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This Week at Physics

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Events on Friday, April 10th, 2015

Physics Department Colloquium
Joint Physics - Astronomy Colloquium
Kinetic and Gyrokinetic Astrophysical Turbulence Above and Below the Mirror and Firehose Stability Thresholds
Time: 12:00 pm
Place: 2241 Chamberlin Hall - Coffee and cookies at 11:45
Speaker: Matt Kunz, Princeton
Abstract: The solar wind is weakly collisional. As such, the particle populations that comprise it exhibit a variety of non-Maxwellian features, which are customarily described in terms of interspecies drifts and pressure anisotropies relative to the magnetic field direction. The solar wind is also turbulent, with a power spectrum extending over many orders of magnitude above and below the ion Larmor scale. These two facts, both well documented by the observational community, are not always treated on equal footing in concomitant theoretical work. Current gyrokinetic and reduced-MHD treatments of solar-wind turbulence take the plasma distribution to be Maxwellian. Analyses of pressure-anisotropy-driven Larmor-scale instabilities rarely focus on their contribution to the kinetic-scale turbulent cascade. These issues borne in mind, I will present some analytical and numerical efforts to construct a more suitable theoretical framework for describing inertial-range and Larmor-scale kinetic turbulence in non-Maxwellian astrophysical plasmas. Implications for turbulence in other weakly collisional environments, such as radiatively inefficient accretion flows and the intracluster medium, will also be discussed.

(coffee and cookies at 11:45)
Host: Boldyrev
Poster: http://www.physics.wisc.edu/twap/posters/2015/3682.pdf
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Physics Department Colloquium
Heinz H. Barschall Colloquium
Search for permanent electric dipole moments of protons and deuterons using storage rings
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Frank Rathmann, Institut fuer Kernphysik , Forschungszentrum Juelich, Germany
Abstract: The Standard Model (SM) of Particle Physics is not capable to account for the apparent matter-antimatter asymmetry of our Universe. Physics beyond the SM is required and is searched for by (i) employing highest energies (e.g., at LHC), and (ii) striving for ultimate precision and sensitivity (e.g., in the search for electric dipole moments (EDMs)). Permanent EDMs of particles violate both time reversal (T) and parity (P) invariance, and are via the CPT-theorem also CP-violating. Finding an EDM would be a strong indication for physics beyond the SM, and pushing upper limits further provides crucial tests for any correspond- ing theoretical model, e.g., SUSY. Direct searches of proton and deuteron EDMs bear the potential to reach sensitivities beyond 10−29 e·cm. For an all-electric proton storage ring, this goal is pursued by the US-based srEDM collaboration, while the newly found Juelich-based JEDI collaboration is in addition pursuing an approach using a combined electric-magnetic lattice which shall allow access to the EDMs of protons, deuterons, and 3He ions in the same machine.

The talk will highlight recent achievements from experimental investigations at COSY toward the search for electric dipole moments of charged hadrons, i.e., proton and deuteron; it will emphasize one of the most spectacular possibilities in modern science: Finding a signal for new physics beyond the Standard Model through the detection of permanent electric dipole moments in a storage ring.
Host: Balantekin
Poster: http://www.physics.wisc.edu/twap/posters/2015/3670.pdf
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