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Category: particle physics

For a while now, there has been a problematic mystery at the heart of the standard cosmological model. Although all observations support the expanding Universe model, observations of the early period of the cosmos give a lower rate of acceleration than more local observations. We call it the Hubble tension problem, and we have no idea how to solve it. Naturally, there have been several proposed ideas: what if general relativity is wrong; what if dark matter doesn’t exist; what if the rate of time isn’t uniform; heck, what if the entire Universe rotates. So, let’s add a new idea to the pile: what if dark matter evolves?

While there have been several models proposing an evolving dark energy, the idea of evolving dark matter hasn’t been widely considered. The reason for this is twofold. First, the observations we have of dark matter are excellent. They point to the presence of some kind of material that doesn’t interact strongly with light. The only major weak point is that we haven’t observed dark matter particles directly. Second, the vast majority of folk opposed to dark matter focus on eliminating it altogether through things like modified gravity. They figure dark matter is fundamentally wrong, not something to be tweaked. That makes this new idea rather interesting.

In this work, the authors look at both evolving dark energy and evolving dark matter and argue that the latter is a much better fit to observational data. The first thing they note is that the two models are somewhat related. Since the evolution of the cosmos depends in part on the ratio of energy density to matter density, a model with constant dark matter and evolving dark energy will always appear similar to a model with evolving dark matter and constant dark energy.

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Researchers at the University of Turku in Finland have developed a simple method to explore a complex area of quantum science. The discovery makes research in this field cheaper and more accessible, which could significantly impact the development of future laser, quantum and high-tech display technologies.

A team of researchers developed a new method for fabricating small structures known as optical microcavities. These structures allow scientists to study how light interacts with matter in a very precise process that can lead to the creation of novel quantum states called polaritons. Polaritons are unusual hybrid particles made from light and matter.

The results have been published in the journal Advanced Optical Materials.

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Medieval alchemists dreamed of transmuting lead into gold. Today, we know that lead and gold are different elements, and no amount of chemistry can turn one into the other.

But our modern knowledge tells us the basic difference between an atom of lead and an atom of gold: the lead atom contains exactly three more . So can we create a gold atom by simply pulling three protons out of a lead atom?

As it turns out, we can. But it’s not easy.

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A team of physicists has uncovered a surprising new way to explore one of science’s greatest challenges: uniting the two fundamental theories that explain how our universe works—Einstein’s theory of gravity and quantum mechanics.

Despite decades of effort, no one has fully explained how gravity—which governs massive objects like planets and stars—fits with , which describes the behavior of the tiniest particles in the universe. But now, scientists believe light may hold the key.

Warner A. Miller, Ph.D., co-author and a professor in the Department of Physics at Florida Atlantic University’s Charles E. Schmidt College of Science in collaboration with scientists at the University of Seoul and Seoul National University, South Korea, found that light’s —the direction it vibrates as it travels—can behave in an unexpected way when passing through curved space. Normally, this polarization shifts slightly due to the warping of space by gravity, a well-known effect.

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MIT physicists have captured the first images of individual atoms freely interacting in space. The pictures reveal correlations among the “free-range” particles that until now were predicted but never directly observed. Their findings, appearing today in the journal Physical Review Letters, will help scientists visualize never-before-seen quantum phenomena in real space.

The images were taken using a technique developed by the team that first allows a cloud of atoms to move and interact freely. The researchers then turn on a lattice of light that briefly freezes the atoms in their tracks, and apply finely tuned lasers to quickly illuminate the suspended atoms, creating a picture of their positions before the atoms naturally dissipate.

The physicists applied the technique to visualize clouds of different types of atoms, and snapped a number of imaging firsts. The researchers directly observed atoms known as “bosons,” which bunched up in a quantum phenomenon to form a wave. They also captured atoms known as “fermions” in the act of pairing up in free space — a key mechanism that enables superconductivity.

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The notion that the quantum realm somehow sits sealed off from the relativistic domain has captured popular imagination for decades. Perhaps this separation is comforting in a way, because it assigns neat boundaries to a notoriously complex theoretical landscape. Yet, a careful look at both cutting-edge research and historical development suggests that no such invisible barrier actually exists. Early quantum pioneers such as Planck (1901) and Heisenberg (1925) laid foundations that seemed confined to the minuscule domain of atoms and subatomic particles. Before long, Einstein (1916) showed us that gravity and motion operate in ways that defy purely Newtonian conceptions, especially at cosmic scales. Despite the apparent chasm between the quantum and relativistic descriptions, threads of continuity run deeper than we once imagined. The famous energy discretization proposed by Planck was intended to solve classical paradoxes at microscopic scales, but the fundamental constants he unveiled remain essential at any size, linking the behavior of infinitesimal systems to grand cosmic events.

Modern experiments push this continuity further into the mainstream conversation. Quantum coherences documented in biological processes illuminate the reality that phenomena once labeled “strictly quantum” can permeate living systems in everyday environments (Engel et al., 2007). Photosynthesizing cells exploit wave-like energy flows, migratory birds appear to navigate using subtle quantum effects, and intriguing evidence suggests that neuronal microtubules might process information at scales once deemed too large for quantum behavior (Hameroff, 1998). If relativity reliably predicts how massive objects curve spacetime, and quantum theory demonstrates how particles and fields manifest as discrete excitations, then the missing piece in unifying these perspectives may hinge on the realization that neither domain is airtight. We stand on a continuum of phenomena, from photosynthetic molecules absorbing photons to astrophysical bodies warping spacetime.

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New theoretical research by Michael Wondrak, Walter van Suijlekom and Heino Falcke of Radboud University has shown that Stephen Hawking was right about black holes, although not completely. Due to Hawking radiation, black holes will eventually evaporate, but the event horizon is not as crucial as had been believed. Gravity and the curvature of spacetime cause this radiation too. This means that all large objects in the universe, like the remnants of stars, will eventually evaporate.

Using a clever combination of quantum physics and Einstein’s theory of gravity, Stephen Hawking argued that the spontaneous creation and annihilation of pairs of particles must occur near the (the point beyond which there is no escape from the gravitational force of a black hole).

A particle and its anti-particle are created very briefly from the quantum field, after which they immediately annihilate. But sometimes a particle falls into the black hole, and then the other particle can escape: Hawking radiation. According to Hawking, this would eventually result in the evaporation of .

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Axions, hypothetical subatomic particles that were first proposed by theoretical physicists in the late 1970s, remain among the most promising dark matter candidates. Physics theories suggest that the interactions between these particles and regular matter are extremely weak, which makes them very difficult to detect using conventional experimental set-ups.

The HAYSTAC (Haloscope at Yale Sensitive to Axion Cold Dark Matter) experiment is a research collaboration between Yale, Berkeley and Johns Hopkins, aimed at detecting axions by searching for the small electromagnetic signals that they could produce within a strong magnetic field.

In a recent paper published in Physical Review Letters, the HAYSTAC collaboration has reported the results of the broadest search for axions performed to date, utilizing a technique known as quantum squeezing, which is designed to reduce quantum noise (i.e., random fluctuations that adversely affect their haloscope’s measurements).

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