EPJ ST Highlight - Using particle accelerators to investigate the quark-gluon plasma of the infant Universe

In the early stages of the Universe, quarks and gluons were quickly confined to protons and neutrons which went on to form atoms. With particle accelerators reaching increasingly higher energy levels the opportunity to study this fleeting primordial state of matter has finally arrived.

Quark-Gluon Plasma (QGP) is a state of matter which existed only for the briefest of times at the very beginning of the Universe with these particles being quickly clumped together to form the protons and neutrons that make up the everyday matter that surrounds us. The challenge of understanding this primordial state of matter falls to physicists operating the world’s most powerful particle accelerators. A new special issue of EPJ Special Topics entitled ‘Quark-Gluon Plasma and Heavy-Ion Phenomenology’ edited by Munshi G. Mustafa, Saha Institute of Nuclear Physics, Kolkata, India, brings together seven papers that detail our understanding of QGP and the processes that transformed it into the baryonic matter around us on an everyday basis.

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EPJ ST Highlight - Gaining insight into the Universe’s most powerful objects and events

A timely new collection reminds us that even in times of great hardship, our understanding of the Universe’s most explosive, spectacular and mysterious events and objects continues to grow

Supernovas, neutron stars, and neutron star mergers are some of the Universe’s most powerful events and mysterious objects, leftover after the burning of nuclear fuel is exhausted within massive stars. A new special issue of EPJ Special Topics entitled ‘Nuclear astrophysics in our time: supernovae, neutron stars and binary neutron star mergers’ edited by Debades Bandyopadhyay, Saha Institute of Nuclear Physics, Kolkata, India, brings together several papers that document our understanding of these astrophysical events and compact stars.

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EPJ ST Highlight - Hunting Dark Energy with Gravity Resonance Spectroscopy

Gravitational quantum states in ultra-cold neutrons

A highly sophisticated technique enables researchers to search for minuscule anomalies in the quantum state transitions of neutrons, which could offer key clues about the elusive nature of Dark Energy

Dark Energy is widely believed to be the driving force behind the universe’s accelerating expansion, and several theories have now been proposed to explain its elusive nature. However, these theories predict that its influence on quantum scales must be vanishingly small, and experiments so far have not been accurate enough to either verify or discredit them. In new research published in EPJ Special Topics, a team led by Hartmut Abele at TU Wien in Austria demonstrate a robust experimental technique for studying one such theory, using ultra-cold neutrons. Named ‘Gravity Resonance Spectroscopy’ (GRS), their approach could bring researchers a step closer to understanding one of the greatest mysteries in cosmology.

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EPJ ST Highlight - GEFS: Searching beyond seismology for earthquake precursors

A proposed collaborative initiative involving researchers in a wide range of fields could lead to better predictions of large-scale seismic events.

To predict when earthquakes are likely to occur, seismologists often use statistics to monitor how clusters of seismic activity evolve over time. However, this approach often fails to anticipate the time and magnitude of large-scale earthquakes, leading to dangerous oversights in current early-warning systems. For decades, studies outside the seismology field have proposed that these major, potentially devastating seismic events are connected to a range of non-seismic phenomena – which can be observed days or even weeks before these large earthquakes occur. So far, however, this idea hasn’t caught on in the wider scientific community. In this special issue, EPJ Special Topics proposes the Global Earthquake Forecasting System (GEFS): the first collaborative initiative between multi-disciplinary researchers devoted to studying a diverse array of non-seismic earthquake precursors.

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EPJ ST Highlight – Introduction to Celestial Mechanics in the XXIst Century

Space exploration is moving into a new era, the turn of the century has seen past glories fade and the focus of science and research move from one-off achievements and firsts, to the establishment of frameworks that will encourage sustainability. At the same time, the more we learn about space, the more we realise that plans must be put in place to mitigate threats from beyond our own atmosphere. As such, the EPJ Special Topics issue on ‘Celestial Mechanics in the XXIst Century’ reflects this shift in attention by spotlighting research that aims to cement humankind’s place amongst the stars.

Here, we present highlights from this issue where we learn how spacecrafts can get a boost in ‘Aerogravity Assisted’ interactions, how we might reduce the risk of space debris collision, and how a tethered diversion might protect Earth from asteroid impact.

EPJ ST Highlight - Spacecrafts get a boost in ‘Aerogravity Assisted’ interactions

The Voyager 2 probe gained the energy boost to escape the solar system from an AGA (NASA/JPL)

New research examines the effect of rotation and other variables in the applications of ‘aerogravity assisted’ manoeuvres to obtain an energy boost for space craft.

In a recent paper published in EPJ Special Topics, Jhonathan O. Murcia Piñeros, a post-doctoral researcher at Space Electronics Division, Instituto Nacional de Pesquisas Espaciais, São José dos Campos, Brazil, and his co-authors, map the energy variations of the spacecraft orbits during ‘aerogravity assisted’ (AGA) manoeuvres. A technique in which energy gains are granted to a spacecraft by a close encounter with a planet or other celestial body via that body’s atmosphere and gravity.

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EPJ ST Highlight - Reducing the risk of space debris collision

Debris plot by NASA / Public Domain

An increase in space launches requires the development of a method to clear space debris which could collide with valuable equipment. One plausible method of achieving this through the use of a tug vehicle requires a successful connection procedure.

As humanity expands its horizons beyond the Earth and begins to consider space missions with extended duration, sustainability necessitates the launch of more space vehicles, increasing the risk of collision with existing space debris. One method of clearing this debris involves a tug vehicle dragging it to a safe region. In a new paper published in EPJ Special Topics, authors Antônio Delson Conceição de Jesus and Gabriel Luiz F. Santos, both from the State University of Feira de Santana, Bahia, Brazil, model the complex rendezvous manoeuvres a tug vehicle clearing space debris would have to undergo to mitigate the risk of a collision that could cause irreparable damage at the moment of coupling.

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EPJ ST Highlight - Protecting Earth from asteroid impact with a tethered diversion

A depiction of a tether connecting two asteroids

The use of a tether assisted system could prevent an asteroid impacting Earth without the risk of fragmentation.

Our planet exists within the vicinity of thousands of Near-Earth Objects (NEOs), some of which –  Potentially Hazardous Asteroids (PHAs)  –  carry the risk of impacting Earth causing major damage to infrastructure and loss of life. Methods to mitigate such a collision are highly desirable. A new paper published in EPJ Special Topics, authored by Flaviane Venditti, Planetary Radar Department, Arecibo Observatory, University of Central Florida, Arecibo, suggests the use of a tether assisted system to prevent PHA impact.

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EPJ ST Highlight - Exploring strangeness and the primordial Universe

Having studied quark-gluon plasma since the late 1970s, Dr Johann Rafelski summarises the evolution in our understanding of the exotic quark signature of this primordial material which once filled the whole Universe.

Physicists believe that in the Universe’s first ten microseconds free quarks and gluons filled all of spacetime, forming a new phase of matter named ‘quark-gluon plasma’ (QGP). Experimental and theoretical work at CERN was instrumental in the discovery of this hot soup of primordial matter, which is recreated today in accelerator-based lab experiments. To discover QGP in such experiments, the observation of exotic ‘strange’ quarks is very important. If QGP is created, strangeness is readily produced through collisions between gluons. In analysis published in EPJ Special Topics, Dr Johann Rafelski from The University of Arizona, United States, also working at CERN, presents how our understanding of this characteristic strangeness production signature has evolved over the span of his long career.

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EPJ ST Highlight - Infinite number of quantum particles gives clues to big-picture behaviour at large scale

Werner Heisenberg. Bundesarchiv, Bild 183-R57262 / Unknown / CC-BY-SA 3.0 [CC BY-SA 3.0 de (https://creativecommons.org/ licenses/by-sa/3.0/de/deed.en)]

Scientists gain a deeper understanding of phenomena at macroscopic scale by simulating the consequences of having an infinite number of physical phenomena at quantum scale

In quantum mechanics, the Heisenberg uncertainty principle prevents an external observer from measuring both the position and speed (referred to as momentum) of a particle at the same time. They can only know with a high degree of certainty either one or the other - unlike what happens at large scales where both are known. To identify a given particle’s characteristics, physicists introduced the notion of quasi-distribution of position and momentum. This approach was an attempt to reconcile quantum-scale interpretation of what is happening in particles with the standard approach used to understand motion at normal scale, a field dubbed classical mechanics.

In a new study published in EPJ Special Topics, Dr J.S. Ben-Benjamin and colleagues from Texas A&M University, USA, reverse this approach; starting with quantum mechanical rules, they explore how to derive an infinite number of quasi-distributions, to emulate the classical mechanics approach. This approach is also applicable to a number of other variables found in quantum-scale particles, including particle spin.

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ISSN: 2195-7045 (Electronic Edition)

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