UNSW@ADFA Mathematics & Physics Seminars 2010
Everyone welcome !
Seminars are usually over 40 minutes plus questions on Fridays at 12.40 in Room P25 on the ground floor of PEMS South (Building 26 on the campus map) unless otherwise stated. Light refreshments (coffee and biscuits) served from 12.30.
A link to the 2009 program, 2008 program and 2007 program of Maths and Physics Seminars is placed here for those interested in last year's activities.
Next Seminar:
Friday 12 March, 12.40am, P25
Using the Magnetic Wombat to achieve a new understanding of the magnetic structure of TbNiAlM4
Presented by: Wayne Hutchison, PEMS
OPAL, the Open Pool Australian Light water reactor, together with an array of neutron beam instruments, is one of Australia’s premier research facilities. The neutron instruments are all named for animals. Among these the high intensity (powder) diffractometer is known as Wombat. With its two dimensional detector and high flux, Wombat is very useful for at looking at magnetic structures, not only in the context of powder diffraction, but also for single crystals. This is particularly useful, for example, in looking at samples in an in situ magnetic field.
The family of metamagnetic compounds RNiAl4 (R=rare earth) exhibit a range of interesting magnetic behaviours. There are multiple magnetic phases, and crystal field driven differences in anisotropy and behaviour when different rare earth ions (R) are present in the compound. TbNiAl4 is one illustrative example. It has two phase transitions (three phases) as a function of temperature in low applied magnetic field, and also at least three phases as a function of applied magnetic field at low temperature. Aligned with the first of these field driven transitions is a large inverse magneto caloric effect (MCE). Here the term inverse implies that application of the magnetic field will result in cooling. This is the opposite of the normal MCE case, in which a higher field implies lower entropy, and the cooling occurs with a reduction of field.
In this talk, neutron diffraction studies carried out on single crystal TbNiAl4, in applied magnetic fields, using Wombat will be presented. In particular, the onset of an incommensurate ordered phase above the first field induced phase transition is apparent. This observation vindicates the existence of a higher entropy state at higher applied field as required for an inverse MCE.
Previous Seminars:
Friday 5 February, 11.10am, P25
Charm quarks and the Mysteries of the Strong Interaction
Presented by: Dr Christoph Hanhart, Juelich Center for Hadron Physics, Institute for Advanced Simulation (IAS-4) at the Institut fuer Kernphysik (IKP-3) Forschungszentrum, Juelich
url: http://www.fz-juelich.de/ikp/theorie/staff/ch.shtml
One of the central issues of basic research is to try to understand the structure of the universe, and thus the conditions of our existence, from first principles. Although our understanding of the fundamental interactions --- collected in the Standard Model (SM) of particle physics --- has improved tremendously in recent years, even today the origin of the apparent matter--antimatter asymmetry in the Universe is unknown. It is natural to expect that missing pieces of the SM, or even signals of an even more fundamental theory, can be found in strongly interacting systems at low energies, as such systems are still poorly understood by the standards of particle physics. Thus, a central goal of current research is to better understand the strong interaction. As well as hunting for sources of matter-antimatter asymmetry, this includes attempts to understand how the structure of matter emerges from first principles.
This talk reviews recent advances and addresses current issues in the strongly interacting sector of particle physics. Special emphasis will be put on what to expect from future experiments, with a focus on particles with charmed quarks.
Seminar Coordinator:
Dr John Taylor
School of PEMS
UNSW@ADFA
Canberra ACT 2600
Email: j.taylor@adfa.edu.au
Phone: (02) 6268 8813