Hubble Constant, why so tense?

by Răzvan Balașov, PhD

31.01.2025

Image credit: Shutterstock

Parallel universe or the mystery of ghost particles?

by Alice Păun, PhD student

24.01.2025

Credit foto: https://source.washu.edu/2014/12/anita-iii-launched-over-antarctica/

ANITA (ANtarctic Impulsive Transient Antenna) is an instrument mounted on a hot-air balloon, optimized to detect polarized radio emissions originating from the electromagnetic component of cosmic ray cascades formed in the atmosphere. ANITA can detect these emissions either reflected off the surface of glaciers or directly, without reflection, from descending events near the horizon. These two types of signals can be easily distinguished due to the phase inversion that occurs when the wave is reflected. Two of the experiment’s flights, ANITA-I and ANITA-III, detected two unusual upward-going events (27.4° and 35° below the horizon) that behave like direct signals, even though they reach the detector at angles typical of reflected signals.

Starting from a 2016 article by the ANITA Collaboration, the observation of these unusual events and the vague explanations regarding their origins led to highly creative but incorrect interpretations by journalists, causing confusion among the general public. Most media reports claimed that researchers had uncovered evidence of an anti-Universe, a parallel universe identical to ours, where time flows backward, and the Big Bang marks its end, not its beginning, as in our universe.

Following this discovery, the scientific community proposed various scenarios, both within the Standard Model (SM) and beyond (BSM), to interpret these high-energy upward-going signals. One of the most promising SM strategies involves neutrinos passing “tangentially” through the Earth (traversing a shorter distance through the planet before exiting), producing electrically charged leptons that lose minimal energy before initiating the particle cascades observed by ANITA. The particle most likely fitting this model is the tau neutrino (ντ), which produces τ leptons through interactions with nucleons. Given the high energies of the two observed events, focusing on tangential neutrinos is explained by the fact that as neutrino energy increases, so does their interaction cross-section (probability of interaction with matter). For energies above 10⁸ GeV, the Earth becomes opaque to neutrinos [Ref1]. While neutrinos are often dubbed the “ghost particles” of the universe due to their near-zero mass and weak interactions, allowing them to travel vast distances unimpeded, at very high energies, their probability of interacting increases, making them more likely to reveal themselves.

Researchers also explored more daring scenarios involving beyond-the-standard-model (BSM) interpretations of these two atypical signals. Proposed models focusing on BSM particles fall into three main categories:

1.    Astrophysical neutrinos interact within the Earth and are converted into BSM particles that propagate through matter and eventually reconvert into SM particles capable of initiating electromagnetic cascades like those observed by ANITA. (https://arxiv.org/abs/1809.09615)

2.    Dark Matter accumulated inside the Earth decays, generating BSM particles that convert into SM particles near the glacier surface, inducing upward-going electromagnetic cascades.

3.    Sterile neutrinos, potentially arising from Dark Matter decay, travel long distances through the Earth, producing τ leptons via interactions with nucleons near the Earth’s surface, which then generate electromagnetic cascades. (https://arxiv.org/abs/1803.11554 , https://doi.org/10.1103/PhysRevD.99.095014)

Up to now, researchers have not provided definitive evidence for any scenario that explains these two high-energy upward-going events within the constraints of the Standard Model. Although none of the proposed BSM scenarios have been confirmed, such a discovery could have significant implications for fundamental physics, potentially bringing us closer to understanding Dark Matter, which, together with Dark Energy, constitutes approximately 95% of the universe, leaving only 5% as ordinary matter. Thus, while no solid explanation for these anomalies exists yet, the purported evidence of a parallel universe remains far from a valid solution to this puzzle.

Pluto "The Conquerer"

by Florentina Pîslan, PhD student 

17.01.2025

Credit image: NASA, APL, SwRI

A recent study published in Nature Geoscience introduces a new theory for how Pluto and its largest moon, Charon, came to be a binary system. Instead of the traditional view that Charon formed from a massive collision, much like Earth’s Moon, researchers propose a gentler, more complex process they call "kiss and capture." This fresh perspective offers new insights into the dynamics of planetary formation in the distant Kuiper Belt. 

For decades, scientists have believed that Pluto and Charon were created through a high-energy impact, where a proto-Charon slammed into Pluto, ejecting material that later coalesced into the moon. However, this theory has some major challenges, particularly because Pluto and Charon are icy worlds, not molten planets like early Earth. A high-speed collision would likely have destroyed them or led to significant mixing of their interiors, which doesn’t match what we see today. 

To investigate a more plausible scenario, researchers from the University of Arizona ran sophisticated computer simulations that factored in the strength of ice and rock—something previous models often overlooked. Their findings suggest that instead of a violent smash, the two bodies initially stuck together in a "snowman-like" shape. For a brief time, they rotated as a single entity before gently pulling apart due to tidal forces, eventually settling into the stable binary system we see today. This "kiss and capture" model not only explains how Pluto and Charon managed to remain largely intact after their encounter, but it also has important implications for Pluto’s internal structure. As Pluto and Charon inched apart, the process probably produced heat through tidal friction — enough  to have kept almost all of an underground ocean from freezing. This is an exciting possibility: Pluto may  still have liquid water rezoning beneath its icy surface. If true, it could be a key clue  in the search for habitable environments in the far reaches of our solar system. 

But the implications  don't end there, this study also provides new insights as to how other binary systems in the Kuiper  Belt may have formed. Many icy bodies in this distant region exist in pairs, and the "kiss and capture" process might help explain their origins as well. This new view of Pluto and Charon’s past is complex and surprising, illustrating the complex planetary  evolution of the Solar System's frozen frontier. And so, rather than a destructive collision, their story may have been one of a cosmic embrace that shaped the worlds we see today.

Quantum internet?

by Maria Ișfan, PhD student 

08.01.2025

Quantum internet is one step closer to becoming reality! A group of scientists from USA achieved the first teleportation of a photon through an operational optical fiber, as reported in their paper published in journal Optica. In other words, alongside the transmission of classical data, the scientists also managed to transmit quantum data!

Quantum teleportation is a process that can be demonstrated in the laboratory. It is one of the cornerstones of quantum networks, which are far more secure than their classical counterparts. It involves transferring the state of one quantum particle (in this case, a photon) to another quantum particle. This state represents quantum information, or data. The first photon contains the data to be teleported, while a second photon, the receiver, is located over 30 km away. The two photons are connected through a telecommunications optical fiber cable, which transmits classical data in the frequency band of 3.7 GHz - 4.2 GHz at a speed of 400 Gb per second. The teleportation of the first photon's state to the second photon was achieved simultaneously with the transmission of classical data. In essence, a photon was teleported from one end of the operational optical fiber to the other, without losing the data it carried.

The success of this teleportation demonstrates the feasibility of quantum networks and opens new perspectives for the practical realisation of quantum telecommunications: from teleporting multiple photons through optical fibers transmitting data a thousand times faster to the realization of the quantum internet. 

SOURCE: Quantum teleportation coexisting with classical communications in optical fiber

quantuminternetalliance.org