In 2009, NASA’s Chandra X-ray Observatory released a captivating image: a pulsar and its surrounding nebula that is shaped like a hand. Since then, astronomers have used Chandra and other telescopes to continue to observe this object. Now, new radio data from the Australia Telescope Compact Array (ATCA) has been combined with Chandra’s X-ray data to provide a fresh view of this exploded star and its environment, to help understand its peculiar properties and shape.
At the center of this new image lies the pulsar B1509-58, a rapidly spinning neutron star that is only about 12 miles in diameter. This tiny object is responsible for producing an intricate nebula (called MSH 15–52) that spans over 150 light-years, or about 900 trillion miles. The nebula, which is produced by energetic particles, resembles a human hand with a palm and extended fingers pointing to the upper right in X-rays.
The collapse of a massive star created the pulsar when much of the star crashed inward once it burned through its sustainable nuclear fuel. An ensuing explosion sent the star’s outer layers outward into space as a supernova.
Photovoltaics (PVs), technological systems that can convert sunlight into electricity are among the most promising and widely adopted clean energy solutions worldwide. While existing silicon-based solar cells have already achieved remarkable performances, energy engineers have been working to develop other photovoltaic technologies that could be even more durable, efficient and affordable.
An emerging type of solar cells that could be manufactured at a lower cost, while still retaining good efficiencies, are those based on a class of materials with a characteristic arrangement of atoms, known as perovskites. These cells, known as perovskite solar cells (PSCs), have been found to attain high power conversion efficiencies and are based on materials that could be easier to synthesize when compared to silicon wafers.
Despite their potential, PSCs still face considerable limitations that have so far prevented their widespread deployment and commercialization. Most notably, improving the efficiency of these cells has been found to adversely impact their stability over time, and vice versa.
Graphene, a single sheet of carbon atoms arranged in a honeycomb lattice, is known for its exceptional strength, flexibility and conductivity. However, despite holding the world record for room-temperature electron mobility, graphene’s performance at cryogenic temperatures has remained below that of the best gallium arsenide (GaAs)-based semiconductor systems, which have benefited from many decades of refinement.
One key obstacle is electronic disorder. In practical devices, graphene is highly sensitive to stray electric fields from charged defects in surrounding materials. These imperfections create spatial fluctuations in charge density, known as electron-hole puddles, that scatter electrons and limit mobility. This disorder has prevented graphene from realizing its full potential as an ultra-clean electronic system.
Now, in two parallel studies, researchers from the National University of Singapore (NUS) and The University of Manchester (UK) report distinct strategies that finally push graphene past this long-standing benchmark. The results set new records for electron mobility, matching and in some cases surpassing GaAs in both transport and quantum mobility, and enabling the observation of quantum effects in unprecedented conditions.
In everyday life, all matter exists as either a gas, liquid, or solid. In quantum mechanics, however, it is possible for two distinct states to exist simultaneously. An ultracold quantum system, for instance, can exhibit the properties of both a fluid and a solid at the same time.
The Synthetic Quantum Systems research group at Heidelberg University has now demonstrated this phenomenon using a new experimental approach, by feeding a small amount of energy into a superfluid. They showed that, in a driven quantum system of this kind, sound waves propagate at two different speeds, which points toward coexisting liquid and solid states, a hallmark of supersolidity. The work is published in the journal Nature Physics.
This surprising and seemingly contradictory behavior of two states of matter existing at the same time does not occur at room temperature. But at ultralow temperatures, quantum mechanics takes over, and matter can exhibit fundamentally different properties. When atoms are cooled to such low temperatures, their wave-like nature is dominant. If brought close enough together, many particles merge into one large wave, known as a Bose-Einstein condensate. This state is a superfluid, a fluid that flows without friction.
The formulation of quantum field theory in Minkowski spacetime, which emerges from the unification of special relativity and quantum mechanics, is based on treating time as a parameter, assuming a fixed arrow of time, and requiring that field operators commute for spacelike separations. This procedure is questioned in the context of quantum field theory in curved spacetime (QFTCS). In 1935, Einstein and Rosen (ER), in their seminal paper [1] proposed that “a particle in the physical Universe has to be described by mathematical bridges connecting two sheets of spacetime” which involved two arrows of time. We further establish that the quantum effects at gravitational horizons aesthetically involve the physics of quantum inverted harmonic oscillators that have phase space horizons. Recently proposed direct-sum quantum theory reconciles the ER’s vision by introducing geometric superselection sectors associated with the regions of spacetime related by discrete transformations. This new understanding of the ER bridges promises a unitary description of QFTCS, along with observer complementarity. Furthermore, we present compelling evidence for our new understanding of ER bridges in the form of large-scale parity asymmetric features in the cosmic microwave background, which is statistically 650 times stronger than the standard scale-invariant power spectrum from the typical understanding of inflationary quantum fluctuations when compared with the posterior probabilities associated with the model given the data. We finally discuss the implications of this new understanding in combining gravity and quantum mechanics.
Gravity and quantum mechanics.
Quantum technologies, devices that work by leveraging quantum mechanical effects, could outperform classical technologies in some fields and settings. The so-called spin (i.e., intrinsic angular momentum) carried by quantum particles is central to the functioning of quantum systems, as it can store quantum information.
To reliably share quantum information across a network, however, spins need to be linked to photons (i.e., particles of light). For decades, engineers and quantum physicists have thus been trying to devise approaches to interface spins and photons.
One strategy to achieve this entails the use of quantum dots, nanoscale semiconductor structures that can trap electrons or holes in distinct energy levels. When placed in carefully engineered optical resonators known as microcavities, these structures can generate individual photons. Nonetheless, ensuring that the coherence of spins is not disrupted by magnetic noise originating from nearby nuclear spins and thus facilitating the preservation of quantum information over time has so far proved challenging.
The Jiangmen Underground Neutrino Observatory (JUNO) has successfully completed filling its 20,000-tons liquid scintillator detector and began taking data on Aug. 26.
After more than a decade of preparation and construction, JUNO is the first of a new generation of very large neutrino experiments to reach this stage. Initial trial operations and data taking show that key performance indicators met or exceeded design expectations, enabling JUNO to tackle one of this decade’s major open questions in particle physics: the ordering of neutrino masses—whether the third mass state (ν₃) is heavier than the second (ν₂).
Prof. Wang Yifang, a researcher at the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences and JUNO spokesperson, said, “Completing the filling of the JUNO detector and starting data taking marks a historic milestone. For the first time, we have in operation a detector of this scale and precision dedicated to neutrinos. JUNO will allow us to answer fundamental questions about the nature of matter and the universe.”