Oxford Physics Public Lectures: Recent Episodes
Oxford University
The Department of Physics public lecture series. An exciting series of lectures about the research at Oxford Physics take place throughout the academic year. Looking at topics diverse as the creation of the universe to the science of climate change.
Features episodes previously published as: (1) 'Oxford Physics Alumni': "Informal interviews with physics alumni at events, lectures and other alumni related activities." (2) 'Physics and Philosophy: Arguments, Experiments and a Few Things in Between': "A series which explores some of the links between physics and philosophy, two of the most fundamental ways with which we try to answer our questions about the world around us. A number of the most pertinent topics which bridge the disciplines are discussed - the nature of space and time, the unpredictable results of quantum mechanics and their surprising consequences and perhaps most fundamentally, the nature of the mind and how far science can go towards explaining and understanding it. Featuring interviews with Dr. Christopher Palmer, Prof. Frank Arntzenius, Prof. Vlatko Vedral, Dr. David Wallace and Prof. Roger Penrose."
Delve into history with Dr Rob Johnson, Director of The Changing Character of War Centre at Oxford, as he explores a pivotal question.
A lecture by Prof Stephen Blundell, Professor of Physics – Condensed Matter - (Department of Physics and Mansfield College).
Explore the history of atomic bomb development with Dr. Georg Viehhauser, Particle Physics Research Lecturer at St John's College, Oxford.
Particle Physics Christmas Lecture, hosted by Prof. Daniela Bortoletto, Head of Particle Physics and senior members of the department with guest speaker, Professor Francis Halzen. Professor Francis Halzen is Wisconsin IceCube Particle Astrophysics Center and Department of Physics, University of Wisconsin - Madison. Prof Halzen is a theoretician studying problems at the interface of particle physics, astrophysics and cosmology. In 1987 he began working on the AMANDA experiment, a prototype neutrino telescope buried under the South Pole. It provided a proof-of-concept for IceCube, a kilometer-scale detector completed in 2010 which in 2013 discovered an extraterrestrial flux of high energy neutrinos. More recently in 2018 the first cosmic source of such neutrinos was tentatively identified. IceCube has also made precision measurements of neutrino oscillations, searched for dark matter and even contributed to our understanding of glaciology. Prof Halzen will discuss these achievements as well as plans for a much bigger detector that will firmly establish neutrino astronomy as a new window on the universe. The IceCube project has transformed a cubic kilometre of natural Antarctic ice into a neutrino detector. The instrument detects more than 100,000 neutrinos per year in the GeV to 10,000 TeV energy range. Among those, we have isolated a flux of high-energy neutrinos of cosmic origin. We will explore the use of IceCube data for neutrino physics and astrophysics emphasizing the significance of the discovery of cosmic neutrinos. We identified their first source: alerted by IceCube on September 22, 2017, several astronomical telescopes pinpointed a flaring galaxy powered by an active supermassive black hole, as the source of a cosmic neutrino with an energy of 310 TeV. Most importantly, the large cosmic neutrino flux observed implies that the Universe’s energy density in high-energy neutrinos is close to that in gamma rays, suggesting that the sources are connected and that a multitude of astronomical objects await discovery.
Particle Physics Christmas Lecture, hosted by Prof. Daniela Bortoletto, Head of Particle Physics and senior members of the department with guest speaker, Professor Francis Halzen. Professor Francis Halzen is Wisconsin IceCube Particle Astrophysics Center and Department of Physics, University of Wisconsin - Madison. Prof Halzen is a theoretician studying problems at the interface of particle physics, astrophysics and cosmology. In 1987 he began working on the AMANDA experiment, a prototype neutrino telescope buried under the South Pole. It provided a proof-of-concept for IceCube, a kilometer-scale detector completed in 2010 which in 2013 discovered an extraterrestrial flux of high energy neutrinos. More recently in 2018 the first cosmic source of such neutrinos was tentatively identified. IceCube has also made precision measurements of neutrino oscillations, searched for dark matter and even contributed to our understanding of glaciology. Prof Halzen will discuss these achievements as well as plans for a much bigger detector that will firmly establish neutrino astronomy as a new window on the universe. The IceCube project has transformed a cubic kilometre of natural Antarctic ice into a neutrino detector. The instrument detects more than 100,000 neutrinos per year in the GeV to 10,000 TeV energy range. Among those, we have isolated a flux of high-energy neutrinos of cosmic origin. We will explore the use of IceCube data for neutrino physics and astrophysics emphasizing the significance of the discovery of cosmic neutrinos. We identified their first source: alerted by IceCube on September 22, 2017, several astronomical telescopes pinpointed a flaring galaxy powered by an active supermassive black hole, as the source of a cosmic neutrino with an energy of 310 TeV. Most importantly, the large cosmic neutrino flux observed implies that the Universe’s energy density in high-energy neutrinos is close to that in gamma rays, suggesting that the sources are connected and that a multitude of astronomical objects await discovery.
Professor Heino Falcke of Radboud University, Nijmegen delivers the 19th Hintze Lecture - reviewing the latest results of the Event Horizon Telescope, its scientific implications and future expansions of the array One of the most bizarre, but perhaps also most fundamental predictions of Einstein’s theory of general relativity are black holes. They are extreme concentrations of matter with a gravitational attraction so strong, that not even light can escape. The inside of black holes is shielded from observations by an event horizon, a virtual one-way membrane through which matter, light and information can enter but never leave. This loss of information, however, contradicts some basic tenets of quantum physics. Does such an event horizon really exist? What are its effects on the ambient light and surrounding matter? How does a black hole really look? Can one see it? Indeed, recently we have made the first image of a black hole and detected its dark shadow in the radio galaxy M87 with the global Event Horizon Telescope experiment. Detailed supercomputer simulations faithfully reproduce these observations. Simulations and observations together provide strong support for the notion that we are literally looking into the abyss of the event horizon of a supermassive black hole. The talk will review the latest results of the Event Horizon Telescope, its scientific implications and future expansions of the array.
Professor Stephen Blundell explores the many universes of quantum materials for the 2019 Quantum Materials Public Lecture. Physicists try to find the laws that govern the Universe, discover new particles and explain phenomena. But what if the rules that govern the Universe were different? What would happen then? This question is not just an academic one. Every new material discovered is behaves like a new Universe, with different laws and sometimes new particles. This talk explains how this idea works in practice and how the different universes discovered in so-called quantum materials are changing the way we think about the physical world.
Bill Diamond, President & CEO The SETI Institute gives an an update on the search for life in the Universe. Hosted by Ian Shipsey, Head of Physics.
What is the Dark Matter which makes 85% of the matter in the Universe? We have been asking this question for many decades and used a variety of experimental approaches to address it, with detectors on Earth and in space. Yet, the nature of Dark Matter remains a mystery. An answer to this fundamental question will likely come from ongoing and future searches with accelerators, indirect and direct detection. Detection of a Dark Matter signal in an ultra-low background terrestrial detector will provide the most direct evidence of its existence and will represent a ground-breaking discovery in physics and cosmology. Among the variety of dark matter detectors, liquid xenon time projection chambers have shown to be the most sensitive, thanks to a combination of very large target mass, ultra-low background and excellent signal-to-noise discrimination. Experiments based on this technology have led the field for the past decade. I will focus on the XENON project and its prospects to continue to be at the forefront of dark matter direct detection in the coming decade.
Professor Elena Aprile is Professor of Physics at Columbia University in New York City. After obtaining her undergraduate degree in Physics in Naples, Italy, she earned her PhD at the University of Geneva, Switzerland. She started her research on noble liquid imaging detectors under the mentorship of Professor Carlo Rubbia, first as a student at CERN and later as postdoc at Harvard University. At Columbia, she pioneered the development of a Compton telescope for gamma-ray astrophysics based on a liquid xenon time projection chamber. She later turned her attention to the dark matter question proposing the XENON project for its direct detection using liquid xenon as target and detector medium. She founded the XENON Dark Matter Collaboration in 2002 and has served as its scientific spokesperson ever since; her international team includes more than 170 scientists and students representing 24 nationalities and 22 institutions. Aprile has been principal investigator on more than 20 research grants worth nearly $30 million over the last three decades and holds a patent for a vacuum ultraviolet light source. She has served on numerous panels and committees, for NASA, NSF, DOE, Fermilab, CNRS, ERC, etc. She is a Fellow of the American Physical Society since 2000. In 2017, she received an honorary degree from the University of Stockholm. She is the recipient of the 2019 AAS Lancelot Berkeley Prize.
The 2019 Halley lecture n February 2016, the Laser Interferometer Gravitational Wave Observatory (LIGO) announced the discovery of the merger of two black holes, each of which weighed around 30 times the mass of the Sun. Shortly thereafter, it was speculated that these black holes might make up the dark matter that has long been known to exist in galaxies (like our own Milky Way). I will review this possibility and explain why the hypothesis may or may not work.
Professor Jacqueline van Gorkom delivers the 18th Hintze Lecture. How do galaxies get their gas and how do they lose it? Theories of galaxy formation predict that the growth of galaxies is regulated by the infall of hydrogen gas. This gas is the fuel for star formation. When galaxies run out of gas star formation stops. Interestingly, observationally we know much more about the stars in galaxies and how the star formation rate has evolved over time than we know about the gas. The gas is hard to observe. Currently a renaissance is taking place in observational radio astronomy, new telescopes have been developed, which can image this gas, and even better ones are being constructed. I will show what we already have learned, discuss remaining puzzles and outline what the future might bring.
Professor Mark Newton describes some of the key events in the discovery and development of Electron Paramagnetic Resonance (EPR). Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy as it is also known is a method for studying systems with unpaired electrons. The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but it is electron spins that are excited instead of the spins of atomic nuclei. EPR was first observed in Kazan State University by Soviet physicist Yevgeny Zavoisky in 1944 and was developed independently at the same time by Brebis Bleaney at the University of Oxford. In the 75 years that have followed EPR has found many applications in physics, chemistry, biology, medicine, geology and archaeology. In this talk I will endeavour to describe some of the key events in the discovery and development EPR but spend most of the time focusing on applications of the technique and its many derivatives. EPR is very much an evolving technique, with detection of single electron spins now routine in some systems, such that we can optimistically look for applications ranging from studies of single molecules, to enhanced sensitivity and spatial resolution in magnetic resonance imaging. This annual lecture commemorating Professor Brebis Bleaney (1915-2006) was endowed by Bleaney's pupil Professor Michael Baker (1930-2017).
The 17th Hintze Lecture, given by Professor Rocky Kolb, Arthur Holly Compton Distinguished Service Professor of Astronomy and Astrophysics, The University of Chicago. In daily life we do not experience the quantum nature of the world on the scale of elementary particles, nor do we sense the expansion and evolution of the universe on cosmic scales. Humans, midway in size between quantum and cosmic scales, evolved to perceive nature not as it actually is, but merely as required to survive in our environment. How remarkable that we have developed an understanding of the quantum realm and the cosmic realm, and realized that the inner space of the quantum and the outer space of the cosmos are intimately connected. In this lecture I will highlight some of the remarkable connections between the quantum and the cosmos.
Dr James Green, current Chief Scientist of NASA gives a talk on the how life may be distributed on Earth and in the Solar System with consideration of the age of our sun. This talk was a joint lecture held by the The Department of Physics and the Worshipful Company of Scientific Instrument Makers. NASA's Gravity Assist podcast, hosted by Dr. James Green: https://www.nasa.gov/mediacast/gravity-assist-explorer-1-jim-green-s-gravity-assist
The 3rd Wetton lecture, 19th June 2018 delivered by Professor David W. Hogg, Center for Cosmology and Particle Physics, New York University In the last 20 years, the astronomical community has found thousands of planets around other stars, and we now know that many or even most stars in our Galaxy host planets. These planets have been found by making exceedingly precise measurements of stars. Some of the planets we find are extremely strange; most known planetary systems are very different from our own Solar System. Here we will look at how these measurements are made, and how planets are found in the data. The data analysis - the search for the planets in the mountains of data - involves cutting-edge ideas from data science and machine learning. These technologies are transforming our capabilities in astronomy.
The 16th Hintze lecture, 25th April 2018 delivered by Professor René Doyon, Director, Mont-Mégantic Observatory & Institute for Research on Exoplanets, University of Montreal, Canada It is now well established that planetary systems are very common in the Solar neighbourhood, in particular small rocky planets, similar to Earth, around low-mass stars. Thanks to new ground-and spaced-based infrared facilities soon to be deployed, it will be possible not only to find the closest habitable worlds but also to detect their atmosphere and obtain constraints on their composition. This will be a major stepping stone towards the detection of life outside the Solar system. This lecture will highlight recent exoplanet discoveries and present an overview of ongoing and future projects aiming for the detection and characterisation of nearby habitable worlds. The detection of a biosignature, the evidence for biological activity beyond the Solar System, may be just a few decades away.
The 2018 Astor Visiting Lecture 14th March 2018 delivered by Professor Adam Leroy, Ohio State University. The Atacama Large Millimeter/sub-millimeter Array (ALMA) is the largest, most complex ground-based telescope ever built. From its perch high in the Chilean Andes, ALMA is now unveiling the birth of planets, stars, and galaxies. I will give a taste of the revolution ushered in by ALMA. This includes resolving the disks that form new Solar systems, finding the seeds of gaseous giant planets, weighing – and maybe even directly imaging – black holes, and watching galaxies form at the edge of the universe. Then, I will show how my colleagues and I are using ALMA to understand the origins of stars in galaxies. As part of ALMA’s largest project to date, we are studying all of the stellar nurseries across the nearby universe. We see that the cold clouds of gas and dust that form stars appear to be shaped by violent, dynamic processes that vary from galaxy to galaxy. We also see that the birth of stars from these clouds is both inefficient and terribly destructive.
Our Universe was created in 'The Big Bang' and has been expanding ever since. Professor Schmidt describes the vital statistics of the Universe, and tries to make sense of the Universe's past, present, and future.
A family-friendly demonstration of superconductors in action. Fran explores the low temperatures we need to make them work, and how we can use superconductors for levitating trains. When something superconducts, it behaves as a magnetic mirror, so will be repelled from magnetic fields. We can use this property to float a superconductor above a bed of magnets. However, for this to work, the superconductor has to be very cold. Graduate student Fran Kirschner uses liquid nitrogen to cool some superconductors (among other things) and show what they can do. Along the way, she explains some of the history and uses of these amazing materials.
Public Lecture organised by the Aeronautical Society of Oxford in conjunction with the Department of Physics.
The 14th Hintze Biannual Lecture 4th May 2017 delivered by Professor Conny Aerts - Director, Institute of Astronomy KU Leuven Thanks to the recent space missions CoRoT and Kepler, a new era of stellar physics has dawned. Asteroseismology, the observation and interpretation of starquakes, has produced a number of surprises about the deep interiors of stars. These results have altered our view of the lifecycle of stars including the generations of stars that preceded the Sun. Starquakes allow us to estimate the distances and ages of stars with unprecedented precision. Asteroseismology from space has revealed radically different physics in the heart of massive stars compared to the Sun. These massive stars are the chemical factories of the Universe, forcing us to rethink the output from the manufacturing sector of our Galaxy. Furthermore asteroseismology has paved the way for archaeological studies of our own Milky Way. After reviewing these developments I will look to the future projects that can address the new open questions posed by starquakes.
Physics Colloquium 17 February 2016 delivered by Professor Valerio Scarani Since its formulation in 1964, Bell's theorem has been classified under "foundations of physics". Ekert's 1991 attempt to relate it to an applied task, quantum cryptography, was quenched by an approach that relied on a different basis and was allegedly equivalent. Ekert's intuition was finally vindicated with the discovery of "device-independent certification" of quantum devices. In this colloquium, I shall revisit the tortuous history of that discovery and mention some of the subsequent results.
Physics Colloquium 27 January 2017 delivered by Professor Nicola Spaldin, ETH Zurich The behaviour of the early universe just after the Big Bang is one of the most intriguing basic questions in all of science, and is extraordinarily difficult to answer because of insurmountable issues associated with replaying the Big Bang in the laboratory. One route towards the answer -- which lies at the intersection between cosmology and materials physics -- is to use laboratory materials to test the so-called "Kibble-Zurek" scaling laws proposed for the formation of defects such as cosmic strings in the early universe. Here Professor Spaldin will show that a popular multiferroic material -- with its coexisting magnetic, ferroelectric and structural phase transitions -- generates the crystallographic equivalent of cosmic strings. Professor Spaldin will describe how straightforward solution of the Schroedinger equation for the material allows the important features of its behaviour to be identified and quantified, and present experimental results of what seem to be the first unambiguous demonstration of Kibble-Zurek scaling in real materials. Professor Spaldin will end with some very recent data showing that things might be less unambiguous than they seem.
Professor John Womersley (STFC) gives the Particle Physics Christmas Lecture. In the past five years particle physicists have made major advances in understanding the nature of our universe – discovering the Higgs boson, and more recently detecting gravitational waves from a distant galaxy. Paradoxically we have also learned a lot more about what we don’t know: that the particles and forces we understand in ever greater detail make up only a small fraction of what’s in the cosmos, and that our theoretical prejudices about what remains to be discovered may have been very wrong. A new generation of ambitious experiments at accelerator laboratories, underground, and studying at the large scale structure of the universe will answer these questions – and surely open up others. I will also outline why it is essential that the country remains at the forefront of frontier research of this kind and how it contributes more broadly to society.
Physics Colloquium 25 November 2016 delivered by Dr Jamie Holder The gamma-ray band of the electromagnetic spectrum probes some of the most extreme environments in the Universe. Photons of these very-high energies can only be produced by the interactions of subatomic particles that have been accelerated to almost the speed of light. This acceleration occurs in a surprisingly wide variety of astrophysical sources: close to black holes and neutron stars, in the blast waves of supernova explosions, and in the relativistic jets of active galaxies. Gamma-ray emission might also result from the interactions of dark matter particles, and so provide a non-gravitational method to detect dark matter in the Universe and to determine its nature. Dr Holder will describe the detection methods for gamma-ray astronomy and highlight some of the most exciting results from the VERITAS observatory, which has been studying astrophysical sources from a mountain in Arizona since 2007. He will also describe the status and prospects for the Cherenkov Telescope Array, a next-generation gamma-ray observatory on a much larger scale.
The 13th Hintze Biannual Lecture delivered by Professor David Spergel Observations of the microwave background, the left-over heat from the big bang, the large-scale distribution of galaxies and the properties of distant supernova have led to a remarkable simple model for our universe. With only five parameters (the density of atoms, the density of matter, the age of the universe, the amplitude of fluctuations in the early universe and their scale dependance), this model can fit a host of astronomical observations. We have now determined these basic parameters at the few percent level or better. While simple, our universe is very strange. Atoms make up only 5% of the universe, most of the universe is made of mysterious dark matter and dark energy. We do not understand how the universe began or why there is more matter than anti-matter. I will review our current understanding and look forward to future measurements that can address these big open questions.
Physics Colloquium 21st October 2016 delivered by Professor Theodore (Ted) Shepherd Pretty much all that is known with any confidence about climate change concerns its energetic and thermodynamic aspects. Atmospheric circulation, which also involves consideration of dynamics, is much more uncertain yet plays a critical role in climate change at the regional scale. How to approach this issue represents a major scientific challenge. In this talk Prof Shepherd will explain the nature of the problem and discuss some of the potential ways forward.
Physics Colloquium 14th October 2016 delivered by Professor Thierry Foglizzo The supernova explosion of massive stars is primarily powered by the gravitational contraction of their core into a neutron star, before the formation of a black hole. Despite numerous observations of supernovae in distant galaxies, the underlying mechanism is still a major challenge to theorists. Prof Foglizzo will review the state of the art, with an emphasis on the multidimensional effects of hydro and MHD instabilities. Non axisymmetric one-armed instabilities known as the Standing Accretion Shock Instability and the corotation instability are able to redistribute angular momentum radially even for moderate rotation rates. Numerical simulations of simplified models are used to evaluate their effect on the explosion and the pulsar spin. Surprisingly, both instabilities can be illustrated with a simple hydraulic experiment based on a shallow water analogy. Results are analyzed in view of the constraints on the angular momentum budget set by stellar evolution on the one hand and by the spin properties of pulsars on the other hand.
Physics Colloquium 10th June 2016 delivered by Professor Swapan Chattopadhyay Tremendous advances have been made in the last two decades in precision ‘Quantum’ technologies and techniques in multiple disciplines e.g. cavity electrodynamics, atomic beam interferometry, SQUIDS, quantum optical “squeezed state” techniques for noise-free single photon detection, qubit-based quantum entanglement techniques, high-Q superconducting cavities, precision NMR detection via designer materials, etc. These advances promise to enable transformational research using ultra-sensitive probes to explore very “weak effects” on a laboratory scale. These weak effects are manifest everywhere in nature in material and living systems from the laboratory to outer space. Potential “mezzo-scale” experiments and facilities can be envisaged using “quantum sensors” to search for ultra-weak physical, chemical or biological signals of fundamental significance to the material and living world around us as well as explore the “inner” and “outer” dimension of “vacuum” believed to be manifest in the so-called “dark” universe. This talk will illustrate this potential via a few exciting examples discussed at the recent US DOE Round Table on Quantum Sensors in February 2016.
3rd Annual Lobanov-Rostovsky Lecture in Planetary Geology delivered by Professor Raymond T Pierrehumbert. Atmospheres are dynamic entities, formed from the volatile substances that accrete when a planet is formed and later in its history, cooked out in the hot-high pressure interior of the planet, and exchanging with the interior through crustal processes (for planets which have a solid surface) or mixing into the deep interior (for fluid planets). Loss of atmosphere to space is also a major mechanism whereby the chemical composition of entire planets evolve. There is thus no distinct boundary between the disciplines of planetary geology and planetary atmospheres, and the dawning age of exoplanet discovery has made it even more essential to think across the boundaries of the two disciplines. The likely characteristics of known exoplanets greatly expand the range of substances that have to be thought of as atmospheric components, with many things thought of as “rocks and minerals” on Earth being atmospheric or cloud forming substances. There are planets hot enough to have permanent magma oceans which may give rise to rock vapor atmospheres, and others where clouds may be formed of enstatite or even sapphire (or more prosaically, corundum). Some of these atmospheres are supersonic and local; others may be global and subsonic. There is also a host of new problems to be thought about in connection with “gas midgets,” which are mostly fluid but small enough that they need not have a hydrogen dominated composition. In this lecture, I will provide a survey of the emerging field of integrated planetary science, and conclude with some thoughts on how to train the next generation of planetary scientists to deal with the leading-edge problems of the future.
Physics Colloquium 20th May 2016 delivered by Ian Shipsey Cochlear implants are the first device to successfully restore neural function. They have instigated a popular but controversial revolution in the treatment of deafness, and they serve as a model for research in neuroscience and biomedical engineering. After a visual tour of the physiology of natural hearing the function of cochlear implants will be described in the context of electrical engineering, psychophysics, clinical evaluation, and my own personal experience. About the speaker: Ian Shipsey is a particle physicist, and a Professor of Physics at Oxford University. He has been profoundly deaf since 1989. In 2002 he heard the voice of his daughter for the first time, and his wife’s voice for the first time in thirteen years thanks to a cochlear implant.
The 2016 Hintze Biannual Lecture delivered by Professor Robert Kennicutt Understanding the birth of stars is one of grand challenges of 21st century astrophysics, with impacts extending from the formation of planets to the birth and shaping of galaxies themselves. The challenge has been all the more difficult because the most active birth sites are largely hidden in visible light. Thanks to a new generation of infrared and submillimetre space telescopes this veil has been lifted, and a complete picture of starbirth in the Universe is emerging. They reveal an extraordinary diversity of activities in galaxies, and an emerging history of star formation cosmic time, extending back to some of the first stars and seeds of galaxies. This talk will summarise what we have learnt about starbirth on cosmic scales, and highlight the challenges and opportunities which lie ahead.
Physics Colloquium 6th May 2016 delivered by Professor William Dorland The Liouville equation describing a collection of charged particles is time-reversible. In the weakly coupled limit, one can reduce this equation to a Fokker-Planck equation, which is irreversible. The problem of the fate of electromagnetic field fluctuations in a plasma in the limit of very weak irreversibility was addressed by Landau, who demonstrated that as long as there are some collisions (even if very rare), and in the absence of sources, gradients, etc, typical field fluctuations are damped with an easily calculated “collisionless” damping rate -- this is Landau damping. The energy of the field fluctuations is converted to particle energy; there is irreversible heating. Landau’s calculation is fine in the limit of small amplitude fluctuations, but what happens when the plasma is turbulent? I will show that in a typical nonlinear system (relevant to many physical observations), Landau damping is overwhelmed and ultimately arrested by turbulent “echoes”. This finding has important implications for detailed predictions of the heating (and in some cases, for the luminosity) of some interesting astrophysical plasmas.
The Final Dennis Sciama Memorial Lecture delivered by Professor David Deutsch Dennis Sciama's 1959 book The Unity of the Universe was ostensibly about the Steady State theory, a cosmological/astrophysical theory which was to be comprehensively and irreversibly refuted by observations only a few years later. But it wasn't really about that. It was really about an idea that was not refuted and is deeper than any cosmology, namely the unity referred to in the title. Whether by coincidence or not, it is re-emerging as important in my current preoccupation, constructor theory.
Physics Colloquium 19th February 2016 delivered by Professor Michel Orrit Optical signals provide unique insights into the dynamics of nano-objects and their surroundings. I shall present some of our experiments of the last few years. i) At low temperatures, single molecules present very sharp lines which enable quantum optical experiments or nanoscale probing, for example of mechanical deformations (see Fig.1). ii) Photothermal microscopy opens the study of non-fluorescent absorbers, down to single-molecule sensitivity. Combining this contrast with photoluminescence, we can measure the luminescence quantum yield on a single-particle basis. The high signal-to-noise ratio of this technique enables uses of individual gold nanoparticles for local plasmonic and chemical probing. iii) Gold nanorods generate strong field enhancements near their tips. Matching the rods’ plasmon to a dye’s spectra, we observe enhancements in excess of thousand-fold for the fluorescence of single Crystal Violet molecules. This method generalizes single-molecule fluorescence to a broad range of weak emitters. iv) We recently studied the dynamics of vapor nanobubbles created in the liquid surrounding a single immobilized gold nanosphere. We found that these nanobubbles form in an instable, explosive process before collapsing (see Fig.2). Nanobubbles can react to reflected sound waves such as those released in the explosion [5].
Physics Colloquium 12th February 2016 delivered by Professor Mark Newman Many systems of interest in science and engineering can be represented as networks: the internet, the power grid, transport networks, metabolic networks, ecological networks and social networks are just a few of the many well studied examples. The structure of these networks has deep implications for the behaviour of the systems they represent (for traffic flow on the internet, for instance, or the spread of a disease over a human social network). Their structure is complex and we need new tools to help make sense of it. Physics, perhaps surprisingly, has proved a rich source of such tools. This talk will introduce some of the fundamental ideas in this growing field. It will also demonstrate how techniques borrowed from quantum and statistical physics are helping us to understand a wide range of networked systems.
The Scientific Legacy of Dick Dalitz On February 11 2016, the weekly seminar of the Particle Theory Group in the Rudolf Peierls Centre for Theoretical Physics was devoted to a celebration of the work of Richard H Dalitz FRS (1925-2006) who founded the group in 1963. His distinguished ex-students Frank Close (DPhil 1969) and Sir Christopher Llewellyn-Smith FRS (DPhil 1971) gave accounts of the seminal contributions Dick made to our understanding of the fundamental structure of matter. The talks were enlivened with personal reminiscences and are being made available on-line especially for the many alumni who could not come to the event.
Physics Colloquium 5th February 2016 delivered by Professor Alán Aspuru-Guzik Quantum computers promise the numerically exact simulation of molecules and materials. Furthermore, they are amongst the algorithms that have the lowest resource requirements for surpassing the power of classical computers. In this talk, I will briefly introduce the basic concepts of quantum computing and quantum simulation. Then, I will review the recent rapid progress in developing more efficient algorithms that have been achieved by many researchers in the field including our research group. I will describe the families of available algorithms (phase estimation, adiabatic and variational quantum eigensolver approaches) as well as the status of several experimental implementations of them either carried out or underway. These implementations span most of the currently available quantum architectures including quantum optics, ion traps, NV centers and superconducting quantum bits. I will provide a prelude of the relevance of these applications to society and will conclude with the prospects of the field.
Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 3rd morning of Theoretical Physics covering the subject of Inner Space Meets Outer Space: Covering the Connections Between Cosmology and Particle Physics
The 2015 Hintze Biannual Lecture delivered by Professor Meg Urry Using multi-wavelength surveys, we measure the growth of supermassive black holes at the centres of galaxies over the last 12 billion years. Most actively growing black holes are heavily obscured and not seen in large optical surveys; at the same time, the deep multi-wavelength surveys too little of the sky to find rare objects like luminous quasars. So completing the census of black hole growth requires a large-volume X-ray survey, to explore hidden, high luminosity and distant black holes. Theorists have suggested that mergers of gas-rich galaxies trigger Active Galactic Nuclei (AGN), whose radiation and outflows may quench star formation and strongly affect galaxy evolution. Our morphological analyses show that mergers probably do trigger luminous quasars but not the far more numerous moderate-luminosity AGN, which grow slowly through secular processes.
Physics Colloquium 20th November 2015 delivered by Professor Tom Ray This year marks the centenary of Einstein’s General Theory of Relativity. As is well known, physicists became convinced that Einstein was right after Eddington’s and Dyson’s famous expedition to measure the gravitational deflection of starlight. Recently the speaker has found the equipment that proved critical in testing Einstein’s theory after it being lost for almost 70 years. Remarkably its discovery has led to the finding that earlier eclipse data may have been conveniently ignored. The finger of suspicion points at Sir Frank Dyson, the Astronomer Royal, who was trying to protect Eddington from being conscripted into the British Army during World War I.
Physics Colloquium 30th October 2015 delivered by Professer Paul Ginsparg Over twenty-five years into the internet era, over twenty years into the WorldWideWeb era, fifteen years into the Google era, and a few years past the Facebook/Twitter era, we’ve yet to converge on a new long-term methodology for scholarly research communication. I will provide a sociological overview of our current metastable state, and then a technical discussion of the practical implications of literature and usage data considered as computable objects, using arXiv as exemplar. From the physics standpoint, there is a surprising amount of statistical mechanics in text-mining and machine learning.
Physics Colloquium 23rd October 2015 delivered by Professor Myles Allen Physics is the foundation of current concerns about climate change, but climate policy sometimes appears like a baroque superstructure built with little reference to the foundations. For example, global temperatures depend on the accumulated stock of carbon dioxide emissions released into the atmosphere over all time, not the flow of emissions in any given year, but climate policy remains overwhelmingly pre-occupied with emission flows, not carbon stocks. Michal Kalecki once called economics “the science of confusing stocks with flows”, and while this is probably unfair on economics, it isn’t a bad characterisation of UN climate negotiations. As physicists, we are professionally concerned with the complexities of the climate system, so it may come as something of a shock to learn that many of the numbers that really matter for major policy decisions, like deciding on the right combination of prices and regulations to reduce greenhouse gas emissions or the “social cost of carbon” to use in evaluating investments, depend on models that are astonishingly simple compared to models of the general circulation of the atmosphere and oceans. I will introduce some of the ideas behind these ‘Integrated Assessment Models’ and show how, even though the units may be PetaDollars rather than ExaJoules, our basic physical intuition can be used to understand how they behave, and how they can give some rather surprising results. This talk should be accessible to anyone interested in the climate problem, and won’t assume any prior knowledge of either climate physics or economics. There will be some maths, but I’ll explain what I’m up to as I go along. Both physicists and economists welcome, to heckle the speaker or each other as they see fit.
The 2015 Halley Lecture delivered by Professor Peter J. Webster Each year the monsoons bring rainfall to nearly half the population of the planet. Small variations in monsoon rainfall can lead to flood or drought, feast or famine. Therefore, explaining the physics driving the monsoon and turning this knowledge into predictions is one of the great problems in science. In 1686 Sir Edmund Halley, with trade and navigation on his mind, suggested that the monsoon was driven by the buoyancy induced by the differential heating between the Indian Ocean and the landmass of South Asia. With a few embellishments, such as noting the importance of the rotation of Earth, his theory has stood the test of time. However, during the last 20 years, advances in our understanding of global fluid dynamics, suggest that a land-sea heating contrast is not sufficient. In fact, at the same latitudes of maximum monsoon summer rainfall, in other parts of the world there are deserts. Here we will develop an alternative, albeit simple, general theory of the monsoons and discuss how this may be translated into useful predictions and a greater understanding of how the monsoons will fair in a changing climate.
Physics Colloquium 12th June 2015 delivered by Professer Swapan Chattopadhyay The frontier of beam physics and accelerator science is advanced via developments in material and microwave superconductivity, integrable and near-integrable nonlinear dynamics, advanced phase-space control techniques, and various novel concepts of plasmas, materials, lasers and quantum optics. We will touch upon some of the emerging ideas of “quantum-degenerate” particle and light beams, nonlinear integrable dissipative systems, laboratory-based free-electron lasers and single-electron quantum optics for various photon science, atomic, molecular and astro-particle physics “laboratory-based” experiments. These will be contrasted with the current conception of “large-scale” potential future particle colliders and high intensity proton accelerators for exploring the subatomic world beyond our current state of understanding.
The 2015 Hintze Lecture delivered by Professor Hitoshi Murayama Where do we come from? Science is making progress on this age-old question of humankind. The Universe was once much smaller than the size of an atom. Small things mattered in the small Universe, where quantum physics dominated the scene. To understand the way the Universe is today, we have to solve remaining major puzzles. The Higgs boson that was discovered recently is holding our body together from evaporating in a nanosecond. But we still do not know what exactly it is. The mysterious dark matter is holding the galaxy together, and we would not have been born without it. But nobody has seen it directly. And what is the very beginning of the Universe?
Physics Colloquium 5th June 2015 delivered by Professor Stephen Briggs The Global Climate Observing System was set up in 1992 to define and advocate for the observations required for climate modelling and prediction in support of United Nations Framework Convention on Climate Change (UNFCCC). It has developed a suite of some 50 Essential Climate Variables (ECVs) which define the observing requirements for climate. Satellite data are relied upon for the primary provision of about half of these parameters, and contribute significantly to the majority of the rest. Space agencies have organised themselves through various mechanisms to provide the relevant ECV observations. Some examples of the types of data which contribute to the ECVs and to the wider provision of data of climate modelling, attributions and mitigation will be presented and the wider aspects of dealing with climate change discussed.
The 2015 Wetton Lecture delivered by Professor Carlos Frenk Cosmology confronts some of the most fundamental questions in the whole of science. How and when did our universe begin? What is it made of? How did galaxies and other structures form? There has been enormous progress in the past few decades towards answering these questions. For example, recent observations have established that our universe contains an unexpected mix of components: ordinary atoms, exotic dark matter and a new form of energy called dark energy. Gigantic surveys of galaxies reveal how the universe is structured. Large supercomputer simulations recreate the evolution of the universe and provide the means to relate processes occurring near the beginning with observations of the universe today. A coherent picture of cosmic evolution, going back to a tiny fraction of a second after the Big Bang, is beginning to emerge. However, fundamental issues, like the identity of the dark matter and the nature of the dark energy, remain unresolved.
The 2015 Cherwell-Simon Lecture delivered by Professor Charles Kane Over the past several years, our understanding of topological electronic phases of matter has advanced dramatically. A paradigm that has emerged is that insulating electronic states with an energy gap fall into distinct topological classes. Interfaces between different topological phases exhibit gapless conducting states that are protected topologically and are impossible to get rid of. In this talk we will discuss the application of this idea to the quantum Hall effect, topological insulators, topological superconductors and the quest for Majorana fermions in condensed matter. We will then show that similar ideas arise in a completely different class of problems. Isostatic lattices are arrays of masses and springs that are at the verge of mechanical instability. They play an important role in our understanding of granular matter, glasses and other ‘soft’ systems. Depending on their geometry, they can exhibit zero-frequency ‘floppy’ modes localized on their boundaries that are insensitive to local perturbations. The mathematical relation between this classical system and quantum electronic systems reveals an unexpected connection between theories of hard and soft matter.
Physics Colloquium 6th March 2015 deliverd by Robert Fosbury Having orchestrated and obtained the Voyager 1 spacecraft’s 1990 “Portrait of the Planets”, which looked back some 6.1 billion km towards its launch site, Carl Sagan coined the iconic name the “Pale Blue Dot” for our home planet. Since that time, nearly 2000 extrasolar planets have been discovered and, due to the developing sensitivity of the discovery methods, an increasing fraction of these are classified as ‘terrestrial’ and a few even reside within the habitable zone around their parent star. We can anticipate the time, perhaps with the next generation of telescopes on the ground and in space, that we can find and begin to investigate a planet that resembles Earth: “Earth’s twin”. Until then, we can hone our observational strategies by observing the Earth itself as an exoplanet and, along the way, see our world from a more holistic standpoint. There are ways in which we can exploit our moon as a proxy observer to gain some very practical experience.
Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 6th morning of Theoretical Physics covering the ways in which ideas from theoretical particle physics guide the high energy accelerator program at CERN
Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 6th morning of Theoretical Physics covering the ways in which ideas from theoretical particle physics guide the high energy accelerator program at CERN
Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 6th morning of Theoretical Physics covering the ways in which ideas from theoretical particle physics guide the high energy accelerator programme at CERN.
Members of the Rudolf Peierls Centre for Theoretical Physics hosted the first Saturday Morning of Theoretical Physics on 22 June 2013. The event focussed on how we use field theory to understand material reality.
Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 3rd morning of Theoretical Physics. The event focused on the interface between theoretical developments in particle physics and astrophysics/cosmology.
Physics Colloquium 5th December 2014 delivered by Dr Asimina Arvanitak The QCD axion was proposed more than thirty years ago to explain the smallness of the electric dipole moment of the neutron and has been looked for ever since. It is an excellent dark matter candidate and its size is significantly larger compared to the elementary particles of the Standard Model: it can easily vary from tens of microns to thousands of kilometers. When its size is similar to that of astrophysical black holes, it binds to them forming a gravitational atom in the sky. The number of axions occupying the levels of this gravitational atom can grow exponentially around rapidly rotating black holes through an effect that is known as super-radiance. This growth slows the black hole down and a Bose Einstein Condensate of axions is formed orbiting the black hole. Just like a laser, this BEC emits gravitational waves as axions can annihilate or transition to different levels of this gravitational atom. These gravitational waves fall within the frequency range of the upcoming Advanced LIGO experiment. Through super-radiance, black holes are thus turned into cosmic particle detectors through the only universal force: gravity.
Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 4th morning of Theoretical Physics covering the subject of Plasmas: the normal form of matter and the key to unlimited energy
The 9th Hintze Lecture delivered by Professor Scott Ransom The most massive stars burn the fastest and brightest and die spectacularly, exploding as supernovae and leaving behind some of the most fantastic objects in the Universe: neutron stars and black holes. These are fascinating objects themselves, but ever since Bell and Hewish discovered the first pulsar over 40 years ago, we've realized that we can use the neutron stars especially as powerful tools for basic physics and astrophysics as well. Specialized "timing" observations of the MSPs are providing a wealth of science, including new tests of general relativity, amazing probes of the interstellar medium, constraints on the physics of ultra-dense matter, new windows into the evolution of stellar systems both simple and complex, and the promise of a direct detection of massive ripples in space-time, gravitational waves.
Physics Colloquium 24th October 2014. Delivered by Professor Andrei Seryi, Director of the John Adams Institute. Science has yielded a rich history of inventions, ones often inspired by Nature itself. Despite all this progress, we have always strived to find more efficient approaches to inventing. In fact, during the second half of the 20th century, the industrial world developed specific methodologies with which to promote inventiveness. Though powerful, these methods were rarely heard of outside of their field, let alone in the scientific community. The most advanced methodology, the so-called “theory of inventive problem solving”, has become, according to Forbes, the bedrock of innovations in such companies as Samsung. While the industrial inventiveness methods were originally created for engineering, their methodologies are universal and can also be applied to science. In this lecture we shall show how the theory of inventive problem solving can be used in various areas of science – from philology to accelerator physics – in order to create a powerful and eye-opening amalgam of science and inventiveness. Prof Andrei Seryi’s forthcoming book, Unifying Physics of Accelerators, Lasers and Plasma, is due to be published by CRC Press / Taylor & Francis in 2015 (http://www.crcpress.com/product/isbn/9781482240580). This book will include detailed descriptions of the topic discussed in this colloquium – the theory of inventive problem solving in application to science and the method of Accelerating Science TRIZ (AS-TRIZ), and will use this method throughout the book in applications to accelerators, lasers and plasma. The book will be suitable for students of various levels between senior undergraduate and graduate students in physics who are interested in enhancing their ability to work successfully on the development of the next generation of facilities, devices, scientific instruments, arising from synergy of accelerators, laser, and plasma. This book could also attract anyone interested in scientific innovations.
Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 5th morning of Theoretical Physics covering the subject of Black holes: where physics reaches its limit.
The 2014 Halley Lecture delivered by Professor Eliot Quataert The infant Universe was remarkably smooth compared to what we see around us today, with only tiny differences in its properties from one part to another. By contrast, there are enormous differences in the properties of the present-day Universe from one place to another: some regions host stars, galaxies, and even black holes while others do not. At the most basic level, we understand how gravity has built up this diversity of structures starting from the small differences present in the early Universe. However, developing a predictive model of how galaxies form requires understanding a broad range of phenomena: How does star formation and stellar death impact galaxies as a whole? How do black holes at the centre’s of galaxies grow and impact their surroundings? How does the hot plasma that pervades galaxies cool to fuel galaxy growth? In this talk, I will provide an overview of how the ,Universe evolved from its smooth beginnings to its present state and will highlight some of the key processes that influence how galaxies form.
Physics Colloquium 30th May delivered by Graham Farmelo Winston Churchill foresaw the nuclear age over a decade before it arrived and was the first national leader to agree to the development of nuclear weapons. His friend and advisor Frederick Lindemann, an Oxford professor of physics, exerted considerable influence on his thinking about nuclear weapons and nuclear power. In this talk, I discuss the surprisingly large role that Churchill played in nuclear history and the notion that he was the first politician to be a nuclear visionary.
Physics Colloquium 23rd May Delivered by Professor Carl M. Bender The average quantum physicist on the street would say that a quantum-mechanical Hamiltonian must be Dirac Hermitian (invariant under combined matrix transposition and complex conjugation) in order to guarantee that the energy eigenvalues are real and that time evolution is unitary. However, the Hamiltonian $H=p^2+ix^3$, which is obviously not Dirac Hermitian, has a positive real discrete spectrum and generates unitary time evolution, and thus it defines a fully consistent and physical quantum theory! Evidently, the axiom of Dirac Hermiticity is too restrictive. While $H=p^2+ix^3$ is not Dirac Hermitian, it is PT symmetric; that is, invariant under combined parity P (space reflection) and time reversal T. The quantum mechanics defined by a PT-symmetric Hamiltonian is a complex generalization of ordinary quantum mechanics. When quantum mechanics is extended into the complex domain, new kinds of theories having strange and remarkable properties emerge. In the past four years, some of these properties have been verified in many laboratory experiments. A particularly interesting PT-symmetric Hamiltonian is $H=p^2-x^4$, which contains an upside-down potential. We will discuss this potential in detail, and explain in intuitive as well as in rigorous terms why the energy levels of this potential are real, positive, and discrete.
10th Dennis Sciama Memorial Lecture by Prof. James Binney. Cosmology tells us that most “ordinary” matter such as we are made of is not in stars or in the interstellar media of galaxies. So it must lie between galaxies. In rich clusters of galaxies it is so dense and so hot that its thermal X-ray emission has long been detected. But cluster galaxies have long had very low star-formation rates, while field galaxies like ours have continued to form stars even though the surrounding intergalactic medium is too rarefied to be detected. Chemical signatures indicate that our Galaxy has continued to accrete relatively pristine gas but there is much evidence that star formation leads to efficient ejection of gas from galaxies. A picture will be assembled of how galaxies like ours exchange matter with the intergalactic medium. This exchange influences the radial distribution of star formation and implies a specific role of massive black holes in galaxy evolution.
Inaugural Lecture by Professor Steven Balbus looking at the history of the universe A one sentence summary of much of the history of our Universe might be that it is the formation of ever more complex and compact structure from a diffuse background. The build-up of a compact core of material from more tenuous surroundings is known as accretion, and it is a process common to much of astrophysics, from the early creation of giant clusters of galaxies to current star, planet, and black hole formation. In this Lecture, I will give a general and personal overview of accretion physics. I will discuss some of the theoretical successes the community has enjoyed in its struggle to understand accretion, together with ongoing challenges. Above all, I will try to convey a sense of the richness of accretion as a physical process, and the role it has played in enhancing a deeper understanding of many astrophysical phenomena.
The 9th Dennis Sciama Memorial Lecture, looking at chaos theory and climate change Lorenz is one of the pioneers of chaos theory. However, over 50 years before Lorenz, Poincaré discovered the sensitive dependence on initial conditions that characterises chaos. So what makes Lorenz’s contribution so important? I argue it is the discovery of the fractal invariant set in state space: the Lorenz attractor. Quite amazingly, properties of the Lorenz attractor can be shown to link the calculus of dynamical systems theory to deep and diverse areas of mathematics such as Wiles’ proof of Fermat’s Last Theorem and Gödel’s incompleteness theorem. But more than this, I argue that the fractal invariant set has implications for physics – not only for practical problems such as climate prediction, but also for the deepest problems of fundamental physics. In particular, I will put some meat on the bones of Penrose’s suggestion that “the correct theory of quantum gravity might be a deterministic but non-computable theory” by treating the universe as a dynamical system with fractal invariant set. The result is a novel perspective, not only on the quantum gravity programme, but also on quantum physics in general.
Halley Lecture 2013 by Professor Dr Ewine van Dishoeck on new developments in astronomy One of the most exciting developments in astronomy is the discovery of planets around stars other than our Sun. Nearly 1000 exo-planets have now been detected. But how do these planets form, and why are they so different from our own solar system? Which ingredients are available to build them? How are their parent stars formed? Thanks to powerful new telescopes, astronomers are starting to address these age-old questions scientifically. In this talk, an overview will be given of how stars and planets are born in the extremely cold and tenuous clouds between the stars in the Milky Way. These clouds also contain water and a surprisingly rich variety of organic material. How and where was the water formed that is now in our oceans on Earth? Can these organic molecules end up on new planets and form the basis for pre-biotic material and eventually life? The Atacama Large Millimeter/submillimeter Array (ALMA), under construction in Chile and planned to be fully operational by late 2013, will be able to zoom into the planet-forming zones of disks around young stars and revolutionize this field in the near future. First exciting and surprising ALMA results will be presented.
The 8th Hintze Lecture by Professor David Charbonneau looking at investigating habitable exoplanets. The investigation of planets orbiting other stars has moved from the study of gas giants to the hunt for smaller planets that are predominantly rock and ice in composition. When such Planets are discovered in edge-on orbits, such that the planet and star undergo mutual eclipses, scientists granted the opportunity to determine directly the planetary masses and sizes. Most interestingly, we can study starlight filtered through the planetary atmosphere to deduce its chemical composition, and perhaps even search for biosignatures. The speaker will summarize the most recent results from the NASA Kepler Mission and describe two surveys intended to find the closest habitable exoplanet.
Professor Wade Allison gives a talk about his book 'Radiation and Reason; The Impact of Science on a Culture of Fear'.
On the inextricable links between physics and philosophy and the ways in which one can lead to the other - how they complement each other in answering the big questions.
Dr Christopher Palmer on the historical ties between physics and philosophy - from ancient philosophical thought through to the scientific revolution and the pioneers of modern physics.
Prof. Frank Arntzenius on whether space and time are absolute entities or simply relational properties derived from the idea of motion - an old debate between Newton and Leibniz, carried on today.
Prof. Vlatko Vedral on the mind-boggling and paradoxical nature of quantum mechanics and its consequences on modern technology - the possibilities of superfast computing and teleportation. This interview was recorded via Skype, so is of a lower audio quality than the other podcasts in this series.
Dr. David Wallace on the many-worlds theory, an explanation of the baffling results that quantum mechanics provides us with - and that there may be more worlds than just our own.
Prof. Sir Roger Penrose on the idea of artificial intelligence and whether consciousness can be replicated by a computer - a discussion of new physics which may take us closer to explaining the mind.