1,171 research outputs found

    Polaron to molecule transition in a strongly imbalanced Fermi gas

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    A single down spin Fermion with an attractive, zero range interaction with a Fermi sea of up-spin Fermions forms a polaronic quasiparticle. The associated quasiparticle weight vanishes beyond a critical strength of the attractive interaction, where a many-body bound state is formed. From a variational wavefunction in the molecular limit, we determine the critical value for the polaron to molecule transition. The value agrees well with the diagrammatic Monte Carlo results of Prokof'ev and Svistunov and is consistent with recent rf-spectroscopy measurements of the quasiparticle weight by Schirotzek et. al. In addition, we calculate the contact coefficient of the strongly imbalanced gas, using the adiabatic theorem of Tan and discuss the implications of the polaron to molecule transition for the phase diagram of the attractive Fermi gas at finite imbalance.Comment: 10 pages, 4 figures, RevTex4, minor changes, references adde

    Nonverbal Communication in Politics: A Review of Research Developments, 2005-2015

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    This article reviews research contributions in political science and communication to the topic of nonverbal communication and politics from 2005 to 2015. The review opens with research on the content of nonverbal communication, then considers studies examining what moderates the impact of nonverbal aspects of political messages on attitudes and behavior and the mechanisms that underpin these effects. Over the period reviewed here, research shows that the nonverbal channel is rich in political information and is consequential for political decision making, particularly under certain circumstances, such as in low-information conditions. Visuals affect political decisions through cognitive and emotional routes. This review article also identifies several directions where further research is required, particularly with regard to social media, nonvisual aspects of nonverbal communication, the interplay of visual and verbal arguments, and the mechanisms behind the effects of nonverbal communication

    Thermodynamic signatures for the existence of Dirac electrons in ZrTe5

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    We combine transport, magnetization, and torque magnetometry measurements to investigate the electronic structure of ZrTe5 and its evolution with temperature. At fields beyond the quantum limit, we observe a magnetization reversal from paramagnetic to diamagnetic response, which is characteristic of a Dirac semi-metal. We also observe a strong non-linearity in the magnetization that suggests the presence of additional low-lying carriers from other low-energy bands. Finally, we observe a striking sensitivity of the magnetic reversal to temperature that is not readily explained by simple band-structure models, but may be connected to a temperature dependent Lifshitz transition proposed to exist in this material.Comment: 5 pages, 4 figure

    Lower bounds on the dilation of plane spanners

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    (I) We exhibit a set of 23 points in the plane that has dilation at least 1.43081.4308, improving the previously best lower bound of 1.41611.4161 for the worst-case dilation of plane spanners. (II) For every integer n≥13n\geq13, there exists an nn-element point set SS such that the degree 3 dilation of SS denoted by δ0(S,3) equals 1+3=2.7321…\delta_0(S,3) \text{ equals } 1+\sqrt{3}=2.7321\ldots in the domain of plane geometric spanners. In the same domain, we show that for every integer n≥6n\geq6, there exists a an nn-element point set SS such that the degree 4 dilation of SS denoted by δ0(S,4) equals 1+(5−5)/2=2.1755…\delta_0(S,4) \text{ equals } 1 + \sqrt{(5-\sqrt{5})/2}=2.1755\ldots The previous best lower bound of 1.41611.4161 holds for any degree. (III) For every integer n≥6n\geq6 , there exists an nn-element point set SS such that the stretch factor of the greedy triangulation of SS is at least 2.02682.0268.Comment: Revised definitions in the introduction; 23 pages, 15 figures; 2 table

    Gabriel Triangulations and Angle-Monotone Graphs: Local Routing and Recognition

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    A geometric graph is angle-monotone if every pair of vertices has a path between them that---after some rotation---is xx- and yy-monotone. Angle-monotone graphs are 2\sqrt 2-spanners and they are increasing-chord graphs. Dehkordi, Frati, and Gudmundsson introduced angle-monotone graphs in 2014 and proved that Gabriel triangulations are angle-monotone graphs. We give a polynomial time algorithm to recognize angle-monotone geometric graphs. We prove that every point set has a plane geometric graph that is generalized angle-monotone---specifically, we prove that the half-θ6\theta_6-graph is generalized angle-monotone. We give a local routing algorithm for Gabriel triangulations that finds a path from any vertex ss to any vertex tt whose length is within 1+21 + \sqrt 2 times the Euclidean distance from ss to tt. Finally, we prove some lower bounds and limits on local routing algorithms on Gabriel triangulations.Comment: Appears in the Proceedings of the 24th International Symposium on Graph Drawing and Network Visualization (GD 2016
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