Events at Physics
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Events on Thursday, April 11th, 2013
- R. G. Herb Condensed Matter Seminar
- The Objective Indefiniteness Interpretation of Quantum Mechanics: Partition logic, logical information theory, and quantum mechanics
- Time: 11:00 am
- Place: 5310 Chamberlin
- Speaker: David Ellerman, University of California, Riverside
- Abstract: Quantum mechanics (QM) is not compatible with the usual Boolean logic of subsets where elements have definite properties "all the way down." But there is a recently developed dual logic of partitions (subsets and partitions are category-theoretically dual) which models indefinite elements that become more definite as distinctions are made. If quantum mechanics was also incompatible with this unique dual logic of partitions, then one might "press the panic button" and postulate unknowable hidden variables to restore definiteness or soar off into the void with "many worlds" or the like.
But quantum mechanics fits perfectly with the dual logic of partitions. There is no need for (more) bizarre flights of fancy to "interpret" QM. This objective indefiniteness approach to QM does not restore our common sense assumption of definiteness down into the quantum realm. But it does restore sanity and understanding to the whole framework. That is, we now have the logic that precisely fits QM--a logic that was developed independently (i.e., without any thought of a QM connection) and that is the unique mathematical dual to ordinary Boolean subset logic, the logic assumed in classical physics. Moreover the normalized counting measure on partitions gives the quantum-relevant logical information theory--just as Boole developed logical probabilities as the normalized counting measure on subsets. Indeed, when the mathematics of partition logic and logical information theory is linearized and lifted to complex vector spaces, then it yields the mathematical framework of quantum mechanics (but not the specifically physical postulates).
The key concepts explicated by this approach are the old ideas of "objective indefiniteness" (emphasized by Abner Shimony), objective probabilities, and the objective realization of information, "its" from "dits" (= distinctions). Since partition logic, logical information theory, and the lifting program "derives" the mathematics of quantum mechanics, it shows how that QM framework can be interpreted--and this set of results gives what might be called the objective indefiniteness interpretation of quantum mechanics.
- Host: Huber
- Quantum Theory Seminar
- A Common Fallacy in Quantum Mechanics: Why Delayed Choice Experiments do NOT imply Retrocausality
- Time: 2:00 pm
- Place: 5310 Chamberlin
- Speaker: David Ellerman, UC-Riverside
- Abstract: There is a common fallacy, here called the separation fallacy, that is involved in the interpretation of quantum experiments involving a certain type of separation such as the: double-slit experiments, which-way interferometer experiments, polarization analyzer experiments, Stern-Gerlach experiments, and quantum eraser experiments. It is the separation fallacy that leads not only to flawed textbook accounts of these experiments but to flawed inferences about retrocausality in the context of "delayed choice" versions of separation experiments.
- Host: Huber
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- The Fermi Large Area Telescope, Astrophysics, Dark Matter Searches and the 130GeV Line
- Time: 2:30 pm
- Place: 4274 Chamberlin
- Speaker: Eric Charles, SLAC
- Abstract: The first four and a half years of Fermi LAT operations have seen numerous exciting scientific results relating to many different topics, some expected and others unexpected. I will present a brief overview of the Fermi mission and the role it plays in current particle astrophysics research. Towards this end I will discuss some recent scientific highlights involving both galactic and extra-galactic sources classes. I will then spend the majority of the talk focusing on searches for signatures of particle dark matter interactions. In particular I will describe the LAT team's search for spectral lines from gamma-ray annihilation or decay, and discuss the status of claims of a line-like feature at 130 GeV near the Galactic center.
- Host: Neilson
- Astronomy Colloquium
- "Examining Galaxy Formation and Evolution with the Milky Way and Its Satellites"
- Time: 3:30 pm
- Place: 4421 Sterling Hall
- Speaker: David Nidever, University of MI
- Abstract: How galaxies form and evolve remains one of the cornerstone questions in our understanding of the universe on grand scales. The Milky Way and its satellites are a local laboratory for studying the evolution and properties of galaxies of various masses in great detail. I will highlight some recent results from three projects that are providing new insights into the structure and formation history of the Magellanic Clouds and the Milky Way. First, an extensive study of the stellar periphery of the Magellanic Clouds reveals that they are much more extended than previously thought which has implications for structure formation on small scales. Second, I have undertaken a large-scale survey to map out the gaseous Magellanic Stream. These observations provide important constraints on the orbits and
interaction history of the Magellanic Clouds with each other and the Milky Way. Finally, I will discuss SDSS-III/APOGEE, a near-infrared, high-resolution spectroscopic survey of ~100,000 stars in the Milky Way. With only the first year of data, APOGEE has already produced a number of important results especially in the Galactic bulge, with many more to come.
- Host: Matt Haffner