Loop quantum cosmology may explain smoothness of cosmic microwave background

 

Loop quantum cosmology may explain the smoothness of the cosmic microwave background

09 May 2025 Sponsored by EPL

Repulsive gravity at the quantum scale would have flattened out inhomogeneities in the early universe

First light: The cosmic microwave background, as imaged by the European Space Agency’s Planck mission. (Courtesy: ESA and the Planck Collaboration)

In classical physics, gravity is universally attractive. At the quantum level, however, this may not always be the case. If vast quantities of matter are present within an infinitesimally small volume – at the centre of a black hole, for example, or during the very earliest moments of the universe – spacetime becomes curved at scales that approach the Planck length. This is the fundamental quantum unit of distance, and is around 1020 times smaller than a proton.

In these extremely curved regions, the classical theory of gravity – Einstein’s general theory of relativity – breaks down. However, research on loop quantum cosmology offers a possible solution. It suggests that gravity, in effect, becomes repulsive. Consequently, loop quantum cosmology predicts that our present universe began in a so-called “cosmic bounce”, rather than the Big Bang singularity predicted by general relativity.

In a recent paper published in EPL, Edward Wilson-Ewing, a mathematical physicist at the University of New Brunswick, Canada, explores the interplay between loop quantum cosmology and a phenomenon sometimes described as “the echo of the Big Bang”: the cosmic microwave background (CMB). This background radiation pervades the entire visible universe, and it stems from the moment the universe became cool enough for neutral atoms to form. At this point, light could suddenly travel through space without being continually scattered by the plasma of electrons and light nuclei that existed before. This freshly liberated light makes up the CMB, so studying it offers clues to the early universe.

 

Abnormal ‘Arnold’s tongue’ patterns appear in a real oscillating system

22 Apr 2025 Isabelle Dumé

Synchronization studies: When the experimenters mapped the laser’s breathing frequency intensity in the parameter space of pump current and intracavity loss (left), unusual features appeared. The areas contoured by blue dashed lines correspond to strong intensity, and represent the main synchronization regions. (right) Synchronization regions extracted from this map highlight their leaf-like structure. (Courtesy: DOI: 10.1126/sciadv.ads3660)

Abnormal versions of synchronization patterns known as “Arnold’s tongues” have been observed in a femtosecond fibre laser that generates oscillating light pulses. While these unconventional patterns had been theorized to exist in certain strongly driven oscillatory systems, the new observations represent the first experimental confirmation.

Scientists have known about synchronization since 1665, when Christiaan Huygens observed that pendulums placed on a table eventually begin to sway in unison, coupled by vibrations within the table. It was not until the mid-20th century, however, that a Russian mathematician, Vladimir Arnold, discovered that plotting specific parameters of such coupled oscillating systems produces a series of tongue-like triangular shapes.

 

The mechanics behind rose petal shapes revealed

03 May 2025 Michael Banks

A rosy outlook: researchers have found that rose petal growth is all about geometric frustration (courtesy: CC BY SA Georges Seguin)

Roses have been cultivated for thousands of years and are admired for their beauty. Despite their use in fragrance, skincare, and even teas and jams, there are some things we still don’t know about these symbolic flowers.

And that includes the physical mechanism behind the shape of rose petals.

The curves and curls of leaves and flower petals arise due to the interplay between their natural growth and geometry.

Uneven growth in a flat sheet, in which the edges grow quicker than the interior, gives rise to strain. In plant leaves and petals, for example, this can result in a variety of shapes, such as saddle and ripple shapes.

 

Euclid mission spots 26 million galaxies in first batch of survey data

19 Mar 2025 Michael Banks

Deep field: An area of Euclid’s Deep Field South featuring galaxies in a variety of shapes and colours (courtesy: ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre, E. Bertin, G. Anselmi)

The European Space Agency (ESA) has released the first batch of survey data from its €1.4bn Euclid mission. The release includes a preview of its “deep field,” where in just one week of observations, Euclid already spotted 26 million galaxies and many transient phenomena such as supernovae and gamma-ray bursts. The dataset is published along with 27 scientific papers that will be submitted to the journal Astronomy & Astrophysics.

The dataset also features a catalogue of 380,000 galaxies detected by artificial intelligence or “citizen science” efforts. These include those with spiral arms, central bars, and “tidal tails,” which indicate merging galaxies.

 

Superfluid phase spotted in molecular hydrogen for the first time

07 Apr 2025 Isabelle Dumé

Ultracold lab: To demonstrate superfluidity in molecular hydrogen, researchers at the University of British Columbia, RIKEN and Kanazawa University confined the molecules within a nanodroplet of helium, then embedded a methane molecule within the hydrogen molecules (left). By shining a laser beam on the methane (right), they set it rotating, and measurements of the rotation led them to identify the onset of superfluidity in hydrogen. (Courtesy: Susumu Kuma, RIKEN)

An international team led by chemists at the University of British Columbia (UBC), Canada, has reported strong experimental evidence for a superfluid phase in molecular hydrogen at 0.4 K. This phase, theoretically predicted in 1972, had only been observed in helium and ultracold atomic gases until now, and never in molecules. The work could give scientists a better understanding of quantum phase transitions and collective phenomena. More speculatively, it could advance the field of hydrogen storage and transportation.

Superfluidity is a quantum mechanical effect that occurs at temperatures near absolute zero. As the temperatures of certain fluids approach this value, they undergo a transition to a zero-viscosity state and begin to flow without resistance—behaviour that is fundamentally different from that of ordinary liquids.

 

Microwaves slow down chemical reactions at low temperatures

16 Apr 2025

Molecular reactant Ball-and-stick model of carbon monoxide. The rate at which the molecule reacts with helium ions can be controlled using microwaves. (Courtesy: Benjah-bmm27)

Through new experiments, researchers in Switzerland have tested models of how microwaves affect low-temperature chemical reactions between ions and molecules. Through their innovative setup, Valentina Zhelyazkova and colleagues at ETH Zurich showed for the first time how the application of microwave pulses can slow down reaction rates via nonthermal mechanisms.

Physicists have studied chemical reactions between ions and neutral molecules for some time. At close to room temperature, classical models can closely predict how the electric fields emanating from ions will induce dipoles in nearby neutral molecules, allowing researchers to calculate these reaction rates with impressive accuracy.

 

Retinal stimulation reveals colour never before seen by the human eye

22 Apr 2025 Tami Freeman

Retinal stimulation reveals colour never before seen by the human eye, 22 Apr 2025, Tami Freeman Oz's principle for stimulating the human retina. Novel technique elicits colour beyond the natural range of human vision. Courtesy: Fong et al. Sci. Adv. 10.1126/sciadv.adu1052

Fullscreen Player Information About Brightcove A new retinal stimulation technique called Oz enabled volunteers to see colours beyond human vision's natural range. Developed by researchers at UC Berkeley, Oz works by stimulating individual cone cells in the retina with targeted microdoses of laser light, while compensating for the eye’s motion.