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ItemUnderstanding the 2020 Nobel Prize in Physics + Q&A( 2020-11-11) Cvitanović, Predrag ; Wells-Bonning, Erin ; Georgia Institute of Technology. School of Physics ; Emory University. Dept. of PhysicsGeorgia Tech School of Physics professor and Glen P. Robinson Chair in Nonlinear Sciences Chair Predrag Cvitanović and Emory University Senior Lecturer and Director of the Planetarium Erin Wells Bonning explain the 2020 Nobel Prize in Physics. After the presentation, the speakers will answer questions from the audience, so come curious! Half of the 2020 Nobel Prize in Physics was awarded to Roger Penrose for the discovery that black hole formation is a robust prediction of the general theory of relativity. In 1957 Penrose, then a graduate student, met Georgia Tech’s late David Ritz Finkelstein in a fateful meeting that changed both men’s lives forever after. It was Finkelstein’s extension of the Schwarzschild metric which provided Penrose with an opening into general relativity and set him on the path to his 1965 discovery celebrated by this year’s prize. The other half of the 2020 Nobel Prize in Physics was awarded jointly to Reinhard Genzel and Andrea Ghez for the discovery of — in Ghez’s words — "The Monster at the heart of the Milky Way," a black hole whose existence had been hypothesized since the early 1970s. In order to visually observe an object that famously does not emit any light, precise measurements of stars moving in the black hole’s gravitational field had to be carried out. The independent work of Genzel and Ghez mapping the positions of these stars over many years has led to the clearest evidence yet that the center of our Milky Way galaxy contains “The Monster”, that possibly every galaxy contains a black hole, and that the environment near it looks nothing like what was expected.
ItemProfessor Debate on the Topic - Do We Live In a Simulation?(Georgia Institute of Technology, 2019-11-12) Cvitanović, Predrag ; Holder, Mary ; Klein, Hans ; Rocklin, D. Zeb ; Turk, Gregory ; Vempala, Santosh S. ; Georgia Institute of Technology. School of Physics ; Georgia Institute of Technology. Center for Nonlinear Science ; Georgia Institute of Technology. School of Psychology ; Georgia Institute of Technology. School of Public Policy ; Georgia Institute of Technology. School of Interactive Computing ; Georgia Institute of Technology. School of Computer ScienceDo we live in a simulation? The School of Physics and the Society of Physics Students will host a public debate between faculty from the College of Science and the College of Computing to answer this question. This event is free and open to the all. There will be time at the conclusion of the debate for audience members to direct questions towards the faculty panel.
ItemNoise is your friend, or: How well can we resolve state space?( 2014-09-05) Cvitanović, Predrag ; Georgia Institute of Technology. School of Civil and Environmental Engineering ; Georgia Institute of Technology. School of PhysicsAll physical systems are affected by some noise that limits the resolution that can be attained in partitioning their state space. What is the best resolution possible for a given physical system? It turns out that for nonlinear dynamical systems the noise itself is highly nonlinear, with the effective noise different for different regions of system's state space. The best obtainable resolution thus depends on the observed state, the interplay of local stretching/contraction with the smearing due to noise, as well as the memory of its previous states. We show how that is computed, orbit by orbit. But noise also associates to each orbit a finite state space volume, thus helping us by both smoothing out what is deterministically a fractal strange attractor, and restricting the computation to a set of unstable periodic orbits of finite period. By computing the local eigenfunctions of the Fokker-Planck evolution operator, forward operator along stable linearized directions and the adjoint operator along the unstable directions, we determine the `finest attainable' partition for a given hyperbolic dynamical system and a given weak additive noise. The space of all chaotic spatiotemporal states is infinite, but noise kindly coarse-grains it into a finite set of resolvable states.