Monthly Archives: June 2020

Physicists have traced three of the four forces of nature the electromagnetic force and the strong and weak nuclear forces to their origins in quantum particles. But the fourth fundamental force, gravity, is different.

Our current framework for understanding gravity, devised a century ago by Albert Einstein, tells us that apples fall from trees and planets orbit stars because they move along curves in the space-time continuum. These curves are gravity. According to Einstein, gravity is a feature of the space-time medium; the other forces of nature play out on that stage.

But near the center of a black hole or in the first moments of the universe, Einsteins equations break. Physicists need a truer picture of gravity to accurately describe these extremes. This truer theory must make the same predictions Einsteins equations make everywhere else.

Physicists think that in this truer theory, gravity must have a quantum form, like the other forces of nature. Researchers have sought the quantum theory of gravity since the 1930s. Theyve found candidate ideas notably string theory, which says gravity and all other phenomena arise from minuscule vibrating strings but so far these possibilities remain conjectural and incompletely understood. A working quantum theory of gravity is perhaps the loftiest goal in physics today.

What is it that makes gravity unique? Whats different about the fourth force that prevents researchers from finding its underlying quantum description? We asked four different quantum gravity researchers. We got four different answers.

Claudia de Rham, a theoretical physicist at Imperial College London, has worked on theories of massive gravity, which posit that the quantized units of gravity are massive particles:

Einsteins general theory of relativity correctly describes the behavior of gravity over close to 30 orders of magnitude, from submillimeter scales all the way up to cosmological distances. No other force of nature has been described with such precision and over such a variety of scales. With such a level of impeccable agreement with experiments and observations, general relativity could seem to provide the ultimate description of gravity. Yet general relativity is remarkable in that it predicts its very own fall.

General relativity yields the predictions of black holes and the Big Bang at the origin of our universe. Yet the singularities in these places, mysterious points where the curvature of space-time seems to become infinite, act as flags that signal the breakdown of general relativity. As one approaches the singularity at the center of a black hole, or the Big Bang singularity, the predictions inferred from general relativity stop providing the correct answers. A more fundamental, underlying description of space and time ought to take over. If we uncover this new layer of physics, we may be able to achieve a new understanding of space and time themselves.

If gravity were any other force of nature, we could hope to probe it more deeply by engineering experiments capable of reaching ever-greater energies and smaller distances. But gravity is no ordinary force. Try to push it into unveiling its secrets past a certain point, and the experimental apparatus itself will collapse into a black hole.

Daniel Harlow, a quantum gravity theorist at the Massachusetts Institute of Technology, is known for applying quantum information theory to the study of gravity and black holes:

Black holes are the reason its difficult to combine gravity with quantum mechanics. Black holes can only be a consequence of gravity because gravity is the only force that is felt by all kinds of matter.If there were any type of particle that did not feel gravity, we could use that particle to send out a message from the inside of the black hole, so it wouldnt actually be black.

The fact that all matter feels gravity introduces a constraint on the kinds of experiments that are possible: Whatever apparatus you construct, no matter what its made of, it cant be too heavy, or it will necessarily gravitationally collapse into a black hole.This constraint is not relevant in everyday situations, but it becomes essential if you try to construct an experiment to measure the quantum mechanical properties of gravity.

Our understanding of the other forces of nature is built on the principle of locality, which says that the variables that describe whats going on at each point in space such as the strength of the electric field there can all change independently. Moreover, these variables, which we call degrees of freedom, can only directly influence their immediate neighbors. Locality is important to the way we currently describe particles and their interactions because it preserves causal relationships: If the degrees of freedom here in Cambridge, Massachusetts, depended on the degrees of freedom in San Francisco, we may be able to use this dependence to achieve instantaneous communication between the two cities or even to send information backward in time, leading to possible violations of causality.

The hypothesis of locality has been tested very well in ordinary settings, and it may seem natural to assume that it extends to the very short distances that are relevant for quantum gravity (these distances are small because gravity is so much weaker than the other forces).To confirm that locality persists at those distance scales, we need to build an apparatus capable of testing the independence of degrees of freedom separated by such small distances. A simple calculation shows, however, that an apparatus thats heavy enough to avoid large quantum fluctuations in its position, which would ruin the experiment, will also necessarily be heavy enough to collapse into a black hole!Therefore, experiments confirming locality at this scale are not possible. And quantum gravity therefore has no need to respect locality at such length scales.

Indeed, our understanding of black holes so far suggests that any theory of quantum gravity should have substantially fewer degrees of freedom than we would expect based on experience with the other forces. This idea is codified in the holographic principle, which says, roughly speaking, that the number of degrees of freedom in a spatial region is proportional to its surface area instead of its volume.

Juan Maldacena, a quantum gravity theorist at the Institute for Advanced Study in Princeton, New Jersey, is best known for discovering a hologram-like relationship between gravity and quantum mechanics:

Particles can display many interesting and surprising phenomena. We can have spontaneous particle creation, entanglement between the states of particles that are far apart, and particles in a superposition of existence in multiple locations.

In quantum gravity, space-time itself behaves in novel ways. Instead of the creation of particles, we have the creation of universes. Entanglement is thought to create connections between distant regions of space-time. We have superpositions of universes with different space-time geometries.

Furthermore, from the perspective of particle physics, the vacuum of space is a complex object. We can picture many entities called fieldssuperimposed on top of one another and extending throughout space. The value of each field is constantly fluctuating at short distances.Out of thesefluctuating fieldsand their interactions, the vacuum state emerges. Particles are disturbances in this vacuum state. We can picture them as small defects in the structure of the vacuum.

When we consider gravity, we find that the expansion of the universe appears to produce more of this vacuum stuff out of nothing. When space-time is created, it just happens to be in the state that corresponds to the vacuum without any defects. How the vacuum appears in precisely the right arrangement is one of the main questions we need to answer to obtain a consistent quantum description of black holes and cosmology. In both of these cases there is a kind of stretching of space-time that results in the creation of more of the vacuum substance.

Sera Cremonini, a theoretical physicist at Lehigh University, works on string theory, quantum gravity and cosmology:

There are many reasons why gravity is special. Let me focus on one aspect, the idea that the quantum version of Einsteins general relativity is nonrenormalizable. This has implications for the behavior of gravity at high energies.

In quantum theories, infinite terms appear when you try to calculate how very energetic particles scatter off each other and interact. In theories that are renormalizable which include the theories describing all the forces of nature other than gravity we can remove these infinities in a rigorous way by appropriately adding other quantities that effectively cancel them, so-called counterterms. This renormalization process leads to physically sensible answers that agree with experiments to a very high degree of accuracy.

The problem with a quantum version of general relativity is that the calculations that would describe interactions of very energetic gravitons the quantized units of gravity would have infinitely many infinite terms. You would need to add infinitely many counterterms in a never-ending process. Renormalization would fail. Because of this, a quantum version of Einsteins general relativity is not a good description of gravity at very high energies. It must be missing some of gravitys key features and ingredients.

However, we can still have a perfectly good approximate description of gravity at lower energies using the standard quantum techniques that work for the other interactions in nature. The crucial point is that this approximate description of gravity will break down at some energy scale or equivalently, below some length.

Above this energy scale, or below the associated length scale, we expect to find new degrees of freedom and new symmetries. To capture these features accurately we need a new theoretical framework. This is precisely where string theory or some suitable generalization comes in: According to string theory, at very short distances, we would see that gravitons and other particles are extended objects, called strings. Studying this possibility can teach us valuable lessons about the quantum behavior of gravity.

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Why Gravity Is Not Like the Other Forces - Quanta Magazine

Manchesters Northern Hive has been appointed by Toronto-based Association Quantum to handle a communications and marketing brief that will drive awareness in the UK and North America. The win is one of a number to come in recent weeks for the Spinningfields-based PR and marketing agency that was founded in 2019.

It also comes at a time when governments and technology giants around the world continue to invest heavily in quantum computing.

Association Quantum is an industry association dedicated to supporting the quantum technology sector; next-generation quantum-based technologies that are in the process of commercialisation. This includes devices that actively create, manipulate and read out the quantum states of matter, often leveraging quantum effects such as superposition and entanglement. Applications for quantum tech include highly accurate next-generation sensors, super-secure communication and quantum computers that would allow for calculations that currently take computers millions or billions of years to solve in a matter of minutes or hours.

Northern Hive, which already enjoys strong links with Canada and the technology sector, has doubled down on creating partnerships with cutting edge companies including in the cybersecurity and quantum computing space.

The campaign brief involves supporting the in-house marketing team and driving a thought-leadership program in collaboration with Association Quantums fourteen academics. The agency will also manage an earned media campaign promoting cutting-edge quantum research and thought-leadership as well as running the press office.

Were already using technologies daily that have benefited from our deep understanding of quantum physics, including; modern camera sensors & screens, GPS, MRI scanners, LEDs & lasers, as well as all the semiconductors powering modern electronics including computer chips. These devices rely on the effects of quantum mechanics. Were excited to have partnered with Northern Hive and look forward to working with the agency to communicate our support of the quantum technology sector says Jeff Lawy, a spokesperson for Association Quantum.

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Toronto-based Association Quantum appoints Northern Hive PR - Business Up North

Bose-Einstein condensate (BEC) is considered as the fifth state of matter in which separate atoms or subatomic particles, cooled to near absolute zero coalesce into a single quantum mechanical entitythat is, one that can be described by a wave functionon a near-microscopic scale.

First predicted in 1924 by Albert Einstein based on the quantum formulations of the Indian physicist Satyendra Nath Bose, the exact properties of Bose-Einstein condensates are notoriously challenging to study.

Physicists from Martin Luther University Halle-Wittenberg (MLU) and Ludwig Maximilian University Munich now have proposed a new theory to describe these quantum systems more effectively and comprehensively.

Dr. Carlos Benavides-Riveros from the Institute of Physics at MLU, said,Many attempts were made to prove their existence experimentally. Finally, in 1995, researchers in the U.S. succeeded in producing the condensates in experiments. In 2001 they received the Nobel Prize for Physics for their work. Since then, physicists around the world have been working on ways to define better and describe these systems that would enable their behavior to be more accurately predicted.

Benavides-Riveros said,In quantum mechanics, the Schrdinger equation is used to describe systems with many interacting particles. But because the number of degrees of freedom increases exponentially, this equation is not easy to solve. This is the so-called many-body problem, and finding a solution to this problem is one of the major challenges of theoretical and computational physics today.

Co-author Jakob Wolff from MLU said,The working group at MLU is now proposing a comparatively simple method. One of our key insights is that the particles in the condensate interact only in pairs. This enables these systems to be described using much simpler and more established methods, like those used in electronic quantum systems.

Jakob Wolff said,Our theory is in principle exact and can be applied to different physical regimes and scenarios, for example, strongly interacting ultracold atoms. And it looks like it will also be a promising way to describe superconducting materials.

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Physicists have proposed a new theory for Bose-Einstein condensates - Tech Explorist

A critical state of the quasiperiodic patterning of a semiconductors polariton cavity. Credit: Aalto University, Jose Lado

Combined theoretical and experimental work unveils a novel mechanism through which criticality emerges in quasiperiodic structures a finding that provides unique insight into the physics on the middle ground between order and disorder.

Quasiperiodic structures, which are ordered but are not strictly periodic, are the source of extraordinary beauty in nature, art, and science. For physicists, quasiperiodic order is both aesthetically and intellectually appealing. Numerous physical processes that are well described in periodic structures fundamentally change their character when they happen in quasiperiodic systems. Add quantum mechanics, and striking new phenomena can emerge that remain not fully understood. Writing in Nature Physics, an international team led by Oded Zilberberg of the Institute of Theoretical Physics at ETH Zurich and by CNRS physics researchers Jacqueline Bloch of the Universit Paris-Saclay and Alberto Amo of Lille University, now describes combined theoretical and experimental work in which they establish versatile tools for exploring the behaviour of quantum systems in a diverse range of one-dimensional quasiperiodic settings and demonstrate the strength of their approach to uncover new physical mechanisms.

The essence, and beauty, of quasiperiodic structures can be grasped by considering floor plates. A floor can be readily tiled without gaps using identical pieces of, for example, triangular, square or hexagonal shape, repeating a simple pattern. But a plane surface can also be fully covered in non-repeating patterns, and that by using just two types of rhomboid tiles, as the English physicist and mathematician Roger Penrose has famously shown (see the figure). In that case, even if local configurations appear in different places, the overall pattern cannot be superimposed with itself by translation and rotation. As such, these systems occupy some sort of middle ground between periodic and randomly disordered structures.

Combined theoretical and experimental work unveils a novel mechanism through which criticality emerges in quasiperiodic structures a finding that provides unique insight into the physics on the middle ground between order and disorder. Credit: ETH Zurich/D-?PHYS Oded Zilberberg

On that middle ground, there is intriguing physics to be explored. Take a perfectly ordered crystal. There, the periodicity permits wavelike propagation of electrons through the material, for instance in a metal. If the crystalline perfection is perturbed by introducing disorder, the behavior changes. For low levels of disorder, the material still conducts, but less well. At some level of disorder though, the electrons stop propagating and become collectively localized, in a process known as Anderson localization. For periodic lattices, this effect has first been described in 1958 (by 1977 Physics Nobel laureate Philip Anderson, who passed away on 29 March this year). But how such processes play out in quasiperiodic structures continues to be an area of active research.

A wide range of unconventional physical phenomena have been described for quasiperiodic systems, but there exists no overarching framework for dealing with wave propagation in quasiperiodic structures. There are, however, various models that make it possible to study specific aspects of transport and localization. Two paradigmatic examples of such models are the AubryAndr and the Fibonacci models, each of which describes different physical phenomena, not least when it comes to localization properties.

In the AubryAndr model, there are two distinct parameter regions in which the particles can be in either extended or localized states (in the same sense as electrons can either propagate through a material or be stuck in an insulating state). By contrast, in the Fibonacci model there is not one specific critical point separating the two regimes, but for any parameter the system is in such a critical state between localized and extended. Despite their sharply contrasting behaviors, the two models are connected to one another, and one can be continuously transformed into one another. This is something Zilberberg, then working at the Weizmann Institute of Science in Israel, had shown in breakthrough work with his colleague Yaacov Kraus in 2012. The question that remained was how the two so different localization behaviors are connected.

To answer that question, Zilberberg with his PhD student Antonio trkalj and his former postdoc Jose Lado (now at Aalto University) teamed up with CNRS experimentalists Jacqueline Bloch and Alberto Amo and their PhD student Valentin Goblot (now at the company STMicroelectronics). The French physicists had perfected a photonic platform so-called cavity-polariton lattices in which light can be guided through semiconductor nanostructures while experiencing interactions similar to those acting on electrons moving through a crystal. Importantly, they found ways to generate quasiperiodic modulations in their photonic wires that enabled them to implement experimentally, for the first time in any system, the KrausZilberberg model. Optical spectroscopy experiments performed locally on these photonic quasi-crystals offer the exquisite possibility of directly imaging light localization in the systems.

By combining their theoretical and experimental tools, the researchers were able to trace how the AubryAndr model evolves to become fully critical in the limit of the Fibonacci model. Counter nave expectation, the team showed that this does not happen in a smooth way, but through a cascade of localizationdelocalization transitions. Starting, for example, from the region of the AubryAndr model where particles are localized, at each step of the cascade process energy bands merge in a phase transition, during which particles are passing through the material. At the other side of the cascaded transition, the localization roughly doubles, sending the states of AubryAndr model gradually towards full criticality as it morphs into the Fibonacci model.

The situation bears some resemblance to what happens to a pile of rice as grains are added one by one. For some time, newly added grains will just sit where they landed. But once the slope at the landing site exceeds a critical steepness, a local avalanche is induced, leading to a rearrangement of parts of the pile surface. Repeating the process eventually leads to a stationary pile where one additional grain can trigger an avalanche on any of the relevant size scales a critical state. In the quasiperiodic systems, the situation is more complex because of the quantum nature of the particles involved, which means that these do not move like particles, but interfere like waves do. But in this setting as well, the evolution towards an overall critical state happens, as in the rice pile, through a cascade of discrete transitions.

With the theoretical description and experimental observation of this cascade to criticality, the teams have successfully connected quantum phenomena on two paradigmatic models of quasiperiodic chains, adding unique insight into the emergence of criticality. Moreover, they developed a flexible experimental platform for further explorations. The significance of these experiments goes firmly beyond light properties. The behavior of electrons, atoms and other quantum entities is governed by the same physics, which could inspire new ways of quantum control in devices. Just as the appeal of quasiperiodic patterns transcends disciplines, the potential to inspire scientific and eventually technological advances seems similarly boundless.

Reference: Emergence of criticality through a cascade of delocalization transitions in quasiperiodic chains by V. Goblot, A. trkalj, N. Pernet, J. L. Lado, C. Dorow, A. Lematre, L. Le Gratiet, A. Harouri, I. Sagnes, S. Ravets, A. Amo, J. Bloch and O. Zilberberg, 1 June 2020, Nature Physics.DOI: 10.1038/s41567-020-0908-7

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Intricate Beauty, Quasiperiodic Structures, and the Cascade to Criticality - SciTechDaily

To explain how this came about, quantum computing, based on quantum physics, has created a theory of the existence of parallel universes. In a separate parallel universe, one could have a coin that is a head, and in another, separate parallel universe, the coin could be a tail. I have just shown the way in which artificial intelligence theory is going today and where it is going.

Add to that the fact that all this is taking place in a computer that looks like a fantastic chandelier that is making its way through the universe, creating a universe that is much more complex than you could probably imagine. When a fateful decision is made in this universe, it takes an alternative path to the other universe. A reality that has been brought into reality by a random event, where it takes place just like ours.

While the scientific establishment has reservations about multiverse theory to say the least, it is one of the most popular theories in the field of known quantum physics. According to this theory, the universe is split into two universes that exist simultaneously, or multiverses, because quantum phenomena can be played out simultaneously in two different universes, just as they are in our universe.

Moreover, quantum physics has given us a description of the universe of multiple universes that makes no sense from the perspective of objective reality and requires observation of consciousness. This sometimes unbelievable realisation contradicts common sense, since consciousness is tantamount to logging into a system. On the contrary, the most important thing in life is that we live in a video game and not in physical reality. Life is a small thing on the scale of our universe, but it is a very important thing in the grand scheme of things.

Eastern traditions, especially the Buddhist tradition, have long maintained that we live in a world of illusions and go through multiple lives, trying to work our way through individual quests in which we save a rendered world. We are part of a gigantic system that creates new situations in which we can achieve our achievements, and we live in this world with illusions.

One remarkable idea is known as the "many-world interpretation" of quantum mechanics, and this interpretation is as valid as any other. In this universe, only one result can occur, but every result that is possible actually happens. With an infinite number of parallel universes, we must consider all these possibilities.

The second place where parallel universes arise in physics is the idea of the multiverse. The Multiverse idea explains this problem simply by the fact that dead universes can coexist in the same universe, but only in one of them.

Universes are special in that life is possible in them, but in Buddhism we have a contradictory philosophy that the universe is timeless. Universes had a big bang, and it took place in all the other universes, and quickly collapsed into a "big crunch," and they immediately went into the big freeze, where the temperature was so cold that life could never begin. So, both in the multiverse and in the universe, many of them are actually dead.

Thumbnail credits: Eileen Rollin

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AI And The Parallel Universe - AI Daily

At the beginning of the 20th century, physicists were aware of a pervasive shower of particles that seemed to rain down from space. By filling glass chambers with highly condensed vapor, they could indirectly see tracks left by these highly energetic particles now known as cosmic rays. In doing so, they quickly discovered the subatomic world was more complex than initially suspected.

The first new matter particle they discovered was the muon. It was a lot like an electron, just more massive. At first, no one knew what to make of it.

Some thought it might be a particle theorized to hold protons and neutrons together in an atom. But a pair of Italians conducting experiments in Rome during World War II proved otherwise.

After discarding a few alternative theoriesincluding one that posited that this particle might be a new kind of electronphysicists were left with one conclusion: They had discovered a particle that nobody had predicted. As Nobel Laureate I.I. Rabi famously quipped, Who ordered that?

Although scientists hadnt realized muons would be on the menu, the discovery of muons eventually led to a discovery about how that menu was set up: Particles can come in different versions, each alike in charge, spin and interactions but different in mass. The muon, for example, has the same charge, spin and electroweak interactions as the electron, but is about 200 times heavier, and theres an even heavier version of the electron and muon, called the tau.

Physicists built on this principle to predict the existence of generations of other particles, such as neutrinos, which with electrons, muons and taus round out the set of particles called leptons. Eventually, scientists would find that all of the matter particles in the Standard Model, including quarks, could be organized into three generations, though only the lightest are stable.

Muons continue to be useful tools for discovery to this day. Two international experiments, one currently underway and the other slated to begin in the early 2020s, are using the previously perplexing particles to push the boundaries of physics.

Each of the three generations is called a different flavor of particle.

At first, scientists assumed that flavor was a property that, like mass or energy, had to be conserved when particles interacted with each other. That wasnt quite right, but in their defense, they did find this to be true almost all of the time.

When you have some kind of an interaction that involves charged leptons, such as nuclear or particle decay or some type of high-energy particle interaction, the number of a given flavor of charged leptons remains the same, says Jim Miller, a professor of physics at Boston University.

When muons decay, for example, they transform into an electron, an anti-electron neutrino, and a muon neutrino. The electron and anti-electron neutrino cancel each other out, flavor-wise, leaving just the muon neutrino, which has the same flavor as the original muon.

Flavor conservation was useful; it allowed physicists to predict the interactions they would observe in particle accelerators and nuclear reactions. And those predictions proved to be correct.

But then physicists discovered that the group of (uncharged lepton) particles called neutrinos are unaware they are expected to follow the rules. On their long journey to Earth from the center of the sun, where they are created in fusion reactions, neutrinos freely oscillate between generations, transforming from electron neutrinos to muon neutrinos to tau neutrinos and back without releasing any additional particles.

This phenomenon, which won researchers Takaaki Kajita and Arthur B. McDonald the Nobel Prize for Physics in 2015, left scientists with a question: If neutrinos could violate flavor conservation, could other particles do it, too?

Physicists hope to answer that exact question with Mu2e, an experiment scheduled to start generating data in the next few years at the US Department of Energys Fermi National Accelerator Laboratory. The experiment is supported by funding from DOEs Office of Science.

Mu2e will search for muons converting into electrons without releasing other particles, a process that would clearly violate flavor conservation.

But why use muons? Its because theyre the just-right middle of the lepton family. Not too big or too small, muons are a sort of Goldilocks particle that are perfectly suited to aid physicists in their search for new physics.

Electrons, the least massive charged leptons, are small and stable. Taus, the most massive ones, are so massive and short-lived that they decay far too quickly for physicists to effectively study. Muons, however, are massive enough to decay but not massive enough to decay too quickly, making them the perfect tool in the search for new physics.

In the Mu2e experiment, physicists will accelerate a beam of low-energy muons toward a target made of aluminum. In the resulting collisions, muons will knock electrons out of their orbits around the aluminum nuclei and take their place, creating muonic atoms for a brief moment in time.

Since the mass of the muon is 200 times greater than the mass of the electron, and its average distance from the nucleus is 200 times smaller, theres an overlap between the muons position and the position of the aluminum nucleus, allowing them to interact, Miller says.

As the muon decays into an electron, physicists predict that the extra energy that usually goes into creating two neutrinos in a typical muon decay will instead be transferred to the atoms nucleus. This would allow the conversion from one flavor to another, muon to electron, without any neutrinos or antineutrinos to provide balance. If observed, this direct transition of a muon into an electron would be the hoped-for discovery of flavor violation among charged leptons.

Mu2e is not the only experiment that will use muons to test our understanding of physics.

Eight years before the discovery of muons, physicist Paul Dirac was developing a theory to describe the motion of electrons. In a single, elegant equation, Dirac successfully described that motionwhile simultaneously merging Albert Einsteins special theory of relativity with quantum mechanics and predicting the existence of antimatter.

Its hard to overstate how important and incredibly accurate Diracs equation turned out to be. Physicists still act giddy whenever its mentioned.

To understand why its important, take a look at the electron.

Diracs equation correctly described exactly how the electromagnetic force worked and gave the correct estimate for how an electrons spin would shiftor precessif placed in a magnetic field, a measurement known as g. (That prediction was later refined through calculations from the field of quantum electrodynamics.)

When muons were discovered in 1936, Diracs equation was used to calculate what their precession rate would be as well. The value g for muons was predicted to be equal to 2.

But when physicists began generating muons in accelerators at CERN in the 1950s to test his predictions, the results were not quite what they expected. Had they found a discrepancy between observation and theory? Although physicists worked hard for the next 20 years, they couldnt generate enough energy with their accelerators to obtain a conclusive answer.

Scientists at Brookhaven National Laboratory were able to test Diracs prediction at higher energies between 1999 and 2001 with an experiment meant to directly determine the anomalous part of the magnetic moment called Muon g-2 (pronounced Muon g minus 2). They found hints of the same anomalous measurement, but even with their improved technology, they lacked sufficient precision to prove a disagreement with theory.

Could Diracs equation turn out to be wrong? Physicists think it could be that their findings in muons are actually hinting at a deeper structure in physics that has yet to be discovered and that studying muons could once again lead to new revelations.

The g-2 factor has been measured for other particles, says Fermilab physicist Tammy Walton. Its been very precisely measured for the electron. Its also been measured for composite particles, like the proton and neutron. But the large mass of muons make them more sensitive to new physics.

Fermilab recently began the next generation Muon g-2 experiment, which physicists hope along with J-PARC in Japan will unequivocally confirm whether or not theory agrees with nature. Funded by the DOE's Office of Science, the experiment at Fermilab has been taking data since 2017.

We hope to get 20 times the number of muons, giving us a fourfold reduction in statistical uncertainty, says Erik Swanson, a research engineer at the University of Washington. If our central value stays the same as that generated at Brookhaven, then we will have confirmed without a doubt the discrepancy between theory and observation. Otherwise it might just be that theory was right all along.

If the theory is broken, physicists will have a lot of explaining to do, which could lead them to a new understanding of the particles and forces that make up our universe and the forces that govern them. Not bad work for a particle nobody ordered.

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The stories a muon could tell - Symmetry magazine