Elsevier retracts dozens of journal articles that were published based on “fictitious” reviews

Learn more about the giant short-faced bear, and how it would have fared against saber-tooth cats and other Ice Age predators.

Deal allows scholars to read paywalled articles for free and will cover open-access fees

Windblown embers can trigger spot fires much further away than expected. Now a new mathematical model of the way the wind interacts with firebrands explains why.

Microscopes traditionally resolve only the thin layer of cellular activity within a narrow focal plane. Now scientists have worked out how to squeeze an entire cell and all its molecular machinery into this space.

Some lakes have grown by more than 40% in recent years, new data show

Hint: It involves finding just the right proteins. With new ingredients and processes, the next generation of substitutes will be not just more egg-like, but potentially more nutritious.

Some animals appear to smile. But the emotion behind the smile can be tricky to decipher.

India’s capital has turned to tech to fight its worst air pollution in eight years.

I have mentioned many times in this column the value of the business awards given by the Institute of Physics (IOP), which can be a real “stamp of approval” for firms developing new technology. Having helped to select the 2024 winners, it was great to see eight companies winning a main IOP Business Innovation Award this time round, bringing the total number of firms honoured over the last 13 years to 86. Some have won awards on more than one occasion, with Fetu being one of the latest to join this elite group.

Set up by Jonathan Fenton in 2016, FeTu originally won an IOP Business Start-up Award in 2020 for its innovative Fenton Turbine. According to Fenton, who is chief executive, it is the closest we have ever got to the ideal, closed-cycle reversible heat engine first imagined by thermodynamics pioneer Nicolas Carnot in 1824. The turbine, the firm claims, could replace compressors, air conditioners, fridges, vacuum pumps and heat pumps with efficiency savings across the board.

Back in 2020, it might have sounded like a “too-good-to-be-true” technology, but Fenton has sensibly set out to prove that’s not the case, with some remarkable results. The turbine is complex to describe but the first version promised to cut the energy cost of compressing gases like air by 25%. They claim has already been proven in independent tests carried out by researchers at the University of Bath.

One challenge of any technology with many different applications is picking which to focus on first.

One challenge of any technology with many different applications is picking which to focus on first. Having decided to focus on a couple of unique selling factors in large markets, FeTu has now won a 2024 Business Innovation Award for developing a revolutionary heat engine that can generate electrical power from waste heat and geothermal sources as low as 40 °C. It has a huge market potential as it is currently not possible to do this economically.

Innovative ideas

Another winner of an IOP Business Innovation Award is Oxford Ionics,  a quantum-computing firm set up in 2019 by Chris Balance and Tom Harty after doing PhDs at the University of Oxford. Their firm’s qubits are based on trapped ions, which traditionally have been controlled with lasers. It’s an approach that works well for small processors, but becomes untenable and error-prone as the size of the processor scales, and the number of qubits increases.

Instead of lasers, Oxford Ionics’ trapped-ion processors use a proprietary, patented electronic system to control the qubits. It was for this system that the company was recognized by the IOP, along with its ability to scale the architecture so that the chips can be made in large quantities on standard semiconductor production lines. That’s essential if we are to build practical quantum computers.

Whilst it’s still early days in the commercialisation of quantum computing, Oxford Ionics is an exciting company to watch. It has already won contracts to supply the UK’s National Quantum Computing Centre at Harwell and has bagged a large contract with its partner Infineon Technologies AG in Munich to build a state-of-the-art portable quantum computer for Germany’s cybersecurity innovation agency. The two firms are one of three independent contractors selected by the agency, which is investing a total of €35m in the project.

I should also mention Dublin-based Equal1, which won the IOP’s £10,000 quantum Business Innovation and Growth (qBIG) Prize in 2024. Equal1 is developing rack-mountable quantum computers powered by a system that integrates quantum and classical components onto a single silicon chip using commercial fabrication processes. The company, which aims to develop compact quantum computers, also won 10 months of mentoring from the award’s sponsors Quantum Exponential.

Meanwhile, Covesion – a photonics and quantum components supplier founded in 2009 – has won an IOP Business Innovation Award for its magnesium-doped, periodically poled, lithium niobate (MgO:PPLN) crystals and waveguides. They allow light to be easily converted from one frequency to another, providing access to wavelengths that are not available from commercial laser sources.

With a manufacturing base in Southampton, Covesion works with customers and industry partners to help them design and make high quality MgO:PPLN products used in a wide range of applications. They include quantum computing, communication, sensing and timing; frequency doubling of femtosecond lasers; mid-infrared generation; atom cooling; terahertz generation and biomedical imaging. The shear breadth and global nature of the customer base is impressive.

Sounds promising

Among the companies to win an IOP Business Start-up Award is Metasonixx, based in Brighton. Spun off from the universities of Bristol and Sussex in 2019, the firm makes mass-produced acoustic metamaterial panels, which can dramatically attenuate sound (10 dB in its Sonoblind) and yet still allow air to flow freely (3 dB or 50% attenuation). That might seem counter-intuitive, but that’s where the innovation comes in and the panels can help with noise management and ventilation, allowing industrial ventilators and heat pumps to be more widely used.

The company really got going in 2020, when it got a grant from UK Research and Innovation to see if its metamaterials could cut noise in hospitals to help patients recovering from COVID-19 and improve the well-being of staff. After Metatronixx won the Armourers and Brasiers Venture Prize in 2021 for their successes on COVID wards, the firm decided to mass-produce panels that could perform as well as traditional noise-reduction solutions but are modular and greener, with one-third of the mass and occupying one-twelfth of the space.

From a physics point of view, panels that can let air and light through in this way are interferential filters, but working over four doublings of frequency (or octaves). With manufacturing and first sales in 2023, their desk separators are now being tested in noisy offices worldwide. Metatronixx believes its products, which allow air to flow through them, could help to boost the use of industrial ventilators and heat pumps, thereby helping in the quest to meet net-zero targets.

Winning awards for Metasonixx is not a new experience, having also picked up a “Seal of Exellence Award” from the European Commission in 2023 and honoured at Bristol’s Tech-Xpo in 2024. Its new IOP award will sit very nicely in this innovative company’s trophy cabinet.

• In his next article, James McKenzie will look at the rest of the 2024 IOP Business Award winners in imaging and medical technology.

The post From qubits to metamaterials: tech that led to Institute of Physics business awards 2024 appeared first on Physics World.

A Swedish startup wants to democratize stem cell treatments, but the finances of the unproven therapies raise ethical questions.

Fine-grained imaging of mouse brain cells suggests “pearling” of axons that researchers think may help with signaling

The two probes have left the solar system and are still collecting data from the interstellar environment—but their atomic hearts are growing weaker and weaker.

Physicists in the US have found an explanation for why electrons in a material called pentalayer moiré graphene carry fractional charges even in the absence of a magnetic field. This phenomenon is known as the fractional quantum anomalous Hall effect, and teams at the Massachusetts Institute of Technology (MIT), Johns Hopkins University and Harvard University/University of California, Berkeley have independently suggested that an interaction-induced topological “flat” band in the material’s electronic structure may be responsible.

Scientists already knew that electrons in graphene could, in effect, split into fractions of themselves in the presence of a very strong magnetic field. This is an example of the fractional quantum Hall effect, which occurs when a material’s Hall conductance is quantized at fractional multiples of e²/h.

In 2023, several teams of researchers introduced a new twist by observing this fractional quantization even without a magnetic field. The fractional quantum anomalous Hall effect, as it was dubbed, was initially observed in material called twisted molybdenum ditelluride (MoTe₂).

Then, in February this year, an MIT team led by physicist Long Ju spotted the same effect in pentalayer moiré graphene. This material consists of a layer of a two-dimensional hexagonal boron nitride (hBN) with five layers of graphene (carbon sheets just one atom thick) stacked on top of it. The graphene and hBN layers are twisted at a small angle with respect to each other, resulting in a moiré pattern that can induce conflicting properties such as superconductivity and insulating behaviour within the structure.

Answering questions

Although Ju and colleagues were the first to observe the fractional quantum anomalous Hall effect in graphene, their paper did not explain why it occurred. In the latest group of studies, other scientists have put forward a possible solution to the mystery.

According to MIT’s Senthil Todadri, the effect could stem from the fact that electrons in two-dimensional materials like graphene are confined in such small spaces that they start interacting strongly. This means that they can no longer be considered as independent charges that naturally repel each other. The Johns Hopkins team led by Ya-Hui Zhang and the Harvard/Berkeley team led by Ashvin Vishwanath and Daniel E Parker came to similar conclusions, and published their work in Physical Review Letters alongside that of the MIT team.

Crystal-like periodic patterns form an electronic “flat” band

Todadri and colleagues started their analyses with a reasonably realistic model of the pentalayer graphene. This model treats the inter-electron Coulomb repulsion in an approximate way, replacing the “push” of all the other electrons on any given electron with a single potential, Todadri explains. “Such a strategy is routinely employed in quantum mechanical calculations of, say, the structure of atoms, molecules or solids,” he notes.

The MIT physicists found that the moiré arrangement of pentalayer graphene induces a weak electron potential that forces electrons passing through it to arrange themselves in crystal-like periodic patterns that form a “flat” electronic band. This band is absent in calculations that do not account for electron–electron interactions, they say.

Such flat bands are especially interesting because electrons in them become “dispersionless” – that is, their kinetic energy is suppressed. As the electrons slow almost to a halt, their effective mass approaches infinity, leading to exotic topological phenomena as well as strongly correlated states of matter associated with high-temperature superconductivity and magnetism. Other quantum properties of solids such as fractional splitting of electrons can also occur.

“Mountain and valley” landscapes

So what causes the topological flat band in pentalayer graphene to form? The answer lies in the “mountain and valley” landscapes that naturally appear in the electronic crystal. Electrons in this material experience these landscapes as pseudo-magnetic fields, which affect their motion and, in effect, do away with the need to apply a real magnetic field to induce the fractional Hall quantization.

“This interaction-induced topological (‘valley-polarized Chern-1’) band is also predicted by our theory to occur in the four- and six-layer versions of multilayer graphene,” Todadri says. “These structures may then be expected to host phases where electron fractions appear.”

In this study, the MIT team presented only a crude treatment of the fractional states. Future work, Todadri says, may focus on understanding the precise role of the moiré potential produced by aligning the graphene with a substrate. One possibility, he suggests, is that it simply pins the topological electron crystal in place. However, it could also stabilize the crystal by tipping its energy to be lower than a competing liquid state. Another open question is whether these fractional electron phenomena at zero magnetic field require a periodic potential in the first place. “The important next question is to develop a better theoretical understanding of these states,” Todadri tells Physics World.

The post Physicists close in on fractionally-charged electron mystery in graphene appeared first on Physics World.

Scientists have discovered a new way of making chocolate that uses the entire cocoa pod to reduce waste and improve farmer revenue streams. But can chocolate made any other way taste as sweet?

At 3 a.m. one morning in June 1925, an exhausted, allergy-ridden 23-year old climbed a rock at the edge of a small island off the coast of Germany in the North Sea. Werner Heisenberg, who was an unknown physics postdoc at the time, had just cobbled together, in crude and unfamiliar mathematics, a framework that would shortly become what we know as “matrix mechanics”. If we insist on pegging the birth of quantum mechanics to a particular place and time, Helgoland in June 1925 it is.

Heisenberg’s work a century ago is the reason why the United Nations has proclaimed 2025 to be the International Year of Quantum Science and Technology. It’s a global initiative to raise the public’s awareness of quantum science and its applications, with numerous activities in the works throughout the year. One of the most significant events for physicists will be a workshop running from 9–14 June on Helgoland, exactly 100 years on from the very place where quantum mechanics supposedly began.

Entitled “Helgoland 2025”, the event is designed to honour Heisenberg’s development of matrix mechanics, which organizers have dubbed “the first formulation of quantum theory”. The workshop, they say, will explore “the increasingly fruitful intersection between the foundations of quantum mechanics and the application of these foundations in real-world settings”. But why was Heisenberg’s work so vital to the development of quantum mechanics? Was it really as definitive as we like to think? And is the oft-repeated Helgoland story really true?

How it all began

The events leading up to Heisenberg’s trip can be traced back to the work of Max Planck in 1900. Planck was trying to produce a formula for the how certain kinds of materials absorb and emit light depending on energy. In what he later referred to as an “act of sheer desperation”, Planck found himself having to use the idea of the “quantum”, which implied that electromagnetic radiation is not continuous but can be absorbed and emitted only in discrete chunks.

Standing out as a smudge on the beautiful design of classical physics, the idea of quantization appeared of limited use. Some physicists called it “ugly”, “grotesque” and “distasteful”; it was surely a theoretical sticking plaster that could soon be peeled off. But the quantum proved indispensable, cropping up in more and more branches of physics, including the structure of the hydrogen atom, thermodynamics and solid-state physics. It was like an obnoxious visitor whom you try to expel from your house but can’t. Worse, its presence seemed to grow. The quantum, remarked one scientist at the time, was a “lusty infant”.

‘Quantum theory’ was like having instructions for how to get from place A to place B. What you really wanted was a ‘quantum mechanics’ – a map that showed you how to go from any place to any other.

Robert P Crease, Stony Brook University

Attempts to domesticate that infant in the first quarter of the 20th century were made not only by Planck but other physicists too, such as Wolfgang Pauli, Max Born, Niels Bohr and Ralph Kronig. They succeeded only in producing rules for calculating certain phenomena that started with classical theory and imposed conditions. “Quantum theory” was like having instructions for how to get from place A to place B. What you really wanted was a “quantum mechanics” – a map that, working with one set of rules, showed you how to go from any place to any other.

Heisenberg was a young crusader in this effort. Born on 5 December 1901 – the year after Planck’s revolutionary discovery – Heisenberg had the character often associated with artists, with dashing looks, good musicianship and a physical frailty including a severe vulnerability to allergies. That summer in 1923, Heisenberg had just finished his PhD under Arnold Sommerfeld at the Ludwig Maximilian University in Munich and was starting a postdoc with Born at the University of Göttingen.

Like others, Heisenberg was stymied in his attempts to develop a mathematical framework for the frequencies, amplitudes, orbitals, positions and momenta of quantum phenomena. Maybe, he wondered, the trouble was trying to cast these phenomena in a Newtonian-like visualizable form. Instead of treating them as classical properties with specific values, he decided to look at them in purely mathematical terms as operators acting on functions. It was then that an “unfortunate personal setback” occurred.

Destination Helgoland

Referring to a bout of hay fever that had wiped him out, Heisenberg asked Born for a two-week leave of absence from Göttingen and took a boat to Helgoland. The island, which lies some 50 km off Germany’s mainland, is barely 1 km² in size. However, its strategic military location had given it an outsized history that saw it swapped several times between different European powers. Part of Denmark from 1714, the island was occupied by Britain in 1807 before coming under Germany’s control in 1890.

During the First World War, Germany turned the island into a military base and evacuated all its residents. By the time Heisenberg arrived, the soldiers had long gone and Helgoland was starting to recover its reputation as a centre for commercial fishing and a bracing tourist destination. Most importantly for Heisenberg, it had fresh winds and was remote from allergen producers.

Heisenberg arrived at Helgoland on Saturday 6 June 1925 coughing and sneezing, and with such a swollen face that his landlady decided he had been in a fight. She installed him in a quiet room on the second floor of her Gasthaus that overlooked the beach and the North Sea. But he didn’t stop working. “What exactly happened on that barren, grassless island during the next ten days has been the subject of much speculation and no little romanticism,” wrote historian David Cassidy in his definitive 1992 book Uncertainty: The Life and Science of Werner Heisenberg.

In Heisenberg’s telling, decades later, he kept turning over all he knew and began to construct equations of observables – of frequencies and amplitudes – in what he called “quantum-mechanical series”. He outlined a rough mathematical scheme, but one so awkward and clumsy that he wasn’t even sure it obeyed the conservation of energy, as it surely must. One night Heisenberg turned to that issue.

“When the first terms seemed to accord with the energy principle, I became rather excited,” he wrote much later in his 1971 book Physics and Beyond. But he was still so tired that he began to stumble over the maths. “As a result, it was almost three o’clock in the morning before the final result of my computations lay before me.” The work still seemed finished yet incomplete – it succeeded in giving him a glimpse of a new world though not one worked out in detail – but his emotions were weighted with fear and longing.

“I was deeply alarmed,” Heisenberg continued. “I had the feeling that, through the surface of atomic phenomena, I was looking at a strangely beautiful interior, and felt almost giddy at the thought that I now had to probe this wealth of mathematical structure nature had so generously spread out before me. I was far too excited to sleep and so, as a new day dawned, I made for the southern tip of the island, where I had been longing to climb a rock jutting out into the sea. I now did so without too much trouble, and waited for the sun to rise.”

What happened on Helgoland?

Historians are suspicious of Heisenberg’s account. In their 2023 book Constructing Quantum Mechanics Volume 2: The Arch 1923–1927, Anthony Duncan and Michel Janssen suggest that Heisenberg made “somewhat less progress in his visit to Helgoland in June 1925 than later hagiographical accounts of this episode claim”. They believe that Heisenberg, in Physics and Beyond, may “have misremembered exactly how much he accomplished in Helgoland four decades earlier”.

What’s more – as Cassidy wondered in Uncertainty – how could Heisenberg have been so sure that the result agreed with the conservation of energy without having carted all his reference books along to the island, which he surely had not. Could it really be, Cassidy speculated sceptically, that Heisenberg had memorized the relevant data?

Alexei Kojevnikov – another historian – even doubts that Heisenberg was entirely candid about the reasons behind his inspiration. In his 2020 book The Copenhagen Network: The Birth of Quantum Mechanics from a Postdoctoral Perspective, Kojevnikov notes that fleeing from strong-willed mentors such as Bohr, Born, Kronig, Pauli and Sommerfeld was key to Heisenberg’s creativity. “In order to accomplish his most daring intellectual breakthrough,” Kojevnikov writes, “Heisenberg had to escape from the authority of his academic supervisors into the temporary loneliness and freedom on a small island in the North Sea.”

Whatever did occur on the island, one thing is clear. “Heisenberg had his breakthrough,” decides Cassidy in his book. He left Helgoland 10 days after he arrived, returned to Göttingen, and dashed off a paper that was published in Zeitschrift für Physik in September 1925 (33 879). In the article, Heisenberg wrote that “it is not possible to assign a point in space that is a function of time to an electron by means of observable quantities.” He then suggested that “it seems more advisable to give up completely on any hope of an observation of the hitherto-unobservable quantities (such as the position and orbital period of the electron).”

To modern ears, Heisenberg’s comments may seem unremarkable. But his proposition certainly would have been nearly unthinkable to those steeped in Newtonian mechanics. Of course, the idea of completely abandoning the observability of those quantities wasn’t quite true. Under certain conditions, it can make sense to speak of observing them. But they certainly captured the direction he was taking.

The only trouble was that his scheme, with its “quantum-mechanical relations”, produced formulae that were “noncommutative” – a distressing asymmetry that was surely an incorrect feature in a physical theory. Heisenberg all but shoved this feature under the rug in his Zeitschrift für Physik article, where he relegated the point to a single sentence.

The more mathematically trained Born, on the other hand, sensed something familiar about the maths and soon recognized that Heisenberg’s bizarre “quantum-mechanical relations” with their strange tables were what mathematicians called matrices. Heisenberg was unhappy with that particular name for his work, and considered returning to what he had called “quantum-mechanical series”.

Fortunately, he didn’t, for it would have made the rationale for the Helgoland 2025 conference clunkier to describe. Born was delighted with the connection to traditional mathematics. In particular he found that when the matrix p associated with momentum and the matrix q associated with position are multiplied in different orders, the difference between them is proportional to Planck’s constant, h.

As Born wrote in his 1956 book Physics in My Generation: “I shall never forget the thrill I experienced when I succeeded in condensing Heisenberg’s ideas on quantum conditions in the mysterious equation pq – qp = h/2πi, which is the centre of the new mechanics and was later found to imply the uncertainty relations”. In February 1926, Born, Heisenberg and Jordan published a landmark paper that worked out the implications of this equation (Zeit. Phys. 35 557). At last, physicists had a map of the quantum domain.

Almost four decades later in an interview with the historian Thomas Kuhn, Heisenberg recalled Pauli’s “extremely enthusiastic” reaction to the developments. “[Pauli] said something like ‘Morgenröte einer Neuzeit’,” Heisenberg told Kuhn. “The dawn of a new era.” But it wasn’t entirely smooth sailing after that dawn. Some physicists were unenthusiastic about Heisenberg’s new mechanics, while others were outright sceptical.

Yet successful applications kept coming. Pauli applied the equation to light emitted by the hydrogen atom and derived the Balmer formula, a rule that had been known empirically since the mid-1880s. Then, in one of the most startling coincidences in the history of science, the Austrian physicist Erwin Schrödinger produced a complete map of the quantum domain stemming from a much more familiar mathematical basis called “wave mechanics”. Crucially, Heisenberg’s matrix mechanics and Schrödinger’s maps turned out to be identical.

Even more fundamental implications followed. In an article published in Naturwissenschaften (14 899) in September 1926, Heisenberg wrote that our “ordinary intuition” does not work in the subatomic realm. “Because the electron and the atom possess not any degree of physical reality as the objects of our daily experience,” he said, “investigation of the type of physical reality which is proper to electrons and atoms is precisely the subject of quantum mechanics.”

Quantum mechanics, alarmingly, was upending reality itself, for the uncertainty it introduced was not only mathematical but “ontological” – meaning it had to do with the fundamental features of the universe. Early the next year, Heisenberg, in correspondence with Pauli, derived the equation Δp Δq ≥ h/4π, the “uncertainty principle”, which became the touchstone of quantum mechanics. The birth complications, however, persisted. Some even got worse.

Catalytic conference

A century on from Heisenberg’s visit to Helgoland, quantum mechanics still has physicists scratching their heads. “I think most people agree that we are still trying to make sense of even basic non-relativistic quantum mechanics,” admits Jack Harris, a quantum physicist at Yale University who is co-organizing Helgoland 2025 with Časlav Brukner, Steven Girvin and Florian Marquardt.

We really don’t fully understand the quantum world yet. We apply it, we generalize it, we develop quantum field theories and so on, but still a lot of it is uncharted territory.

Igor Pikovsky, Stevens Institute, New Jersey

“We really don’t fully understand the quantum world yet,” adds Igor Pikovsky from the Stevens Institute in New Jersey, who works in gravitational phenomena and quantum optics. “We apply it, we generalize it, we develop quantum field theories and so on, but still a lot of it is uncharted territory.” Philosophers and quantum physicists with strong opinions have debated interpretations and foundational issues for a long time, he points out, but the results of those discussions have been unclear.

Helgoland 2025 hopes to change all that. Advances in experimental techniques let us ask new kinds of fundamental questions about quantum mechanics. “You have new opportunities for studying quantum physics at completely different scales,” says Pikovsky. “You can make macroscopic, Schrödinger-cat-like systems, or very massive quantum systems to test. You don’t need to debate philosophically about whether there’s a measurement problem or a classical-quantum barrier – you can start studying these questions experimentally.”

One phenomenon fundamental to the puzzle of quantum mechanics is entanglement, which prevents the quantum state of a system from being described independently of the state of others. Thanks to the Einstein–Podolsky–Rosen (EPR) paper of 1935 (Phys. Rev. 47 777), Chien-Shiung Wu and Irving Shaknov’s experimental demonstration of entanglement in extended systems in 1949, and John Bell’s theorem in 1964 (Physics 1 195), physicists know that entanglement in extended systems is a large part of what’s so weird about quantum mechanics.

Understanding all that entanglement entails, in turn, has led physicists to realize that information is a fundamental physical concept in quantum mechanics. “Even a basic physical quantum system behaves differently depending on how information about it is stored in other systems,” Harris says. “That’s a starting point both for deep insights into what quantum mechanics tells us about the world, and also for applying it.”

Helgoland 2025 will therefore focus on the two-way street between foundations and applications in what promises to be a unique event. “The conference is intended to be a bit catalytic,” Harris adds. “[There will be] people who didn’t realize that others were working on similar issues in different fields, and a lot of people who will never have met each other”. The disciplinary diversity will be augmented by the presence of students as well as poster sessions, which tend to bring in an even broader variety of research topics.

There will be people [at Helgoland] who work on black holes whose work is familiar to me but who I haven’t met yet.

Ana Maria Rey, University of Colorado, Boulder

One of those looking forward to such encounters is Ana Maria Rey – a theoretical physicist at the University of Colorado, Boulder, and a JILA fellow who studies quantum phenomena in ways that have improved atomic clocks and quantum computing. “There will be people who work on black holes whose work is familiar to me but who I haven’t met yet,” she says. Finding people should be easy: Helgoland is tiny and only a hand-picked group of people have been invited to attend (see box above).

What’s also unusual about Helgoland is that it has as many practically-minded as theoretically-minded participants. But that doesn’t faze Magdalena Zych, a physicist from Stockholm University in Sweden. “I’m biased because academically I grew up in Vienna, where Anton Zeilinger’s group always had people working on theory and applications,” she says.

Zych’s group has, for example, recently discovered a way to use the uncertainty principle to get a better understanding of the semi-classical space–time trajectories of composite particles. She plans to talk about this research at Helgoland, finding it appropriate given that it relies on Heisenberg’s principle, is a product of specific theoretical work and is valid more generally. “It relates to the arch of the conference, looking both backwards and forwards, and from theory to applications.”

Sadly, participants will not be able to visit Heisenberg’s Gasthaus, nor any other building where he might have been. During the Second World War, Germany again relocated Helgoland’s inhabitants and turned the island into a military base. After the war, the Allies piled up unexploded ordinances on the island and set them off, in what is said to be one of the biggest conventional explosions in history. The razed homeland was then given back to its inhabitants.

We will not be 300 Heisenbergs going for hikes. [Attendees] certainly won’t be trying to get away from each other.

Jack Harris, Yale University

Helgoland still has rocky outcroppings at its southern end, one of which may or may not be the site of Heisenberg’s early morning climb and vision. But despite the powerful mythology of his story, participants at Helgoland 2025 are not being asked to herald another dawn. “We will not,” says Harris, “be 300 Heisenbergs going for hikes. They certainly won’t be trying to get away from each other.”

The historian of science Mario Biagioli once wrote an article entitled “The scientific revolution is undead”, underlining how arbitrary it is to pin key developments in science – no matter how influential or long-lasting – to specific beginnings and endings, for each new generation of scientists finds ever more to mine in the radical discoveries of predecessors. With so many people working on so many foundational issues set to be at Helgoland 2025, new light is bound to emerge. A century on, the quantum revolution is alive and well.

The post Return to Helgoland: celebrating 100 years of quantum mechanics appeared first on Physics World.

Forecasting is both art and science, reliant on both rigor and luck—but you can develop a mindset that anticipates and plans ahead.

The giant holes in galaxies’ centers shouldn’t be able to combine, yet combine they do. Scientists suggest that an unusual form of dark matter may be the solution.

As a gargantuan plume of magma rises from the depths, tectonic forces are wrenching the island nation apart, triggering the outpouring of lava.

You'd need a pretty big drill to make it through Earth's crust.

New constraints on a theory that says dark matter was created just after the Big Bang  – rather than at the Big Bang – have been determined by Richard Casey and  Cosmin Ilie at Colgate University in the US. The duo calculated the full range of parameters in which a “Dark Big Bang” could fit into the observed history of the universe. They say that evidence of this delayed creation could be found in gravitational waves.

Dark matter is a hypothetical substance that is believed to play an important role in the structure and dynamics of the universe. It appears to account for about 27% of the mass–energy in the cosmos and is part of the Standard Model of cosmology. However, dark matter particles have never been observed directly.

The Standard Model also says that the entire contents of the universe emerged nearly 14 billion years ago in the Big Bang. Yet in 2023, Katherine Freese and Martin Winkler at the University of Texas at Austin introduced a captivating new theory, which suggests that the universe’s dark matter may have been created after the Big Bang.

Evidence comes later on

Freese and Winkler pointed out that presence of photons and normal matter (mostly protons and neutrons) can be inferred from almost immediately after the Big Bang. However, the earliest evidence for dark matter comes from later on, when it began to exert its gravitational influence on normal matter. As a result, the duo proposed that dark matter may have appeared in a second event called the Dark Big Bang.

“In Freese and Winkler’s model, dark matter particles can be produced as late as one month after the birth of our universe,” Ilie explains. “Moreover, dark matter particles produced via a Dark Big Bang do not interact with regular matter except via gravity. Thus, this model could explain why all attempts at detecting dark matter – either directly, indirectly, or via particle production – have failed.”

According to this theory, dark matter particles are generated by a certain type of scalar field. This is an energy field that has a single value at every point in space and time (a familiar example is the field describing gravitational potential energy). Initially, each point of this scalar field would have occupied a local minimum in its energy potential. However, these points could have then transitioned to lower-energy minima via quantum tunnelling. During this transition, the energy difference between the two minima would be released, producing particles of dark matter.

Consistent with observations

Building on this idea, Casey and Ilie looked at how predictions of the Dark Big Bang model could be consistent with astronomers’ observations of the early universe.

“By focusing on the tunnelling potentials that lead to the Dark Big Bang, we were able to exhaust the parameter space of possible cases while still allowing for many different types of dark matter candidates to be produced from this transition,” Casey explains. “Aside from some very generous mass limits, the only major constraint on dark matter in the Dark Big Bang model is that it interacts with everyday particles through gravity alone.” This is encouraging because this limited interaction is what physicists expect of dark matter.

For now, the duo’s results suggest that the Dark Big Bang is far less constrained by past observations than Freese and Winkler originally anticipated. As Ilie explains, their constraints could soon be put to the test.

“We examined two Dark Big Bang scenarios in this newly found parameter space that produce gravitational wave signals in the sensitivity ranges of existing and upcoming surveys,” he says. “In combination with those considered in Freese and Winkler’s paper, these cases could form a benchmark for gravitational wave researchers as they search for evidence of a Dark Big Bang in the early universe.”

Subtle imprint on space–time

If a Dark Big Bang happened, then the gravitational waves it produced would have left a subtle imprint on the fabric of space–time. With this clearer outline of the Dark Big Bang’s parameter space, several soon-to-be active observational programmes will be well equipped to search for these characteristic imprints.

“For certain benchmark scenarios, we show that those gravitational waves could be detected by ongoing or upcoming experiments such as the International Pulsar Timing Array (IPTA) or the Square Kilometre Array Observatory (SKAO). In fact, the evidence of background gravitational waves reported in 2023 by the NANOGrav experiment – part of the IPTA – could be attributed to a Dark Big Bang realization,” Casey says.

If these studies find conclusive evidence for Freese and Winkler’s original theory, Casey and Ilie’s analysis could ultimately bring us a step closer to a breakthrough in our understanding of the ever-elusive origins of dark matter.

The research is described in Physical Review D.

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