Events at Physics |
Events During the Week of January 20th through January 27th, 2008
Monday, January 21st, 2008
- No events scheduled
Tuesday, January 22nd, 2008
- Chaos & Complex Systems Seminar
- Sleep need and synaptic homeostasis
- Time: 12:05 pm
- Place: 4274 Chamberlin Hall
- Speaker: Chiara Cirelli, UW Department of Psychiatry
- Abstract: Any proposal about the function of sleep should be able to provide a convincing explanation of why the proposed function can only be fulfilled by sleep and not by quiet wakefulness. Otherwise, why would sleep--a potentially dangerous behavior characterized by loss of contact with the environment--be so universal, and why would sleep pressure be so overwhelming? I will discuss a novel hypothesis--the synaptic homeostasis hypothesis (SHY)--which claims that sleep plays a role in the regulation of synaptic weight in the brain. SHY states that during wakefulness many brain circuits undergo synaptic potentiation, resulting in a net increase in the strength of synaptic connections between neurons, and that the homeostatic increase in slow wave activity (SWA) during the subsequent sleep is a direct reflection of this synaptic potentiation. SHY also predicts that SWA mediates synaptic downscaling, which is tied to several beneficial effects of sleep, including performance enhancement. In summary, according to this hypothesis, sleep is the price we have to pay for plasticity, and its goal is the homeostatic regulation of the total synaptic weight impinging on neurons. I will discuss evidence supporting the hypothesis, its implications, as well as current limitations and unresolved issues.
Wednesday, January 23rd, 2008
- No events scheduled
Thursday, January 24th, 2008
- R. G. Herb Condensed Matter Seminar
- How Difficult is Quantum Many-Body Theory?
- Time: 10:00 am
- Place: 5310 Chamberlin Hall
- Speaker: Matthew Hastings, Physics, Los Alamos National Laboratory
- Abstract: The basic problem of much of condensed matter and high energy physics, as well as quantum chemistry, is to find the ground state properties of some Hamiltonian. Many algorithms have been invented to deal with this problem, each with different strengths and limitations. Ideas such as entanglement entropy from quantum information theory and quantum computing enable us to understand the difficulty of various problems. I will discuss recent results on area laws and use these to prove that we can use matrix product states to efficiently represent ground states for one-dimensional systems with a spectral gap, while certain other one-dimensional problems, without the gap assumption, almost certainly have no efficient way for us to even represent the ground state on a classical computer. I will also discuss recent results on higher-dimensional matrix product states, in an attempt to extend the remarkable success of matrix product algorithms beyond one dimension.
- Host: Vavilov
Friday, January 25th, 2008
- Phenomenology Seminar
- Very Energetic Top Quarks and the Search for New Physics at the LHC
- Time: 2:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Ulrich Baur, SUNY at Buffalo
- Physics Department Colloquium
- From ASDEX Upgrade to ITER: Preparing the Next Step in Fusion Research
- Time: 4:00 pm
- Place: 2241 Chamberlin Hall (coffee at 3:30 pm)
- Speaker: Hartmut Zohm, Max Planck Institute
- Abstract: Nuclear Fusion research has progressed steadily over the past 40 years from small table top experiments to large facilities that allow to create on earth hydrogen plasmas hotter than the centre of the sun. In the area of magnetic plasma confinement, the technological development goes together with huge progress in the understanding of magnetized hot, nearly collisionless plasmas, covering a wide range of phenomena, the most prominent areas being turbulent transport of heat and particles, large scale MHD stability and plasma wall interaction. Based on this the Next Step in fusion research, the ITER experiment, is aimed at generating significant amounts of fusion power, i.e. at least 10 times the external power used to heat the plasma. The talk will briefly review our present knowledge of fusion plasma physics and the related fields and then describe the role of the ITER experiment on the way to a fusion reactor. In the second part of the talk, I will discuss the role of present day fusion experiments in preparing ITER, exemplified by experimental results and plans from the ASDEX Upgrade tokamak, a medium size fusion facility operated by Max-Planck-Institut für Plasmaphysik in Garching. Experimental results from ASDEX Upgrade range from improving central plasma parameters by optimizing confinement and stability properties to the first successful operation of a fusion machine with plasma facing components fully covered by Tungsten, the material foreseen for a fusion reactor, that was achieved in ASDEX Upgrade this year.
- Host: Forest