room and run simulations to improve the performance of filters that were designed to pick out subtle signs of radiation left over from the Big Bang.

Harlow particularly appreciated the general approach of the labs leader, Amber Miller, who was then a junior faculty member.

She had this great way she ran her group, where she wasnt so hung up on publications or getting things done on a short timescale, Harlow recalls. She just let us play around.

Open questions

That mental freedom to explore new ideas would stay with Harlow throughout his career. From Columbia, he went west to Stanford University in 2006. Within the physics department, he found he aligned most naturally with Professor Leonard Susskind, a theoretical physicist and leader in the study of string theory.

His strong desire to identify the things that arent important and set them aside so you can focus on the essence of the problem that was also the way I try to think, says Harlow, who ended up choosing Susskind as his advisor. Lenny said, work on whatever you want, and Ill talk to you about it.

With this open invitation, Harlow kept an ear on conversations within Susskinds group to get a sense of the big questions in the field. What he heard was a problem that would shape the rest of his research career: the question of how to connect quantum mechanics with general relativity, in the context of cosmology, and scientists understanding of the large-scale structure and evolution of the universe.

In search of an answer, Harlow read up on everything he could find on both theories. His reading also bled into quantum information science primarily, a field that focuses on applying principles of quantum mechanics and information theory to the study and development of quantum computers.

Whenever I have a hint that some tool will be important for a problem Im trying to solve, I learn much more about it than what I think I need, Harlow says. More often than not, that investment pays off.

At the end of his time at Stanford, Harlow decided to take a hard turn, pivoting from cosmology to black holes, which he considered to be a simpler system to study for any fundamental threads connecting quantum mechanics and general relativity.

In 2012, he went back east to Princeton for a three-year postdoc, during which he began to explore the quantum behavior of gravitational black holes. To simplify the problem, he did so in a boomerang universe what physicists know as anti-de Sitter space, named after the physicist who studied the curvature of the universe. As Harlow read more on quantum information, he noticed, and ultimately confirmed, an unexpected overlap in the physics of gravity around black holes and the quantum error-correcting codes designed to protect information.

That was a very exploratory, transformative time, Harlow says. Im still exploring a lot of the paths that I started there.

After a second postdoc at Harvard University, Harlow joined MIT as a junior faculty member in 2017, where he continues to make surprising connections in the study of quantum gravity and quantum information science. At the Institute, and in the field of theoretical physics more broadly, hes enjoyed a collegial, productive disregard for authority.

This is a community where I can go up to the most famous theoretical physicist in the world, tell them that theyre wrong, and if I have an argument, theyll listen to me, Harlow says. People are open. Theres this core shared agreement that, what matters is that we find the right answer. It matters less who finds it.

Among Harlow's accomplishments since coming to MIT are a proof that there are strong restrictions on the possible symmetries of quantum gravity, a deeper understanding of the nature of energy in gravitational systems, and a concrete mathematical framework for understanding the interiors of quantum mechanical black holes.

Beyond research, Harlow is working to bring more diverse voices and perspectives into the field of physics. In addition to mentoring and advocacy work outside of MIT, he is running a program within the physics department that invites students from underrepresented and underprivileged backgrounds to carry out physics research at MIT each summer.

Unfortunately physics remains rather white and male, and making it more welcoming and accessible to a broader slice of humanity is one of my priorities going forward, he says.

Looking ahead, Harlow is considering taking a new turn in his research path, perhaps to focus less on black holes in a hologram universe, and more on cosmology, and the quantum structure and evolution of our actual universe.

Ive been living in anti-de Sitter space for a long time, Harlow says. Thats fine, but I do want to understand the world we live in too. And that should be fun.

Excerpt from:

Life in a hologram | MIT News | Massachusetts Institute of Technology - MIT News

Hawking radiation is one of the most famous physical processes in astronomy. Through Hawking radiation, the mass, and energy of a black hole escape over time. Its a brilliant theory, and it means that black holes have a finite lifetime. If Hawking radiation is true. Because as famous as it is, Hawking radiation is unproven. The theory is not even theoretically proven.

Hawking proposed the idea of black hole radiation while studying ways to integrate Einsteins classical theory of gravity with the quantum theory of atoms and light. We dont have a fully quantum theory of gravity, so Hawking used a semiclassical approach, where matter is treated as quantum while gravity is treated classically. From this, Hawking showed that quantum fields could escape the event horizon of a black hole.

The Hawking process is typically represented by virtual pair production. One approach to quantum physics argues that within the vacuum of empty space pairs of particles can appear and disappear spontaneously due to Heisenbergs uncertainty principle. The fuzziness of quantum theory means that space can never be truly empty. In empty regions of space, these particles dont have any real effect and thus are virtual particles. But near the event horizon of a black hole one member of a virtual pair could be trapped by the black hole, leaving the other to escape as real radiation.

The virtual particle visualization is appealing, but it isnt without its problems. Hawkings approach can lead to things such as the firewall paradox, where the region near a black hole event horizon should be both empty and ablaze with realized virtual particles. Without a fully quantum approach to gravity, we cant resolve these paradoxes easily.

There are, however, other semi-classical approaches to gravity than the one Hawking used. Most of them also predict black holes will radiate, but argue it from a different approach. For example, one approach is to look at the matter trapped within a black hole as a quantum wavefunction bound by intense gravity. Since the gravitational pull of a black hole is never infinite at the event horizon, the wavefunction is essentially bound within a finite container. Through a process called quantum tunneling, quantum objects can escape any finite container in time. So, you get black hole radiation without the need for virtual particles.

This is where a new study comes in. For this work, the team looked at a different formulation of Hawking radiation, somewhat similar to the wavefunction approach. They found that when it comes to Hawking radiation, the event horizon of a black hole isnt particularly special. Any concentrated mass, from neutron stars to pet rocks, has a gravitational well that acts like a finite container. So quantum particles can always escape. This has long been known, but what the team showed was that if you express this in terms of Hawkings virtual particles, then virtual particles can become real near any mass, not just black holes. Black holes are by far the most effective generators of Hawking radiation, but if you wait long enough, even your favorite rock will radiate its mass away.

This model doesnt change our understanding of black holes, but it could have significant consequences for long-term cosmology. If everything disappears in a poof of radiation given enough time, then the universe will fade into a cold sea of radiation.

Reference: Wondrak, Michael F., Walter D. van Suijlekom, and Heino Falcke. Gravitational Pair Production and Black Hole Evaporation. Physical Review Letters 130.22 (2023): 221502.

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If Black Holes Evaporate, Everything Evaporates - Universe Today