Synchrotron radiation in strongly coupled conformal field theories

Using gauge/gravity duality, we compute the energy density and angular distribution of the power radiated by a quark undergoing circular motion in strongly coupled ${\cal N}=4$ supersymmetric Yang-Mills (SYM) theory. We compare the strong coupling results to those at weak coupling, and find the same angular distribution of radiated power, up to an overall prefactor. In both regimes, the angular distribution is in fact similar to that of synchrotron radiation produced by an electron in circular motion in classical electrodynamics: the quark emits radiation in a narrow beam along its velocity vector with a characteristic opening angle $\alpha \sim 1/\gamma$. To an observer far away from the quark, the emitted radiation appears as a short periodic burst, just like the light from a lighthouse does to a ship at sea. Our strong coupling results are valid for any strongly coupled conformal field theory with a dual classical gravity description.Comment: 20 pages, 8 figures. v2: published version. v4: factor-of-two error corrected in the time-averaged angular distribution of the power radiated in scalars in weak coupling N=4 SYM theory; correcting this error has interesting ramification

Strongly Correlated Quantum Fluids: Ultracold Quantum Gases, Quantum Chromodynamic Plasmas, and Holographic Duality

Strongly correlated quantum fluids are phases of matter that are intrinsically quantum mechanical, and that do not have a simple description in terms of weakly interacting quasi-particles. Two systems that have recently attracted a great deal of interest are the quark-gluon plasma, a plasma of strongly interacting quarks and gluons produced in relativistic heavy ion collisions, and ultracold atomic Fermi gases, very dilute clouds of atomic gases confined in optical or magnetic traps. These systems differ by more than 20 orders of magnitude in temperature, but they were shown to exhibit very similar hydrodynamic flow. In particular, both fluids exhibit a robustly low shear viscosity to entropy density ratio which is characteristic of quantum fluids described by holographic duality, a mapping from strongly correlated quantum field theories to weakly curved higher dimensional classical gravity. This review explores the connection between these fields, and it also serves as an introduction to the Focus Issue of New Journal of Physics on Strongly Correlated Quantum Fluids: from Ultracold Quantum Gases to QCD Plasmas. The presentation is made accessible to the general physics reader and includes discussions of the latest research developments in all three areas.Comment: 138 pages, 25 figures, review associated with New Journal of Physics special issue "Focus on Strongly Correlated Quantum Fluids: from Ultracold Quantum Gases to QCD Plasmas" (http://iopscience.iop.org/1367-2630/focus/Focus%20on%20Strongly%20Correlated%20Quantum%20Fluids%20-%20from%20Ultracold%20Quantum%20Gases%20to%20QCD%20Plasmas

Jets in strongly-coupled N = 4 super Yang-Mills theory

We study jets of massless particles in N=4 super Yang-Mills using the AdS/CFT correspondence both at zero and finite temperature. We set up an initial state corresponding to a highly energetic quark/anti-quark pair and follow its time evolution into two jets. At finite temperature the jets stop after traveling a finite distance, whereas at zero temperature they travel and spread forever. We map out the corresponding baryon number charge density and identify the generic late time behavior of the jets as well as features that depend crucially on the initial conditions.Comment: 21 pages, 12 figures. Added discussion regarding string profiles in more than one spatial dimension. Refs adde

Design and Autonomous Stabilization of a Ballistically Launched Multirotor

Aircraft that can launch ballistically and convert to autonomous, free flying drones have applications in many areas such as emergency response, defense, and space exploration, where they can gather critical situational data using onboard sensors. This paper presents a ballistically launched, autonomously stabilizing multirotor prototype (SQUID, Streamlined Quick Unfolding Investigation Drone) with an onboard sensor suite, autonomy pipeline, and passive aerodynamic stability. We demonstrate autonomous transition from passive to vision based, active stabilization, confirming the ability of the multirotor to autonomously stabilize after a ballistic launch in a GPS denied environment.Comment: Accepted to 2020 International Conference on Robotics and Automatio

Classification of magnetized star--planet interactions: bow shocks, tails, and inspiraling flows

Close-in exoplanets interact with their host stars gravitationally as well as via their magnetized plasma outflows. The rich dynamics that arises may result in distinct observable features. Our objective is to study and classify the morphology of the different types of interaction that can take place between a giant close-in planet (a Hot Jupiter) and its host star, based on the physical parameters that characterize the system. We perform 3D magnetohydrodynamic numerical simulations to model the star--planet interaction, incorporating a star, a Hot Jupiter, and realistic stellar and planetary outflows. We explore a wide range of parameters and analyze the flow structures and magnetic topologies that develop. Our study suggests the classification of star--planet interactions into four general types, based on the relative magnitudes of three characteristic length scales that quantify the effects of the planetary magnetic field, the planetary outflow, and the stellar gravitational field in the interaction region. We describe the dynamics of these interactions and the flow structures that they give rise to, which include bow shocks, cometary-type tails, and inspiraling accretion streams. We point out the distinguishing features of each of the classified cases and discuss some of their observationally relevant properties. The magnetized interactions of star--planet systems can be categorized, and their general morphologies predicted, based on a set of basic stellar, planetary, and orbital parameters.Comment: Accepted for publication in A&

European Arctic Initiatives Compendium

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