| Physics and Astronomy |  |
2003 |
Most Fridays at 11:00 am here in the Department Seminar Room 701.
Scroll down to view Seminars
Thursday 14 December 2006
Dr. Richard Wigmans
Texas Tech University
Neutrinos in an Expanding Universe
The observable Universe contains several billion neutrinos for every baryon. During the first second after the Big Bang (the Leptonic Era), these neutrinos were in thermal equilibrium with the other constituents of the Universe. At the end of this Era, they decoupled. For all practical purposes, they no longer interacted with other particles from that point onwards.
In this talk, we follow these relic neutrinos throughout the history of the Universe. We will see how their properties changed as the Universe went through an expansion by 10 orders of magnitude. At the present time, they are extremely non-relativistic, with typical velocities of a few hundred km/s. This means that they have become susceptible to gravitational forces and that gravitation locally may have changed their spectra. I will show that this, under certain assumptions, may have led to a phenomenon that would explain two of today’s great mysteries: The large-scale structure of the Universe and the increasing rate at which it expands. This explanation does not involve new forces or unknown forms of energy, but is based on a well-known quantum mechanical effect: the Pauli Exclusion Principle.
The proposed mechanism makes it possible to calculate the present value of the Hubble constant from first principles and sets a lower limit on the neutrino mass.
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Friday 8 December 2006
Terry Goldman
Los Alamos National Laboratory
Sterile Neutrinos in a 6X6 Matrix Approach
We show by examples that mixing of active and sterile neutrinos can affect the structure of matter oscillations relevant to extraction of neutrino mixing parameters from solar and atmospheric neutrino data.
Long ago, this approach predicted large neutrino mixing amplitudes and we show in an analytic example how this and pseudo-Dirac pairing can develop, within the conventional see-saw mechanism, from small intrinsic mixing strengths.
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Friday 1 December 2006
Prof. Peter West
King's College, London
The Role of Symmetry in a Unified Theory of Physics.
The standard model, discovered in 1969, unifies the electromagnetic, nuclear weak and nuclear strong forces in a way that is consistent with the principles of relativity and quantum mechanics. Essential to the construction of this model are symmetries which are a generalisation of those first found in Maxwell's equations of electromagnetism.
The remaining force of gravity is usually described by Einstein's theory of gravity. This latter theory, together with the standard model, account for almost all observed phenomenon, at least as a matter of principle.
However, Einstein's theory of gravity is not likely to be consistent with the principles of quantum mechanics and so can not be combined with the standard model into a single unified theory.
Supersymmetry is a new kind of symmetry that exchanges fermions with bosons and plays an important role in extending the standard model.
As such, it is hoped that supersymmetry will be discovered in the forthcoming experiments at the CERN collider. Supersymmetry also provides non-trivial extensions of Einstein's theory, called supergravity theries. However, supersymmetry by itself is not thought to provide a consistent unified theory of physics.
The standard model is based on particles, however, it has been found that strings have remarkable properties when combined with the principles of relatively and quantum mechanics. Indeed, when strings also incorporate supersymmetry, they appear to unify all four forces of nature in a consistent and natural way. However, we do not have have a complete theory of strings and a substantial part of our understanding is based on certain unique supergravity theories which contain all the effects of superstring theory at low energy. I will also explain that these supergravity theories contain hints of a symmetry that is much larger and more general than those used so far in physics.
Friday 24 November 2006
Robert L. Jaffe
Morningstar Professor of Physics and MacVicar Faculty Fellow Center for Theoretical Physics, NE25-4027, Massachusetts Institute of Technology
The Casimir Effect: Physical Manifestations of the Quantum Vacuum
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Friday 17 November 2006
Show Day - no seminar
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Friday 10 November 2006
Dr Loretta Dunne
School of Physics and Astronomy, University of Nottingham
The Cold Universe The Cosmic Infrared Background suggests that around half of the starlight ever emitted since the Big Bang has been absorbed and re-radiated by dust.
This interstellar dust is heated to around 20-50 K and re-radiates the energy at Far Infra-red and submillimetre wavelengths(40-1000 microns). This talk will describe the recent 'revolution' in observing in the sub-mm waveband and what we have learned about the 'Cold Universe' ranging from planetary systems through to the formation of the most massive galaxies at high redshifts. I will also explore the question of the origin of all this dusty material. This is a relatively young area in astronomy and is progressing at a frantic pace. The world's first submillimetre camera (SCUBA) was only commissioned in 1997 and effectively revolutionised the field. It was retired in 2005 and its successor (imaginatively named SCUBA2) will be available in the next year or so. I will briefly describe the quantum leap in performance we expect from the new instrument and some of the exciting science we hope do with it.
Friday 3 November 2006
Prof. Laurence A. Marschall,
W.K.T. Sahm Professor of Physics, Gettysburg College,
THE TRANSIT OF VENUS: The Space Race of the 19th Century
What do John Philip Sousa, Captain Cook, Emily Dickinson, and THE DA VINCI CODE have in common? They're all involved in the story of the Transit of Venus. On June 8, 2004 (and again in 2012), people around the world were treated to a sight no one alive had seen before: the planet Venus was silhouetted against the face of the sun for about 6 hours. This so-called "transit of Venus" is a rare occurrence; the last time it was seen was over a century ago, on December 6, 1882. In 2004, diehard astronomy buffs traveled halfway around the world to see the rare even in its entirety, but millions watched it in the comfort of their homes over the internet.
That 2004 Venus transit was a pleasant curiosity, but in the 1700's and 1800's the observation of these rare Transits of Venus was a matter of national importance. England sent Mason and Dixon to observe a transit of Venus in 1761, despite the danger posed by bitter warfare with France. Captain Cook was sent around the world, at great expense, to observe the 1769 transit from a remote island in the South Pacific. And in the 19th Century, the superpowers-and even many smaller nations---sent out over 50 expeditions, at a cost of millions of dollars, just to put observers under the shadow of Venus for a few hours. What was so important about the Transit of Venus?
I'll answer this question and present technical details, pictures, movies(!), and stories from past and present transit expeditions, to both entertain us and help us understand this rare celestial event. I will also demonstrate newly developed software from Project CLEA that uses images from the GONG global network of telescopes to enable students to emulate the measurements of earlier explorers (with better results)---- CDROM’s of that software will be available for distribution at the talk. The software also includes images of the 2003 Transit of Mercury, an event which will be repeated from New Zealand on November 9, 2006.
Friday 27 October
Dr Slava Kitaeff
Unitech New Zealand, Auckland
Cosmological Epoch of Reionization and Galactic Radio Recombination Lines. Observational Challenges and Prospective .
Several problems of contemporary astrophysics and cosmology drive the development of low frequency radio telescopes in the world after two decades of lull. Cosmological Epoch of Reionization (EoR) and low frequency Radio Recombination Lines (RRL) are perhaps the two problems which have attracted attention most of all.
Our current Universe is a world of stars and galaxies. Starting from the Big Bang of the Hot Universe scenario, it has passed through the stages marked in the time domain: inflation, nucleus synthesis, recombination (neutral hydrogen era), formation of the first stars and galaxies, and modern Universe finally the almost fully ionized. Therefore in the history of the Universe there must have been an intermitted Epoch of Reionization which is a central point of interests of modern cosmology. Recent discovery of the high redshift galaxies at z≈6.2 marks the end of EoR, but when was the beginning? All we have is a guess that it was when the Universe was 1 billion y.o. (redshift 20-25). Many more questions are to be answered through the observations yet. W hat was the energy source for re-ionization – massive stars or/and miniquasars? What were the physical conditions during this important stage in the Universe? When were the first stars and galaxies formed?
Detecting the signal from EoR has become one of the main objectives for several campaigns in development of new radio astronomy instrumentation for VHF-UHV bands (LOFAR, MWA, LWA, PAPER, CoRE, CMA21). However indifferently the radio telescope configuration and technique, the EoR experiments will meet the greatest challenge to remove the foreground signal which includes the diffuse and compact radio sources as well as the multi-frequency signal from the RRLs originated in our Galaxy. Although the signal from RRLs is quite weak and requires a radio telescope of a significant sensitivity in order to be detected, RRLs are considered as the most difficult and serious contamination to the EoR signal. These became the motivation for several RRLs survey campaigns in the world. Low frequency RRLs themselves originated by the giant atoms in the interstellar medium (ISM) of the Galaxy carry an important and accurate information about the physical conditions of the ISM. Being a part of Pushchino Radio Astronomy Observatory group which studied RRLs in 80s and 90s of the last century I will introduce this topic providing a few details.
Then I will focus on the observational techniques which can be effectively used for studying RRLs and EoR. This techniques use the advantage of the rapid progress in digital electronics and high performance computers, both make possible applying the digital signal processing techniques to the single antennas and arrays with a simple analogue front-end design and comprehensive digital data processing back-end.
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Dr Y.L. Khong
Asian Institute of Medicine, Science and Technology, Malaysia
"Laser-microwave Photoconductance of Minority Carrier Recombination in Silicon"
Silicon is the key material in most modern electronic devices. Silicon has enabled a strong electronic industry with manufacturing activities largely centred in the Asia-Pacific region today, providing many job opportunities for Physics graduates. A brief overview of this industry shall be presented.
The behavior of charged carriers in silicon governs the perfomance of devices. Hence the interest to study them. This talk shall focus primarily on some investigations on the recombination processes of minority carriers by a laser-microwave technique.
As electron-hole pairs are generated by a laser beam, they recombine directly or via trapping centers in the silicon material. The presence of the bulk and surface traps affects the recombination rate of the minority carriers. The microwave reflectance is a function of carrier density in the bulk silicon material. This ability to directly measure the lifetime of minority carriers presents opportunities to investigate the nature of the trapping processes in silicon.
A discussion shall be presented on aspects of the trapping activities in doped silicon with some details presented on novel transient trapping effects observed through UV irradiation of the silicon surface.
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Friday 13 October 2006
Dr Steve Maddox
School of Physics & Astronomy, University of Nottingham
Large-scale structure of the universe
I will introduce the basic ideas behind structure formation in the universe and describe some models of the evolution of structure.
Observational measurements from the cosmic microwave background and large galaxy surveys can be used to constrain the models. In particular, statistics of the galaxy distribution in large surveys show that the link between galaxies and mass is not simple: galaxies of different type different luminosity trace the structure in different ways. Although we now have a consistent framework of structure the physics of galaxy formation is still not well understood.
Friday 6 October
Dr David L Wiltshire
Department of Physics & Astronomy University of Canterbury
Cosmic clocks, cosmic variance and cosmic averages
What is meant by the expansion of space? Can we associate a "kinetic energy" to it? Where is infinity? When must Einstein's relation, E=mc 2, for the energy of a particle at rest be modified? What is the largest scale on which the Equivalence Principle can be applied? How can a notion of an isotropic homogeneous expansion for the Universe be reconciled with the observed large-scale inhomogeneous distribution of clusters of galaxies in filaments and bubbles surrounding voids? In this talk I will explore the conceptual basis of what I propose as a major part of the answer to the question "What is the Universe made of?" I will propose specific answers to the foundational questions above in the context of ordinary general relativity with initial conditions set by inflation, while explaining how we have come to misidentify quasilocal gravitational energy as "dark energy making up 3/4 of the stuff in the Universe".
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Friday 29 September
Alex Nielsen
Department of Physics & Astronomy, University of Canterbury
Evolving Black Holes and the Growth of Horizons
Recently there has been some interest in quasi-local definitions of black holes. The key features of these definitions will be discussed and simple examples will be given in the context of fully dynamical, spherically symmetric spacetimes. These models give useful insights into both black hole accretion and black hole evaporation.
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Friday 22 September
David Beach Formerly of KiwiStar Optics, IRL, Auckland
Tidal flow as an energy source
Cook Strait potentially offers an immense resource of electrical energy because of the strong currents and the forthcoming availability of suitable turbines. There is, however a need for more knowledge of the spatial distribution of currents in the Strait, and the influence of weather on the deeper regions of the Strait. Also discussed will be the astronomical aspects of the tidal forcing. Although there are as many as forty known harmonic components in the geo-lunar-solar gravitational relationship, there are only a few major components in the harmonic analysis of tides.
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Friday 11 August
Visiting Oxford Fellow, University of Oxford,
Why is general relativity a geometric theory? II. The role of the strong equivalence principle
Bimetric theories of gravitation, whether empirically correct or not, are a reminder that a dynamical metric field need not have chrono-geometric significance: its null geodesics need not characterize the motion of light, nor need it be surveyed by physical rods and clocks. In standard GR, the chronometric nature of the metric field is a consequence of the strong equivalence principle, which is not a consequence of the Einstein field equations. It is argued that in understanding the special theory of relativity as the appropriate limit of general relativity, the interpretation of special relativity that best tallies with the above insight is the dynamical one defended by Pauli, Jánossy, Bell and others."
Friday 4 August
Solar-Terrestrial Environment Laboratory, Nagoya University
Microlensing Survey: Extra-Solar Planet and the Galactic structure
I will review what microlensing survey groups, such as MOA and OGLE are doing, and what we can do with this data. The current hot topic is finding extraa-solar planets. I will show how we can find extra-solar planets via microlensing and present some results. I will also talk about how we can use these large amounts of data to learn about the Galactic structure.
Friday 28 July
Visiting Oxford Fellow, University of Oxford,
Why is general relativity a geometric theory? I. The redshift argument revisited
A common heuristic argument in general relativity textbooks for gravity to be associated with space-time curvature is based on the redshift effect. In this talk I want to critically analyse this argument, and in particular its formulation in recent textbooks by Hartle and Carroll.
Friday 21 July
University of Texas , Dallas
Global Circuit, Cosmic Rays, Clouds and Climate
There is considerable evidence that much of the linkage from cosmic ray variations to variations in clouds and climate is via changes in the downward current density Jz in the global electric circuit. The global circuit also responds to other space weather inputs, including polar cap ionospheric potential changes, solar energetic particle events, and relativistic electron flux changes. Responses to such inputs are found in clouds and atmospheric transparency; tropospheric temperature and dynamics; and high latitude surface pressure, all of which correlate with the Jz changes, either observed or inferred. The responses consist of small repeated perturbations on the day-to-day timescale and have high statistical significance for Jz changes of amplitude of order 10%. There are also Jz changes that are due to the tropical thunderstorm generator variability, and we have shown that high latitude surface pressure responds to this internal forcing, as well as to the external forcing. Much greater changes in tropospheric dynamics and climate are found during multi-decadal solar minima and as correlations with millennial timescale cosmic ray variations, when the changes in Jz are inferred to be an order of magnitude larger than solar cycle variations. Some suggested cloud microphysical mechanisms responding to Jz changes will be discussed.
Friday 7 July
Director of the American Association of Variable Star Observers (AAVSO)
Our Violent Universe
Planets are being swallowed by stars. Stars are crashing into black holes. Asteroids cause mass species extinctions on the Earth. Neutron stars ionize the Earth's atmosphere. Dying stars radiate the Earth with gamma rays. Contrary to the peaceful, starlit nights everyone enjoys, our Universe is full of violent events that change the course of its history. Come to this talk to find out what is happening on a cosmic scale!
Friday 23 June
Defence Technology Agency, Auckland
"Diverse problems and unconventional analysis techniques in military science"
The Defence Technology Agency (DTA) is the principal scientific adviser to the New Zealand Defence Force. As part of that remit DTA is presented with a diverse range of problems to solve. Development and application of models and simulations is an important part of the process that helps DTA address these questions.
This presentation will begin with an outline of DTA and its areas of research and development. I will then explain how we are applying cellular automata based models to some of the problems we are posed in the operations analysis area. Such models have a number of applications in the physical sciences, and in particular are valuable for helping to study less tangible aspects associated with military research. I will highlight some particular successes we have had, such as the use of genetic algorithms to efficiently search large and sometimes pathological solution spaces.
Friday 16 June
Professor of Astronomy at the University of Cape Town and Planetarium Astronomer at Iziko Museums of Cape Town.
Professor Fairall completed a B.Sc. Hons at UCT, and a Ph.D. at the University of Texas. His research career spans more than 30 years. He has produced some 200 research papers, written a university textbook and three popular-level books, the most recent of which (April 2006) is “Stargazing from Game Reserves”. He is an Associate of the Royal Astronomical Society (UK), and a Fellow of the University of Cape Town. He is also a Fellow of the International Planetarium Society.
“Mapping the Cosmic Labyrinth”
Our picture of the nearby Universe today is somewhat different to the ‘Realm of the Nebulae’ opened by Edwin Hubble some eighty years ago. Galaxies are found to congregate into a labyrinth of interconnected ‘large-scale’ structures separated by giant voids. Various tools allow us to map and quantify characteristics of these structures. In particular this talk will explore the use of percolation techniques and minimal spanning trees. It will also introduce ‘Labyrinth’ software developed to visualise the large-scale structures. Visualisations of the almost complete 6dF Survey give a more detailed picture of the nearby Universe than has previously been available.
Friday 9 June
Williams College, Hopkins Observatory,
Williamstown , Massachusetts USA
http://www.williams.edu/astronomy
Syzygy x 2: Eclipses and Transits
At Williams College, we study a variety of events when three bodies are in a line: syzygies. We have been studying a variety of such events with collaborations between Jay Pasachoff and Bryce Babcock, who will be en route to Mt. John for the June 12/13 occultation of a distant star by Pluto. I will first discuss the most recent total solar eclipses, which we observed from Ceduna, Australia, in 2002, and from Kastellorizo, Greece, in 2006. Our scientific studies are pointed toward choosing between classes of models for coronal heating based on searches for high-frequency oscillations on coronal loops.
I will next discuss our recent transit work, including occultations of stars by Pluto in 2002 and by Charon in 2005. Our 2002 work led to the discovery of global warming in Pluto's atmosphere, which we hope to further study on Mt. John. Our 2005 work led to improved measurements of Charon's size, density, and rock-ice fraction and a sensitive limit on any atmosphere.
Our occultation work is joint with James Elliot's group at MIT and is funded by NASA. Our eclipse work is funded by the U.S.
National Science Foundation, NASA, and the National Geographic Society.
Friday 2 June
Erskine Visitor from
The Department of Physics, University of Waterloo
and Canadian Institute for Advanced Research/Quantum Materials Program
"The New Glassy Understanding of Superconductors in a Magnetic Field"
High-temperature superconductivity in copper-based oxide materials was discovered twenty years ago.
Not only have these materials proved to be an enormous challenge to our understanding of strongly correlated electron systems, they also exposed our incomplete understanding of the thermodynamic properties a superconductor when subject to an applied magnetic field and in presence of random disorder ("dirt"), which is ubiquitous in high-temperature superconductors. In this talk, I will discuss how , thanks to numerous theoretical, experimental and numerical studies, the so-called mixed-state of “dirty” superconductors subject to an applied field is now generally understood in terms of glass-like phases of superconducting vortices.
Note: This is a general physics talk and has very little to do with my previous three talks.
Friday 19 May
(Erskine Visitor from Department of Physics, University of Waterloo and Canadian Institute for Advanced Research/Quantum Materials Program)
"At last, a Magnetic Analogue of Water Ice: Spin Ice"
The common phase of water ice is a complex condensed state of matter where the oxygens atoms are arranged on a regular hexagonal crystalline lattice while the hydrogens (protons) are disordered, endowing this state with an extensive entropy first estimated by Linus Pauling in 1935.In 1997 a novel class of surprisingly frustrated ferromagnetic materials were identified as the first experimental realization of a magnetic analogue of water ice. These "spin ices" exhibit a number of interesting thermodynamic and magnetic properties that raise a number of fundamentally important questions of statistical mechanics nature.The discovery of spin ice is one of the most exciting development in the field of magnetism over the past ten years, having attracted much attention from both theorists and experimentalists.
In this talk, I will review the story of spin ice, discussing problems that have been resolved and those that remain. This talk builds on my last week general talk on frustrated magnetis and will solely targets spin ice. It will have much more concrete and specific experimental and theoretical results than the talk last week. I.E. It will be more a condensed matter seminar than a general physics colloquium.
Friday 12th May
Erskine Visitor from Department of Physics, University of Waterloo
and Canadian Institute for Advanced Research/Quantum Materials Program
"Geometrical Frustration"
Frustration is ubiquitous in condensed matter physics: it arises whenever interacting degrees of freedom on a lattice cannot locally minimize their total classical energy by minimizing the pairwise interaction energy pair by pair.
For example, it occurs in the phenomenon of protein folding, in liquid crystals, in molecular crystals and in superconductors. However, geometrical frustration is probably best exposed in the context of magnetic systems where exotic phenomena such as "spin ice" and "quantum spin liquid" can emerge. In this talk, I will introduce the topic of geometrical frustration and discuss some examples where new phenomena driven by "high frustration" have recently been experimentally discovered as well as some new and interesting and fundamental theoretical developments. This talk is aimed at a general physics audience with no prior specialized knowledge beyond fourth year undergraduate physics.
Friday 5 May
Dept of Physics & Astronomy, University of Sussex
"The supersymmetric standard model from the Z_6' orientifold?"
Using D-branes in Type II superstring theory offers an attractive, "bottom-up" method of constructing the standard model of particle physics. Indeed, precisely the matter content of the (non-supersymmetric) standard model has been obtained using intersecting D6-branes and a toroidal compactification T^6 of the six extra dimensions. However, such models are unstable and beset with flavour-changing neutral current problems. The use of a (supersymmetric) orbifold T^6/P, with point group P, rather than T^6 stabilises (some) moduli and gives supersymmetric matter at the intersections. This talk will show how the use of the point group P=Z_6' permits an essential first step to be made towards the construction of a supersymmetric standard model using intersecting D6-branes.
Friday 7 April
Department of Physics, University of Georgia
"Novel approaches for Energy Efficient Lighting"
Lighting consumes a large fraction of the global energy production, thus economic and environmental concerns dictate the development of energy efficient light sources.
After a brief comparison of standard light sources, we will present novel approaches to increase the efficiency of fluorescent lamps, including quantum cutting phosphors and mercury free fluorescent lamps. Finally, an overlook is given on the state-of-the-art of solid state white light sources, based on blue or UV light emitting diodes that are coated with down-conversion phosphor materials.
Monday 27 March
Department of Physics, University of Otago
"The Sun as a Bully: A little help from our AARDDVARK Craig Rodger"
The Intergovernmental Panel on Climate Change (3rd Assessment Report) recognises that solar variability may have a role to play in global climate change, albeit with significant uncertainty as to its importance. In my talk I will concentrate upon the impact of different particle-inputs to the Earth's atmosphere. This will include those which come directly from the largest explosions in the (current) solar system in the form of Solar Proton Events. I also hope to discuss relativistic electron occurring locally near the Earth but triggered by forcing from the Sun. I will also describe some of the conclusions from the joint Otago University-British Antarctic Survey lead AARDDVARK network of energetic precipitation monitors.
Friday 24 March, 2006
Director of the Sternwarte of the Universität Bonn
"The Milky Way: Structure of Disk and Halo – Is there Dark Matter?"
Discovering the shape and structure of the Milky Way has taken long and required painstaking classical astronomical work. The methods are reviewed. The discrepancies found in relation with classic models for the structure resulted in the invention of Dark Matter.
Details of recent research on the nature of gas in the Milky Way halo as well as on the vertical distribution of stars is presented. It shows our Milky Way is still a developing entity.
Thursday 23 March, 2006
Department of Physics, University of Waterloo Canadian Institute for Advanced Research/Quantum Materials Program
"TITLE: Twenty Years of Paradoxes with the Quantum Magnetism of LiHo xY {1 - x} F4"
The Ising model of magnetism constitutes the simplest example of a system exhibiting a phase transition driven by thermal fluctuations.
Similarly, the transverse field Ising model (TFIM) where Ising spins are subject to an magnetic field applied perpendicular to the direction of the magnetic moments is one of the simplest system that possess a quantum phase transition at zero temperature driven by quantum fluctuations. In this latter context, the LiHo xY {1 - x }F4 material has over the past twenty years attracted most attention from experimentalists as a physical realization of the TFIM. A magnetic field perpendicular to direction of the Ho {3+} spins causes quantum tunneling between the up and the down directions. A field larger than a few Teslas destroys the magnetic order via a quantum phase transition at zero temperature. While the quantum phase transition for the pure LiHoF4 (x = 1) material is now reasonably quantitatively well understood, the quantum phase transition when x < 1 is quite perplexing and not qualitatively understood. Most interesting, it appears that no static frozen order exist for x<0.05 even when no transverse field is applied, possibly suggesting a novel type of quantum disordered ground state. In this talk, I will review the experimental situation as per physics of the TFIM as offered (or rather not!) by LiHo xY {1 - x} F4. I will argue how this material is in disguise not a TFIM, but a novel realization of a cornerstone of the field of statistical mechanics of disordered materials: the random field Ising model (RFIM). Unfortunately, no explanation for the origin of the quantum disordered state for x < 0.05 will be offered at this time.
Friday 17 March, 2006
University of New South Wales
"Globular cluster systems and galaxy formation"
We discuss the origin of physical properties of globular cluster systems (GCSs) in galaxies in terms of galaxy formation and evolution processes. Based on numerical simulations of dynamical evolution of GCSs in galaxies, we particularly discuss (1) the origin of radial density profiles of GCSs, (2) kinematics of GCSs in elliptical galaxies, (3) transformation from nucleated dwarf galaxies into GCSs (e.g., omega Centauri), (4) the origin of GCSs in the Large Magellanic Cloud, and (5) formation of intragroup and intracluster GCs.
Thursday 16 March, 2006
Duke University , CDF experiment at Fermilab
"Particle Physics at the Energy Frontier"
Near the end of 2007 the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland, is scheduled to turn on and produce proton-proton collisions at unprecedented energies. The highly anticipated physics that will result is expected to uncover many discoveries and change the way we think about the Universe. I will show how we got to this point, by discussing selected physics results that have been produced at the currently running Tevatron collider at Fermilab, and some of the questions that still remain.
Monday 13 March, 2006
Department of Physics & Astronomy, University of Canterbury
"Clifford algebra to categories: A journey through physical theory"
Dirac predicted many years ago that as we strive to formulate evermore fundamental explanations of the physical world the mathematical machinery required will become increasingly more sophisticated and abstract. Increasingly we find a new bread of researchers called mathematical physicists who believe a detailed understanding of mathematical structures is required to make further progress toward the next generation of fundamental theory. The aim of this talk is to take you on my journey in mathematical physics, a case study if you like, by providing an overview of motivations, where the research has been and where I believe it is going. This will begin with the geometric insights of Clifford algebra, origins of symmetries in our world, quantisation of many particle systems and finally many body quantum theories. The last step will reveal the underlying mathematical structure to be category theoretic in nature. Be assured this seminar is a survey, not a detailed exposition, of important perspectives in post-modern physics.
Friday 10 March, 2006
University of Freiburg
(Specialist in Solid State Physics and the Physics of Atomic Clusters)
Thermodynamics of finite systems: melting of small particles and atomic clusters
Clusters of a few hundred atoms are studied experimentally and it is shown that they can behave in quite unexpected ways. Two examples will be discussed: 1) the melting temperature fluctuates rapidly with clusters size, and 2) the heat capacity can become negative.
Bonn Observatory Argelander Institute for Astronomy
Astronomy was initiated in Bonn in the early nineteenth century. Due to special coincidences it could start blooming by mid-century. Developments are sketched up to the most recent structural change as of January 2006. Aspects of current astronomical research at the University of Bonn are presented.
Monday 27 February 2006 (Additional seminar)
The impact of the Antarctic ozone hole on climate change at the Earth's surface
The observed climate change of the past few decades is characterized not only by increases in global mean temperatures, but also by substantial changes in the atmospheric circulation. In the Southern Hemisphere, the changes in the atmospheric flow are dominated by a poleward contraction of the westerly winds around the Southern Ocean. In this talk, I will review the observed climate change in the Southern Hemisphere and present evidence that suggests the trends are consistent with forcing by the Antarctic ozone hole. The attendant implications for surface temperatures and precipitation over New Zealand will be discussed.
Wednesday 22nd February, 2006 (ADDITIONAL SEMINAR)
Department of Radiation Therapy, University of Würzburg
Image-guided radiotherapy is not a new concept within radiotherapy, however, in recent years it has regained in popularity and attention. This can be attributed to the fact that it is now possible to deliver highly conformal dose distributions with a very high degree of geometrical and dosimetrical accuracy. This has lead to the development of new imaging approaches and the integration of existing techniques to achieve the following goals: a) to ensure that the actual treatment deviates as little as possible from the planned treatment, i.e. to account for patient set-up errors and changes in the anatomy and the daily tumour location and b) to visualize not just anatomical but also functional/biological information in order to target tumour cells more specifically.
The first part of the presentation focuses on introducing image guided radiotherapy and looks at the correction of both translational and rotational errors based on the interplay between 3D volume imaging (cone-beam CT) and a robotic treatment couch. Some experimental work dealing with real-time tracking of lung tumours is also included.
The second part of the presentation deals with the integration of functional imaging into radiotherapy planning and addresses problems associated with this.
Tuesday 21st February, 2006 (ADDITIONAL SEMINAR)
Physics Department, University of Oregon
"Fractal Conductance in Nano-scale Devices"
The use of nanotechnology has a profound impact on electronic behaviour. A powerful example is the emergence of chaos in the electron dynamics of a range of sub-micron devices. A highly topical question concerns whether the chaotic behaviour of the electrons’ classical trajectories will influence the device’s quantum behaviour – ‘quantum chaos.’ We can perform controlled transitions between classical and quantum behaviour using cryogenic equipment: phase-disrupting processes are suppressed by cooling the devices to helium temperatures and the quantum wave properties of the electrons become important. Our research shows that introduction of wave coherence is accompanied by the emergence of fractal behaviour in the device conductance. This represents a rare measurable phenomenon for testing theoretical predictions of quantum chaos.
We have observed fractal conductance up to temperatures of 138K and, based on the experimentally observed temperature dependence, our research predicts that fractals will dominate room temperature conductance of sub-50nm nano-particles. The results have important implications for both fundamental and applied physics. In terms of fundamental physics, the observed evolution of the fractals with device parameters is inconsistent with current theories, indicating that quantum conduction through solid-state devices is not fully understood. In terms of applied physics, the extreme sensitivity of fractal fluctuations to the device’s electrostatic environment highlights the potential for novel applications such as ultra-sensitive electronic switches and sensors.
In this talk, I will describe experiments performed on semiconductor heterostructures constructed using the “top-down” fabrication approach in which component devices are defined within a high quality macroscopic material. The control and precision offered by these devices allows a systematic study of the physical origins of this novel conduction phenomenon. I will also describe planned experiments on devices using ‘bottom-up’ technologies, where nano-scale components are assembled to form a device. These devices include arrays of nanoscale (5-50nm) metallic particles deposited on templates of DNA strands. Preliminary experiments show the high potential of such devices for room temperature studies and applications.
Friday 17th February, 2006
Institute of Fundamental Sciences, Massey University
"The Spin Dependent Structure Functions of the Proton"
Over the last two decades the spin dependent structure functions of both the proton and neutron have been the subject of intense experimental and theoretical scrutiny. These investigations have shown conclusively that the spin of these baryons is not carried by their valence quarks alone. Significant angular momentum must also be carried by at least one of i) the sea quarks, ii) the gluons, or iii) orbital motion of quarks and gluons. I shall review the progress in our understanding of the spin structure of protons and neutrons and show that a quark-meson model of baryon structure (the meson cloud model) can give a good description of the current data, as well as insight into which degrees of freedom are important in carrying the spin of the proton.
Tuesday 14th February, 2006 (ADDITIONAL SEMINAR)
Department of Mathematics, University of Zacatecas, Mexico
"A broad-brush look at the new observationally posed questions Speaker"
This talk is in the nature of a well-defined broad brush argument as it emerges from the data in astrophysics and cosmology. The data suggests that something non-luminous, possibly beyond the standard model of particle physics, adds roughly 60 kilometers a heart beat to the solar orbital motion in its journey in the Milky way. What lies behind the darkness of this non-luminous element of existence is then posed as a question, and a simple answer is suggested for the origin of the darkness of this dark matter. Next, we walk in the realm of the dark energy and find that it has the possibility to take us in the `new' physics where the notion of spacetime is asked to undergo a well-defined change which alters the notion of `quantum' and `gravity' at their interface.
Friday 10th February, 2006
Bartol Research Institue, University of Delaware
"Searching for the UHE (EeV) neutrinos in Antarctica"
A cosmic flux of EeV (10^18 eV) neutrinos is predicted from cosmic ray observations and established accelerator physics. A discovery instrument for this flux needs to be of order 100 km^3. Such a large detector is possible using radio receivers in the GHz region to detect showers produced by the neutrinos in large volumes of a radio transparent medium, such as ice or salt. I will discuss the prototype RICE and ANITA experiments, and the possibilities for a detector with a larger exposure.