Theoretical Physics - From Outer Space to Plasma

This talk explains how qubits are used to represent numbers in a way that permits 'quantum-mechanical parallel' computing. We show how this can used to achieve fast factorisation of large numbers, and hence the breaking of current codes. We end by explaining how entangled pairs of particles can be used to provide an alternative and entirely secure cryptographic system.

This talk reviews how to deal with quantum systems that are coupled to the outside world, as in reality all systems are. We first introduce density operators and explain how quantum states give rise to them. We then turn to measures of entanglement that can be computed from a density operator, and show that entanglement grows with time. Finally, we show how the interaction with the environment gives rise to the phenomenon of decoherence.

This talk reviews the modern formulation of the basic ideas of quantum mechanics. We start by explaining what quantum amplitudes are, how they lead to the idea of a quantum state and how these states evolve in time. We then discuss what happens when a measurement is made before describing correlated ('entangled') systems. Applying these ideas to two-state systems ('qubits') we point out that the complexity of computing the evolution of an N qubit system grows like exp(N)

Dr Ralph Schoenrich will talk about the chemical evolution side Spiral density waves patterns re-distribute stars throughout the entire system, making it impossible to know a star's origin from just its kinematics. However, stars are more than just points in phase space: every star is labelled with the elemental abundances of the gas cloud from which it was formed. Over the last few years a number of observational campaigns have started to measure these labels for millions of stars in our own Galaxy's disc. Ralph Schoenrich will describe how chemodynamical models are being used to piece together the evolution of our Galactic environment from presolar times to the present.

Dr John Magorrian will talk about the dynamics of galaxy discs In galaxy discs it is energetically favourable for angular momentum to move outwards and mass to move inwards. This transportation is effected by spiral arms, but what causes them? Simple linear response calculations demonstrate that even the smallest perturbation is amplified manyfold, while the differential rotation of the disc means that the response is stretched out into a spiral-like pattern. John Magorrian will introduce the notion of the disc as a resonant cavity, within which spiral density perturbations rattle back and forth.

Prof James Binney FRS will talk about stellar systems: a new state of matter The long range of gravity means that many concepts from undergraduate statistical mechanics do not apply: energy is not extensive; there is no microcanonical or canonical ensemble. Stars and dark matter particles have long mean free paths, which means that to a very good approximation their motion is determined by the mean-field gravitational potential. James Binney will identify a hierarchy of timescales, explaining how the Boltzmann equation for the full 6N-dimensional many-particle phase space distribution function can be reduced to an evolutionary equation of a function of a mere 3 variables that is governed by the resonances among the particles' orbital frequencies.

In this talk, Siddharth Parameswaran discusses how a topological approach to 2D systems reveal that they can indeed become superfluid, and lead to surprising and beautiful universal results whose implications continue to resonate today. Superfluids spontaneously break a continuous symmetry linked to the conservation of particle number in a many-body system. Standard lore holds that such symmetries must remain unbroken at any temperature above absolute zero in a two-dimensional material, such as a thin sheet or film, apparently precluding superfluidity in such systems.

Stephen Blundell reviews a theory of superconductivity that was developed in Oxford in the 1930’s by Fritz London. The idea is that under certain conditions quantum coherent effects can become manifest on a large scale. In an effect such as superconductivity, this idea can be put to use in such applications as magnetic resonance imaging, in which a living human patient is inserted inside a quantum coherent wave function. He will explain how coherent effects can be measured in real superconductors.

John Chalker discusses how the laws of quantum mechanics lead us from the microscopic world to macroscopic phenomena. The notion that atoms of a given isotope are indistinguishable has profound consequences in the quantum world. For liquids made of identical bosons, indistinguishability forces the particles into a quantum condensate at low temperature, where they all dance in perfect synchrony. Treated gently, such a condensate has no viscosity: once it is set in motion --say around a circular pipe -- flow will persist indefinitely (so long as the fluid is kept sufficiently cold!).

John March-Russell gives a talk about gravitational wave signals of stringy physics, a ‘soundscape’ connected to the landscape of string vacua.

Subir Sarkar reviews the detection of the ‘chirrup’ signal from a pair of merging massive black holes by the Laser Interferometer Gravitational-Wave Observatory, as well as subsequent experimental developments.

James Binney gives a talk about the mathematics that describe Gravitational waves.

Fasten Your Seat Belts: Turbulent Flows in Nature. Turbulence is ubiquitous in nature, and it often causes us headaches both literal and metaphorical. From unpredictable weather to the mixing of milk in our coffee, Michael Barnes will talk about how turbulence arises and our ongoing struggle to control it.

Ramin Golestanian will introduce you to Life at Low Reynolds number and ask how microorganisms can swim, navigate, and coordinate their activities. You will discover how the left-right symmetry is first broken in a developing embryo, and investigate the medically important question of how mucus is shifted in our lungs and what happens when things go wrong.

Julia Yeomans will talk about fluids and flows all around us: from superhydrophobic surfaces and how animals and plants keep dry, to bouncing droplets and balloons.

Third lecture "More is different" - how states of matter emerge from quantum theory Saturday morning of Theoretical Physics. With Professor Steve Simon, introduction by Professor John WheelerThird Steve Simon will focus on the recent realization that Landau’s classification, thought to be complete for most of the twentieth century, in fact misses some of the most exciting, yet subtle, physics. The new missing ingredient is naturally cast in the language of the mathematical field of topology, giving rise to a host of what we now call topological states of matter. In particular, we have now realized that fundamentally new types of electronic materials exist --- some of which, in fact, have been hiding under our noses for decades! More on this mini-series; The properties of all forms of matter, from the most mundane to the most exotic kinds produced in advanced laboratories, are consequences of the laws of quantum mechanics. Understanding how macroscopic behaviour emerges from microscopic laws in a system of many particles is one of the intellectually most demanding, yet most important, challenges of physics, and is the subject of this series of lectures.

Second lecture "More is different" - how states of matter emerge from quantum theory Saturday morning of Theoretical Physics. With Professor Fabian Essler, introduction by Professor John Wheeler. Fabian Essler will discuss the hugely successful framework for classifying possible states of quantum matter, pioneered by the great Russian Nobel Laureate, Lev Landau. This framework is conceptually remarkably simple, but is broad enough to describe physics ranging from magnets to superconductors to fundamental physics in the guise of relativistic quantum field theory and the Higgs phenomenon. More on this mini-series; The properties of all forms of matter, from the most mundane to the most exotic kinds produced in advanced laboratories, are consequences of the laws of quantum mechanics. Understanding how macroscopic behaviour emerges from microscopic laws in a system of many particles is one of the intellectually most demanding, yet most important, challenges of physics, and is the subject of this series of lectures.

First lecture in the "More is different" - how states of matter emerge from quantum theory Saturday morning of Theoretical Physics. With Professor John Chalker, introduction by Professor John Wheeler. John Chalker will review the quantum mechanics of identical particles which forms the foundation for our understanding of why diamond is transparent and why gold conducts electricity. He will also explain how we can control the motion of electrons in certain devices to make resistances quantised with an accuracy of a few parts in a billion. More on this mini-series; The properties of all forms of matter, from the most mundane to the most exotic kinds produced in advanced laboratories, are consequences of the laws of quantum mechanics. Understanding how macroscopic behaviour emerges from microscopic laws in a system of many particles is one of the intellectually most demanding, yet most important, challenges of physics, and is the subject of this series of lectures.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the ninth Saturday Morning of Theoretical Physics on 21st May 2016. Talk 3 by Dr Andrei Starinets.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the ninth Saturday Morning of Theoretical Physics on 21st May 2016. Talk 2 by Professor Andre Lukas.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the ninth Saturday Morning of Theoretical Physics on 21st May 2016. Talk 1 by Professor Joseph Conlon.

The power of available computers has now grown exponentially for many decades. The ability to discover numerically the implications of equations and models has opened our eyes to previously hidden aspects of physics. Many exciting phenomena observed in condensed matter systems, such as superconductivity and the quantum Hall effect, emerge due to the quantum mechanical interplay of many electrons. The laws of quantum physics are governed by the Schrödinger equation, whose complexity grows exponentially with the number of particles it describes. Hence, even an approximate numerical solution of the Schrödinger equation is impossible for only just a few particles, not to mention for the millions of particles that are present in real materials. This talk focuses on a new approximation scheme in terms of so-called Tensor Network States, which allow for an arbitrarily accurate description of realistic quantum solid state systems at merely a polynomial overhead in the particle number, thus enabling efficient simulations of such systems on today's computers.

The power of available computers has now grown exponentially for many decades. The ability to discover numerically the implications of equations and models has opened our eyes to previously hidden aspects of physics. In physics, "complex systems" are systems of many similar interacting parts, such as the interacting atoms that make up a solid or liquid, but also interacting organisms in an ecosystem, or interacting traders in the stock market. This lecture will discuss how recent advances in modeling and computer simulation have allowed us to apply physics-style approaches to these previously challenging real-world systems to learn about such things as the spread of diseases, the flow of traffic or the structure of entire human societies.

The power of available computers has now grown exponentially for many decades. The ability to discover numerically the implications of equations and models has opened our eyes to previously hidden aspects of physics. In this lecture, Myles Allen addressed how computers have transformed our understanding of the role of chaos and exponential error growth in weather forecasting; and our understanding of how climate change is impacting regional weather. He showed how research in Oxford Physics, made possible by high-end computing, is demonstrating the crucial role of eddies in controlling ocean climate; and how the probability of extreme weather events may respond to rising greenhouse gas concentrations. He concluded by throwing out a more controversial suggestion that super-computers haven’t really contributed very much to the problem of predicting century-timescale changes in global average temperature, however much they may have contributed to understanding the regional implications of large-scale warming.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the eighth Saturday Morning of Theoretical Physics on 19 September 2015. Talk 3 by Professor James Binney.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the eighth Saturday Morning of Theoretical Physics on 19 September 2015. Talk 2 by Professor John Wheater.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the eighth Saturday Morning of Theoretical Physics on 19 September 2015. Talk 3 by Pedro Ferreira.

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 7th morning of Theoretical Physics covering the idea of quantum computation and the strange behaviour of certain types of fundamental particle.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 7th morning of Theoretical Physics covering the idea of quantum computation and the strange behaviour of certain types of fundamental particle.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 7th morning of Theoretical Physics covering the idea of quantum computation and the strange behaviour of certain types of fundamental particle.

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 program at CERN.

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.

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.

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.

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.

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.

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.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 3rd morning of Theoretical Physics covering the connections between cosmology and particle physics.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 3rd morning of Theoretical Physics covering the connections between cosmology and particle physics.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 3rd morning of Theoretical Physics covering the connections between cosmology and particle physics.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 1st morning of Theoretical Physics covering how we use field theory to understand material reality.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 2nd morning of Theoretical Physics covering ideas from theoretical physics currently being applied to living systems.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 1st morning of Theoretical Physics covering how we use field theory to understand material reality.

Members of the Rudolf Peierls Centre for Theoretical Physics hosted the 1st morning of Theoretical Physics covering how we use field theory to understand material reality.