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Colloquium

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November 21, 2014

November 20 Colloquium

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Peter Fischer, Lawrence Berkeley National Laboratory & University of California, Santa Cruz

Magnetic Soft X-­ray Spectromicroscopy: From Nanoscale Behavior to Mesoscale Phenomena

Abstract:

The era of nanomagnetism, which aims to understanding and controlling magnetic properties and behavior on the nanoscale, is currently expanding into the mesoscale [1]. This will harness enhanced complexity and novel functionalities, which are essential parameters to meet future challenges in terms of speed, size and energy efficiency of spin driven devices. The development and application of multidimensional visualization techniques, such as tomographic magnetic imaging and investigations of fast and ultrafast spin dynamics down to fundamental magnetic length and time scales with elemental sensitivity in emerging multi-component materials will be crucial to achieve mesoscience goals.

Magnetic soft X-ray spectromicroscopy is a unique analytical technique combining X-ray magnetic circular dichroism (X-MCD) as element specific magnetic contrast mechanism with a spatial resolution down to currently about 20nm. In addition, utilizing the inherent time structure of current synchrotron sources fast magnetization dynamics in ferromagnetic elements can be performed with a stroboscopic pump-probe scheme with 70ps time resolution [2, 3]. I will review in this talk recent achievements with full-field magnetic soft x-ray transmission microscopy (MTXM) with examples from magnetic vortex structures [4] and their application to novel magnetic logic elements [5], magnetic spectromicroscopy of domain walls [6], and first attempts to image the 3dim magnetic domain structures in rolled-up Ni nanotubes [7].

This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, of the U.S. Department of Energy under Contract No. DE-AC02-05-CH1123 and by the Leading Foreign Research Institute Recruitment Program (Grant No. 2012K1A4A3053565) through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (MEST).

References
[1] R. Service, Science 335 1167 (2012)
[2] P. Fischer, Materials Science & Engineeering R72 81-95 (2011)
[3] W. Chao, et al., Optics Express 20(9) 9777 (2012)
[4] M.-Y. Im, et al., Nature Communications 3 983 (2012)
[5] H. Jung, et al., Scientific Reports 1 59 (2011)
[6] M.J. Robertson, et al., JAP (2014) under review
[7] R. Streubel, Adv. Mater 26 316 (2014)

Host: Ben McMorran

November 13 Colloquium

Itay Yavin, McMaster University & Perimeter Institute for Theoretical Physics

Dark Matter as a Fundamental Particle

Abstract:

In this talk I will review past and present ideas about dark matter as a new fundamental particle, exploring both the underlying theoretical structures as well as the variety of experimental frontiers. Along the way I will try to give you a flavor of some of the most recent developments as well as future plans and prospects.

Host: Spencer Chang

November 6 Colloquium

Tracy Slatyer, Massachusetts Institute of Technology

A Potential Dark Matter Signal in Light from the Central Milky Way

Abstract:

Dark matter comprises five-sixths of the matter in the universe, and is one of the strongest pieces of evidence for new physics beyond the Standard Model. To date, dark matter has only been detected via its gravitational interactions, but its annihilation or decay could produce high-energy particles observable by Earth-based telescopes. In this talk, I will describe an unexplained glow of gamma rays observed from the inner regions of the Milky Way, and discuss its possible origins, including the exciting possibility that it might arise from dark matter annihilation.

Host: Spencer Chang

October 30 Colloquium

 

Gray Rybka, University of Washington

The Generation 2 Axion Dark Matter Experiment

Abstract:

Axions are an exceptionally well-motivated dark matter candidate in addition to being a consequence of the Peccei-Quinn solution to the strong CP problem. ADMX (Axion Dark Matter eXperiment) has recently been selected as the axion search for the US DOE Second-Generation Dark Matter Program. I will discuss the imminent upgrade of ADMX to a definitive search for micro-eV mass dark matter axions as well as the ongoing research and development of new technologies to expand the reach of ADMX to the entire plausible dark matter axion mass range.

Host: Spencer Chang

October 16, 2014

October 23 Colloquium

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Graham Kribs, University of Oregon, Physics

What’s So Super About Symmetries

Abstract:

I’ll review why exact and approximate symmetries occupy such a central role in our understanding of fundamental building blocks of the universe. New (approximate) symmetries, such as supersymmetry, may yet play a significant role in our understanding of nature. I’ll briefly highlight implications of supersymmetry, focusing on a specific model (pioneered by my collaborators and myself) that has an even further enlarged symmetry.

This model stabilizes the Higgs mass, and can (at least partially) explain why the LHC and other indirect experiments have not yet seen evidence for supersymmetry near the weak scale.

 

 

October 10, 2014

October 16 Colloquium

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Kyle Cranmer, New York University

What’s Next For the Large Hadron Collider

Abstract:

The discovery of the Higgs boson in 2012 was a huge success for the Large Hadron Collider.

So what’s next? I will discuss how the discovery of the Higgs (and nothing else) has influenced our thinking and the potential for our second run with higher energies and flux.

 

October 4, 2014

October 9 Colloquium

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Edward “Joe” Redish, University of Maryland

Reinventing Introductory Physics for Life Scientists (IPLS)

Abstract:

A two-term class in physics has been a staple of the education of life scientists for many years. At many large universities life-science students have become a dominant element in this course, their numbers surpassing the number of engineers taking physics. In addition, the biology and medical school communities have begun calling for a more sophisticated and biologically oriented curriculum, one stressing the building of generalized scientific competencies and taking a more interdisciplinary perspective.[1]

A multi-disciplinary team of scientists centered at the University of Maryland (UMd) has been reinventing the IPLS course as part of the National Experiment in Undergraduate Science Education (NEXUS).[2] Since life science students have an immense diversity of potential careers, we focus on the common elements of biology curricula: molecular and cellular biology together with building general scientific competencies accessible in introductory physics, such as mathematical modeling, reasoning from core principles, and multi-representation translation. The class is positioned as a second-year class with prerequisites that include calculus, chemistry, and biology. This lets us discuss atomic and molecular examples from the first and include lessons with authentic biological value. In addition to building the basic ideas of the Newtonian framework, electric currents, and optics, NEXUS/Physics[3] includes a significant effort on atomic interactions and chemical bonding, random motion and diffusion, thermodynamics (including entropy and free energy), and spectroscopy. These elements are integrated into laboratories as well as into the lecture part of the class. An important aspect of our development is a strong collaboration between the Physics Education Research and Biophysics Research groups at UMd, permitting a combination of cutting-edge biophysics research with front-line pedagogy. While in development, materials are publically available on the web for observation, use, and comment.[4]



[1] Scientific Foundations for Future Physicians (AAMC & HHMI, 2009);
Vision and Change in Undergraduate Biology Education: A call to action (AAAS 2009);
BIO 2010: Transforming Undergraduate Education for Research Biologists (NRC 2011)

September 12, 2014

October 2 Colloquium

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Ray Frey, University of Oregon

State of the Physics Department and Gamma-Ray Bursts

Abstract:

May 29, 2014

June 5 Colloquium

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Dean Karlen, University of Victoria and TRIUMF

T2K: Investigating Nature’s Ghostly Particles, The Neutrinos

Host: Jim Brau

Abstract: T2K is the name of an experiment in Japan that has been studying the most mysterious of fundamental particles – the neutrinos. An intense beam of neutrinos are sent through the ground towards the gigantic SuperKamiokande detector, almost 200 miles away. Some of the neutrinos interact inside the detector and reveal a change in their identity. These measurements have established that there is complete mixing of the three kinds of neutrino. More data from T2K and other neutrino experiments will be collected in years to come to look for differences between neutrinos and anti-neutrinos, in order to ascertain whether neutrinos could be responsible for the missing anti-matter in the Universe.

May 22, 2014

May 29 Colloquium

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Vera Luth, SLAC National Accelerator Laboratory

Observation of Time Reversal Violation in B Meson Decays

Host: Dietrich Belitz

Abstract: While discrete symmetries and conservation laws are basic concepts of physics, the search for broken symmetries has been a very interesting topic for both experimentalists and theorists. In particle physics, the violation of charge conjugation and parity in weak interactions was observed 60 years ago, and CP violation was found to be violated in neutral kaon decays and more recently in B mesons. It has been much more difficult to detect the violation of time reversal at the microscopic level. The BABAR Collaboration has recently found first and very convincing evidence for T Violation in neutral B mesons. The result is consistent with equal CP and T violation and with CPT invariance.

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