stable superconductivity ambient pressure

Physicists Achieve Stable Superconductivity at Ambient Pressure

Breakthrough in Ambient-Pressure Superconductivity

Researchers at the University of Houston's Texas Center for Superconductivity have reached another groundbreaking milestone in their pursuit of ambient-pressure high-temperature superconductivity, advancing the quest for superconductors that function in real-world conditions and paving the way for next-generation energy-efficient technologies.

Investigating Superconductivity in Bi₀.₅Sb₁.₅Te₃ (BST)

Research by Liangzi Deng and Paul Ching-Wu Chu

Professors Liangzi Deng and Paul Ching-Chu of the UH Department of Physics investigated the induction of superconductivity in Bi₀.₅Sb₁.₅Te₃ (BST) under pressure while preserving its chemical and structural properties, as detailed in their study, "Creation, stabilization, and investigation at ambient pressure of pressure-induced superconductivity in Bi₀.₅Sb₁.₅Te₃" published in the Proceeding of the National Academy of Sciences.

Link Between Pressure, Topology, and Superconductivity

"The idea that high-pressure treatment of BST might reconfigure its Fermi surface topology and enhance thermoelectric performance emerged in 2001," Deng stated. "That intricate relationship between pressure, topology and superconductivity drew our interest."

Challenges in High-Pressure Superconductors

Metastable States and Practical Limitations

"As materials scientist Pol Duwez once observed, most industrially significant solids exist in a metastable state," Chu explained. "The challenge lies in the fat that many of the most intriguing superconductors require high pressure to function, making them difficult to analyze and even more challenging to implement in real-world applications."

Deng and Chu's innovation offers a solution to this pressing issue.

The Pressure-Quench Protocol (PQP) - A Key Innovation

Deng and Chu pioneered the pressure-quench protocol (PQP), a method introduced in an October UH news release, to stabilize BST's superconducting states at ambient pressure—removing the necessity for high-pressure environments.

Significance of This Discovery

A Novel Approach to Material Phases

Why is this significant? It introduces a novel approach to preserving valuable material phases that typically require high-pressure conditions, enabling both fundamental research and practical applications.

Evidence of High-Pressure Phase Stability

"This experiment provides clear evidence that high-pressure-induced phases can be stabilized at ambient pressure through a delicate electronic transition, without altering symmetry," Chu stated. "This breakthrough opens new possibilities for preserving valuable material phases typically confined to high-pressure conditions and could aid in the quest for superconductors with higher transition temperatures."

Exploring New States of Matter

"Remarkably, this experiment unveiled a groundbreaking method for identigying new states of matter that neither naturally exist at ambient pressure nor emerge under high-pressure conditions," Deng noted. "It underscores PQP's potential as a powerful tool for mapping and expanding material phase diagrams."

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Physicists at the University of Houston have unlocked a new path to stable superconductivity at ambient pressure, paving the way for next-generation energy-efficient technologies. This revolutionary advancement could transform materials science, energy storage, and beyond.

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Scientists Create Invisible Electric Wire Using Sound Waves

The Role of Electric Sparks in Technology

Electric sparks play a crucial role in welding, electronic, germ elimination and fuel ignition in certain car engines. However, despite their utility, they are difficult to control in open environments, often splitting into erratic branches that naturally gravitate toward nearby metallic objects.

Breakthrough in Electricity Transport Through Air

Researchers have discovered a way to transport electricity through air using ultrasonic waves, as detailed in a recent Science Advances study. This innovation enables controlled spark movement, allowing for obstacle navigation and precise targeting, even on insulating materials.

Scientific Discovery and Experimentation

Dr. Asier Marzo, lead researcher at the Public University of Navarre, stated, "We discovered this phenomenon more than a year ago, but it took months to control it and even longer to uncover the scientific explanation behind it."

How Ultrasound Controls Electric Sparks

This directional control happens as the sparks heat the surrounding air, causing it to expand and become less dense. Ultrasonic waves then channel the heated air toward regions of higher sound intensity, guiding subsequent sparks along these low-density pathways due to their reduced breakdown voltage.

Applications of Controlled Sparks

"The precise manipulation of sparks paves the way for applications atmospheric sciences, biological processes and controlled circuit activation," says Prof. Ari Salmi from the University of Helsinki.

Advancements Over Traditional Methods

Previously, guiding sparks relied on laser-induced discharges, commonly referred to as 'electrolasers,' which necessitated high-powered lasers and precise timing between the laser pulse and electric discharge. This new approach, utilizing ultrasound instead of laser, ensures:

• Safety for both eyes and skin
• Compact and affordable equipment
• Continuous operation feasibility

Future Potential of Contactless Electricity Transport

"I find it exciting to explore the use of extremely faint sparks for generating precise tactile sensations in the hand, which could lead to the development of the first contactless Braille system," says Josu Irisarri, lead author from the Public University of Navarre.

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"The discovery of electricity transport through sound waves opens exciting possibilities for wireless energy transmission, electronics and even contactless Braille technology. As researchers continue exploring this breakthrough, its application could transform various industries.

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revolutionary altermagnetism digital memory technologies

Revolutionary Third Class of Magnetism Unveiled: Transforming Digital Memory Technologies

Introduction to Altermagnetism and Its Significance

For the first time, scientists have captured images of altermagnetism, a newly discovered class of magnetism, which holds promise for next-generation magnetic memory devices with significantly enhanced speeds.

What is Altermagnetism?

Altermagnetism represents a unique magnetic order characterized by antiparallel alignment of individual magnetic units, with each unit hosted within a structure that is rotationally offset from its neighbors.

Groundbreaking Research from the University of Nottingham

Researchers from the University of Nottingham's School of Physics and Astronomy have demonstrated the existence and controllability of this novel third class of magnetism in microscopic devices, with their findings featured in Nature.

Insights from Professor Peter Wadley

Professor Peter Wadley, the lead researcher, describes altermagnets as magnetic moments aligned anti-parallel to their neighbors, with each crystal segment rotated relative to the others. "It's akin to anti-ferromagnetism with a twist." he explains, "but this slight variation has profound implications."

Impact on Magnetic Memory and Microelectronics

Magnetic materials form the backbone of most long-term computer memory and modern microelectronics. While this industry is critical and expansive, it also contributes significantly to global carbon emissions. Introducing altermagnetic materials as replacements for key components could dramatically enhance speed and efficiency while reducing reliance on rare and hazardous heavy elements central to traditional ferromagnetic technologies.

Advantages of Altermagnetic Materials

Altermagnets integrate the advantageous characteristics of both ferromagnets and antiferromagnets into one material, offering the promise of a thousandfold boost in microelectronic and digital memory speeds, coupled with enhanced durability and energy efficiency.

Insights from the Research Team

Senior Research Fellow and study co-author Oliver Amin, who led the experiment, remarked, "Our experimental work has connected theoretical ideas to real-world applications, potentially paving the way for altermagnetic materials in practical technologies."

The Experimental Setup at MAX IV International Facility

The experimental research was conducted at the MAX IV international facility in Sweden, a synchrotron resembling a massive metallic doughnut, which accelerates electrons to generate X-rays.

High-Resolution Imaging with X-rays

Using X-rays to illuminate the magnetic material, the electrons ejected from its surface are detected through a specialized microscope, enabling the production of high-resolution images of the material's magnetism, including features as small as the nanoscale.

The Role of Alfred Dal Din in Altermagnet Research

Alfred Dal Din, a Ph.D. student, has spent the last two years investigating altermagnets, marking this latest discovery as another significant milestone in his project.

Personal Reflections from Alfred Dal Din

He reflects, "Being one of the first to observe the effects and properties of this promising new class of magnetic materials during my Ph.D. has been both an incredibly rewarding and challenging privilege."

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Soft Unclustered Energy at 13 TeV: A First Search in Proton-Proton Collisions

Introduction to Hidden Valley Models and SUEPs

Many physics studies aim to experimentally uncover exotic phenomena extending beyond the Standard Model (SM), as outlined by theoretical frameworks. Among these are hidden valley models, which propose a dark sector where particles interact via a strong, dark force. These models predict particles and interactions with unique decay characteristics.

CMS Collaboration's Groundbreaking Search for SUEPs

In a recent publication in Physical Review Letters, researchers from the CMS (Compact Muon Solenoid) collaboration at CERN reported the results of the first search for soft unclustered energy patterns (SUEPs), a unique signal predicted by hidden valley models in high-energy particle collisions.

SUEPs and Their Role in Extending the Standard Model

"SUEPs belong to a broader class of theories aimed at extending the Standard Model to address unresolved phenomena in universe, such as dark matter and matter-antimatter asymmetry," said Luca Lavezzo of the CMS search team in an interview with Phys.

Theoretical Foundations of Hidden Valley Models

Specifically, these phenomena are among the predictions derived from hidden valley theories. Introduced nearly two decades ago by Matt Strassler and Kathryn Zurek, these theories propose a "Dark Sector" distinct from the Standard Model, characterized by its own strong, confining force, analogous to the Standard Model's strong force that binds quarks and gluons into hadrons such as protons and neutrons.

Challenges in Validating Hidden Valley Predictions

Many of the fascinating predictions made by hidden valley models have yet to undergo experimental validation. When these theories were first proposed, the technological limitations of the time rendered searches for the predicted dark sectors impractical, deferring such efforts to future studies.

Revisiting Hidden Valley Theories with Colliders

"Several years ago, as interest in investigating complex dark sectors grew within the scientific community, theorists and experimentalists revisited the unusual predictions of hidden valley theories, realizing that some could now be explored using colliders," said Lavezzo.

New Search Strategies for SUEPs and Other Phenomena

Soft unclustered energy patterns (SUEPs), semivisible jets, and emerging jets represent the initial set of searches aimed at validating specific predictions from hidden valley models, all published within the last few years.

Characterizing SUEPs in High-Energy Collisions

Hidden valley models suggest that high-energy particle collisions might produce distinct signatures, such as SUEPs, characterized by numerous low-momentum particles arranged in a spherical pattern within particle colliders like those used in the CMS experiment.

Challenges in Identifying SUEPs in Collider Events

"This is a highly distinct signature compared to Standard Model predictions. However, identifying a SUEP in a typical collider event is challenging due to the presence of several dozen simultaneous collisions, each generating numerous low-energy particles," Lavezzo explained.

Refining Trigger Mechanisms to Capture SUEP Events

"Additionally, our trigger mechanisms—criteria determining which proton—proton collisions are deemed noteworthy—are specifically configured to capture events involving high-energy particles, making it challenging to select those with naturally low energy."

New Strategies in Search of SUEPs

To overcome the challenges that hindered previous searches for these particles, the CMS Collaboration first ensured that the particle responsible for generating a SUEP—acting as the 'Portal' between the Standard Model and Hidden Valley models—recoiled against an SM particle, specifically a jet in their experiment. This recoil results in an event where both particles exhibit substantial yet balanced energy, enabling the event to be triggered on the SM jet.

Differentiating Between SUEPs and Standard Model Jets

"By employing this strategy, the SUEP's structure shifts from a spherical pattern to one resembling a broader version of an SM jet—s shower of particles from a quark," explained Lavezzo.

Challenges in Comparing Predictions to Experimental Observations

"The challenge now is to differentiate between SM jets and SUEPs. However, obtaining reliable predictions through our traditional methods proves difficult in these complex environments and events, which is essential for comparing our measurements to theoretical models and determining if there is any evidence of SUEPs or if the observations align with Standard Model expectations."

Innovative Methods for Estimating SM Contributions

The CMS collaboration chose to estimate the contribution of SM events directly from the data they gathered during their search. This was done by utilizing the extended-ABCD method, a method that helps assess the SM contribution in the signal region.

Successful Exclusion of SUEP Theorie's Phase Space

"We are the first team to conduct a search for SUEPs at colliders, and we successfully excluded a significant portion of the available phase space for SUEP theories. Additionally, we've established a set of methods that we hope will be further developed in future studies," stated Lavezzo. "The response from theorists, including Matt Strassler who originally proposed SUEPs, was incredibly positive. They were excited about our experimental findings, as it opens the door for testing more hypotheses."

Future Directions and Open Questions in SUEP Research

The recent search undertaken by this research group has provided new constraints that will inform future strategies for detecting SUEPs in particle colliders. Hidden Valley models suggest that SUEPs should be fully visible, meaning that all dark sector particles decay to Standard Model particles. However, this assumption may not necessarily apply.

The Possibility of Stable, Undetectable, SUEPs

"SUEPs may decay into the Standard Model after a certain lifespan, or some could remain stable and undetectable, leading to distinct signatures that previous searches might have missed," explained Lavezzo. "Further focused searches could be conducted in areas where our approach was not optimized; notably, low-mass portals remain largely unconstrained.

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semi dirac fermions zrsis physics breakthrough

Physicists Observe Directional Mass-Only Particle for the First Time

Introduction to the Discovery of Semi-Dirac Fermions

Researchers have successfully identified, for the first time, a semi-Dirac Fermion-a quasiparticle characterized by being massless in one direction and possessing mass in the other. Though hypothesized 16 years ago, it was only recently observed within a ZrSiS semi-metal crystal. This breakthrough holds promise for transformative applications in technologies such as sensors and batteries.

Researchers from Penn State and Columbia University recently unveiled their findings in Physical Review X.

The Surprise Discovery and Its Significance

Unanticipated Findings

"This discovery came as a complete surprise," said Yinming Shao, assistant professor of physics at Penn State and the study's lead author. "Our initial research was not focused on semi-Dirac ferminos, but unexpected signatures in the data led us to realize we had made the first observation of these remarkable quasiparticles, which alternately behave as if they have mass or are massless."

Understanding Massless Particles

Particles are considered massless when their energy originates entirely from motion, making them pure energy traveling at the speed of light. For instance, photons, the particles of light, are massless as they always move at light speed. Albert Einstein's special relativity states that no object with mass can achieve this velocity.

"In solid materials, the collective dynamics of numerous particles, referred to as quasiparticles, can exhibit properties distinct from those of individual particles. In this case, this phenomenon resulted in particles possessing mass in only one direction," Shao explained.

The Concept of Semi-Dirac Ferminos and Their Theoretical Origins

Theoretical Predictions

The existence of Semi-Dirac ferminos was first proposed between 2008 and 2009 by multiple research teams, including scientists from Université Paris Sud in France and the University of California, Davis. Theoretical models suggested that these quasiparticles would exhibit directional mass-shifting behavior, appearing massless along one axis while possessing mass along another.

Unexpected Observation

After 16 years, Shao and his collaborators accidentally identified the predicted quasiparticles through magneto-optical spectroscopy, a technique that uses infrared light and a strong magnetic field to study reflected light. Their goal to examine quasiparticle properties in silver-colored ZrSiS crystals.

Landau level spectroscopy provides insights into semi-Dirac fermions at the inter-section of two nodal lines within a semi-metal material. (Left: Fermi surface of a nodal-line crossing model; Right: Band structure of the material). Credit: Yinming Shao.

The Experiment and Methods Used

Magneto-Optical Spectroscopy at the National High Magnetic Field Laboratory

The experiments were carried out at the National High Magnetic Field Laboratory in Florida, which houses the world's most powerful hybrid magnet. This magnet generates a sustained magnetic field approximately 900,000 times stronger than Earth's magnetic field—strong enough to levitate small objects like water droplets.

Conducting the Experiments at Extremely Low Temperatures

The researchers reduced the temperature of a ZrSiS sample to -452°F, just a few degrees above absolute zero, before subjecting it to the lab's strong magnetic field and illuminating it with infrared light to investigate the quantum interactions within the material.

Analyzing the Unusual Results

"We were investigating how the material's electrons respond to light, focusing on their optical response," said Shao. "By analyzing the light signals, we hoped to uncover any intriguing aspects of the material's underlying physics. What are found was a mix of expected features typical of a semi-metal crystal, along with surprising phenomena that left us completely puzzled."

Uncovering the Semi-Dirac Fermion Behavior

Unexpected Magnetic Field Behavior

"When a magnetic field is applied to a material, the energy levels of its electrons are quantized into distinct Landau levels," Shao explained. "These levels are discrete, similar to climbing stairs with no intermediate steps. The spacing between them is determined by the electron's mass and the strength of the magnetic field. As the magnetic field intensifies, the energy levels should increase in fixed increments based on the electron's mass—yet, in this case, that didn't happen."

Identifying the Power Law and Collaboration with Theoretical Physicists

By utilizing the powerful magnet in Florida, the researchers discovered that the energy transitions of the Landau levels in the ZrSiS crystal exhibited an entirely unexpected relationship with the strength of the magnetic field. This distinct pattern, identified by theorists years ago as the 'B2/3 power law,' is a hallmark characteristic of semi-Dirac fermions.

Explaining the Particle Behavior

A Model for Electron Behavior in ZrSiS

To unravel the unusual behavior they observed, the experimental physicists collaborated with theoretical physicists to create a model that explained the electronic structure of ZrSiS. Their focus was on the possible paths along which electrons could move and intersect, in order to understand how electrons in the material were losing mass when traveling in one direction but not in another.

Understanding the Massless and Massive Transitions

"Picture the particle as a miniature train confined to a network of tracks, which represent the material's fundamental electronic structure," explained Shao. "At specific intersections, the particle train moves along a fast track at light speed, but when it encounters an intersection and switches to a perpendicular track, it suddenly gains resistance and mass. In this way, the particles either remain pure energy or acquire mass depending on the direction they travel along the material's 'tracks.'"

Implications for Future Technologies

The Role of ZrSiS in Emerging Technologies

The team's analysis revealed the presence of semi-Dirac fermions at the crossing points. These particles were massless when moving along a linear path but acquired mass when traveling in a perpendicular direction. Shao further explained that ZrSiS is a layered material, similar to graphite, composed of carbon atom layers that can be exfoliated into graphene sheets just one atom thick. Graphene plays a vital role in the development of emerging technologies, such as batteries, supercapacitors, solar cells, sensors, and biomedical devices.

Looking Ahead: Unresolved Questions and Future Research

"This is a layered material," said Shao. "Once we figure out how to isolate a single layer of this compound, we could harness the unique properties of semi-Dirac fermions and control them with the same precision that we do with graphene. However, the most exciting aspect of this experiment is that the data we collected cannot yet be fully explained. There are still many unresolved questions, and our focus is on understanding them."

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decade neutrino research cosmic mysteries

Unlocking the Universe: Physicists Plan a Decade of Neutrino Research to Solve Cosmic Mysteries

Introduction to Neutrino Research

Physicists are on the brink of uncovering answers to fundamental cosmic mysteries by delving deeper into the properties of subatomic particles.

Professor Alexandre Sousa of the University of Cincinnati has published a paper forecasting global neutrino research developments for the next decade.

The Importance of Neutrinos in Physics

What Are Neutrinos?

Neutrinos, the universe's most plentiful massive particles, have become a key focus for scientists seeking deeper insights into their properties.

Origins and Behavior of Neutrinos

Neutrinos are produced during nuclear fusion in the sun, radioactive decay in reactors or Earth's crust, and particle accelerator experiments. They oscillate among three distinct flavors as they travel.

The Quest for a Fourth Neutrino: The Sterile Neutrino

The Hypothesis of the Sterile Neutrino

However, unexpected experimental findings led physicists to hypothesize the existence of a fourth neutrino type, termed the sterile neutrino, which is unaffected by three of the four fundamental forces.

• "In theory, it interacts only with gravity, remaining unaffected by the weak nuclear force, strong nuclear force, or electromagnetic force," Sousa explained.

The Collaborative Effort: Snowmass 2021/2022

An Overview of the White Paper

Sousa and his collaborators address perplexing experimental anomalies in neutrino research in a white paper recently published in Journal of Physics G: Nuclear and Particle Physics. This work stems from the Particle Physics Community Planning Exercise, known as "Snowmass 2021/2022."

The Role of High-Energy Physics Experts

Every decade, experts in high-energy physics convene to shape the direction of particle physics in the U.S. and with global collaborators.

The Team Behind the Research

The paper also included contributions from UC Professor Jure Zupan, Associate Professor Adam Aurisano, visiting scholar Tarak Thakore, postdoctoral fellow Michael Wallbank, and physics students Herilala Razafinime and Miriama Rajaoalisoa.

Progress and Challenges in Neutrino Physics

Key Areas of Focus

According to Zupan, progress in the field of neutrino physics is expected to occur on various fronts.

In addition to the search for sterile neutrinos, Zupan mentioned that physicists are investigating various experimental anomalies—discrepancies between data and theoretical predictions—that will soon be tested with upcoming experiments.

The Nobel Prize and Its Implications

Gaining deeper insights into neutrinos could revolutionize our long-held views on physics. Neutrino research has already earned the highest scientific accolade, the Nobel Prize, with the discovery of neutrino oscillations awarded in 2015. Nations, including the United States, are committing billions of dollars to these initiatives due to their profound scientific significance.

Why Neutrinos Matter: Addressing Cosmic Questions

The Matter-Antimatter Dilemma

A key question in physics is why the universe contains more matter than antimatter, despite the Big Bang theoretically producing both in equal amounts. According to Sousa, neutrino research may hold the answer.

• "While it may not impact your daily life, our goal is to understand the reason for our existence," Sousa said. "Neutrinos ap pear to be central to addressing these profound questions."

Major Neutrino Research Initiatives

The Deep Underground Neutrino Experiment (DUNE)

Sousa is involved in one of the most significant neutrino research initiatives, the Deep Underground Neutrino Experiment (DUNE), managed by the Fermi National Accelerator Laboratory. The project involves excavating the former Homestake gold mine to a depth of 5,000 feet to house neutrino detectors. Sousa noted that the elevator ride alone takes approximately 10 minutes to reach the detector chambers.

Researchers place detectors deep underground to protect them from cosmic rays and background radiation, which facilitates the isolation of particles created in experiments.

Project Overview

The experiment, scheduled to launch in 2029, will initially use two detector modules to measure atmospheric neutrinos. By 2031, Fermilab researchers will direct a high-energy neutrino beam 800 miles through Earth to the detector in South Dakota, as well as one in Illinois. the initiative involves over 1,400 international engineers, physicists, and scientists.

Technical and Scientific Goals

Sousa remarked that with these two detector modules and the most powerful neutrino beam to date, significant advancements are possible. The launch of DUNE is anticipated to be highly exciting and will be the most sophisticated neutrino experiment ever conducted.

The paper was a substantial effort, involving over 170 contributors from 118 universities and institutes, supported by 14 editors, including Sousa.

• "The project was a prime example of teamwork involving scientists from varied backgrounds. Although not always straightforward, seeing is truly gratifying," he commented.

NOvA Experiment

At the same time, Sousa and UC's Aurisano are participating in another Fermilab neutrino experiment known as NOvA, which explores the mechanisms behind neutrino flavor changes. In June, their research team shared their accurate neutrino mass measurements to date.

Hyper-Kamiokande (Hyper-K)

Hyper-Kamiokande, or Hyper-K, is another significant neutrino observatory and experiment currently being built in Japan, with operations potentially starting by 2027. It, too, seeks evidence of sterile neutrinos and explores other research questions.

Future Outlook and Collaborative Efforts

A Decade of Research and Global Participation

According to Sousa, "The combination of these findings, particularly when considered alongside DUNE, will yield highly significant results. Together, these experiments will greatly enhance our understanding. We expect to have some answers by the 2030s."

The Potential of Neutrino Physics

Zupan from UC stated that these multibillion-dollar initiatives have the potential to provide answers to fundamental questions regarding matter, antimatter, and the universe's origins.

Zupan explained that, so far, the only parameter in particle physics that has been found to have a nonzero value is connected to quark properties. The possibility of a comparable property for neutrinos is still an open and fascinating question.

The Road Ahead

Sousa mentioned that researchers globally are engaged in numerous neutrino experiments that could yield answers or spark new questions.

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cosmological model dark matter inflation

Cosmological Model Links Dark Matter Creation to Pre-Big Bang Inflation

The Mystery of Dark Matter and Its Origins

Physicists, grappling with the mystery of dark matter—constituting 80% of the universe's matter yet remaining undetected-propose a model suggesting its origin predates the Big Bang.

The Role of Inflation in Dark Matter Formation

Emergence During Inflationary Phase

The researchers propose that dark matter emerged during a brief inflationary phase when the universe underwent rapid exponential expansion. Their findings were published in Physical Review Letters by a team of three scientists from Texas, USA.

Understanding the Dark Matter Production Mechanism

The Freeze-Out and Freeze-In Processes

Cosmologists propose that dark matter's origin lies in its interaction with a particle-filled thermal bath, with its abundance arising from "freeze-out" or "freeze-in" processes.

• Freeze-Out Model Explained: In the freeze-out model, dark matter achieves chemical equilibrium with the bath in the early universe.
• Freeze-In Model and Quantum Field Theory: In the freeze-in framework, dark matter remains out of equilibrium with the thermal bath. This weak interaction can be attributed to quantum field theory processes, either via infrared or ultraviolet freeze-in.
• Untraviolet Freeze-In Details: In ultraviolet (UV) freeze-in, the thermal bath's temperature remains consistently below the masses of particles mediating interactions between dark matter and the Standard Model of particle physics.

Understanding Inflation and Its Implications

The Concept of Inflation

The inflationary theory, developed approximately 45 years ago, describes an era in the early universe marked by exponential expansion, with the universe growing by a factor of 10²⁶ within 10⁻³⁶ seconds, after which expansion slowed but persisted.

Addressing Cosmological Challenges

Billions of years later, dark energy initiated the accelerated expansion observed today. Inflation elegantly addresses key cosmological challenges, including the flatness, homogeneity, and monopole problems, and attributes the universe's structure to magnified quantum fluctuations.

While inflation is widely embraced by cosmologists as a component of the Big Bang model supported by evidence, its underlying mechanism remains unidentified, and some dissent persists.

The Role of the Inflaton

The term "inflaton" is used by cosmologists to describe a hypothesized spanning all spacetime, possibly involving a scalar (spin-zero) particle such as the Higgs field, though alternatives remain plausible.

The Supercooled State and Reheating

Inflation progresses with extraordinary rapidity, resulting in a supercooled state where the temperature drops by about 100,000-fold.

The low temperature is maintained throughout the inflationary period. Upon the conclusion of inflation, the temperature reverts to its pre-inflationary levels during a process known as reheating, where the inflaton field decays into Standard Model particles, including photons.

Research revels that the thermal bath's temperature can surpass the reheating temperature, with ultraviolet freeze-in dark matter production being determined by the bath's peak temperature.

To date, studies have not examined the potential for significant dark matter production during the inflationary expansion that resists subsequent dilution.

Dark Matter Production During Inflation

The WIFI Model Explained

The paper's WIFI model, or Warm Inflation via ultraviolet Freeze-In, proposes that dark matter arises from rare interactions in a high-energy environment, occurring during cosmic inflation, predating the Big Bang.

Challenging Conventional Views

While unconventional, many cosmologists now believe that inflation preceded the Big Bang, as the concept of a singularity with infinite desity and curvature appears implausible.

The Evolution of the Universe Post-Inflation

Following inflation, the universe is thought to have attained a modest size, approximately 10²⁶ meters in diameter, initiating radiation and particle production, followed by nucleosynthesis to shape its content.

Key Insights and Future Research Directions

Unique Mechanism for Dark Matter Formation

The team suggested a unique perspective on how inflation contributes to the formation of dark matter using the freeze-in model.

Katherine Freese, Director of the Weinberg Institute of Theoretical Physics and lead author, explained, "Our model is unique because it successfully produces dark matter during inflation. In contrast, most models see any matter created during inflation being rapidly 'inflated away' due to the universe's exponential expansion, resulting in nearly no remnants."

Potential for Further Investigations

In this novel mechanism, it is proposed that the dark matter we observe today may have originated during the brief period of inflation before the Big Bang. During this phase, the quantum field responsible for inflation, known as the inflaton, transfers some of its energy to radiation, which subsequently lead to the creation of dark matter particles through the freeze-in process. However, the question remains: what existed before inflation? Physicists have no definitive answer.

Next Steps for Verifying the WIFI Model

The WIFI model has yet to be verified through observations. However, a crucial aspect of this scenario—warm inflation—is set to be examined over the next decade by cosmic microwave background experiments. Validating warm inflation would mark a major advancement for the dark matter production hypothesis proposed by the WIFI model.

Broader Implications for Future Research

According to Barmak Shams Es Haghi, one of the co-authors along with Gabriele Montefalcone, "Our study primarily examined dark matter production, but the WIFI model suggests it could have broader implications, such as generating other particles that could be significant for the evolution of the early universe. This points to exciting possibilities for further investigations."

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