2,122 research outputs found

    Emergence of Kinetic Behavior in Streaming Ultracold Neutral Plasmas

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    We create streaming ultracold neutral plasmas by tailoring the photoionizing laser beam that creates the plasma. By varying the electron temperature, we control the relative velocity of the streaming populations, and, in conjunction with variation of the plasma density, this controls the ion collisionality of the colliding streams. Laser-induced fluorescence is used to map the spatially resolved density and velocity distribution function for the ions. We identify the lack of local thermal equilibrium and distinct populations of interpenetrating, counter-streaming ions as signatures of kinetic behavior. Experimental data is compared with results from a one-dimensional, two-fluid numerical simulation.Comment: 8 pages, 6 figure

    Graduate Recital: Thomas S. Killian, percussion

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    Dicta and the Rule of Law

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    This Essay is about dicta. Like Olson, the Essay will not spend much time arguing about the definition of dicta. Rather, it analyzes rule of law issues as they pertain to dicta. Does the definition of dicta matter? Does reliance on dicta by subsequent courts raise rule of law concerns? The answer to both questions is yes

    An Illusion of Sacrifice: The Incompatibility of Binding Stipulations in CAFA Cases

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    Ever since the enactment of the Class Action Fairness Act of 2005 (“CAFA”), plaintiffs attorneys have sought to circumvent it. Because class certification is more difficult to obtain in federal court than it is in certain state courts, plaintiffs typically prefer to litigate in state court. One method of avoiding CAFA’s removal provision is to limit damages to less than $5 million, thus rendering the action too small to be subjected to the statute. And plaintiffs attorneys have proven willing to stipulate to such diminished damages even where the action is far more valuable. This Note examines whether such stipulations should be permitted. The note begins by introducing the topic and proceeds to place CAFA in a historical perspective and describe early techniques used to circumvent it. Because an understanding of why federal courts seem to disfavor class actions is important in examining how legitimate plaintiffs’ concerns vis-à-vis class certification are, the Note traces the history of the device in federal courts, starting in 1966 with the amendments to Rule 23 that created the modern class action and concluding with Wal-Mart Stores Inc. v. Dukes, which represents the latest example in a series of Supreme Court decisions that tend to make certification harder to obtain. The Note then provides an overview of how district and circuits courts have analyzed this question and how circuits seem to be splitting. Binding stipulations create problems on three planes—Rule 23 conflicts, federalism and the Dormant Commerce Clause difficulties, and a bad fit in the modern landscape of complex litigation. After identifying these issues, the Note explicates the shortcomings of judicial approaches employed thus far before addressing how the Federal Courts Jurisdiction and Venue Clarification Act of 2011 is a step in the right direction. Ultimately, the Note concludes that—for reasons legal, theoretical, and practical—binding stipulations cause more harm than good in the class action context and should be prohibited

    Theory of the cold collision frequency shift in 1S--2S spectroscopy of Bose-Einstein-condensed and non-condensed hydrogen

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    We show that a correct formulation of the cold collision frequency shift for two photon spectroscopy of Bose-condensed and cold non-Bose-condensed hydrogen is consistent with experimental data. Our treatment includes transport and inhomogeneity into the theory of a non-condensed gas, which causes substantial changes in the cold collision frequency shift for the ordinary thermal gas, as a result of the very high frequency (3.9kHz) of transverse trap mode. For the condensed gas, we find substantial corrections arise from the inclusion of quasiparticles, whose number is very large because of the very low frequency (10.2Hz) of the longitudinal trap mode. These two effects together account for the apparent absence of a "factor of two" between the two possibilities. Our treatment considers only the Doppler-free measurements, but could be extended to Doppler-sensitive measurements. For Bose-condensed hydrogen, we predict a characteristic "foot" extending into higher detunings than can arise from the condensate alone, as a result of a correct treatment of the statistics of thermal quasiparticles.Comment: 16 page J Phys B format plus 6 postscript figure
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