theoretical physics (14)

Nanos Gigantum Humeris Insidentes...


Colleagues remember Peter Higgs as an inspirational scientist who remained humble despite his fame. Credit: Graham Clark/Alamy

Topics: CERN, Higgs Boson, High Energy Physics, Nobel Prize, Particle Physics, Quantum Mechanics, Theoretical Physics

Few scientists have enjoyed as much fame in recent years as British theoretical physicist Peter Higgs, the namesake of the boson that was discovered in 2012, who died on 8 April, aged 94.

It was 60 years ago when Higgs first suggested how an elementary particle of unusual properties could pervade the universe in the form of an invisible field, giving other elementary particles their masses. Several other physicists independently thought of this mechanism around the same time, including François Englert, now at the Free University of Brussels. The particle was a crucial element of the theoretical edifice that physicists were building in those years, which later became known as the standard model of particles and fields.

Two separate experiments at the Large Hadron Collider (LHC) near Geneva, Switzerland — ATLAS and the CMS — confirmed Higgs’ predictions when they announced the discovery of the Higgs boson half a century later. It was the last missing component of the standard model, and Higgs and Englert shared a Nobel Prize in 2013 for predicting its existence. Physicists at the LHC continue to learn about the properties of the Higgs boson, but some researchers say that only a dedicated collider that can produce the particle in copious amounts — dubbed a ‘Higgs factory’ — will enable them to gain a profound understanding of its role.

“Besides his outstanding contributions to particle physics, Peter was a very special person, an immensely inspiring figure for physicists around the world, a man of rare modesty, a great teacher and someone who explained physics in a very simple yet profound way,” said Fabiola Gianotti, director-general of CERN in an obituary posted on the organization’s website; Gianotti who announced the Higgs boson’s discovery to the world at CERN. “I am very saddened, and I will miss him sorely.”

Many physicists took to X, formerly Twitter, to pay tribute to Higgs and share their favorite memories of him. “RIP to Peter Higgs. The search for the Higgs boson was my primary focus for the first part of my career. He was a very humble man that contributed something immensely deep to our understanding of the universe,” posted Kyle Cranmer, physicist at the University of Wisconsin Madison and previously a senior member of the Higgs search team at the CMS.

Nanos gigantum humeris insidentes is a Latin phrase that translates to "dwarfs standing on the shoulders of giants." It's a Western metaphor that expresses the idea of "discovering truth by building on previous discoveries." The phrase is derived from Greek mythology, where the blind giant Orion carried his servant Cedalion on his shoulders.

English scientist Sir Isaac Newton also coined the phrase "to stand on (someone's) shoulders" in his letter, "If I have seen further it is by standing on the shoulders of Giants." This means that we are who we are because of the hard work of the people who came before us. Newton was talking about collective learning, or our species' ability to share, preserve, and build upon knowledge over time. Source: AI overview

Peter Higgs: science mourns giant of particle physics, Davide Castelvecchi, Nature

Read more…

Science, or Spectacle...


Avi Loeb, a Harvard University astrophysicist, displays a small vial of material recovered from the floor of the Pacific Ocean. The material, Loeb says, includes fragments of a meteorite that he claims came from another star system—and perhaps even from an alien spacecraft. Credit: Anibal Martel/Anadolu Agency via Getty Images

Topics: Astronomy, Astrophysics, Civilization, Cosmology, Existentialism, Theoretical Physics

Reanalysis of a meteor that fell to Earth has cast some doubt on its origin—and its final destination.

This much is certain: on January 8, 2014, an object now cataloged as CNEOS 2014-01-08 entered Earth’s atmosphere somewhere overhead off the northern coast of Papua New Guinea in the South Pacific, heating to become a blazing, shockwave-generating fireball during its plunge from space. Such events are not rare; meteors enter our atmosphere all the time. But estimates of the object’s speed, touted at some 45 kilometers per second, led to suggestions that it might be interstellar in origin—a space rock from some alien and distant planetary system. While we have seen interstellar objects passing through our solar system before, no such objects were known to have ever made planetfall on Earth. So interest in CNEOS 2014-01-08 was piqued, given that its fragments could potentially offer a first direct sample of material sourced from another star.

In June 2023 Avi Loeb—a theoretical physicist at Harvard University—mounted a $1.5-million expedition to find pieces of the meteor. Loeb has been the leading proponent of the notion that this meteor was indeed interstellar in origin—and has even speculated that it may be linked to putative alien spacecraft. His recovery expedition—which was part of his UFO-studying Galileo Project—became a public sensation, further padding Loeb’s already long list of high-profile media spots, which included interviews on prime-time national television shows and with the easily enraptured podcast host Joe Rogan. Loeb has written countless blog posts and a bestselling book on his unorthodox approach to studying extraterrestrial life and intelligence. He has even gone so far as to appear on a giant billboard in Times Square promoting the Galileo Project’s efforts to find the interstellar meteor fragments.

His approach to the topic has, at times, been abrasive, and many other astrobiology-inclined researchers have found his sensational claims too difficult to parse and potentially damaging to their field. But as with any scientific investigation, particularly with findings as provocative as those suggested by Loeb, there is invariably interest in trying to find flaws in the methodology and to offer alternative, more plausible solutions. This latest episode is no exception; it focuses on one very specific data point from this purported interstellar object.

Loeb’s recovery expedition used a boat-dragged magnetic “sled” to scrape samples of sediments from strips of seafloor in an 11-kilometer-wide square where the team believed the meteor had fallen. That zone of inquiry primarily emerged from triangulating the meteor’s presumptive debris field using sensor data from a classified network of U.S. military satellites that were scrubbed of sensitive details and made public as part of NASA’s Center for Near Earth Object Studies (CNEOS). Loeb’s pinpointing also used a local seismometer on Manus Island, Papua New Guinea, which recorded vibrations from an event around the time the meteor supposedly entered the atmosphere to reduce the search area to a strip that was one-kilometer wide.

After studying those seismometer data, however, Benjamin Fernando, a planetary scientist at Johns Hopkins University, has concluded that Loeb’s analysis was flawed. The seismometer, Fernando says, recorded not a celestial object but something much more mundane and closer to home—a passing heavy truck—meaning that the location Loeb and his team searched would not have been in the path of the falling object. “We think that what they picked up from the seafloor is nothing to do with this meteor at all,” says Fernando, who posted the research on the preprint server and presented it at the Lunar and Planetary Science Conference (LPSC) in Texas on Tuesday, March 12.

Fernando and his colleagues maintain that the seismic spike used by Loeb’s team was decidedly similar to other signals likely caused by “cultural noise”—that is, vibrations from vehicles and other hefty, human-made sources. A signal’s polarization can be used to estimate the direction of the source, and in this case, it suggested a movement from “southwest to north over about 100 seconds,” Fernando says. That matches the orientation of a road near the seismometer that runs to a local hospital and aligns with another matching signal that perhaps came from the same vehicular source that was detected earlier in the day (when no known fireballs were overhead). “It’s actually just a truck driving by,” he says. Using information from a separate network of infrasound sensors meant to look for clandestine atomic explosions as part of the Comprehensive Nuclear-Test-Ban Treaty, Fernando and his team provide a different entry point for the meteor some 170 kilometers from where Loeb’s group searched. They also argue that the meteor mostly burned up in the atmosphere anyway, scattering few, if any, notable pieces onto the land or sea below. “You wouldn’t go looking for bits of a firework,” Fernando says.

In the list of logical fallacies, I found unfortunately two (depending on the source, the total list can number 20, 24, more, etc.), that I reflected on as I read this article: "Hasty Generalization," and "Ought-Is."

Hasty Generalization means what this looks like, drawing some really spectacular conclusions on what appears to be limited evidence. The second, "Ought-Is," along with the recent scandal of 10,000 papers retracted in 2023 due to (I think) the pressure to "see your name(s)" in high-impact journals, has taken on the similitude of getting "likes" on social media, and has put the scientific enterprise, the hallmark of the Enlightenment, in crisis. "Ought-Is" fallacies are another word for wishful thinking. At that point, scientific progress grinds to a halt, and we slowly start limping back to the dark ages.

"The Demon-Haunted World: Science as a Candle in the Dark," by Carl Sagan (1995).

The demons appear to be winning.

‘Interstellar’ Meteor Signal May Have Been a Truck—So What Was Collected from the Ocean Floor? Jonathan O'Callaghan, Scientific American

Read more…

Dark Matter, Ordinary Matter...


Topics: Astronomy, Astrophysics, Dark Matter, Research, Theoretical Physics

Dark matter, composed of particles that do not reflect, emit, or absorb light, is predicted to make up most of the matter in the universe. However, its lack of interactions with light prevents its direct detection using conventional experimental methods.

Physicists have been trying to devise alternative methods to detect and study dark matter for decades, yet many questions about its nature and its presence in our galaxy remain unanswered. Pulsar Timing Array (PTA) experiments have been trying to probe the presence of so-called ultralight dark matter particles by examining the timing of an ensemble of galactic millisecond radio pulsars (i.e., celestial objects that emit regular millisecond-long radio wave pulses).

The European Pulsar Timing Array, a multinational team of researchers based at different institutes that are using 6 radio-telescopes across Europe to observe specific pulsars, recently analyzed the second wave of data they collected. Their paper, published in Physical Review Letters, sets more stringent constraints on the presence of ultralight dark matter in the Milky Way.

"This paper was basically the result of my first Ph.D. project," Clemente Smarra, co-author of the paper, told "The idea arose when I asked my supervisor if I could carry out research focusing on gravitational wave science, but from a particle physics perspective. The main aim of the project was to constrain the presence of the so-called ultralight dark matter in our galaxy."

Ultralight dark matter is a hypothetical dark matter candidate, made up of very light particles that could potentially address long-standing mysteries in the field of astrophysics. The recent study by Smarra and his colleagues was aimed at probing the possible presence of this type of dark matter in our galaxy via data collected by the European Pulsar Timing Array.

"We were inspired by previous efforts in this field, especially by the work of Porayko and her collaborators," Smarra said. "Thanks to the longer duration and the improved precision of our dataset, we were able to put more stringent constraints on the presence of ultralight dark matter in the Milky Way,"

The recent paper by the European Pulsar Timing Array makes different assumptions than those made by other studies carried out in the past. Instead of probing interactions between dark matter and ordinary matter, it assumes that these interactions only occur via gravitational effects.

"We assumed that dark matter interacts with ordinary matter only through gravitational interaction," Smarra explained. "This is a rather robust claim: in fact, the only sure thing we know about dark matter is that it interacts gravitationally. In a few words, dark matter produces potential wells in which pulsar radio beams travel. But the depth of these wells is periodic in time; therefore, the travel time of the radio beams from pulsars to the Earth changes with a distinctive periodicity as well."

New constraints on the presence of ultralight dark matter in the Milky Way, Ingrid Fadelli,

Read more…

In Medias Res...


Image source: Link below

Topics: Applied Physics, Astrophysics, Computer Modeling, Einstein, High Energy Physics, Particle Physics, Theoretical Physics

In the search for new physics, a new kind of scientist is bridging the gap between theory and experiment.

Traditionally, many physicists have divided themselves into two tussling camps: the theorists and the experimentalists. Albert Einstein theorized general relativity, and Arthur Eddington observed it in action as “bending” starlight; Murray Gell-Mann and George Zweig thought up the idea of quarks, and Henry Kendall, Richard Taylor, Jerome Freidman and their teams detected them.

In particle physics especially, the divide is stark. Consider the Higgs boson, proposed in 1964 and discovered in 2012. Since then, physicists have sought to scrutinize its properties, but theorists and experimentalists don’t share Higgs data directly, and they’ve spent years arguing over what to share and how to format it. (There’s now some consensus, although the going was rough.)

But there’s a missing player in this dichotomy. Who, exactly, is facilitating the flow of data between theory and experiment?

Traditionally, the experimentalists filled this role, running the machines and looking at the data — but in high-energy physics and many other subfields, there’s too much data for this to be feasible. Researchers can’t just eyeball a few events in the accelerator and come to conclusions; at the Large Hadron Collider, for instance, about a billion particle collisions happen per second, which sensors detect, process, and store in vast computing systems. And it’s not just quantity. All this data is outrageously complex, made more so by simulation.

In other words, these experiments produce more data than anyone could possibly analyze with traditional tools. And those tools are imperfect anyway, requiring researchers to boil down many complex events into just a handful of attributes — say, the number of photons at a given energy. A lot of science gets left out.

In response to this conundrum, a growing movement in high-energy physics and other subfields, like nuclear physics and astrophysics, seeks to analyze data in its full complexity — to let the data speak for itself. Experts in this area are using cutting-edge data science tools to decide which data to keep and which to discard and to sniff out subtle patterns.

Opinion: The Rise of the Data Physicist, Benjamin Nachman, APS News

Read more…

Pines' Demon...


Lurking for decades: researchers have discovered Pines' demon, a collection of electrons in a metal that behaves like a massless wave. It is illustrated here as an artist’s impression. (Courtesy: The Grainger College of Engineering/University of Illinois Urbana-Champaign)

Topics: Particle Physics, Quantum Mechanics, Research, Solid-State Physics, Theoretical Physics

For nearly seven decades, a plasmon known as Pines’ demon has remained a purely hypothetical feature of solid-state systems. Massless, neutral, and unable to interact with light, this unusual quasiparticle is reckoned to play a key role in certain superconductors and semimetals. Now, scientists in the US and Japan say they have finally detected it while using specialized electron spectroscopy to study the material strontium ruthenate.

Plasmons were proposed by the physicists David Pines and David Bohm in 1952 as quanta of collective electron density fluctuations in a plasma. They are analogous to phonons, which are quanta of sound, but unlike phonons, their frequency does not tend to zero when they have no momentum. That’s because finite energy is needed to overcome the Coulomb attraction between electrons and ions in a plasma in order to get oscillations going, which entails a finite oscillation frequency (at zero momentum).

Today, plasmons are routinely studied in metals and semiconductors, which have conduction electrons that behave like a plasma. Plasmons, phonons, and other quantized fluctuations are called quasiparticles because they share properties with fundamental particles such as photons.

In 1956, Pines hypothesized the existence of a plasmon which, like sound, would require no initial burst of energy. He dubbed the new quasiparticle a demon in honor of James Clerk Maxwell’s famous thermodynamic demon. Pines’ demon forms when electrons in different bands of metal move out of phase with one another such that they keep the overall charge static. In effect, a demon is the collective motion of neutral quasiparticles whose charge is screened by electrons from another band.

Demon quasiparticle is detected 67 years after it was first proposed. Edwin Cartlidg, Physics World.

Read more…

Challenging the Standard Model...


Excited helium nuclei inflate like balloons, offering physicists a chance to study the strong nuclear force which binds the nucleus’s protons and neutrons. Kristina Armitage/Quanta Magazine

Topics: Modern Physics, Nobel Prize, Particle Physics, Quantum Mechanics, Steven Weinberg, Theoretical Physics

A new measurement of the strong nuclear force, which binds protons and neutrons together, confirms previous hints of an uncomfortable truth: We still don’t have a solid theoretical grasp of even the simplest nuclear systems.

To test the strong nuclear force, physicists turned to the helium-4 nucleus, which has two protons and two neutrons. When helium nuclei are excited, they grow like an inflating balloon until one of the protons pops off. Surprisingly, in a recent experiment, helium nuclei didn’t swell according to plan: They ballooned more than expected before they burst. A measurement describing that expansion, called the form factor, is twice as large as theoretical predictions.

“The theory should work,” said Sonia Bacca, a theoretical physicist at the Johannes Gutenberg University of Mainz and an author of the paper describing the discrepancy, which was published in Physical Review Letters. “We’re puzzled.”

For many years, physicists didn’t understand how to use the strong force to understand the stickiness of protons and neutrons. One problem was the bizarre nature of the strong force — it grows stronger with increasing distance rather than slowly dying off. This feature prevented them from using their usual calculation tricks. When particle physicists want to understand a particular system, they typically parcel out a force into more manageable approximate contributions, order those contributions from most important to least important, then simply ignore the less important contributions. With the strong force, they couldn’t do that.

Then in 1990, Steven Weinberg found a way to connect the world of quarks and gluons to sticky nuclei. The trick was to use an effective field theory — a theory that is only as detailed as it needs to be to describe nature at a particular size (or energy) scale. To describe the behavior of a nucleus, you don’t need to know about quarks and gluons. Instead, at these scales, a new effective force emerges — the strong nuclear force transmitted between nucleons by the exchange of pions.

A New Experiment Casts Doubt on the Leading Theory of the Nucleus, Katie McCormick, Quanta Magazine

Read more…

Removing the Spookiness...


Conceptual artwork of a pair of entangled quantum particles. Credit: Science Photo Library/Alamy Stock Photo

Topics: Modern Physics, Particle Physics, Quantum Mechanics, Theoretical Physics

Quantum entanglement is a complex phenomenon in physics that is usually poorly described as an invisible link between distant quantum objects that allows one to affect the other instantly. Albert Einstein famously dismissed this idea of entanglement as “spooky action at a distance.” Entanglement is better understood as information, but that’s admittedly bland. So nowadays, every news articleexplaineropinion piece, and artistic interpretation of quantum entanglement equates the phenomenon with Einstein’s spookiness. The situation has only worsened with the 2022 Nobel Prize in Physics going to Alain Aspect, John F. Clauser, and Anton Zeilinger for quantum entanglement experiments. But it’s time to cut this adjective loose. Calling entanglement spooky completely misrepresents how it actually works and hinders our ability to make sense of it.

In 1935, physicist Erwin Schrödinger coined the term entanglement, emphasizing that it was “not one but rather the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought.” He was writing in response to a famous paper (known simply to physicists as the EPR argument) by Einstein, Boris Podolsky, and Nathan Rosen that claimed quantum physics was incomplete. The New York Times headline read, “Einstein attacks quantum theory,” which solidified the widespread perception that Einstein hated quantum physics.

The EPR argument concerns the everyday notion of reality as a collection of things in the world with physical properties waiting to be revealed through measurement. This is how most of us intuitively understand reality. Einstein’s theory of relativity fits into this understanding and says reality must be local, meaning nothing can influence anything else faster than the speed of light. But EPR showed that quantum physics isn’t compatible with these ideas—that it can’t account for a theory of local reality. In other words, quantum physics was missing something. To complete quantum physics, Einstein suggested scientists should look for a “deeper” theory of local reality. Many physicists responded in defense of quantum theory, but the matter remained unresolved until 1964 when physicist John S. Bell proposed an experiment that could rule out the existence of local reality. Clauser was the first to perform the test, which was later improved and perfected by Aspect and Zeilinger.

Quantum Entanglement Isn’t All That Spooky After All, Chris Ferrie, Scientific American

Read more…

AAAS Science Awards...


Topics: Diversity in Science, Education, Research, STEM, Theoretical Physics

The American Association for the Advancement of Science has announced the 2023 winners of eight longstanding awards that recognize scientists, engineers, innovators, and public servants for their contributions to science and society.

The awards honor individuals and teams for a range of achievements, from advancing science diplomacy and engaging the public in order to boost scientific understanding to mentoring the next generation of scientists and engineers.

The 2023 winners were first announced on social media between Feb. 23 and Feb. 28; see the hashtag #AAASAward to learn more. The winners were also recognized at the 2023 AAAS Annual Meeting, held in Washington, D.C., March 2-5. The winning individuals and teams were honored with tribute videos and received commemorative plaques during several plenary sessions.

Six of the awards include a prize of $5,000, while the AAAS David and Betty Hamburg Award for Science Diplomacy award the winning individual or team $10,000, and the AAAS Newcomb Cleveland Prize awards the winning individual or team $25,000.

Learn more about the awards’ history, criteria, and selection processes via the AAAS awards page, and read on to learn more about the individuals and teams who earned the 2023 awards.


Sekazi Mtingwa is the recipient of the 2023 AAAS Philip Hauge Abelson Prize, which recognizes someone who has made significant contributions to the scientific community — whether through research, policy, or civil service — in the United States. The awardee can be a public servant, scientist, or individual in any field who has made sustained, exceptional contributions and other notable services to the scientific community. Mtingwa exemplifies a commitment to service and dedication to the scientific community, research workforce, and society. His contributions have shaped research, public policy, and the next generation of scientific leaders, according to the award’s selection committee.

As a theoretical physicist, Mtingwa pioneered work on intrabeam scattering that is foundational to particle accelerator research. Today a principal partner at Triangle Science, Education and Economic Development, where he consults on STEM education and economic development, Mtingwa has been affiliated during his scientific career with North Carolina A&T State University, Harvard University, the Massachusetts Institute of Technology, and several national laboratories.

His contributions to the scientific community have included a focus on diversity, equity, and inclusion in physics. He co-founded the National Society of Black Physicists, which today is a home for more than 500 Black physicists and students. His work has also contributed to rejuvenating university nuclear science and engineering programs and paving the way for the next generation of nuclear scientists and engineers. Mtingwa served as the chair of a 2008 American Physical Society study on the readiness of the U.S. nuclear workforce, the results of which played a key role in the U.S. Department of Energy allocating 20% of its nuclear fuel cycle R&D budget to university programs.

“I have devoted myself to being an apostle for science for those both at home and abroad who face limited research and training opportunities,” said Mtingwa. “Receiving the highly prestigious Philip Hauge Abelson Prize affirms that I have been successful in this mission. Moreover, it provides me with the armor to press onward to even greater contributions.”

AAAS Recognizes 2023 Award Winners for Contributions to Science and Society, Andrea Korte

Read more…

Spooky Action Between Friends...


Credit: Petrovich9/Getty Images

Topics: Entanglement, Particle Physics, Quantum Mechanics, Research, Theoretical Physics

Reference: Albert Einstein colorfully dismissed quantum entanglement—the ability of separated objects to share a condition or state—as “spooky action at a distance.”

For the first time, scientists have observed quantum interference—a wavelike interaction between particles related to the weird quantum phenomenon of entanglement—occurring between two different kinds of particles. The discovery could help physicists understand what goes on inside an atomic nucleus.

Particles act as both particles and waves. And interference is the ability of one particle’s wavelike action to diminish or amplify the action of other quantum particles like two boat wakes crossing in a lake. Sometimes the overlapping waves add up to a bigger wave, and sometimes they cancel out, erasing it. This interference occurs because of entanglement, one of the weirder aspects of quantum physics, which was predicted in the 1930s and has been experimentally observed since the 1970s. When entangled, the quantum states of multiple particles are linked so that measurements of one will correlate with measurements of the others, even if one is on Jupiter and another is on your front lawn.

Dissimilar particles can sometimes become entangled, but until now, these [mismatched] entangled particles weren’t known to interfere with one another. That’s because part of measuring interference relies on two wavelike particles being indistinguishable from each other. Imagine two photons, or particles of light, from two separate sources. If you were to detect these photons, there would be no way to determine which source each came from because there is no way to tell which photon is which. Thanks to the quantum laws governing these very small particles, this ambiguity is actually measurable: all the possible histories of the two identical photons interfere with one another, creating new patterns in particles’ final wavelike actions.

Scientists See Quantum Interference between Different Kinds of Particles for the First Time, Stephanie Pappas, Scientific American

Read more…

DUNE Detector...


The ore pass at the Sanford Underground Research Facility in South Dakota. (Courtesy of Sanford Underground Research Facility, CC BY-NC-ND 4.0.)

Topics: Applied Physics, Modern Physics, Particle Physics, Theoretical Physics

The Deep Underground Neutrino Experiment (DUNE) will be the world’s largest cryogenic particle detector. Its aim is to study the most elusive of particles: neutrinos. Teams from around the world are developing and constructing detector components that they will ship to the Sanford Underground Research Facility, commonly called Sanford Lab, in the Black Hills of South Dakota. There the detector components will be lowered more than a kilometer underground through a narrow shaft to the caverns, where they will be assembled and operated while being sheltered from the cosmic rays that constantly rain down on Earth’s surface.

For at least two decades, the detector will be exposed to the highest-intensity neutrino beam on the planet. The beam will be generated 1300 km away by a megawatt-class proton accelerator and beamline under development at Fermilab in Batavia, Illinois. A smaller detector just downstream of the beamline will measure the neutrinos at the start of their journey, thereby enabling the experiment’s precision and scientific reach.

Building a ship in a bottle for neutrino science, Anne Heavey, FERMILAB, Physics Today

Read more…

Double Slit...


Complementarity A new twist on the double-slit experiment. (Courtesy: Shutterstock/Andrey VP)

Topics: Modern Physics, Quantum Mechanics, Theoretical Physics

One of the most counterintuitive concepts in physics – the idea that quantum objects are complementary, behaving like waves in some situations and like particles in others – just got a new and more quantitative foundation. In a twist on the classic double-slit experiment, scientists at Korea’s Institute for Basic Sciences (IBS) used precisely controlled photon sources to measure a photon’s degree of wave-ness and particle-ness. Their results, published in Science Advances, show that the properties of the photon’s source influence its wave and particle character – a discovery that complicates and challenges the common understanding of complementarity.

The double-slit experiment is the archetypal example of complementarity at work. When a single photon encounters a barrier with two thin openings, it produces an interference pattern on a screen placed behind the openings – but only if the photon’s path is not observed. This interference pattern identifies the photon as a wave since a particle would create only one point of light on the screen. However, if detectors are placed at the openings to determine which slit the photon went through, the interference pattern disappears, and the photon behaves like a particle. The principle of complementarity states that both experimental outcomes are needed to fully understand the photon’s quantum nature.

Wave-particle duality quantified for the first time, Karmela Padavic-Callaghan, Physics World

Read more…



Image Source: Link below

Topics: Particle Physics, Quantum Computer, Quantum Mechanics, Theoretical Physics

Flatland: “The book used the fictional two-dimensional world of Flatland to comment on the hierarchy of Victorian culture, but the novella’s more enduring contribution is its examination of dimensions.” Source: Wikipedia

After decades of exploration in nature’s smallest domains, physicists have finally found evidence that anyons exist. First predicted by theorists in the early 1980s, these particle-like objects only arise in realms confined to two dimensions, and then only under certain circumstances — like at temperatures near absolute zero and in the presence of a strong magnetic field.

Physicists are excited about anyons not only because their discovery confirms decades of theoretical work, but also for practical reasons. For example, Anyons are at the heart of an effort by Microsoft to build a working quantum computer.

This year brought two solid confirmations of the quasiparticles. The first arrived in April, in a paper featured on the cover of Science, from a group of researchers at the École Normale Supérieure in Paris. Using an approach proposed four years ago, physicists sent an electron gas through a teeny-tiny particle collider to tease out weird behaviors — especially fractional electric charges — that only arise if anyons are around. The second confirmation came in July when a group at Purdue University in Indiana used an experimental setup on an etched chip that screened out interactions that might obscure anyon behavior.

MIT physicist Frank Wilczek, who predicted and named anyons in the early 1980s, credits the first paper as the discovery but says the second lets the quasiparticles shine. “It’s gorgeous work that makes the field blossom,” he says. Anyons aren’t like ordinary elementary particles; scientists will never be able to isolate one from the system where it forms. They’re quasiparticles, which means they have measurable properties like a particle — such as a location, maybe even a mass — but they’re only observable as a result of the collective behavior of other, conventional particles. (Think of the intricate geometric shapes made by group behavior in nature, such as flocks of birds flying in formation or schools of fish swimming as one.)

The known universe contains only two varieties of elementary particles. One is the family of fermions, which includes electrons, as well as protons, neutrons, and the quarks that form them. Fermions keep to themselves: No two can exist in the same quantum state at the same time. If these particles didn’t have this property, all matter could simply collapse to a single point. It’s because of fermions that solid matter exists.

The rest of the particles in the universe are bosons, a group that includes particles like photons (the messengers of light and radiation) and gluons (which “glue” quarks together). Unlike fermions, two or more bosons can exist in the same state at the same time. They tend to clump together. It’s because of this clumping that we have lasers, which are streams of photons all occupying the same quantum state.

Physicists prove the existence of two-dimensional particles called 'anyons', Stephen Omes, Astronomy (December 2020)

Read more…

The Weirdest Matter...


This simulation shows how a fracton-filled material would be expected to scatter a beam of neutrons.
H. Yan et al., Physical Review Letters


Topics: Condensed Matter Physics, Quantum Mechanics, Theoretical Physics

Your desk is made up of individual, distinct atoms, but from far away its surface appears smooth. This simple idea is at the core of all our models of the physical world. We can describe what’s happening overall without getting bogged down in the complicated interactions between every atom and electron.

So when a new theoretical state of matter was discovered whose microscopic features stubbornly persist at all scales, many physicists refused to believe in its existence.

“When I first heard about fractons, I said there’s no way this could be true because it completely defies my prejudice of how systems behave,” said Nathan Seiberg, a theoretical physicist at the Institute for Advanced Study in Princeton, New Jersey. “But I was wrong. I realized I had been living in denial.”

The theoretical possibility of fractons surprised physicists in 2011. Recently, these strange states of matter have been leading physicists toward new theoretical frameworks that could help them tackle some of the grittiest problems in fundamental physics.

Fractons are quasiparticles — particle-like entities that emerge out of complicated interactions between many elementary particles inside a material. But fractons are bizarre even compared to other exotic quasiparticles because they are totally immobile or able to move only in a limited way. There’s nothing in their environment that stops fractons from moving; rather it’s an inherent property of theirs. It means fractons’ microscopic structure influences their behavior over long distances.

“That’s totally shocking. For me it is the weirdest phase of matter,” said Xie Chen, a condensed matter theorist at the California Institute of Technology.

The ‘Weirdest’ Matter, Made of Partial Particles, Defies Description, Thomas Lewton, Quanta Magazine

Read more…

Schrödinger’s Clock...


Credit: Getty Images

Topics: Modern Physics, Quantum Mechanics, Theoretical Physics

Albert Einstein’s twin paradox is one of the most famous thought experiments in physics. It postulates that if you send one of two twins on a return trip to a star at near light speed, they will be younger than their identical sibling when they return home. The age difference is a consequence of something called time dilation, which is described by Einstein’s special theory of relativity: the faster you travel, the slower time appears to pass.

But what if we introduce quantum theory into the problem? Physicists Alexander Smith of Saint Anselm College and Dartmouth College and Mehdi Ahmadi of Santa Clara University tackle this idea in a study published today in the journal Nature Communications. The scientists imagine measuring a quantum atomic clock experiencing two different times while it is placed in superposition—a quirk of quantum mechanics in which something appears to exist in two places at once. “We know from Einstein’s special theory of relativity that when a clock moves relative to another clock, the time shown on it slows down,” Smith says. “But quantum mechanics allows you to start thinking about what happens if this clock were to move in a superposition of two different speeds.”

Superposition is a strange aspect of quantum physics where an object can initially be in multiple locations simultaneously, yet when it is observed, only one of those states becomes true. Particles can be placed in superposition in certain experiments, such as those using a beam splitter to divide photons of light, to show the phenomenon in action. Both of the particles in superposition appear to share information until they are observed, making the phenomenon useful for applications such as encryption and quantum communications.

Quantum Time Twist Offers a Way to Create Schrödinger’s Clock, Jonathan O'Callaghan, Scientific American

Read more…