2011: archived seminars
16 December
Bhanu Pratap Das
Theoretical Physics and Astrophysics Group,Indian Institute of Astrophysics, Bangalore, India
The Role of Atomic Theory in the Determination of the Electric Dipole Moment of the Electron
Atomic theory has been successfully applied to a number of fundamental problems in physics. One of the latest examples being its application to the search of the electric dipole moment (EDM) of the electron.
My talk will touch upon the connection between the EDM of the electron and the standard model of particle physics and also time-reversal violation which implies CP violation via the CPT theorem. However, its major emphasis will be on the development of a unique relativistic many-body theory of atoms and its crucial role in obtaining a new limit for the electron EDM. The implications of this limit will be discussed.
2nd December
Roy Johnston
School of Chemistry, University of Birmingham
Two metals can be better than one: computational studies of
bimetallic nanoalloys
Nanoalloys (bi- or multi-metallic nanoparticles) are attracting growing interest in fields ranging from catalysis to opto-electronics and magnetics, due to the enhanced tunability of properties (both chemical and physical) that they offer compared to mono-metallic nanoparticles. In this talk, I will start by giving a brief introduction to the field of nanoalloys and some of the challenges that they present for theoretical studies.
I will then go through a number of examples of systems (e.g. Pd-Pt, Cu-Ag, Au-Ag) that we have studied, using empirical potentials and DFT calculations - including the development of a genetic algorithm for direct global optimisation at the DFT level. I will also describe some recent calculations of the structures and chemical ordering of Au-Pd nanoalloys on the (100) surface of MgO.
Thursday (special) 24th November
Jay M. Pasachoff
Williams College, Williamstown, Massachusetts, USA
Transits of Venus and Mercury: Transits of Venus are among the rarest predicted, visible astronomical events, coming in pairs separated by 8 years and then a gap of 105.5 or 122.5 years until the next pair. Nobody on Earth had seen such a transit until the 2004 event. We observed it from the ground in Greece and from several solar spacecraft. Based on spacecraft observations of the 1999 transit of Mercury (an event that happens about 15 times each century), we had resolved the question of the cause of the black-drop effect that had prevented accurate measurement of the Earth-Sun distant for centuries by diminishing the accuracy of the measurements necessary for Edmond Halley's 1716 method. I will describe our use of NASA's ACRIMsat to measure the total solar irradiance drop of 0.1% from the transit of Venus in 2004 and the attempt for a similar measurement at transits of Mercury, relating the work to measurements now widely under way on exoplanet transits. I will describe our high-resolution spacecraft observations of the 2004 transit of Venus and the appearance of Venus's atmosphere for part of ingress and egress. I will end by relating our plans for ground-based and space-based observations of the 6 June 2012 transit of Venus, which will be fully visible from New Zealand.
Jay Pasachoff is Field Memorial Professor of Astronomy at Williams College, Williamstown, Massachusetts, and director of their Hopkins Observatory, the oldest in the U.S. He is past president of the IAU's Commission on Education and Development and Chair of the IAU's Working Group on Eclipses. He is a member of the IAU's Working Group on Johannes Kepler and of John Hearnshaw's Program Group on the Worldwide Development of Astronomy. He is Vice-Chair and Chair-Elect, Historical Astronomy Division of the American Astronomical Society, and Chair of the IAU's Program Group on Public Education at the Time of Eclipses and Transits.
His work on the 2012 transit of Venus is supported by a grant from the Committee for Research and Exploration of the National Geographic Society. He will be in New Zealand to observe the 25 November 2011 partial solar eclipse, his 54nd solar eclipse, from Invercargill.
11th November - Show Day - No Seminar
7th November (Monday) Chemistry Room 531, 11 am
Dr. Cather Simpson
Department of Physics, University of Auckland
Converting Light to Useful Energy
Last year, the laser had its 50th birthday. This innovation has come a long way from those early days, when it was an exotic new technology looking for an application. In the Photon Factory, a multiuser laser facility at the University of Auckland, we exploit the characteristics of pulsed lasers to further research in physics, chemistry, engineering, biology and medicine. This presentation will focus upon how we explore fast chemical processes using ultrafast time resolved spectroscopy, in an attempt to understand the fundamental mechanisms of how molecules 'decide' what to do with the energy they absorb in the form of light. I will also briefly discuss applications of these laser pulses to advances in micromachining, from the construction of a device to help understand how fish survive in the Antarctic to the generation of nanostructures in metals.
4 November, Friday
Olaf Morgenstern and Guang Zeng,
National Institute of Water and Atmospheric Research, Lauder, New Zealand
Atmospheric Composition Research in Transition:
From Ozone Hole to Climate Change
In 1987 the Montreal Protocol was implemented to prevent dangerous anthropogenic damage to the ozone layer. Emission reductions agreed under the Protocol are causing the stratospheric chlorine and bromine loadings to decline. Consequently, polar ozone is expected to largely “heal” during this century. This development is widely hailed as a major success for international environmental protection, yet it may lead to the perception that further research into ozone chemistry is no longer needed. Ozone recovery will coincide with progressive climate change due to emissions of long-lived greenhouse gases. These changes will also affect the ozone layer. Recent research suggests that stratospheric ozone recovery will lead to a seasonal increase of tropospheric ozone, particularly in the Southern Hemisphere. We reassess this question, also taking into account the impact of ozone recovery on tropospheric photochemistry due to decreased actinic fluxes in the near-UV region. We find a substantial impact on the tropospheric ozone burden due to this photochemical effect. The tropospheric abundance of the hydroxyl radical, which acts as the principal detergent of the troposphere, is substantially decreased when stratospheric ozone recovery is taken into account, particularly in northern-hemisphere polluted regions. Associated with this is an increase of surface ozone which had not been modelled in earlier studies that did not account for the impact of ozone recovery on tropospheric photochemistry.
3rd November, Thursday
Pat Scott
Department of Physics, McGill University, Montréal, QC Canada
I will briefly describe two different applications of searches for dark matter annihilation. In the first, I will explain how moderate-amplitude cosmological density perturbations can collapse shortly after matter-radiation equality to form extremely dense minihalos of dark matter. Non-observation of such objects so far with e.g. the Fermi gamma-ray space telescope places extremely competitive limits on the amplitude of the primordial perturbations, at much smaller scales than probed by traditional methods like the CMB. In the second, I will discuss implications for supersymmetry of searches for neutrinos from dark matter annihilation in the Sun, with IceCube. In particular, I will describe a technique for quickly and directly comparing event-level IceCube data with arbitrary annihilation spectra in supersymmetric model scans.
Wednesday (special)
2nd November
Mohamad Jaafar
Assoc. Prof. and Chairman of Medical Physics Programme,
School of Physics, Universiti Sains Malaysia
Low Level Laser Research in USM
1. Light Propagation in Human Skin Tissue and Influence of Skin Types and Hair Parameters on the Light Dose Delivery
MS Jaafar, Farhad H. Mustafa and M. N. Salihin Yusoff
The Graphics Processing Units (GPU) based Monte Carlo for Multi-Layered media (MCML) program was used to simulate the propagation of light in human skin tissue. The program is capable of running bulk data. This study shows that the program provides an appropriate result compared to previous studies with the advantage of graphic image and extremely practical computation time. The optical simulation program ASAP (Advanced Systems Analysis Program) which permits the simulation of photon propagation and the power density recording of laser in the skin layers was used to create realistic tissue phantoms for the investigation of the optical properties of skin. The present study shows that the present hair parameters on the scalp in PDT induce slight changes in the light dose delivery into the depth of the skin, and has a weakly role in reducing photodynamic dose activation. Thus, the hair parameter was not a main responsible factor for the reduction of light dose delivery into the depth of skin in PDT. it was shown that the PDT is sensitive with the human skin colour in laser-tissue interaction. The result proves that skin colour is an essential factor in PDT.
2. Study on Hemolysis and Effects of Laser Irradiation on Human Blood
MS Jaafar, Hend A. A. Houssein, ZA Timimi, M Y Bermakai, AL Ahmad and NE Ismail
Visible light were used to investigate hemolysis in the whole-blood due to time storage. The presence of free hemoglobin plasma (FHP) in samples increased the light absorbance. Highest absorption by human blood was at 415.0 nm which corresponds to the violet-blue region. The hematocrit, FHP and hemolysis were found to increase significantly for the first 3 days.
A 632.8 nm HeNe and 10,600 nm CO2 lasers were each employed to irradiate human blood samples and 2D contour and 3D profile images were acquired before and after irradiation. The statistical analysis shows consistencies with previous research. This can become a significant indicator for blood analysis, thus leading the way as a vibrant diagnosis tool to clarify diseases associated with blood cells.
A 532 nm 100 mW diode laser was used to study the effects on rheological properties of human blood in vitro. The counts of RBC, WBC, HGB, HCT, MCV, MCHC, PLT and neutrophils were obtained. The findings of this research showed that LLLT affects various rheological properties of different blood cells for example red cell deformability, aggregation of cells, critical stress on the cells during preservation time, leucocytarory, erytherocytatory indices, ESR etc. The study proved that LLLT with diode laser 532 nm and low power of 100 mw is advantageous for revitalizing the functional capability of preserved blood.
28th October
Growth and characterisation of carbon-based semiconductors using real-time spectroscopy.
Professor Andy Evans
Institute of Mathematics and Physics
Abyerystwyth University,
Wales
Carbon-based semiconductors based on conjugated organic molecules and sp3-bonded materials such as diamond and SiC offer new solutions for applications in areas such as photovoltaics, UV photonics, sensors and electronics in harsh conditions. They are also enabling new science, for example exploiting the unique physical properties of graphene. We have developed an in-situ method, based on real-time photoelectron spectroscopy, to probe the electronic and chemical structure of such materials during their growth and processing. As a first example, the interface energetics for an entire organic PV structure have been determined during a single growth run. As a second example, the mechanism for rectifying contacts in diamond devices has been shown to correlate with temperature and chemical reaction and finally, the technique has provided a new solid-state method for the production of graphene films on semiconductor substrates.
Andrew Evans - Biography
Andrew Evans is Professor of Materials Physics at the Institute of Mathematics and Physics at Aberystwyth, Wales and is currently at the University of Canterbury as a visiting Erskine fellow. His main research interests are the surfaces and interfaces of electronic and photonic materials, in particular carbon-based semiconductors such as conjugated organic molecules, diamond and graphene. This activity operates within the Centre for Advanced Functional Materials and Devices, a partnership between physical scientists at Aberystwyth and Bangor of which he is co-director. His research involves the development and application of electron, optical and x-ray spectroscopy using fabrication and characterisation methods within the centre and at central synchrotron radiation facilities. He is currently chair of the working group to develop a new versatile soft x-ray beamline at the Diamond Light Source in the UK.
14th October
Frederique Vanholsbeeck
Physics Department, University of Auckland
Biomedical imaging at the Physics department at the University of Auckland
During the past years, the biophotonics group has developed several new optical probes based on fluorescence imaging and optical coherence tomography. The fluorescence optical probe (optrode) is a spectrally and time resolved fluorescence probe that allows for example to measure action potential in the beating heart or to monitor bacteria growth and activity in bioremediation experiments. We also plan to use it to assess water safety. Optical coherence tomography (OCT) is an interferometric imaging technique that allows high resolution in vivo 3D measurements. Typically the resolution is 1-10 microns with a penetration depth up to 1 mm. OCT fills the gap between confocal microscopy and ultrasound and is currently widely used in ophthalmology. We have been working on improving dispersion compensation in the setup and sample dispersion correction. We have also made some attempt at building polarisation sensitive setup. During the talk both techniques will be presented along with some specific applications in which both the optrode or the OCT has currently trialed.
7 October
D. V. Ahluwalia
Senior Lecturer, Physics and Astronomy Department
On the latest neutrino data
I will summarise the latest neutrino data and attempt to put this into context. I shall also take the liberty of presenting some of my own ideas on the subject.
30 September
Tony Cotterill, Team Leader, Emergency Response.
Dr Murray Matthews, expert on radioactive material in the environment.
National Radiation Laboratory, Christchurch
The accident at Japan’s Fukushima Daiichi nuclear power plant was caused by the disastrous earthquake and tsunami which struck Japan on 11 March 2011. Releases of radioactive material to the environment from the battered facility have continued since. Japanese authorities have classified the accident to be at level 7 (the highest level) on the International Nuclear and Radiological Event Scale (INES). The INES scale is designed for communicating to the public and others in consistent terms the safety significance of events at nuclear facilities. An accident rated at level 7 is a major accident involving a major release of radioactive material and is the same classification as that given to the Chernobyl accident.
Although the consequences of the accident for persons, the environment and the future of nuclear power have yet to be fully understood lessons can already be learned.
In this presentation the causes of the accident and NRL’s response to the emergency, acting in its role as the national competent authority for radiation safety and security, will be described. The implications of the lessons learned so far for radiation emergency preparedness will be discussed.
Both presenters are part of NRL’s emergency response team providing scientific analysis and advice to Government agencies and the public.
23rd September
Prof Anatoly Rozenfeld Professor and Director of the Centre of Radiation Physics (University of Wollongong)
Real Time Semiconductor Dosimetry
Highly conformal modern radiation therapy (RT) allows dose enhancement in the treatment target while sparing healthy tissue and is associated with steep dose gradients. Safe application of these radiotherapy modalities requires sophisticated tools for quality assurance (QA), both in a phantom and during the treatment: Real time dosimetry. Semiconductor dosimetry is an attractive option for QA in RT due to the small size of the radiation detectors, the ability to produce pixelated detectors for 1D and 2D dosimetry with high spatial resolution, reproducibility in manufacturing and availability of ASICs for multichannel readout. Overview of real time semiconductor dosimetry in contemporary radiation therapy with applications in proton therapy will be presented.
MOSFET dosimetry. Recently developed at the CMRP is the new version of MOSFET dosimetry, the MOSkin detector. A dual stacked MOSkin detector with angular uniformity of response better than 2% have found unique applications for quality assurance in radiotherapy. The application of the MOSkin dosimeter for in vivo real time dosimetry in both prostate and head and neck cancer treatment in HDR brachytherapy, 3D conformal RT, IMRT, Tomotherapy and proton therapy will be presented.
16th September
Robert Foot (University of Melbourne)
Research Fellow in
Theoretical Particle Physics
Mirror dark matter in light of the DAMA, CoGeNT and CRESST experiments.
Over the last few years intriguing evidence for dark matter direct detection has emerged from DAMA, CoGeNT and, very recently, the CRESST experiments. These exciting results indicate that we are on the verge of discovering the identity of dark matter. One theoretical dark matter candidate, mirror dark matter, can explain all of these experiments. Future tests of this theory will also be discussed.
9th September
Howard Carmichael, University of Auckland
The driven Jaynes-Cummings model: from atoms and cavities to superconducting circuits and quantum dots
The Jaynes-Cummings Hamiltonian accounts for the interaction of one qubit (two-state quantum system) and a single mode of the electromagnetic field ‒ adding an external field and dissipation defines the Driven Jaynes-Cummings Model. Through two decades of development, this elementary model has served as a bridge connecting a diverse array of experiments, all focused on the manipulation and control of photons: thus, qubits are realized with Rydberg atoms, optical transitions in atoms and quantum dots, and Josephson junction devices; microwave cavities, optical resonators or photonic crystals, and microwave striplines define the requisite mode of the field. This talk reviews some of the highlights from this history. It follows a trajectory from experiments with thermal atomic beams and optical cavities to recent spectacular experiments with superconducting circuits. In its role of “bridge”, the Driven Jaynes-Cummings Model carries the physics of photon interactions from microwave to optical frequencies, from two-state atoms to the Cooper-pair box, while accounting for the central importance of interactions between these elements and their environment.
11am Thursday 18 August, Rutherford 701 (the physics department seminar room)
Shawn Fostner - formerly at McGill University, Montreal; a recent arrival in Simon Brown’s group
Controlled nanoscale device fabrication on insulating surfaces under ultrahigh vacuum
Our goal is to use UHV AFM to image the atomic structure of electrically contacted molecules on insulators. This is particularly critical for molecular electronics measurements where a detailed knowledge of both the contact geometry and chemical nature are crucial to critically test theoretical models.
In order to make this connection from the macroscopic realm to the nanometer scale of individual molecules we use a combination of techniques, including micrometer scale stenciling techniques, electromigration of nanoscale wires, and field assisted deposition of metallic atoms from metallic scanning probe tips. Silicon stencils are used on flat bulk insulating substrates in UHV to deposit nanoscale metal wires. Electromigration of these wires is used to create gaps 1-100 nm in size. Field emission from gold coated atomic force microscope tips are used to deposit metallic atoms on the insulating surface in an attempt to bridge electromigrated gaps to a molecules and thus create a molecular device in a configuration that can be imaged by SPM techniques. The positioning and trapping of molecules will also be discussed, this is controlled using single layer deep pits created in the insulating surface, as well as the order of metal and molecule deposition which affects nucleation and growth.
4:00pm, Thursday 18th August, Rutherford 701 (Physics seminar room). (Note new day and time)
Professor Chris Abell, Department of Chemistry University of Cambridge.
Making money from molecules
Chris's research interests include studying enzyme mechanism and inhibition. He has specific interests in targeting enzymes involved in vitamin biosynthesis an cancer. He also runs a second research group developing microdroplets as a new experimental platform. Chris is a cofounder of Astex Therapeutics, Akubio and Sphere Fluidics, a founding scientist in Ionscope, and a director of Cambridge Enterprise (the University's tech transfer arm). Astex has 5 compounds in clinical trials and is about to launch on the Nasdaq.
He will use his experiences to frame a discussion about entrepreneurship in academia, briefly describing the various companies and the very different strategies that have been adopted to develop them.
12th August 2011
Melanie Johnston-Hollitt<Melanie.Johnston-Hollitt@vuw.ac.nz>
Victoria University, Wellington, New Zealand
An overview of the physics of galaxy clusters with next generation radio surveys
Galaxy clusters are the largest bound structures in the universe and typically contain hundreds to thousands of galaxies embedded in a hot plasma. Clusters are a rich laboratory for studying the evolution of galaxies and a powerful tool for testing cosmology. We will present an overview on the observational properties of galaxy clusters, exhibiting the rich variety of objects we find within them. In particular we will present new science expected from next generation radio surveys in which NZ scientists are involved.
PHYS/ASTR/MAPH 480 Project Presentations Part I
[Mike Reid/Juergen Meyer]
Rescheduled Friday, 29th July (due to snow on Monday 25th)
11:00 Fane Bastin, Cosmic accelerators
11:15 Andrew Johnson, Gravity and holographic universe
11:30 Rosa Hughes-Currie, Excitons in Yb2+ materials
11:45 Fraser Dennison, Climate models and sea ice
12:00 Matt Davie, Non-radial oscillations in stars
Tuesday, July 26
2:00 Hayden Lee, Cosmological background and perturbations
2:15 Chris Bateman, MARS imaging
2:30 Kane O'Donnell, Discreet universes - Lindquist-Wheeler model
2:45 Cathy Neil, General relativistic galaxy models
Friday 22 July - 11:00am, Dept Seminar Room 701, Level 7, Rutherford Building
Prof. Chris Tinney, School of Physics, University of NSW
The Age of Exoplanetary Science: As scientists, we are truly privileged to be living in the era when the dream of finding and understanding planets orbiting other stars has gone from science fiction to just-plain-science. Hundreds of planets have now been detected orbiting hundreds of stars. Much as our astronomers a hundred years ago were struggling to digest the meaning of the first surveys of other galaxies, exoplanetary scientists (the astronomers searching for and studying these extra-solar planets) are now endeavouring to understand what these discoveries are telling us about how planets form and how common planets are in the Universe.
The measurements required to detect exoplanets require observations of mind-boggling accuracies - equivalent to detecting motions on our detectors at a size scale of just 30-40 silicon atoms. Despite this, the technologies that underlie the construction of our optical spectrographs have not really changed significantly in several hundred years. The next advance in this field is set to come from the construction of photonically-fed spectrographs - an advance the Exoplanetary Science Group at UNSW would like to lead.
Download flyer by clicking here.
Friday 10th June, 11 am, Room 701, Rutherford Building
Assoc. Prof. Mike F. Reid,
[UC Research Profile];
Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
Excitons and traps in rare-earth materials probed by a free-electron laser
For the last 18 months Jon Wells, Pubudu Senanayake, and I have been travelling to the Netherlands to use the FELIX free-electron laser facility to study the excited states of rare-earth (lanthanide) materials. In our experiments a UV laser is used to excite Yb2+ ions in various fluoride host crystals. The excited state is then probed by the free-electron laser (FEL), which produces intense pulsed, tunable IR radiation.
The physics of the excited states in these materials is interesting and complex. The excited electron is delocalized, so the state may be considered to be a “bound exciton”. The FEL induces transitions between internal states of the exciton, giving us information about the internal syucture that was previously inaccessible. Furthermore, the FEL can liberate electrons that have been trapped in lattice defects. Such defects are the basis of technology such as X-ray storage phosphors and persistent luminescence materials, and the FEL gives us a unique way of studying their dynamics.
Friday 27th May, 11 am, Room 701, Rutherford Building
Dr Teppo Mattsson
Postdoctoral Fellow, Physics & Astronomy Dept, University of Canterbury
The effect of cosmological structures on the average expansion of the universe
Due to the nonlinear backreaction of the cosmological structures, the evolution of the average expansion of the universe does not follow a homogeneous Friedmann solution - unlike the standard model of cosmology assumes. The backreaction is determined by the variance of the expansion rate minus the non-negative average shear. A way to estimate the backreaction is to evaluate the variance of the expansion rate over different Friedmann models. This method yields significant backreaction but neglects the shear. Using the exact spherically symmetric inhomogeneous dust solution of the Einstein equation, we demonstrate that the shear can suppress the backreaction by several orders of magnitude. Testing the generality of the results requires more sophisticated solutions.
Friday 13 May, 11am, Room 701, Rutherford Building
Sudhakar Panda, Visiting Erskine Fellow with the Dept from 27th Feb to 20th May
Harish-Chandra Research Institute, Allahabad
"Searching for a Unified Theory". In this talk, we will point out the obstacles in finding a theory that unifies all interactions of the nature and motivate how and why String Theory is a possible candidate for the Unified Theory.
Wednesday, 4th May, Noon, Room 213 Physics & Astronomy Department, Rutherford
Dr. Du-Caines
Atmospheric Tides & Statistical Modelling of Relative Humidity
This talk will be divided into two parts which includes my past research highlights and visions for future research as following.
Part I - Atmospheric tides: while gravitationally forced lunar tides generate significant amplitude periodic oscillations in the global oceans, it is the thermally forced solar tides dominating the mesosphere and lower thermosphere (MLT) region. Conserving energy and propagating vertically through the atmosphere these tides can reach significant amplitudes of 30-50 m/s in the horizontal wind field and 10-20K in the temperature field of the MLT region before breaking or dissipating. In this part of the talk, I will provide a brief overview of the solar forced atmospheric tides, results from current modelling efforts and discuss recent observations from space and ground-based instruments. One of the potential generation mechanisms for the atmospheric tides - non-linear interactions between waves and the transport effect of atmospheric tides in the MLT region are also briefly discussed.
Part II - Statistical modelling of relative humidity: Water vapor is the atmosphere's strongest greenhouse gas, and roughly doubles the expected surface temperature change due to changes in CO2 (water vapor feedback process). Key to this amplification is that absolute humidity increases with increasing temperature. Numerical general circulation models
(GCMs) predict a change in absolute humidity due to changes in atmospheric temperatures that roughly corresponds to a constant relative humidity. A statistical model is built based on the relative humidity observations from the Atmospheric Infrared Sounder (AIRS) (2002-2010) on board the AQUA satellite to explain why global mean relative humidity stays roughly constant.
Monday, May 2nd, 2:10pm, Room 213 Physics & Astronomy Dept, Rutherford Building
Dr Soebur Razzaque, (US Naval Research Laboratory, Washington DC, USA)
High energy neutrinos in ice: High-energy (> GeV) neutrinos are produced naturally near the Earth when very high energy cosmic-ray particles hit the atmosphere, producing extended air showers. They are also expected to be produced in astrophysical objects such as gamma-ray bursts, active galactic nuclei, supernovae, novae and neutron stars. Detection of astrophysical neutrinos can reveal the yet unknown sources of the highest-energy cosmic rays. Recent data release on atmospheric neutrino measurements by the IceCube neutrino observatory at the South pole can be used to search for the existence of sterile neutrino(s) and address the outstanding questions of the number of neutrino species and total mass.
Thursday 28th April 11am Venue: E14
Dr Ishwaree Neupane, (Dept of Physics and Astronomy, University of Canterbury)
The Dark Energy Problem: An Inspiration for New Physics
Cosmology is a young science -- one which attempts to reconstruct and comprehend (and also explain) the entire cosmic evolution of our Universe from nearly 14 billions of years ago. A long held view is that the early Universe experienced an era of accelerated expansion known as "inflation". However, peering back so far in time (through observations) is extremely difficult. An added difficulty is that many of the theoretical pillars of physics upon which the models of inflation, the behaviour of elementary particles and fields, and the role of quantum dimensions rest have only been proposed within the last 3 decades or so. That hasn't given theoretical physicists much time to fully flesh out and comprehend the situation. There is a possibility that we're going to find a fatal flaw in our prevailing view on models of concurrent cosmology, including interpretation of dark energy.
In this talk, I will discuss on recent attempts made to understand and explore a much desired connection between fundamental theories of gravity, including models inspired by string theory, and the current standard model of cosmology which seems to work only by invoking unknown sources of dark energy and dark matter. I will focus on the questions of how models of canonical quantum gravity could evolve from a higher dimensional realism to one that reproduces the observed 4-dimensional world and help in the understanding of the early history of our Universe, including an inflationary epoch, and provide deeper insights into some other problems in physics, including the mass hierarchy and the cosmological constant problems.
Monday 18th April, 11:00 a.m. ELEC309
Dr Suruj Seunarine, (University of the West Indies, Barbados)
Lots of good stuff, the physics of IceCube: Each year dozens of astrophysicists migrate from the cold northern winter to the long days of the southern summer. Once south and on the warmth of the ice, the rituals of construction, calibration and commissioning of IceCube take place, a carefully choreographed dance designed to ensure the survival of the species for at least for the next few decades. IceCube construction was completed this year and soon the full detector will be turned on. In this talk I discuss to physics of IceCube, recent results, and outlook for the future of this neutrino observatory.
Thursday 14 April, 11am – Room E14 click here for directions
Dr Christopher Gordon, (University of Oxford, UK)
Reconstructing the Early Universe
Cosmology has the ambitious aim of describing the past, present, and future behaviour of the whole Universe. Fortunately, there is a wealth of data to help us do this. Also, the Universe appears to have been very simple in its past, as it was extremely close to being spatially homogenous. The cosmic microwave background allows us to study the state of the Universe almost 14 billion years ago. In order to explain the length scales of the correlations in the density fluctuations at that stage it seems the early Universe is likely to have undergone an era of accelerated expansion known as "inflation". The main candidate for having caused this era is one or more potential dominated scalar fields. Current research aims at finding as much information about this era as possible. For example, we would like to know how many fields were involved in inflation and at what energy scale inflation occurred. I will describe what we know so far and how future data will allow us to probe the inflationary era to much greater accuracy.
Monday, 11th April, 2pm
Dr Ralf Lehnert, Universidad Nacional Autonoma de Mexico
Special Relativity on the Test Bench
One of the most difficult open questions in present-day physics concerns the quantum structure of spacetime. There are various theoretical approaches to this question, but experimental progress is hampered in this research field because many models predict deviations from established physics that are below the detection threshold of current and near-future experiments. However, tests of Special Relativity provide a promising avenue to overcome this phenomenological obstacle: Many models for underlying physics can accommodate a small breakdown of Lorentz invariance. Moreover, numerous feasible Lorentz-symmetry tests have the sensitivity required to measure such effects. This talk gives a brief survey of various theoretical ideas and experimental efforts along these lines.
Friday, 1st April
Chris Blake, Centre for Astrophysics and Supercomputing, Swinburne University of Technology.
Probing Dark Energy With Galaxy Surveys:[pdf 290 KB]
The discovery that the expansion of the Universe is speeding up represents one of the most intriguing and compelling puzzles in astronomy. I review the evidence for the "accelerating Universe" and explain how galaxy surveys can test the nature of this "dark energy" by measuring the history of cosmic expansion and growth. I present the latest results on this topic from the recently-completed WiggleZ Galaxy Redshift Survey at the Anglo-Australian Telescope, and discuss how these observations, and future galaxy surveys, can help elucidate the physics of dark energy.
Friday, 25 March 11:00 a.m. West Melton Observatory (click here for directions)
Sushil Kumar
School of Engineering and Physics, The University of the South Pacific, Suva, Fiji. kumar_su@usp.ac.fj
ELF –VLF Radio Waves: Diagnostic Tools to Study Upper Atmosphere:The major part of ELF (extremely low frequency: 3 Hz-3 kHz) and VLF (very low frequency: 3 kHz-30 kHz) radio waves generated by lightning discharges (ELF and VLF) and by navigational transmitters (VLF) propagate in the atmospheric waveguide formed between the earth and lower conducting layer of the upper atmosphere called ionosphere (70-90 km). This waveguide is called Earth-Ionosphere Waveguide (EIWG) in which ELF-VLF signals propagate large distances due to little attenuation. Atmospherics or sferics that originate from lightning discharges on propagating large distances in the EIWG, particularly at the night, form dispersed sferics called tweeks which are novel diagnostic tools to monitor the nighttime D-region (lower) ionosphere. The signals from VLF transmitters are used to study the diurnal variation of signal strength and hence the lower ionosphere and short term VLF perturbations due to lightings and space weather events such as solar flares and geomagnetic storms. The University of the South Pacific (USP), Fiji, is one of the hosts of World-Wide Lightning Location Network (WWLLN) since 2003 with 40 other institutes and universities all over the world participating currently in WWLLN. Some observations of ELF-VLF signals using WWLLN experimental set-up and their applications will be presented.
Wednesday 23 March, 9:00am, Big Top Too
Steve Maddox, University of Nottingham
Galaxy Surveys and Clustering: Wide-area galaxy surveys map out the structure of the universe, telling us about cosmology and galaxy formation. Optical surveys from the APM to the 2dF have given evidence for a cosmological constant, baryon oscillations and luminosity bias. The Herschel-ATLAS is a new wide-area survey which is mapping the sky at wavelengths from 100 to 500 micron. The sources detected give a sample of sub-mm galaxies which is very different to optical samples. About a half of the sub-mm sources can be associated to low redshift optical galaxies using a likelihood ratio analysis.
The rest are at higher redshift. The clustering of the H-ATLAS sources show a mix of local 'normal' galaxies, and a more clustered high redshift galaxy population.
Monday 21 March, 3:00pm, Big Top Too
Loretta Dunne, University of Nottingham
Digging up the Dirt on Galaxies: Around half the optical/UV energy in the Universe has been absorbed by interstellar dust. This energy is re-emitted in the far infrared (FIR)/sub-mm part of the spectrum and with FIR surveys we can recover this stolen starlight. Herschel-ATLAS is the widest area survey being carried out with the Herschel Space Observatory. It will cover 550 square degrees in 5 FIR/sub-mm bands from 100-500 microns and detect ~200,000 sources out to redshift z~3. One of the main goals of H-ATLAS is to carry out the first benchmark for dust and obscured star formation in the 'local' Universe out to z=0.5 as Herschel is sensitive to all the dust in a galaxy (not just the warm stuff as IRAS was). In this talk I will give an overview of the survey and what we are learning about the evolution of dust and obscuration in galaxies over the past 4 billion years, plus a look at what the future has to offer.
Wednesday 16 March, 10:00am
Venue: Big Top Too (tent on the carpark outside Speech & Language Therapy, Engineering Road)
Vardha Nicola Bennert, University of California Santa Barbara
The Co-Evolution of Black Holes and their Host Galaxies
Over the past years, there has been growing evidence that massive black holes exist in the center of galaxies.
Even more enticing, tight correlations have been discovered between the mass of the central black hole and the
properties of their host galaxy. These relations have been interpreted as a close connection between galaxy
formation and evolution and the growth of black holes. However, the reason for such a connection is hotly debated.
A promising way to a deeper understanding of the physical origin of these scaling relations is to look at their
evolution with cosmic time. This is a chicken-and-egg problem: which came first, the black hole or the galaxy?
I will discuss how using telescopes as time machines helped us finding an answer to this question.
Friday 18th February
Professor Theodore Shepherd, Department of Physics, University of Toronto, Canada
Abstract: TBA: Three-dimensional chemistry-climate models have recently reached the stage where they are becoming mainstream tools for understanding and predicting the behaviour of the atmosphere. In order to develop confidence in models, it is necessary to compare them with measurements. This is not a simple task, however. Several examples will be given of model-measurement comparison with the Canadian Middle Atmosphere Model (CMAM), including ground-based and balloon data. These illustrate how such comparisons can be used not only to test the model but also to better understand and characterize the measurements, e.g. by assessing their representativeness.
The second half of the talk will present recent CMAM results concerning the interaction between ozone depletion/recovery and climate change in the Antarctic, and discuss possible implications for ocean circulation, carbon uptake, and ice sheet stability.
All Welcome
Friday 18 February 2011
Time: 3:30-4:30pm
Location: Tekapo Seminar Room, NIWA Christchurch
Michaela I. Hegglin (Institute: Department of Physics, University of Toronto) on
Ozone in the upper troposphere/lower stratosphere Why do we care? (PDF, 58KB)
Friday 11th February
Prof. Phil Gregory
Professor Emeritus, Physics and Astronomy Dept, UNIVERSITY OF BRITISH COLUMBIA
Extra-solar planets via Bayesian model fitting: Recent advances in astronomy have yielded a rich harvest of over 500 extra-solar planets (exoplanets) including the detection of a possible super earth in the habitable zone surrounding Gliese 581.This and other remarkable successes on the part of the observers is motivating a significant effort to improve the statistical tools for analyzing the data. Much of the recent work has highlighted a Bayesian Markov chain Monte Carlo (MCMC) approach as a way to better understand parameter uncertainties, degeneracies and to compute model probabilities.
In this talk I will provide an introduction to Bayesian inference and MCMC. Model fitting is a frequent challenge faced by experimental researchers so it is useful to be exposed to a state of the art Bayesian approach. I will highlight a new fusion MCMC algorithm which incorporates parallel tempering, simulated annealing and genetic crossover operations. Each of these features facilitate the detection of a global minimum in chi-squared in a multi-modal environment. By combining all three, the algorithm greatly increases the probability of realizing this goal. When applied to the exoplanet Kepler problem it acts as a powerful Bayesian multi-planet Kepler periodogram. The performance of the algorithm will be illustrated with some recent successes.
All Welcome
Friday 4th February
CANCELLED (SPEAKER HAS TO RETURN TO USA EARLIER THAN PLANNED)
Karsten M. Heeger, Physics Department, University of Wisconsin
Probing New Physics in Low-Energy Neutrino Experiments: Neutrino mass and mixing are amongst the major discoveries of recent years and demand that we make the first significant revision of the Standard Model in decades. From the first observation of the free antineutrino to the discovery of neutrino oscillations with atmospheric, solar, and reactor neutrinos, non-accelerator experiments have played an essential role in the history of neutrino physics. They continue to provide some of the best measurements of neutrino oscillation parameters and are used as astrophysical probes. Many important questions remain: Are neutrinos their own antiparticles? What is their mass scale? Can we use neutrinos to search for CP violation? I will describe the prospects for understanding neutrino mass with the bolometric CUORE double beta decay experiment, and discuss precision measurements of neutrino oscillation with the KamLAND and Daya Bay reactor experiments.
Friday 21st January
Ruth Williams, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, UK
Classical and Quantum Discrete Gravity: Regge calculus is a discrete version of general relativity. The scheme will be reviewed and applications (including some work in progress) will be described in classical gravity and in the search for a theory of quantum gravity.
Wednesday 19th January
Dr Clare Worley, Observatoire de la Cote d'Azur
THE AMBRE Project: Tests of MATISSE on large spectral datasets from the ESO archive: The automated stellar classification algorithm, MATISSE, has been developed at the Observatoire de la Cote d'Azur (OCA) as a means of determining stellar effective temperatures, surface gravities and chemical abundances for large samples of stellar spectra. MATISSE is one of the key programmes to be used in the analysis of the spectra that will be obtained by the Radial Velocity Spectrometer (RVS) on the European Space Agency's (ESA) Gaia satellite. In preparation for the Gaia mission, rigorous testing of MATISSE is currently being carried out using large datasets of spectra from the European Southern Observatory (ESO) archive (The AMBRE Project, a collaboration between ESO and OCA). The derived stellar parameters will be delivered to ESO in order to make them available to the astronomical community via the Virtual Observatory.
The analysis of the archived spectra of the first of the ESO spectrographs, FEROS, is nearing completion. This initial analysis has been the testbed for producing many of the tools that will also be used in the analysis of the UVES, HARPS and Flames/GIRAFFE archived spectra. These tools have been integrated into an analysis pipeline which feeds the processed spectra into MATISSE for derivation of the spectral parameters. Key stellar samples have been identified within the FEROS spectral dataset using the PASTEL database. This has provided a crucial comparison between the MATISSE results and the results of other comprehensive stellar studies.
Monday, 17th January 2011
Danielle A. Berg,
University of Minnesota, Department of Astronomy
Re-examining High Abundance SDSS Mass-Metallicity Outliers: Normal Abundance, Evolved W-R Galaxies?
Observational evidence indicates that a galaxy’s mass is directly related to its oxygen abundance (metallicity), giving rise to the so-called mass-metallicity relationship. These two quantities probe a galaxy’s star formation history and the impact of feedback processes, which together describe the enrichment of heavy elements that we see today. As such, this relationship provides strong constraints on the theories of galaxy evolution. Peeples et al. (2008) analyzed ~53,000 galaxies from the Sloan Digital Sky Survey (SDSS), finding a sample of 40 low-mass, high-oxygen abundance outliers from the mass-metallicity relationship. If these objects are true outliers from the mass-metallicity relationship, then their properties contradict our understanding of galaxy evolution. To investigate this disagreement, I will present new spectroscopic observations of four dwarf galaxies from this sample that showed significant oxygen abundance offsets from the MB luminosity-metallicity relation. The metallicity estimates made by Peeples et al. lie in the range 8.5 ≤ 12 + log (O/H) ≤ 8.8 for these objects.
The new observations extend the wavelength coverage to include the [O II] λλ3726,3729 emission line doublet, which adds leverage in oxygen abundance estimates. All four spectra show the targets to be very low excitation (small values of λ5007/λ3727) and to have relatively high N/O ratios (N/O ≥ 0.10). As such, these spectra all fall in a regime where the “standard” strong line methods for metallicity determinations are not well calibrated either empirically or by photoionization modeling. By comparison with photoionization models, I constrained estimated oxygen abundances to the range of 7.9 ≤ 12 + log (O/H) ≤ 8.3, within the scatter of the mass-metallicity relation. Furthermore, I will discuss the physical nature of these outliers that leads to their unusual spectra (and thus results in their outlier classification), concluding that their low excitation, elevated N/O ratios, and strong Balmer absorption features are consistent with the properties expected from galaxies evolving past the rare “Wolfe-Rayet galaxy” phase.
Wed 12 Jan, 11 am
Dr Liz Wylie de Boer, Research School of Astronomy and Astrophysics, Australian National University
Galactic Archaeology - the search for the Holy Grail: Galactic Archaeology is the study of the history of the Milky Way. It is the search for understanding of the formation and evolution of our Galaxy. The endless quest for knowledge about the Universe around us by looking
in our own cosmological backyard. Several different approaches and current projects will be presented. Come and find out more about this intriguing astronomical journey - the search for the Holy Grail.