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This Week at Physics

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Events During the Week of May 11th through May 18th, 2014

Monday, May 12th, 2014

Condensed Matter Theory Group Seminar
Quench dynamics of the anisotropic Heisenberg model through an exact approach
Time: 4:30 pm
Place: Chamberlin 5310
Speaker: Wenshuo Liu, Rutgers University
Abstract: In this talk I will present the analytical approach we developed for the study of the quench dynamics of the anisotropic Heisenberg model (XXZ model) on the infinite line. Our approach gives the exact time-dependent wavefunctions after a quench in an integral form for any initial state and for any anisotropy ∆ by means of a generalized Yudson contour representation. We calculate the evolution of several observables from two particular initial states: starting from a local N`eel state we calculate the time evolution of the antiferromagnetic order parameter --staggered magnetization; starting from a state with consecutive flipped spins (1) we calculate the evolution of the local magnetization and express it in terms of the propagation of magnons and bound state excitations; (2) we predict the evolution of the induced spin currents. These predictions can be confronted with experiments in ultracold gases in optical lattices. We also show how the “string” solutions of Bethe Ansatz equations emerge naturally from the contour approach.
Host: Vavilov
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Tuesday, May 13th, 2014

No events scheduled

Wednesday, May 14th, 2014

No events scheduled

Thursday, May 15th, 2014

R. G. Herb Condensed Matter Seminar
Realization of a Single-Cooper-Pair Josephson Laser
Time: 10:00 am
Place: 5310 Chamberlin Hall
Speaker: Alex Rimberg, Dartmouth
Abstract: The non-linear interaction of light with matter, long studied in the context of atomic systems, has recently been extended to condensed matter systems through the advent of quantum optical experiments based on superconducting circuits. Application of quantum optical techniques in this context has led to new regimes of ultrastrong coupling between light and matter, manipulation and readout of qubits, generation of quantum states of light and development of ultra-low-noise quantum amplifiers. A particularly familiar application of quantum optics is the laser, which in the single emitter regime has in atomic systems led to the production of pure photon number states and sub-Poissonian photon statistics. We have recently produced a device consisting of a Cooper pair transistor embedded in a high-Q superconducting microwave cavity (cCPT) that acts as a single emitter laser and may offer a path toward simple, continual production of non-classical photons. Similar devices may also allow for ultrastrong coupling of microwave photons to other quantum systems such as spin qubits and nanomechanical resonators.
Host: Eriksson
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Special Talk
Calibrating the radio continuum-star formation relation in WSRT SINGS galaxies
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Volker Heesen, University of Southhampton
Abstract: Radio continuum (RC) emission holds the promise of being an accurate because unobscured tracer for star formation (SF), allowing us to measure the evolution of the Cosmic star formation rate (SFR) in dusty high-z galaxies. We use WSRT RC observations at 22 cm and state-of-the-art hybrid SFR density maps, combining GALEX FUV data, tracing un-obscured SF, and Spitzer 24 mu data, tracing SF embedded in dust. With these data we calibrate the well-known RC-SFR relation as proposed by Condon (1992) on a spatially resolved basis in a sample of 17 nearby galaxies. We find that for integrated measurements Condon's relation works quite well: the absolute value of the RC derived SFR is in agreement with the hybrid SFR, and the RC-SFR relation is almost linear with RC ~ SFRD^(1.11pm0.05). The same holds true for azimuthally averaged data, where the ratio of RC to hybrid derived SFR density is almost constant with only quasi-periodic fluctuations of 25% amplitude. The spatially resolved data, however, shows that on a 1 kpc scale the RC-SFR relation is sub-linear, which we attribute largely to the effect of cosmic-ray transport. We study the dependence of the RC-SFR relation on various galaxy parameters and find none, meaning that the RC-SFR relation is universal.
Host: Professor and Dept Chair, Ellen Zweibel
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Friday, May 16th, 2014

Special Friday Colloquium
The interplay between condensation and chemistry in the formation of solid particles in the ejecta of supernova explosions
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Davide Lazzati
Abstract: Dust is a minor component of the interstellar medium but
plays a major role in the evolution of the universe and on our
capability to observe it. Despite recent advances, some fundamental aspects of the physics of formation of cosmic dust are still poorly understood. This leads, for example, to theoretical predictions of dust yields from supernova explosions that are at least two orders of magnitude larger than observed. In this talk I will use carbonaceous dust formation in core-collapse supernovae as a case study to discuss
the current status and recent advances on our understanding of the
physical and chemical mechanisms at the base of the gas-solid phase transition in the astrophysical environment. I will discuss different approaches to the problem and compare their results to available observations. I will conclude by introducing a new framework for studying the outcomes of collisions between dust agglometates to study their compactification, growth, and fragmentation.

Host: Brian Morsony
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Department of Physics
Undergraduate Majors Reception
Time: 5:00 pm
Place: 2241 Chamberlin Hall
Speaker: Department of Physics
Abstract: The department will be having reception for the undergraduate majors in Physics and their parents. Please RSVP if you plan to attend the event.

Please RSVP at:
https://www.physics.wisc.edu/GraduationRecognitionRSVP2014
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"This Week at Physics" poster: http://www.physics.wisc.edu/twap/posters/2014/2014-05-12.pdf

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