Physics World

The obscure physics theory that helped Chinese science emerge from the shadows

Robert P Crease — Wed, 21 Jan 2026 11:00:52 +0000

“The Straton Model of elementary particles had very limited influence in the West,” said Jinyan Liu as she sat with me in a quiet corner of the CERN cafeteria. Liu, who I caught up with during a break in a recent conference on the history of particle physics, was referring to a particular model of elementary particle physics first put together in China in the mid-1960s. The Straton Model was, and still largely is, unknown outside that country. “But it was an essential step forward,” Liu added, “for Chinese physicists in joining the international community.”

Liu was at CERN to give a talk on how Chinese theorists redirected their research efforts in the years after the Cultural Revolution, which ended in 1976. They switched from the Straton Model, which was a politically infused theory of matter favoured by Mao Zedong, the founder of the People’s Republic of China, to mainstream particle physics as practised by the rest of the world. It’s easy to portray the move as the long-overdue moment when Chinese scientists resumed their “real” physics research. But, Liu told me, “actually it was much more complicated”.

A physicist by training, Liu received her PhD on contemporary theories of spontaneous charge-parity (CP) violation from the Institute of Theoretical Physics at the Chinese Academy of Sciences (CAS) in 2013. She then switched to the CAS Institute for History of Natural Sciences, where she was its first member with a physics PhD. Her initial research topic was the history and development of the Straton Model.

The model is essentially a theory of the structure of hadrons – either baryons (such as protons and neutrons) or mesons (such as pions and kaons). But the model’s origins are as improbable as they are labyrinthine. Mao, who had a keen interest in natural science, was convinced that matter was infinitely divisible, and in 1963 he came across an article by the Marxist-inspired Japanese physicist Shoichi Sakata (1911–1970).

First published in Japanese in 1961 and later translated into Russian, Sakata’s paper was entitled “Dialogues concerning a new view of elementary particles”. It restated Sakata’s belief, which he had been working on since the 1950s, that hadrons are made of smaller constituents – “elementary particles are not the ultimate elements of matter” as he put it. With some Chinese scholars back then still paying close attention to publications from the Soviet Union, their former political and ideological ally, that paper was then translated into Chinese.

Mao Zedong was engrossed in Shoichi Sakata’s paper, for it seemed to offer scientific support for his own views.
+

This version appeared in the Bulletin of the Studies of Dialectics of Nature in 1963. Mao, who received an issue of that bulletin from his son-in-law, was engrossed in Sakata’s paper, for it seemed to offer scientific support for his own views. Sakata’s article – both in the original Japanese and now in Chinese – cited Friedrich Engels’ view that matter has numerous stages of discrete but qualitatively different parts. In addition, it quoted Lenin’s remark that “even the electron is inexhaustible”.

A wider dimension

“International politics now also entered,” Liu told me, as we discussed the issue further at CERN. A split between China and the Soviet Union had begun to open up in the late 1950s, with Mao breaking off relations with the Soviet Union and starting to establish non-governmental science and technology exchanges between China and Japan. Indeed, when China hosted the Peking Symposium of foreign scientists in 1964, Japan brought the biggest delegation, with Sakata as its leader.

At the event, Mao personally congratulated Sakata on his theory. It was, Sakata later recalled, “the most unforgettable moment of my journey to China”. In 1965, Sakata’s paper was retranslated from the Japanese original, with an annotated version published in Red Flag and the newspaper Renmin ribao, or “People’s Daily”, both official organs of the Chinese Communist Party.

Chinese physicists realized that they could capitalize on Mao’s enthusiasm to make elementary particle physics a legitimate research direction.
+

Chinese physicists, who had been assigned to work on the atomic bomb and other research deemed important by the Communist Party, now started to take note. Uninterested in philosophy, they realized that they could capitalize on Mao’s enthusiasm to make elementary particle physics a legitimate research direction.

As a result, 39 members of CAS, Peking University and the University of Science and Technology of China formed the Beijing Elementary Particle Group. Between 1965 and 1966, they wrote dozens of papers on a model of hadrons inspired by both Sakata’s work and quark theory based on the available experimental data. It was dubbed the Straton Model because it involved layers or “strata” of particles nested in each other.

+ +

Liu has interviewed most surviving members of the group and studied details of the model. It differed from the model being developed at the time by the US theorist Murray Gell-Mann, which saw quarks as not physical but mathematical elements. As Liu discovered, Chinese particle physicists were now given resources they’d never had before. In particular, they could use computers, which until then had been devoted to urgent national defence work. “To be honest,” Liu chuckled, “the elementary particle physicists didn’t use computers much, but at least they were made available.”

+ +

The high-water mark for the Straton Model occurred in July 1966 when members of the Beijing Elementary Particle Group presented it at a summer physics colloquium organized by the China Association for Science and Technology. The opening ceremony was held in Tiananmen Square, in what was then China’s biggest conference centre, with attendees including Abdus Salam from Imperial College London. The only high-profile figure to be invited from the West, Salam was deemed acceptable because he was science advisor to the president of Pakistan, a country considered outside the western orbit.

The proceedings of the colloquium were later published as “Research on the theory of elementary particles carried out under the brilliant illumination of Mao Tse-Tung’s thought”. Its introduction was what Liu calls a “militant document” – designed to reinforce the idea that the authors were carrying Mao’s thought into scientific research to repudiate “decadent feudal, bourgeois and revisionist ideologies”.

Participants in Beijing had expected to make their advances known internationally by publishing the proceedings in English. But the Cultural Revolution had just begun two months before, and publications in English were forbidden. “As a result,” Liu told me, “the model had very limited influence outside China.” Sakata, however, had an important influence on Japanese theorists having co-authored the key paper on neutrino flavour oscillation (Prog. Theoretical. Physics 28 870).

A resurfaced effort

In recent years, Liu has shed new light on the Straton Model, writing a paper in the journal Chinese Annals of History of Science and Technology (2 85). In 2022, she also published a 2022 Chinese-language book entitled Constructing a Theory of Hadron Structure: Chinese Physicists’ Straton Model, which describes the downfall of the model after 1966. None of its predicted material particles appeared, though a candidate event once occurred in a cosmic ray observatory in the south of China.

By 1976, quantum chromodynamics (QCD) had convincingly emerged as the established model of hadrons. The effective end of the Straton Model took place at a conference in January 1980 in Conghua, near Hong Kong. Hung-Yuan Tzu, one of the key leaders of the Beijing Group, gave a paper entitled “Reminiscences of the Straton Model”, signalling that physics had moved on.

During our meeting at CERN, Liu showed me photos of the 1980 event. “It was a very important conference in the history of Chinese physics,” she said, “the first opening to Chinese physicists in the West”. Visits by Chinese expatriates were organized by Tsung-Dao Lee and Chen-Ning Yang, who shared the 1957 Nobel Prize for Physics for their work on parity violation.

The critical point

It is easy for westerners to mock the Straton Model; Sheldon Glashow once referred to it as about “Maons”. But Liu sees it as significant research that had many unexpected consequences, such as helping to advance physics research in China. “It gave physicists a way to pursue quantum field theory without having to do national defence work”.

The model also trained young researchers in particle physics and honed their research competence. After the post-Cultural Revolution reform and its opening to the West, these physicists could then integrate into the international community. “The story,” Liu said, “shows how ingeniously the Chinese physicists adapted to the political situation.”

The post The obscure physics theory that helped Chinese science emerge from the shadows appeared first on Physics World.

A surprising critical state emerges in active nematic materials

Lorna Brigham — Wed, 21 Jan 2026 07:47:29 +0000

Nematics are materials made of rod‑like particles that tend to align in the same direction. In active nematics, this alignment is constantly disrupted and renewed because the particles are driven by internal biological or chemical energy. As the orientation field twists and reorganises, it creates topological defects-points where the alignment breaks down. These defects are central to the collective behaviour of active matter, shaping flows, patterns, and self‑organisation.

In this work, the researchers identify an active topological phase transition that separates two distinct regimes of defect organisation. As the system approaches this transition from below, the dynamics slow dramatically: the relaxation of defect density becomes sluggish, fluctuations in the number of defects grow in amplitude and lifetime, and the system becomes increasingly sensitive to small changes in activity. At the critical point, defects begin to interact over long distances, with correlation lengths that grow with system size. This behaviour produces a striking dual‑scaling pattern, defect fluctuations appear uniform at small scales but become anti‑hyperuniform at larger scales, meaning that the number of defects varies far more than expected from a random distribution.

A key finding is that this anti‑hyperuniformity originates from defect clustering. Rather than forming ordered structures or undergoing phase separation, defects tend to appear near existing defects, creating multiscale clusters. This distinguishes the transition from well‑known defect‑unbinding processes such as the Berezinskii-Kosterlitz-Thouless transition in passive nematics or the nematic-isotropic transition in screened active systems. Above the critical activity, the system enters a defect‑laden turbulent state where defects are more uniformly distributed and correlations become short‑ranged and negative.

The researchers confirm these behaviours experimentally using large‑field‑of‑view measurements of endothelial cell monolayers which are the cells that line blood vessels. The same dual‑scaling behaviour, long‑range correlations, and clustering appear in these living tissues, demonstrating that the transition is robust across system sizes, parameter variations, frictional damping, and boundary conditions.

Read the full article

Anti-hyperuniform critical states of active topological defects

Simon Guldager Andersen et al 2025 Rep. Prog. Phys. 88 108101

Do you want to learn more about this topic?

Active phase separation: new phenomenology from non-equilibrium physics M E Cates and C Nardini (2025)

The post A surprising critical state emerges in active nematic materials appeared first on Physics World.

Non-Abelian anyons: anything but easy

Paul Mabey — Wed, 21 Jan 2026 07:42:34 +0000

Topological quantum computing is a proposed approach to building quantum computers that aims to solve one of the biggest challenges in quantum technology: error correction.

In conventional quantum systems, qubits are extremely sensitive to their environment and even tiny disturbances can cause errors. Topological quantum computing addresses this by encoding information in the global properties of a system: the topology of certain quantum states.

These systems rely on the use of non-Abelian anyons, exotic quasiparticles that can exist in two-dimensional materials under special conditions.

The main challenge faced by this approach to quantum computing is the creation and control of these quasiparticles.

One possible source of non-Abelian anyons is the fractional quantum Hall state (FQH): an exotic state of matter which can exist at very low temperatures and high magnetic fields.

These states come in two forms: even-denominator and odd-denominator. Here, we’re interested in the even-denominator states – the more interesting but less well understood of the two.

In this latest work, researchers have observed this exotic state in gallium arsenide (GaAs) two-dimensional hole systems.

Typically, FQH states are isotropic, showing no preferred direction. Here, however, the team found states that are strongly anisotropic, suggesting that the system spontaneously breaks rotational symmetry.

This means that it forms a nematic phase – similar to liquid crystals – where molecules align along a direction without forming a rigid structure.

This spontaneous symmetry breaking adds complexity to the state and can influence how quasiparticles behave, interact, and move.

The observation of the existence of spontaneous nematicity in an even-denominator fractional quantum Hall state is the first of its kind.

Although there are many questions left to be answered, the properties of this system could be hugely important for topological quantum computers as well as other novel quantum technologies.

Read the full article

Even-denominator fractional quantum Hall states with spontaneously broken rotational symmetry – IOPscience

C. Wang et al 2025 Rep. Prog. Phys. 88 100501

The post Non-Abelian anyons: anything but easy appeared first on Physics World.

Physicist Norbert Holtkamp takes over as head of Fermilab

Michael Banks — Tue, 20 Jan 2026 17:49:05 +0000

Particle physicist Norbert Holtkamp has been appointed the new director of Fermi National Accelerator Laboratory. He took up the position on 12 January, replacing Young-Kee Kim from the University of Chicago, who held the job on an interim basis following the resignation of Lia Merminga last year.

With a PhD in physics from the Technical University in Darmstadt, Germany, Holtkamp has managed large scientific projects throughout his career.

Holtkamp is the former deputy director of the SLAC National Accelerator Laboratory at Stanford University where he managedthe construction of the Linac Coherent Light Source upgrade, the world’s most powerful X-ray laser, along with more than $2bn of onsite construction projects.

Holtkamp also previously served as the principal deputy director general for the international fusion project ITER, which is currently under construction in Cadarache, France.

+ +

Holtkamp worked at Fermilab between 1998 and 2001, where he worked on commissioning the Main Injector and also led a study on the feasibility of an intense neutrino source based on a muon storage ring.

One of Holtkamp’s main aims as Fermilab boss will be to oversee the completion of the $5bn Long-Baseline Neutrino Facility-Deep Underground Neutrino Experiment (LBNF-DUNE) at Fermilab, which is expected to come online towards the end of the decade.

LBNF-DUNE will study the properties of neutrinos in unprecedented detail, as well as the differences in behaviour between neutrinos and antineutrinos. The DUNE detector, which lies about 1300 km from Fermilab, will measure the neutrinos that are generated by Fermilab’s accelerator complex, which is just outside Chicago.

In a statement, Holtkamp said he is “deeply honoured” to lead the lab. “Fermilab has done so much to advance our collective understanding of the fundamentals of our universe,” he says. “I am committed to ensuring the laboratory remains the neutrino capital of the world, and the safe and successful completion of LBNF-DUNE is key to that goal. I’m excited to rejoin Fermilab at this pivotal moment to guide this project and our other important modernization efforts to prepare the lab for a bright future.”

Managerial experience

Fermilab has experienced a difficult few years, with questions raised about its internal management and external oversight. In August 2024 a group of anonymous self-styled whistleblowers published a 113-page “white paper” on the arXiv preprint server, asserting that the lab was “doomed without a management overhaul”.

Then in October that year, a new organization – Fermi Forward Discovery Group – was announced to manage the lab for the US Department of Energy. That move came under scrutiny given it is dominated by the University of Chicago and Universities Research Association (URA), a consortium of research universities, which had already been part of the management since 2007. Then a month later, almost 2.5% of Fermilab’s employees were laid off.

“We’re excited to welcome Norbert, who brings of a wealth of scientific and managerial experience to Fermilab,” noted University of Chicago president Paul Alivisatos, who is also chair of the board of directors of Fermi Forward Discovery Group.

Alivisatos thanked Kim for her “tireless service” as director. “[Kim] played a critical role in strengthening relationships with Fermilab’s leading stakeholders, driving the lab’s modernization efforts, and positioning Fermilab to amplify DOE’s broader goals in areas like quantum science and AI,” added Alivisatos.

The post Physicist Norbert Holtkamp takes over as head of Fermilab appeared first on Physics World.

CERN accepts $1bn in private cash towards Future Circular Collider

Michael Banks — Mon, 19 Jan 2026 13:00:02 +0000

The CERN particle-physics lab near Geneva has received $1bn from private donors towards the construction of the Future Circular Collider (FCC). The cash marks the first time in the lab’s 72-year history that individuals and philanthropic foundations have agreed to support a major CERN project. If built, the FCC would be the successor to the Large Hadron Collider (LHC), where the Higgs boson was discovered.

CERN originally released a four-volume conceptual design report for the FCC in early 2019, with more detail included in a three-volume feasibility study that came out last year. It calls for a giant tunnel some 90.7 km in circumference – roughly three times as long as the LHC – that would be built about 200m underground on average.

+ +

The FCC has been recommended as the preferred option for the next flagship collider at CERN in the ongoing process to update the European Strategy for Particle Physics, which will be passed over to the CERN Council in May 2026.If the plans are given the green light by CERN Council in 2028, construction on the FCC electron-positron machine, dubbed FCC-ee, would begin in 2030. It would start operations in 2047, a few years after the High Luminosity LHC (HL-LHC) closes down, and run for about 15 years until the early 2060s.

The FCC-ee would focus on creating a million Higgs particles in total to allow physicists to study its properties with an accuracy an order of magnitude better that possible with the LHC. The FCC feasibility study then calls for a hadron machine, dubbed FCC-hh, to replace the FCC-ee in the existing 91 km tunnel. It would be a “discovery machine”, smashing together protons at high energy – about 85 TeV – with the aim of creating new particles. If built, the FCC-hh will begin operation in 2073 and run to the end of the century.

The funding model for the FCC-ee, which is expected to have a price tag of about $18bn, is still a work in progress. But it is estimated that at least two-thirds of the construction costs will come from CERN’s 24 member states with the rest needing to be found elsewhere. One option to plug that gap is private donations and in late December CERN received a significant boost from several organizations including the Breakthrough Prize Foundation, the Eric and Wendy Schmidt Fund for Strategic Innovation, and the entrepreneurs John Elkann and Xavier Niel. Together, they pledged a total of $1bn towards the FCC-ee.

Costas Fountas, president of the CERN Council says CERN is “extremely grateful” for the interest. “This once again demonstrates CERN’s relevance and positive impact on society, and the strong interest in CERN’s future that exists well beyond our own particle physics community,” he notes.

Eric Schmidt, who founded Google, claims that he and Wendy Schmidt were “inspired by the ambition of this project and by what it could mean for the future of humanity”. The FCC, he believes, is an instrument that “could push the boundaries of human knowledge and deepen our understanding of the fundamental laws of the Universe” and could lead to technologies that could benefit society “in profound ways” from medicine to computing to sustainable energy.

The cash promised has been welcomed by outgoing CERN director-general Fabiola Gianotti. “It’s the first time in history that private donors wish to partner with CERN to build an extraordinary research instrument that will allow humanity to take major steps forward in our understanding of fundamental physics and the universe,” she said. “I am profoundly grateful to them for their generosity, vision, and unwavering commitment to knowledge and exploration.”

Further boost

The cash comes a few months after the Circular Electron–Positron Collider (CEPC) – a rival collider to the FCC-ee that also involves building a huge 100 km tunnel to study the Higgs in unprecedented detail – was not considered for inclusion in China’s next five-year plan, which runs from 2026–2030. There has been much discussion in China whether the CEPC is the right project for the country, with the collider facing criticism from particle physicist and Nobel laureate Chen-Ning Yang, before he died last year.

Wang Yifang of the Institute of High Energy Physics (IHEP) in Beijing says they will submit the CEPC for consideration again in 2030 unless FCC is officially approved before then. But for particle theorist John Ellis from Kings College London, China’s decision to effectively put the CEPC on the back burner “certainly simplifies the FCC discussion”. “However, an opportunity for growing the world particle physics community has been lost, or at least deferred [by the decision],” Ellis told Physics World.

Ellis adds, however, that he would welcome China’s participation in the FCC. “Their accelerator and detector [technical design reviews] show that they could bring a lot to the table, if the political obstacles can be overcome,” he says.

However, if the FCC-ee goes ahead China could perhaps make significant “in-kind” contributions rather like those that occur with the ITER experimental fusion reactor, which is currently being built in France. In this case, instead of cash payments, the countries provide components, equipment and other materials.

Those considerations and more will now fall to the British physicist Mark Thomson, who took over from Gianotti as CERN director-general on 1 January for a five-year term. As well as working on funding requirements for the FCC-ee, top of his in-tray will actually be shutting down the LHC in June to make way for further work on the HL-LHC, which involves installing powerful new superconducting magnets and improving the detection.

About 90% of the 27 km LHC accelerator will be affected by the upgrade with a major part being to replace the magnets in the final focus systems of the two large experiments, ATLAS and CMS. These magnets will take the incoming beams and then focus them down to less than 10 microns in cross section. The upgrade includes the installation of brand new state-of-the-art niobium-tin (Nb₃Sn) superconducting focusing magnets.

The HL-LHC will probably not turn on until 2030, which is when Thomson’s term will nearly be over but that doesn’t deter him from leading the world’s foremost particle-physics lab. “It’s an incredibly exciting project,” Thomson told the Guardian. “It’s more interesting than just sitting here with the machine hammering away.”

The post CERN accepts $1bn in private cash towards Future Circular Collider appeared first on Physics World.

Polarization-sensitive photoacoustic microscopy reveals heart tissue health

Tami Freeman — Mon, 19 Jan 2026 09:30:58 +0000

Imaging tissue fibrosis (a) Mid-infrared dichroism-sensitive photoacoustic microscopy (MIR-DS-PAM) images of cell-induced fibrosis (CIF) and normal control (NC) tissue; (c) MIR-DS-PAM images of drug-induced fibrosis (DIF) and NC tissue; (b) and (d) show the corresponding confocal fluorescence microscopy (CFM) images. Scale bars: 500 µm. (Courtesy: CC-BY 4.0/Light Sci. Appl. 10.1038/s41377-025-02117-0)

Many of the tissues in the human body rely upon highly organized microstructures to function effectively. If the collagen fibres in heart muscle become disordered, for instance, this can lead to or reflect disorders such as fibrosis and cancer. To image and analyse such structural changes, researchers at Pohang University of Science and Technology (POSTECH) in Korea have developed a new label-free microscopy technique and demonstrated its use in engineered heart tissue.

The ability to assess the alignment of microstructures such as protein fibres within tissue’s extracellular matrix provides a valuable tool for diagnosing disease, monitoring therapy response and evaluating tissue engineering models. Currently, however, this is achieved using histological imaging methods based on immunofluorescent staining, which can be labour-intensive and sensitive to the imaging conditions and antibodies used.

Instead, a team headed up by Chulhong Kim and Jinah Jang is investigating photoacoustic microscopy (PAM), a label-free imaging modality that relies on light absorption by endogenous tissue chromophores to reveal structural and functional information. In particular, PAM with mid-infrared (MIR) incident light provides bond-selective, high-contrast imaging of proteins, lipids and carbohydrates. The researchers also incorporated dichroism-sensitive (DS) functionality, resulting in a technique referred to as MIR-DS-PAM.

+ +

“Dichroism-sensitivity enables the quantitative assessment of fibre alignment by detecting the polarization-dependent absorption of anisotropic materials like collagen,” explains first author Eunwoo Park. “This adds a new contrast mechanism to conventional photoacoustic imaging, allowing simultaneous visualization of molecular content and microstructural organization without any labelling.”

Park and colleagues constructed a MIR-DS-PAM system using a pulsed quantum cascade laser as the light source. They tuned the laser to a centre wavelength of 6.0 µm to correspond with an absorption peak from the C=O stretching vibration in proteins. The laser beam was linearly polarized, modulated by a half-wave plate and used to illuminate the target tissue.

Tissue analysis

To validate the functionality of their MIR-DS-PAM technique, the researchers used it to image a formalin-fixed section of engineered heart tissue (EHT). They obtained images at four incident angles and used the acquired photoacoustic data to calculate the photoacoustic amplitude, which visualizes the protein content, as well as the degree of linear dichroism (DoLD) and the orientation angle of linear dichroism (AoLD), which reveal the extracellular matrix alignment.

“Cardiac tissue features highly aligned extracellular matrix with complex fibre orientation and layered architecture, which are critical to its mechanical and electrical function,” Park explains. “These properties make it an ideal model for demonstrating the ability of MIR-DS-PAM to detect physiologically relevant histostructural and fibrosis-related changes.”

The researchers also used MIR-DS-PAM to quantify the structural integrity of EHT during development, using specimens cultured for one to five days before fixing. Analysis of the label-free images revealed that as the tissue matured, the DoLD gradually increased, while the standard deviation of the AoLD decreased – indicating increased protein accumulation with more uniform fibre alignment over time. They note that these results agree with those from immunofluorescence-stained confocal fluorescence microscopy.

Next, they examined diseased EHT with two types of fibrosis: cell-induced fibrosis (CIF) and drug-induced fibrosis (DIF). In the CIF sample, the average photoacoustic amplitude and AoLD uniformity were both lower than found in normal EHT, indicating reduced protein density and disrupted fibre alignment. DIF exhibited a higher photoacoustic amplitude and lower AoLD uniformity than normal EHT, suggesting extensive extracellular matrix accumulation with disorganized orientation.

Both CIF and DIF showed a slight reduction in DoLD, again signifying a disorganized tissue structure, a common hallmark of fibrosis. The two fibrosis types, however, exhibited diverse biochemical profiles and different levels of mechanical dysfunction. The findings demonstrate the ability of MIR-DS-PAM to distinguish diseased from healthy tissue and identify different types of fibrosis. The researchers also imaged a tissue assembly containing both normal and fibrotic EHT to show that MIR-DS-PAM can capture features in a composite sample.

+ +

They conclude that MIR-DS-PAM enables label-free monitoring of both tissue development and fibrotic remodelling. As such, the technique shows potential for use within tissue engineering research, as well as providing a diagnostic tool for assessing tissue fibrosis or remodelling in biopsied samples. “Its ability to visualize both biochemical composition and structural alignment could aid in identifying pathological changes in cardiological, musculoskeletal or ocular tissues,” says Park.

“We are currently expanding the application of MIR-DS-PAM to disease contexts where extracellular matrix remodelling plays a central role,” he adds. “Our goal is to identify label-free histological biomarkers that capture both molecular and structural signatures of fibrosis and degeneration, enabling multiparametric analysis in pathological conditions.”

The researchers describe their microscopy technique in Light: Science & Applications.

The post Polarization-sensitive photoacoustic microscopy reveals heart tissue health appeared first on Physics World.

Astronomer Daniel Jaffe named president of the Giant Magellan Telescope project

Fri, 16 Jan 2026 15:30:52 +0000

Scientific collaborations increasingly more likely to be led by Chinese scientists, finds study

No Author — Thu, 06 Nov 2025 15:09:37 +0000

International research collaborations will be increasingly led by scientists in China over the coming decade. That is according to a new study by researchers at the University of Chicago, which finds that the power balance in international science has shifted markedly away from the US and towards China over the last 25 years (Proc. Natl. Acad. Sci. 122 e2414893122).

To explore China’s role in global science, the team used a machine-learning model to predict the lead researchers of almost six million scientific papers that involved international collaboration listed by online bibliographic catalogue OpenAlex. The model was trained on author data from 80 000 papers published in high-profile journals that routinely detail author contributions, including team leadership.

- -

The study found that between 2010 and 2012 there were only 4429 scientists from China who were likely to have led China-US collaborations. By 2023, this number had risen to 12714, meaning that the proportion of team leaders affiliated with Chinese institutions had risen from 30% to 45%.

Key areas

If this trend continues, China will hit “leadership parity” with the US in chemistry, materials science and computer science by 2028, with maths, physics and engineering being level by 2031. The analysis also suggests that China will achieve leadership parity with the US in eight “critical technology” areas by 2030, including AI, semiconductors, communications, energy and high-performance computing.

- -

For China-UK partnerships, the model found that equality had already been reached in 2019, while EU and China leadership roles will be on par this year or next. The authors also found that China has been actively training scientists in nations in the “Belt and Road Initiative” which seeks to connect China closer to the world through investments and infrastructure projects.

This, the researchers warn, limits the ability to isolate science done in China. Instead, they suggest that it could inspire a different course of action, with the US and other countries expanding their engagement with the developing world to train a global workforce and accelerate scientific advancements beneficial to their economies.

The post Scientific collaborations increasingly more likely to be led by Chinese scientists, finds study appeared first on Physics World.

Unlocking the potential of 2D materials: graphene and much more

Hamish Johnston — Thu, 06 Nov 2025 14:49:34 +0000

This episode explores the scientific and technological significance of 2D materials such as graphene. My guest is Antonio Rossi, who is a researcher in 2D materials engineering at the Italian Institute of Technology in Genoa.

- -

Rossi explains why 2D materials are fundamentally different than their 3D counterparts – and how these differences are driving scientific progress and the development of new and exciting technologies.

Graphene is the most famous 2D material and Rossi talks about today’s real-world applications of graphene in coatings. We also chat about the challenges facing scientists and engineers who are trying to exploit graphene’s unique electronic properties.

Rossi’s current research focuses on two other promising 2D materials – tungsten disulphide and hexagonal boron nitride. He explains why tungsten disulphide shows great technological promise because of its favourable electronic and optical properties; and why hexagonal boron nitride is emerging as an ideal substrate for creating 2D devices.

Artificial intelligence (AI) is becoming an important tool in developing new 2D materials. Rossi explains how his team is developing feedback loops that connect AI with the fabrication and characterization of new materials. Our conversation also touches on the use of 2D materials in quantum science and technology.

IOP Publishing’s new Progress In Series: Research Highlights website offers quick, accessible summaries of top papers from leading journals like Reports on Progress in Physics and Progress in Energy. Whether you’re short on time or just want the essentials, these highlights help you expand your knowledge of leading topics.

The post Unlocking the potential of 2D materials: graphene and much more appeared first on Physics World.

Ultrasound probe maps real-time blood flow across entire organs

Tami Freeman — Thu, 06 Nov 2025 09:35:19 +0000

Microcirculation – the flow of blood through the smallest vessels – is responsible for distributing oxygen and nutrients to tissues and organs throughout the body. Mapping this flow at the whole-organ scale could enhance our understanding of the circulatory system and improve diagnosis of vascular disorders. With this aim, researchers at the Institute Physics for Medicine Paris (Inserm, ESPCI-PSL, CNRS) have combined 3D ultrasound localization microscopy (ULM) with a multi-lens array method to image blood flow dynamics in entire organs with micrometric resolution, reporting their findings in Nature Communications.

“Beyond understanding how an organ functions across different spatial scales, imaging the vasculature of an entire organ reveals the spatial relationships between macro- and micro-vascular networks, providing a comprehensive assessment of its structural and functional organization,” explains senior author Clement Papadacci.

The 3D ULM technique works by localizing intravenously injected microbubbles. Offering a spatial resolution roughly ten times finer than conventional ultrasound, 3D ULM can map and quantify micro-scale vascular structures. But while the method has proved valuable for mapping whole organs in small animals, visualizing entire organs in large animals or humans is hindered by the limitations of existing technology.

To enable wide field-of-view coverage while maintaining high-resolution imaging, the team – led by PhD student Nabil Haidour under Papadacci’s supervision – developed a multi-lens array probe. The probe comprises an array of 252 large (4.5 mm²) ultrasound transducer elements. The use of large elements increases the probe’s sensitive area to a total footprint of 104 x 82 mm, while maintaining a relatively low element count.

Each transducer element is equipped with an individual acoustic diverging lens. “Large elements alone are too directive to create an image, as they cannot generate sufficient overlap or interference between beams,” Papadacci explains. “The acoustic lenses reduce this directivity, allowing the elements to focus and coherently combine signals in reception, thus enabling volumetric image formation.”

Whole-organ imaging

After validating their method via numerical simulations and phantom experiments, the team used a multi-lens array probe driven by a clinical ultrasound system to perform 3D dynamic ULM of an entire explanted porcine heart – considered an ideal cardiac model as its vascular anatomies and dimensions are comparable to those of humans.

- -

The heart was perfused with microbubble solution, enabling the probe to visualize the whole coronary microcirculation network over a large volume of 120 x 100 x 82 mm, with a spatial resolution of around 125 µm. The technique enabled visualization of both large vessels and the finest microcirculation in real time. The team also used a skeletonization algorithm to measure vessel radii at each voxel, which ranged from approximately 75 to 600 µm.

As well as structural imaging, the probe can also assess flow dynamics across all vascular scales, with a high temporal resolution of 312 frames/s. By tracking the microbubbles, the researchers estimated absolute flow velocities ranging from 10 mm/s in small vessels to over 300 mm/s in the largest. They could also differentiate arteries and veins based on the flow direction in the coronary network.

In vivo demonstrations

Next, the researchers used the multi-lens array probe to image the entire kidney and liver of an anaesthetized pig at the Veterinary school of Maison Alfort, with the probe positioned in front of the kidney or liver, respectively, and held using an articulated arm. They employed electrocardiography to synchronize the ultrasound acquisitions with periods of minimal respiratory motion and injected microbubble solution intravenously into the animal’s ear.

In vivo imaging Left: 3D microbubble density map of the porcine kidney. Centre: 3D flow map of microbubble velocity distribution. Right: 3D flow map showing arterial (red) and venous (blue) flow. (Courtesy: CC BY 4.0/Nat. Commun. 10.1038/s41467-025-64911-z)

The probe mapped the vascular network of the kidney over a 60 x 80 x 40 mm volume with a spatial resolution of 147 µm. The maximum 3D absolute flow velocity was approximately 280 mm/s in the large vessels and the vessel radii ranged from 70 to 400 µm. The team also used directional flow measurements to identify the arterial and venous flow systems.

Liver imaging is more challenging due to respiratory, cardiac and stomach motions. Nevertheless, 3D dynamic ULM enabled high-depth visualization of a large volume of liver vasculature (65 x 100 x 82 mm) with a spatial resolution of 200 µm. Here, the researchers used dynamic velocity measurement to identify the liver’s three blood networks (arterial, venous and portal veins).

“The combination of whole-organ volumetric imaging with high-resolution vascular quantification effectively addresses key limitations of existing modalities, such as ultrasound Doppler imaging, CT angiography and 4D flow MRI,” they write.

- -

Clinical applications of 3D dynamic ULM still need to be demonstrated, but Papadacci suggests that the technique has strong potential for evaluating kidney transplants, coronary microcirculation disorders, stroke, aneurysms and neoangiogenesis in cancer. “It could also become a powerful tool for monitoring treatment response and vascular remodelling over time,” he adds.

Papadacci and colleagues anticipate that translation to human applications will be possible in the near future and plan to begin a clinical trial early in 2026.

The post Ultrasound probe maps real-time blood flow across entire organs appeared first on Physics World.

Inge Lehmann: the ground-breaking seismologist who faced a rocky road to success

Kate Gardner — Wed, 05 Nov 2025 14:00:18 +0000

Enigmatic Inge Lehmann around the time she quit her job at Denmark’s Geodetic Institute in 1953. (Courtesy: GEUS)

In the 1930s a little-known Danish seismologist calculated that the Earth has a solid inner core, within the liquid outer core identified just a decade earlier. The international scientific community welcomed Inge Lehmann as a member of the relatively new field of geophysics – yet in her home country, Lehmann was never really acknowledged as more than a very competent keeper of instruments.

It was only after retiring from her seismologist job aged 65 that Lehmann was able to devote herself full time to research. For the next 30 years, Lehmann worked and published prolifically, finally receiving awards and plaudits that were well deserved. However, this remarkable scientist, who died in 1993 aged 104, rarely appears in short histories of her field.

In a step to address this, we now have a biography of Lehmann: If I Am Right, and I Know I Am by Hanne Strager, a Danish biologist, science museum director and science writer. Strager pieces together Lehmann’s life in great detail, as well as providing potted histories of the scientific areas that Lehmann contributed to.

A brief glance at the chronology of Lehmann’s education and career would suggest that she was a late starter. She was 32 when she graduated with a bachelor’s degree in mathematics from the University of Copenhagen, 40 when she received her master’s degree in geodosy and was appointed state geodesist for Denmark. Lehmann faced a litany of struggles in her younger years, from health problems and money issues to the restrictions placed on most women’s education in the first decades of the 20th century.

The limits did not come from her family. Lehmann and her sister were sent to good schools, she was encouraged to attend university, and was never pressed to get married, which would likely have meant the end of her education. When she asked her father’s permission to go to the University of Cambridge, his objection was the cost – though the money was found and Lehmann duly went to Newnham College in 1910. While there she passed all the preliminary exams to study for Cambridge’s legendarily tough mathematical tripos but then her health forced her to leave.

- -

Lehmann was suffering from stomach pains; she had trouble sleeping; her hair was falling out. And this was not her first breakdown. She had previously studied for a year at the University of Copenhagen before then, too, dropping out and moving to the countryside to recover her health.

The cause of Lehmann’s recurrent breakdowns is unknown. They unfortunately fed into the prevailing view of the time that women were too fragile for the rigours of higher learning. Strager attempts to unpick these historical attitudes from Lehmann’s very real medical issues. She posits that Lehmann had severe anxiety or a physical limitation to how hard she could push herself. But this conclusion fails to address the hostile conditions Lehmann was working in.

In Cambridge Lehmann formed firm friendships that lasted the rest of her life. But women there did not have the same access to learning as men. They were barred from most libraries and laboratories; could not attend all the lectures; were often mocked and belittled by professors and male students. They could sit exams but, even if they passed, would not be awarded a degree. This was a contributing factor when after the First World War Lehmann decided to complete her undergraduate studies in Copenhagen rather than Cambridge.

More than meets the eye

Lehmann is described as quiet, shy, reticent. But she could be eloquent in writing and once her career began she established connections with scientists all over the world by writing to them frequently. She was also not the wallflower she initially appeared to be. When she was hired as an assistant at Denmark’s Institute for the Measurement of Degrees, she quickly complained that she was being using as an office clerk, not a scientist, and she would not have accepted the job had she known this was the role. She was instead given geometry tasks that she found intellectually stimulating, which led her to seismology.

Unfortunately, soon after this Lehmann’s career development stalled. While her title of “state geodesist” sounds impressive, she was the only seismologist in Denmark for decades, responsible for all the seismographs in Denmark and Greenland. Her days were filled with the practicalities of instrument maintenance and publishing reports of all the data collected.

Intrepid Inge Lehmann at the Ittoqqortootmitt (Scoresbysund) seismic station in Greenland c. 1928. A keen hiker, Lehmann was comfortable in cold and remote environments. (Courtesy: GEUS)

Despite repeated requests Lehmann didn’t receive an assistant, which meant she never got round to completing a PhD, though she did work towards one in her evenings and weekends. Time and again opportunities for career advancement went to men who had the title of doctor but far less real experience in geophysics. Even after she co-founded the Danish Geophysical Society in 1934, her native country overlooked her.

The breakthrough that should have changed this attitude from the men around her came in 1936, when she published “P’ ”. This innocuous sounding paper was revolutionary, but based firmly in the P wave and S wave measurements that Lehmann routinely monitored.

In If I Am Right, and I Know I Am, Strager clearly explains what P and S waves are. She also highlights why they were being studied by both state seismologist Lehmann and Cambridge statistician Harold Jeffreys, and how they led to both scientists’ biggest breakthroughs.

After any seismological disturbance, P and S waves propagate through the Earth. P waves move at different speeds according to the material they encounter, while S waves cannot pass through liquid or air. This knowledge allowed Lehmann to calculate whether any fluctuations in seismograph readings were earthquakes, and if so where the epicentre was located. And it led to Jeffreys’ insight that the Earth must have a liquid core.

Lehmann’s attention to detail meant she spotted a “discontinuity” in P waves that did not quite match a purely liquid core. She immediately wrote to Jeffreys that she believed there was another layer to the Earth, a solid inner core, but he was dismissive – which led to her writing the statement that forms the title of this book. Undeterred, she published her discovery in the journal of the International Union of Geodesy and Geophysics.

Home from home

In 1951 Lehmann visited the institution that would become her second home: the Lamont Geological Observatory in New York state. Its director Maurice Ewing invited her to work there on a sabbatical, arranging all the practicalities of travel and housing on her behalf.

Here, Lehmann finally had something she had lacked her entire career: friendly collaboration with colleagues who not only took her seriously but also revered her. Lehmann took retirement from her job in Denmark and began to spend months of every year at the Lamont Observatory until well into her 80s.

Valued colleague A farewell party held for Inge Lehmann in 1954 at Lamont Geological Observatory after one of her research stays. (Courtesy: GEUS)

Though Strager tells us this “second phase” of Lehmann’s career was prolific, she provides little detail about the work Lehmann did. She initially focused on detecting nuclear tests during the Cold War. But her later work was more varied, and continued after she lost most of her vision. Lehmann published her final paper aged 99.

If I Am Right, and I Know I Am is bookended with accounts of Strager’s research into one particular letter sent to Lehmann, an anonymous (because the final page has been lost) declaration of love. It’s an insight into the lengths Strager went to – reading all the surviving correspondence to and from Lehmann; interviewing living relatives and colleagues; working with historians both professional and amateur; visiting archives in several countries.

But for me it hit the wrong tone. The preface and epilogue are mostly speculation about Lehmann’s love life. Lehmann destroyed a lot of her personal correspondence towards the end of her life, and chose what papers to donate to an archive. To me those are the actions of a woman who wants to control the narrative of her life – and does not want her romances to be written about. I would have preferred instead another chapter about her later work, of which we know she was proud.

But for the majority of its pages, this is a book of which Strager can be proud. I came away from it with great admiration for Lehmann and an appreciation for how lonely life was for many women scientists even in recent history.

2025 Columbia University Press 308 pp, £25hb

The post Inge Lehmann: the ground-breaking seismologist who faced a rocky road to success appeared first on Physics World.

Rapidly spinning black holes put new limit on ultralight bosons

No Author — Wed, 05 Nov 2025 12:28:51 +0000

The LIGO–Virgo–KAGRA collaboration has detected strong evidence for second-generation black holes, which were formed from earlier mergers of smaller black holes. The two gravitational wave signals provide one of the strongest confirmations to date for how Einstein’s general theory of relativity describes rotating black holes. Studying such objects also provides a testbed for probing new physics beyond the Standard Model.

- -

Over the past decade, the global network of interferometers operated by LIGO, Virgo, and KAGRA have detected close to 300 gravitational waves (GWs) – mostly from the mergers of binary black holes.

In October 2024 the network detected a clear signal that pointed back to a merger that occurred 700 million light-years away. The progenitor black holes were 20 and 6 solar masses and the larger object was spinning at 370 Hz, which makes it one of the fastest-spinning black holes ever observed.

Just one month later, the collaboration detected the coalescence of another highly imbalanced binary (17 and 8 solar masses), 2.4 billion light-years away. This signal was even more unusual – showing for the first time that the larger companion was spinning in the opposite direction of the binary orbit.

Massive and spinning

While conventional wisdom says black holes should not be spinning at such high rates, the observations were not entirely unexpected. “With both events having one black hole, which is both significantly more massive than the other and rapidly spinning, [the observations] provide tantalizing evidence that these black holes were formed from previous black hole mergers,” explains Stephen Fairhurst at Cardiff University, spokesperson of the LIGO Collaboration. If this were the case, the two GW signals – called GW241011 and GW241110 – are first observations of second-generation black holes. This is because when a binary merges, the resulting second-generation object tends to have a large spin.

The GW241011 signal was particularly clear, which allowed the team to make the third-ever observation of higher harmonic modes. These are overtones in the GW signal that become far clearer when the masses of the coalescing bodies are highly imbalanced.

The precision of the GW241011 measurement provides one of the most stringent verifications so far of general relativity. The observations also support Roy Kerr’s prediction that rapid rotation distorts the shape of a black hole.

Kerr and Einstein confirmed

“We now know that black holes are shaped like Einstein and Kerr predicted, and general relativity can add two more checkmarks in its list of many successes,” says team member Carl-Johan Haster at the University of Nevada, Las Vegas. “This discovery also means that we’re more sensitive than ever to any new physics that might lie beyond Einstein’s theory.”

This new physics could include hypothetical particles called ultralight bosons. These could form in clouds just outside the event horizons of spinning black holes, and would gradually drain a black hole’s rotational energy via a quantum effect called superradiance.

- -

The idea is that the observed second-generation black holes had been spinning for billions of years before their mergers occurred. This means that if ultralight bosons were present, they cannot have removed lots of angular momentum from the black holes. This places the tightest constraint to date on the mass of ultralight bosons.

“Planned upgrades to the LIGO, Virgo and KAGRA detectors will enable further observations of similar systems,” Fairhurst says. “They will enable us to better understand both the fundamental physics governing these black hole binaries and the astrophysical mechanisms that lead to their formation.”

Haster adds, “Each new detection provides important insights about the universe, reminding us that each observed merger is both an astrophysical discovery but also an invaluable laboratory for probing the fundamental laws of physics”.

The observations are described in The Astrophysical Journal Letters.

The post Rapidly spinning black holes put new limit on ultralight bosons appeared first on Physics World.

Making quantum computers more reliable

Lorna Brigham — Wed, 05 Nov 2025 08:42:53 +0000

Quantum error correction codes protect quantum information from decoherence and quantum noise, and are therefore crucial to the development of quantum computing and the creation of more reliable and complex quantum algorithms. One example is the five-qubit error correction code, five being the minimum number of qubits required to fix single-qubit errors. These contain five physical qubits (a basic off/on unit of quantum information made using trapped ions, superconducting circuits, or quantum dots) to correct one logical qubit (a collection of physical qubits arranged in such a way as to correct errors). Yet imperfections in the hardware can still lead to quantum errors.

A method of testing quantum error correction codes is self-testing. Self-testing is a powerful tool for verifying quantum properties using only input-output statistics, treating quantum devices as black boxes. It has evolved from bipartite systems consisting of two quantum subsystems, to multipartite entanglement, where entanglement is among three or more subsystems, and now to genuinely entangled subspaces, where every state is fully entangled across all subsystems. Genuinely entangled subspaces offer stronger, guaranteed entanglement than general multipartite states, making them more reliable for quantum computing and error correction.

In this research, self-testing techniques are used to certify genuinely entangled logical subspaces within the five-qubit code on photonic and superconducting platforms. This is achieved by preparing informationally complete logical states that span the entire logical space, meaning the set is rich enough to fully characterize the behaviour of the system. They deliberately introduce basic quantum errors by simulating Pauli errors on the physical qubit, which mimics real-world noise. Finally, they use mathematical tests known as Bell inequalities, adapted to the framework used in quantum error correction, to check whether the system evolves in the initial logical subspaces after the errors are introduced.

Extractability measures tell you how close the tested quantum system is to the ideal target state, with 1 being a perfect match. The certification is supported by extractability measures of at least 0.828 ± 0.006 and 0.621 ± 0.007 for the photonic and superconducting systems, respectively. The photonic platform achieved a high extractability score, meaning the logical subspace was very close to the ideal one. The superconducting platform had a lower score but still showed meaningful entanglement. These scores show that the self-testing method works in practice and confirm strong entanglement in the five-qubit code on both platforms.

This research contributes to the advancement of quantum technologies by providing robust methods for verifying and characterizing complex quantum structures, which is essential for the development of reliable and scalable quantum systems. It also demonstrates that device-independent certification can extend beyond quantum states and measurements to more general quantum structures.

Read the full article

Certification of genuinely entangled subspaces of the five qubit code via robust self-testing

Yu Guo et al 2025 Rep. Prog. Phys. 88 050501

Do you want to learn more about this topic?

Quantum error correction for beginners by Simon J Devitt, William J Munro and Kae Nemoto (2013)

The post Making quantum computers more reliable appeared first on Physics World.