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This Week at Physics

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Events During the Week of September 21st through September 28th, 2014

Monday, September 22nd, 2014

Plasma Physics (Physics/ECE/NE 922) Seminar
"Kinetic-fluid hybrid simulation of energetic particle interaction with MHD instabilities in toroidal plasmas"
Time: 12:00 pm
Place: 2255 Engineering Hall
Speaker: Guo-Yong Fu, Princeton Plasma Physics Laboratory
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Cosmology Journal Club
An Informal discussion about a broad variety of arXiv papers related to Cosmology
Time: 12:15 pm
Place: 5242 Chamberlin Hall
Abstract: Please visit the following link for more details:
    http://cmb.physics.wisc.edu/journal/index.html
Please feel free to bring your lunch!
If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Le Zhang (lzhang263@wisc.edu)
Host: Peter Timbie
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PUMP
Prospective Undergraduate Majors in Physics
Time: 4:30 pm
Place: 2241 Chamberlin Hall
Speaker: UW Madison Department of Physics
Poster: http://www.physics.wisc.edu/twap/posters/2014/3475.pdf
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Tuesday, September 23rd, 2014

Chaos & Complex Systems Seminar
Wisconsin State Energy Office – Forecasting, monitoring, and responding to energy crises
Time: 12:05 pm
Place: 4274 Chamberlin Hall (Refreshments will be served)
Speaker: Jim Mapp, Dark Energy Associates
Abstract: Since the 1970s Wisconsin has experienced several petroleum crises, natural gas supply limitations, coal shortages, and electric power brownouts, blackouts and supply uncertainty. There have been crises related to propane shortages, extremes in cold weather, hot weather, rain events, and floods. We will discuss the role of the Wisconsin State Energy Office in forecasting, preparing for, monitoring and responding to these various energy related crises and the often chaotic conditions surrounding these events. This past winter’s propane shortage provided an example of a recent energy crisis. Propane as a liquid fuel is used for crop drying, home heating in rural areas, and as a supplemental fuel in areas where natural gas is not available. The coming fall and winter heating season may provide an example of the various factors that combine to generate chaos in the supply and demand of propane and steps that can be taken to respond to a possible crisis. Possible supply constraints may include; propane pipeline supply limitations, expanded propane export market, limitations on rail car availability, wet harvest conditions and record corn harvest leading to increased demand for propane for crop drying. Early onset of cold weather could increase the demand for heating fuels such as propane. Possible responses may include coordinating efforts with other Wisconsin agencies, other states, various federal authorities, or various national organizations.
Host: Clint Sprott
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Theory Seminar (High Energy/Cosmology)
The Goldstone Exception: Spontaneously broken global symmetry, i.e. the Goldstone theorem, protects the Higgs from a Fine Tuning (FT) Problem
Time: 3:00 pm
Place: 5280 Chamberlin Hall
Speaker: Bryan Lynn, University College London and Case Western University
Abstract: More than four decades ago, B.W. Lee and K. Symanzik proved that, in the O(4) Gell-Mann Levy (GML) model with Partially Conserved Axial-vector Currents (PCAC), global Ward Takahashi Identities (WTI) force all Ultra-Violet Quadratic Divergences (UVQD) into the renormalized pseudo Nambu-Goldstone-Boson (NGB) pion mass-squared. Tadpole renormalization is un-necessary.

We prove (to all-orders perturbations) that all UVQD, together with all other relevant operators, therefore vanish identically in GML’s spontaneous symmetry broken (SSB) Goldstone-mode, where pions are true NGB (i.e. exactly massless). A weak-scale Higgs mass is natural in SSB GML, the Higgs mass and vacuum expectation value (VEV) are stable against quantum corrections and not FT: SSB GML has no Higgs FT problem. Neither do the SSB O(4) Schwinger model (PCAC=0) or the Standard Model (SM). No-Higgs-FT is simply another (albeit unfamiliar) consequence of WTI and the Goldstone Theorem.

A huge class of high-mass-scale (M_{Heavy}>>m_{Higgs}) extensions of GML, Schwinger and SM also demonstrate naturalness, no-FT and heavy particle decoupling. We display two examples: a heavy (M_S >> m_{Higgs}) real scalar field; and a right-handed Type 1 See-Saw Majorana neutrino with M_R >> m_{Higgs}. We prove that for |q^2| << M_{Heavy}^2, the heavy degrees of freedom contribute only irrelevant and marginal operators. Phenomenological consequences include the renewed possibility of thermal lepto-genesis in the neutrino-MSM. It is also easy to construct no-Higgs-FT models with very high-scale SUSY breaking.

We conjecture that, since classical General Relativity (GR) couples democratically to spin=0, ½ and 1 quantum particles, GR+SM (and maybe certain quantum gravity theories) will also retain naturalness, avoiding FT problems. Absent a SM FT problem, there should be no expectation that LHC14 will discover physics beyond the SM which is unrelated to neutrino mixing, the only known experimental failure of the SM.
Host: Ran Lu
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Wednesday, September 24th, 2014

No events scheduled

Thursday, September 25th, 2014

R. G. Herb Condensed Matter Seminar
Entanglement in many body systems
Time: 10:00 am
Place: Chamberlin 5310
Speaker: Israel Klich, University of Virginia
Abstract: In this talk, I will review work on entanglement entropy in many body systems, it's scaling, relation to numerics and possible experimental checks. I will then describe some recent results on effective entanglement hamiltonians in conformal quantum field theories. In particular, I will show how the free fermion entanglement Hamiltonian in 1d can be obtained by solving a Riemann-Hilbert problem and how finite size corrections to the Hamiltonian may be obtained by perturbing around the Riemann-Hilbert solutions, as well as explore subtle difference between the Neveu-Schwartz and Ramond sectors of free fermion fields.
Host: Maxim Vavilov
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Astronomy Colloquium
SPECIAL TIME! 2:30 PM
Angular Momentum Transport via Internal Gravity Waves in Evolving Stars
Time: 2:30 pm
Place: 4421 Sterling Hall
Speaker: Jim Fuller, Caltech
Abstract: Recent asteroseismic advances have allowed for direct measurements of the internal rotation rates of many sub-giant and red giant stars. Unlike the nearly rigidly rotating Sun, these evolved stars contain radiative cores that spin much faster than their overlying convective envelopes, but much slower than they would in the absence of internal angular momentum transport. We investigate the role of internal gravity waves in angular momentum transport in evolving low mass stars. In agreement with previous results, we find that convectively excited gravity waves can prevent the development of strong differential rotation in the radiative cores of Sun-like stars. As stars evolve into sub-giants, however, low frequency gravity waves become strongly attenuated and cannot propagate below the hydrogen burning shell, allowing the spin of the core to decouple from the convective envelope. This decoupling occurs at the base of the sub-giant&lt;br&gt;branch when stars have surface temperatures of roughly 5500K. However, gravity waves can still spin down the upper radiative region, implying that the observed differential rotation is likely confined to the deep core near the hydrogen burning shell. The torque on the upper radiative region may also prevent the core from accreting high-angular momentum material and slow the rate of core spin-up. The observed spin-down of cores on the red giant branch cannot be totally attributed to gravity waves, but the waves may enhance shear within the radiative region and thus increase the efficacy of viscous/magnetic torques.
Host: Professor and Dept Chair, Ellen Zweibel
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
PeV neutrinos from right handed neutrino dark matter
Time: 2:30 pm
Place: 5280 Chamberlin Hall
Speaker: Ryosuke Sato, KEK
Abstract: The Standard Model of particle physics fails to explain the important
pieces in the standard cosmology, such as inflation, baryogenesis, and
dark matter of the Universe. We consider the possibility that the
sector to generate small neutrino masses is responsible for all of
them; the inflation is driven by the Higgs field to break B−L gauge
symmetry which provides the Majorana masses to the right-handed
neutrinos, and the reheating process by the decay of the B−L Higgs
boson supplies the second lightest right-handed neutrinos whose CP
violating decays produce B−L asymmetry, a la, leptogenesis. The
lightest right-handed neutrinos are also produced by the reheating
process, and remain today as the dark matter of the Universe. In the
minimal model of the inflaton potential, one can set the parameter of
the potential by the data from CMB observations. In such a scenario,
the mass of the dark matter particle is predicted to be of the order
of PeV. We find that the decay of the PeV right-handed neutrinos can
explain the high-energy neutrino flux observed at the IceCube
experiments if the lifetime is of the order of 10^28 s.
Host: Ran Lu
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Friday, September 26th, 2014

Physics Department Colloquium
Hunting for topological dark matter with atomic clocks
Time: 3:30 pm
Place: Chamberin
Speaker: Andrei Derevianko, University of Nevada, Reno
Abstract: Atomic clocks are arguably the most accurate scientific instruments ever build. Modern clocks are astonishing timepieces guaranteed to keep time within a second over the age of the Universe. Attaining this accuracy requires that the quantum oscillator be well protected from environmental noise and perturbations well controlled and characterized. This opens intriguing prospects of using clocks to study subtle effects, and it is natural to ask if such accuracy can be harnessed for dark matter searches.

The cosmological applications of atomic clocks so far have been limited to searches of the uniform-in-time drift of fundamental constants. We point out that a transient in time change of fundamental constants can be induced by dark matter objects that have large spatial extent, and are built from light non-Standard Model fields. The stability of this type of dark matter can be dictated by the topological reasons. We point out that correlated networks of atomic clocks, such as atomic clocks onboard satellites of the GPS constellation, can be used as a powerful tool to search for the topological defect dark matter. In other words, one could envision using GPS as a 50,000 km-aperture topological dark-matter detector.
Host: Saffman
Poster: http://www.physics.wisc.edu/twap/posters/2014/3381.pdf
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