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String theory vs Loop quantum gravity: Wild hunt for Quantum Gravity

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The gauge bosons of the standard model of particle physics are responsible for 3 of the 4 known forces in the universe. A force is conferred is through the exchange of virtual bosons. So for example in electromagnetism, an exchange of virtual photons results in an exchange of momentum which results in two like charges repelling each other.

Gravity is missing from this picture because in General relativity, gravity is not a force, but is a curvature of space-time. The problem is that stars and planets are made of molecules, atoms and radiation. And the forces that hold the atoms together are due to discrete units of virtual particles. It is the exchange or swapping of these virtual bosons that holds or breaks up atoms and molecules.

Quantum mechanics conflicts with general relativity, because QM treats every thing as being discrete, and GR treats everything as being continuous. We need a theory that combines the two because we live in one reality, not two different realities.

This is why most physicists believe General relativity is incomplete. Why can’t quantum mechanics be the one that is incomplete?
Of the 4 fundamental forces, 3 have very robust quantum mechanical theories. Only gravity lacks a quantum description. Quantum mechanics also has almost all of classical physics within in its limits. Classical physics like general relativity, does not have quantum effects. We have learned is that Quantum physics is the fundamental language of reality.

One way to quantize gravity is to quantize space-time itself. This is what loop quantum gravity or LQG does. It shows that the fabric of space-time is not continuous, but is made up of discrete quanta, like the pixels on a TV screen. This is different than string theory, because in string theory, space is the background or the canvas, on which strings vibrate.

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When the Environment Writes the Rules of Quantum Dynamics

The transitions of hydrogen molecules embedded in a crystal depend on the surroundings—a behavior that could be used to tailor molecular quantum dynamics.

In quantum physics, we often learn that the rules governing a system are set by its symmetry. These rules—known as selection rules—determine which transitions between quantum states are allowed and which are forbidden. For example, rotational symmetry constrains how an atom’s angular momentum can change. But what if those rules are not fixed? A recent study of hydrogen (H2)—one of the simplest molecules in nature—showed that the allowed pathways between quantum states are determined not solely by the molecule’s internal symmetry but also by its surroundings. By embedding hydrogen molecules in different crystalline environments, Nathan McLane and colleagues from the University of Maryland, College Park, have demonstrated that the symmetry of the host material can selectively enable or suppress nuclear-spin transitions [1]. In doing so, the team revealed that quantum dynamics is not just an intrinsic property—it can be shaped by the environment.

H2 is one of the simplest systems for exploring quantum behavior. Its two identical protons can align their spins in two different ways: In so-called orthohydrogen the nuclear spins are parallel, whereas in parahydrogen they are antiparallel. Although this difference is subtle, it leads to markedly different physical properties for the two forms. Crucially, transitions between them are highly constrained: In an isolated hydrogen molecule, the overall wave function is symmetric under exchange of the two protons, and this exchange symmetry forbids direct conversion between ortho and para states [2]. This restriction makes H2 a textbook example of how symmetry governs quantum dynamics.

A flower-like pattern exposes chiral superconductivity’s long-sought fingerprint

With a carefully designed experiment and a handful of tin atoms, University of Tennessee, Knoxville’s physicists have found a long-sought form of superconductivity, taking one more step toward creating custom quantum materials.

Scientists have known about superconductivity for more than a century. At low temperatures, resistance in certain materials vanishes and they carry electrical current without losing any energy. Superconductors are part of particle accelerators and magnetic resonance imaging machines. While they need extremely cool environments to work, the mechanism that drives them is quite well understood: electrons, which normally repel each other, form pairs and carry the current.

Spintronics at BESSY II: Real-time analysis of magnetic bilayer systems

Spintronic devices enable data processing with significantly lower energy consumption. They are based on the interaction between ferromagnetic and antiferromagnetic layers. Now, a team from Freie Universität Berlin, HZB and Uppsala University has succeeded in tracking—separately for each layer—how the magnetic order changes after a short laser pulse has excited the system. The researchers were also able to identify the main cause of the loss of antiferromagnetic order in the oxide layer: The excitation is transported from the hot electrons in the ferromagnetic metal to the spins in the antiferromagnet. The findings are published in the journal Physical Review Letters.

While conventional microelectronics involves the movement of electric charges, spintronics is based on electron spins. Manipulating spins requires less energy than transporting charged particles. Consequently, spintronic components offer the potential for significant energy savings and high processing speeds.

However, future applications will require clock speeds in the terahertz range, which are not yet achievable today. The clock speeds of current spin-based applications are up to a hundred times lower. In order to advance spintronics, a large team at the Transregio Collaborative Research Center CRC/TRR 227 is investigating spin dynamics in solids at atomic resolution and on ultrafast timescales.

Microscopic sensors uncover how liquids turn glassy without structural change

A scientific discovery by researchers at Tel Aviv University’s School of Chemistry offers a new perspective on a long-standing scientific mystery: how does a flowing liquid suddenly become a rigid, almost frozen material, without changing its structure? This phenomenon, known as the “glass transition,” has puzzled physicists for over a hundred years. The study proposes a new experimental approach to observing this elusive process—by tracking the motion of tiny particles that serve as microscopic “sensors” within the material.

The study was conducted by Prof. Haim Diamant and Prof. Yael Roichman of the School of Chemistry at Tel Aviv University, together with the research group of Prof. Stefan Egelhaaf at Heinrich Heine University Düsseldorf. The findings were published in the journal Nature Physics.

Observing exotic quasiparticle states in kagome superconductor CsV₃Sb₅

A research team led by Prof. Hao Ning of the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, in collaboration with Anhui University and the University of Science and Technology of China, has identified two distinct types of unusual low-energy quasiparticle states in the kagome superconductor CsV3Sb5 using single-atom impurities as local “quantum probes” combined with scanning tunneling spectroscopy.

The study was recently published in Nature Physics.

CsV3Sb5 has attracted growing interest for its unusual crystal structure and complex quantum phenomena. Evidence for time-reversal symmetry breaking remains under debate, and the mechanism of its superconductivity is still not fully understood. Studying its response to single-atom impurities provides a promising way to address these questions.

Gravity’s subtle effect on light could improve groundwater, volcano and carbon storage monitoring

A study by University of Wollongong (UOW) physicist Dr. Enbang Li has demonstrated that gravity can subtly influence the behavior of light, a breakthrough that could underpin future technologies for monitoring groundwater, tracking glacier melt, locating mineral deposits and detecting underground changes linked to volcanic activity and carbon storage.

The study, published in Scientific Reports, shows early experimental evidence that photons—particles of light—interact with Earth’s gravitational field in measurable ways, laying the groundwork for a new generation of ultra-sensitive gravity sensors.

Dr. Li said the work could lead to more precise and compact next-generation sensing technologies for environmental monitoring, navigation and underground mapping.

Chemists stabilize rare three‑atom metal ring, revealing new form of aromaticity

In a world first, the team, led by Professor Stephen Liddle, discovered a new type of aromatic molecule made entirely of metal atoms, the heaviest of its kind ever confirmed. The team stabilized an extremely rare three‑atom ring of bismuth, held between two large metal atoms (uranium or thorium) in a structure known as an “inverse‑sandwich” complex.

This breakthrough provides fresh insight into one of chemistry’s most familiar concepts—aromaticity—and shows it can occur not only in carbon‑based rings like benzene, but also in unusual clusters of heavy metals. The paper is published in the journal Nature Chemistry.

‘Poor man’s Majoranas’ can be used as quantum spin probes

A Majorana fermion is a particle that would be identical to its antiparticle. Such an object has not yet been found. However, certain solid materials exhibit analogous behavior as if Majorana fermions were present through collective excitations of the system called quasiparticles.

In addition to generating interest in basic science as key components for understanding the material world, Majorana fermions have primarily been studied due to their potential technological applications in areas such as fault-tolerant quantum computing.

The main theoretical model used in this study is the Kitaev wire. It is a one-dimensional superconducting chain formed by electrons or collective excitations. Under certain conditions, it generates an isolated Majorana fermion at each end without altering the total energy of the system.

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