Physics World Discovery

The detection of gravitational waves has ushered in a new era of gravitational wave astronomy and added a new medium to multi-messenger astronomy. This book examines the theoretical foundation of gravitational waves and the state of the art of gravitational wave detection including interferometric detectors and pulsar timing arrays. The design and sensitivity of the LIGO interferometers are examined. The source and data analysis method for each of the four main classes of gravitational waves (compact binary coalescence, burst, continuous, and stochastic) are described. A summary of the gravitational waves that have been detected as of January 2019 is presented along with what gravitational wave astronomy has been extracted from these observations. Finally, what the future of gravitational wave exploration looks like in terms of ground-based and space-based detectors is presented.

Each of the tens of trillions of cells making up your body contains about two metres of DNA, which need to fit within the 10 microns container that is its nucleus—roughly a tenth of the diameter of a human hair. How is the DNA arranged in such a tight spot? A liver and a brain cell contain exactly the same genetic material, as they come from the same egg cell, yet they work very differently, because the patterns of genes that are on and off in the two is completely distinct. How is this at all possible? Biophysicists have found general principles that are beginning to answer these and similar questions. In this ebook we explore some of these principles, and describe a selection of topics where physicists have contributed to our current understanding of DNA and chromosomes.

Since 2003 there has been an explosion in the observation of new hadronic states that cannot be classified by the well-tested quark model of mesons (quark-antiquark) and baryons (three quarks or antiquarks). The properties of these states indicate that they are combinations of four, five, or more, quarks and antiquarks, making them manifestly exotic. A recent high-profile example was the discovery of two pentaquark candidates by the LHCb collaboration at the CERN Large Hadron Collider (LHC). No scientific consensus has yet emerged to explain the exotic hadron spectrum, demanding a new set of experimental observations that will feed the development of theoretical models to describe the dynamics of multiquark states. In this Discovery book we will take you on a tour of quantum chromodynamics, explain about the latest research into the physics of exotic hadrons and describe the exciting opportunities that are offered by the next generation of particle physics experiments.

Is carbon capture and storage (CCS) the technology that could be key to slowing climate change or an expensive diversion? Few people are aware that we already have the technology to remove most of the carbon dioxide emissions from fossil fuelled power and industry. This same technology is needed to deliver the negative emissions called for in almost all integrated assessment models. Collectively, this rather prosaic and unexciting technology is termed Carbon Capture and Storage, CCS-or Bio-energy with CCS, BECCS, when delivering negative emissions. This short book describes the technology, and takes a brief look at some of the reasons why society is not yet urgently reaching for it.

The combination of printing technology with manufacturing electronic devices enables a new paradigm of printable electronics, where 'smart' functionality can be readily incorporated into almost any product at low cost. Over recent decades, rapid progress has been made in this field, which is now emerging into the industrial and commercial realm. However, successful development and commercialisation on a large scale presents some significant technical challenges. For fully-printable electronic systems, all the component parts must be deposited from solutions (inks), requiring the development of new inorganic, organic and hybrid materials. A variety of traditional printing techniques are being explored and adapted for printing these new materials in ways that result in the best performing electronicdevices. Whilst printed electronics research has initially focused on traditional types of electronic device such as light-emitting diodes, transistors, and photovoltaics, it is increasingly apparent that a much wider range of applications can be realised. The soft and stretchable nature of printable materials makes them perfect candidates for bioelectronics, resulting in a wealth of research looking at biocompatible printable inks and biosensors. Regardless of application, the properties of printed electronicmaterials depend on the chemical structures, processing conditions, device architecture,and operational conditions, the complex inter-relationships of which are driving ongoing research. We focus on three particular hot topics', where attention is currently focused: novel materials, characterisation techniques, and device stability. With progress advancing very rapidly, printed electronics is expected to grow over the next decade into a key technology with an enormous economic and social impact.

Nanomaterials are changing the world we live in, and one of the most exciting applications they can have is the creation of new electronic devices. But what are they, how can we build devices from them, and how can nanoelectronics give us new ways to interact with light, our environments and even our brains? This ebook will explore the unique physics of different types of nanomaterials, and lay out different devices that harness this unique physics to create optoelectronic components, chemical sensors, and novel paradigms for memory and computing. After outlining the current state of the art, the final section looks to grand challenges and opportunities in nanoelectronics.

Biological imaging at the cellular level, particularly in vivo, is a key enabling tool for understanding biological processes, disease diagnosis and drug development. Unfortunately, specimens under observation often introduce optical aberrations that degrade the imaging resolution, particularly when imaging deep into tissue. Adaptive optics counteracts these effects. This technology, originally developed and applied in astronomy, has been increasingly applied to ophthalmics and microscopy. This book introduces the key concepts and technologies behind adaptive optics. The wide diversity of imaging methods used in biological imaging requires multiple approaches to adaptive optics. Methods fall into two broad categories—those that use a direct measurement of the aberration and those that do not. Relative advantages of each are described. Application results are presented. Finally, current technology trends and promising future application areas are discussed.

Following the discovery of the Higgs boson in 2012, particle physics has entered its most exciting and crucial period for over 50 years. In this book, I first summarise our current understanding of particle physics, and why this knowledge is almost certainly incomplete. We will then see that the Large Hadron Collider provides the means to search for the next theory of particle physics by performing precise measurements of the Higgs boson, and by looking directly for particles that can solve current cosmic mysteries such as the nature of dark matter. Finally, I will anticipate the next decade of particle physics by placing the Large Hadron Collider within the wider context of other experiments. The results expected over the next ten years promise to transform our understanding of what the Universe is made of and how it came to be.

One of the most active areas in atomic, molecular and optical physics is the use of ultracold atomic gases in optical lattices to simulate the behaviour of electrons in condensed matter systems. The larger mass, longer length scale, and tuneable interactions in these systems allow the dynamics of atoms moving in these systems to be followed in real time, and resonant light scattering by the atoms allows this motion to be probed on a microscopic scale using site-resolved imaging. This book reviews the physics of Hubbard-type models for both bosons and fermions in an optical lattice, which give rise to a rich variety of insulating and conducting phases depending on the lattice properties and interparticle interactions. It also discusses the effect of disorder on the transport of atoms in these models, and the recently discovered phenomenon of many-body localization. It presents several examples of experiments using both density and momentum imaging and quantum gas microscopy to study the motion of atoms in optical lattices. These illustrate the power and flexibility of ultracold-lattice analogues for exploring exotic states of matter at an unprecedented level of precision.

With the recent discovery of gravitational waves and high-energy cosmic neutrinos, we are witnessing the beginning of a new era in multimessenger astronomy. The exploration of the Universe through these new messengers, along with electromagnetic radiation and cosmic rays, gives us new insights into the most extreme energetic cosmic events, environments and particle accelerators. The objects of interest range from galaxies with accreting supermassive black holes in their centre to collapsing stars and coalescing stellar black holes. In this ebook we provide an introduction to the scientific questions surrounding these new messengers and the detectors and observational techniques used to study them, together with an overview of current and future directions in the field.

Space weather—changes in the Earth's environment that can often be traced to physical processes in the Sun—can have a profound impact on critical Earth-based infrastructures such as power grids and civil aviation. Violent eruptions on the solar surface can eject huge clouds of magnetized plasma and particle radiation, which then propagate across interplanetary space and envelop the Earth. These space weather events can drive major changes in a variety of terrestrial environments, which can disrupt, or even damage, many of the technological systems that underpin modern societies. The aim of this book is to offer an insight into our current scientific understanding of space weather, and how we can use that knowledge to mitigate the risks it poses for Earth-based technologies. It also identifies some key challenges for future space-weather research, and considers how emerging technological developments may introduce new risks that will drive continuing investigation.

Cancer therapy is a multi-modality approach including surgery, systemic or targeted chemotherapy, radiation (external beam or radionuclide), and immunotherapy. Radiation is typically administered using external beam photon therapy. Proton therapy has been around for more than 60 years but was restricted to research laboratories until the 1990s. Since then clinical proton therapy has been growing rapidly with currently more than 50 facilities worldwide. The interest in proton therapy stems from the physical properties of protons allowing for advanced dose sculpting around the target and sparing of healthy tissue. This review first evaluates the basics of proton therapy physics and technology and then outlines some of the current physical, biological, and clinical challenges. Solving these will ultimately determine whether proton therapy will continue on its path to becoming mainstream.

Rydberg physics is the land of gentle giants—highly-excited electronic states where an electron is, on average, far from the nucleus. They are created with a lot of energy, have unusually large size and live relatively long. They are useful because they are extremely sensitive to their environment; so much so that a single photon of light can change the behaviour of not only one, but dozens or hundreds of them, over distances we can easily see under an optical microscope. Wherever Rydberg states are created—in atoms, molecules or solids—they all share common features that are exemplified by the physical description of highly-excited hydrogen atoms, with energy levels described by the Rydberg formula.

Units are at the heart of science and technology. Most measurements require units to express their result. The International System of Units (SI) provides a widely used coherent framework of units. While the present SI is fit for purpose for all measurements, it has several shortcomings. Most notably, the kilogram is defined via an artifact that limits its realization to a specific place and certain times. To solve this problem and to take advantage of advances in quantum metrology made in the last 50 years, a revision of the SI is planned. This revision will modify the foundation of the SI from base units to fundamental constants of nature. While the revision presents a huge shift in philosophy, the size of the units will not change, and hence the revision will go mostly unnoticed.

With the discovery of the Higgs boson our picture of the subatomic world—the Standard Model—is complete. But looking at the Universe on a larger scale, there are things the Standard Model cannot explain, including gravity, dark matter and several others. The Standard Model must be just part of a larger picture, and one of the most obvious places to look for evidence of this larger picture is the biggest experiment studying the subatomic world: the Large Hadron Collider (LHC). The first part of this book describes an example of how the experiments at the LHC search for new particles. I'll be focusing here on the two 'general purpose' experiments: ATLAS (of which I am a member) and CMS. Searches remain central to the work of these two experiments, but the data so far have not revealed any surprises and there is increased interest in making sure we haven't missed something along the way: new discoveries may lie in unconventional signatures, or perhaps we simply haven't had the right idea yet. The rest of book will focus on what some of these unconventional signatures are, and how we are making our ongoing measurements and searches 'future-proof'—i.e., being able to use measurements we make today to test any new ideas that are developed in the future. The rest of book will focus on these two areas.

Nuclear waste—the radioactive by-product from nuclear power generation, nuclear weapons and medical isotope production—is one of the most challenging types of waste for our society to manage. Its high radioactivity requires that it be safely isolated from humans and the environment until it no longer poses a hazard; of the order of a million years. This review will show that nuclear waste management is a world of materials science and engineering challenges that must stand the test of time, from designing engineered facilities to isolate waste from future civilisations, to inventing new materials to immobilise weapons-grade and surplus civil plutonium. Due to the ever-changing nature of nuclear waste, which transforms its chemical composition and physical properties through radioactive decay processes, nuclear waste management is also a race against time that will continue to drive research and development for many years to come.

Why does our universe consist purely of matter, even though the same amount of antimatter and matter should have been produced at the moment of the Big Bang 13.8 billion years ago? One of the most potentially fruitful approaches to address the mystery is to study the properties of antihydrogen and antiprotons. Because they are both stable, we can in principle make measurement precision as high as we need to see differences between these antimatter systems and their matter counterparts, i.e. hydrogen and protons. This is the goal of cold antihydrogen research. To study a fundamental symmetry–charge, parity, and time reversal (CPT) symmetry—which should lead to identical spectra in hydrogen and antihydrogen, as well as the weak equivalence principle (WEP), cold antihydrogen research seeks any discrepancies between matter and antimatter, which might also offer clues to the missing antimatter mystery. Precision tests of CPT have already been carried out in other systems, but antihydrogen spectroscopy offers the hope of reaching even higher sensitivity to violations of CPT. Meanwhile, utilizing the Earth and antihydrogen atoms as an experimental system, the WEP predicts a gravitational interaction between matter and antimatter that is identical to that between any two matter objects. The WEP has been tested to very high precision for a range of material compositions, but no such precision test using antimatter has yet been carried out, offering hope of a telltale inconsistency between matter and antimatter. In this Discovery book, we invite you to visit the frontiers of cold antimatter research, focusing on new technologies to form beams of antihydrogen atoms and antihydrogen ions, and new ways of interrogating the properties of antimatter.

Quantum computer technology is progressing rapidly with dozens of qubits and hundreds of quantum logic gates now possible. Although current quantum computer technology is distant from being able to solve computational problems beyond the reach of non-quantum computers, experiments have progressed well beyond simply demonstrating the requisite components. We can now operate small quantum logic processors with connected networks of qubits and quantum logic gates, which is a great stride towards functioning quantum computers. This book aims to be accessible to a broad audience with basic knowledge of computers, electronics and physics. The goal is to convey key notions relevant to building quantum computers and to present state-of-the-art quantum-computer research in various media such as trapped ions, superconducting circuits, photonics and beyond.

There are some physics controversies that no amount of physics research can answer. Why is doing string theory scientific despite its lack of empirical predictions? How should we interpret quantum mechanics? What is the nature of time and space? What constitutes fundamental physics? One can answer these questions dogmatically by appealing to textbooks or by making rough and ready pronouncements, but the issues behind them can often be significantly clarified by the sort of systematic, critical reflection that philosophy practices. Philosophy comes in several traditions. Three of these—known as 'analytic,' 'pragmatic' and 'continental'—have paid particular attention to physics. This ebook illustrates philosophy of physics in action, and how it can help physics, by using four examples from physics to exhibit the aims and value of these philosophical approaches.

As renewable energy use expands there will be a need to develop ways to balance its variability. Storage is one of the options. Presently the main emphasis is for systems storing electrical power in advanced batteries (many of them derivatives of parallel developments in the electric vehicle field), as well as via liquid air storage, compressed air storage, super-capacitors and flywheels, and, the leader so far, pumped hydro reservoirs. In addition, new systems are emerging for hydrogen generation and storage, feeding fuel cell power production. Heat (and cold) is also a storage medium and some systems exploit thermal effects as part of wider energy management activity. Some of the more exotic ones even try to use gravity on a large scale. This short book looks at all the options, their potentials and their limits. There are no clear winners, with some being suited to short-term balancing and others to longer-term storage. The eventual mix adopted will be shaped by the pattern of development of other balancing measures, including smart-grid demand management and super-grid imports and exports.

CERN is the world's largest particle physics research laboratory. Since it was established in 1954, it has made an outstanding contribution to our understanding of the fundamental particles and their interactions, and also to the technologies needed to analyse their properties and behaviour. The experimental challenges have pushed the performance of particle accelerators and detectors to the limits of our technical capabilities, and these groundbreaking technologies can also have a significant impact in applications beyond particle physics. In particular, the detectors developed for particle physics have led to improved techniques for medical imaging, while accelerator technologies lie at the heart of the irradiation methods that are widely used for treating cancer.

Indeed, many important diagnostic and therapeutic techniques used by healthcare professionals are based either on basic physics principles or the technologies developed to carry out physics research. Ever since the discovery of x-rays by Roentgen in 1895, physics has been instrumental in the development of technologies in the biomedical domain, including the use of ionizing radiation for medical imaging and therapy. Some key examples that are explored in detail in this book include scanners based on positron emission tomography, as well as radiation therapy for cancer treatment. Even the collaborative model of particle physics is proving to be effective in catalysing multidisciplinary research for medical applications, ensuring that pioneering physics research is exploited for the benefit of all.

Just over 95% of our Universe comes in the shrouded form of dark energy and dark matter that we can neither explain nor directly detect. Together, these two dark entities play out a cosmic battle of epic proportions, with the gravity of dark matter slowly pulling structures in the Universe together, and dark energy fuelling the Universe's accelerated expansion, making it ever harder for those structures to grow. In this book we will explore this dark enigma and introduce the cosmologist's toolkit of observations and techniques that allow us to confront different theories on the dark Universe. I'll explain why I believe that, to truly understand the dark Universe, we will need some new physics that will forever change our cosmic view.

Quantitative finance is a field that has risen to prominence over the last few decades. It encompasses the complex models and calculations that value financial contracts, particularly those which reference events in the future, and apply probabilities to these events. While adding greatly to the flexibility of the market available to corporations and investors, it has also been blamed for worsening the impact of financial crises. But what exactly does quantitative finance encompass, and where did these ideas and models originate? We show that the mathematics behind finance and behind games of chance have tracked each other closely over the centuries and that many well-known physicists and mathematicians have contributed to the field.

The emerging field of complex light—the study and application of custom light beams with tailored intensity, polarization or phase—is a focal point for fundamental breakthroughs in optical science. As this review will show, those advances in fundamental understanding, coupled with the latest developments in complex light generation, are translating into a range of diverse and cross-disciplinary applications that span microscopy, high-data-rate communications, optical trapping and quantum optics. We can expect more twists along the way, too, as researchers seek to manipulate and control the propagation speed of complex light beams, while others push the more exotic possibilities afforded by complex light in quantum-entanglement experiments.