College of Sciences (CoS)
http://hdl.handle.net/1853/6018
Since Georgia Tech first opened its doors in 1888, science has been used to drive Georgia Tech forward, endow students with the knowledge to lead in an increasingly technological world, and strengthen Georgia through interaction with industry.Sat, 01 Oct 2016 10:38:00 GMT2016-10-01T10:38:00ZIce Fishing for Neutrinos
http://hdl.handle.net/1853/55878
Ice Fishing for Neutrinos
Halzen, Francis
The IceCube project at the South Pole has melted eighty-six holes over 1.5 miles deep in the Antarctic icecap for use as astronomical observatories.
The project recently discovered a flux of neutrinos reaching us from the cosmos, with energies more than a million times those of the neutrinos produced at accelerator laboratories. These neutrinos are astronomical messengers from some of the most violent processes in the universe associated with starbursts, giant black holes gobbling up stars in the heart of quasars and gamma-ray bursts, the biggest explosions since the Big Bang. We will discuss the IceCube telescope and highlight its first scientific results.
Presented on September 12, 2016 at 6:00 p.m. in the Clough Undergraduate Learning Commons, Room 144.; Francis Halzen is a theoretician studying problems at the interface of particle physics, astrophysics and cosmology. Since 1987, he has been working on the AMANDA experiment, a first-generation neutrino telescope at the South Pole. AMANDA observations represent a proof of concept for IceCube, a kilometer-scale observatory recently completed.; Runtime: 65:22 minutes
Mon, 12 Sep 2016 00:00:00 GMThttp://hdl.handle.net/1853/558782016-09-12T00:00:00ZHalzen, FrancisThe IceCube project at the South Pole has melted eighty-six holes over 1.5 miles deep in the Antarctic icecap for use as astronomical observatories.
The project recently discovered a flux of neutrinos reaching us from the cosmos, with energies more than a million times those of the neutrinos produced at accelerator laboratories. These neutrinos are astronomical messengers from some of the most violent processes in the universe associated with starbursts, giant black holes gobbling up stars in the heart of quasars and gamma-ray bursts, the biggest explosions since the Big Bang. We will discuss the IceCube telescope and highlight its first scientific results.The Complexity of Random Functions of Many Variables
http://hdl.handle.net/1853/55818
The Complexity of Random Functions of Many Variables
Arous, Gérard Ben
A function of many variables, when chosen at random, is typically very complex. It has an exponentially large number of local minima or maxima, or critical points. It defines a very complex landscape, the topology of its level lines (for instance their Euler characteristic) is surprisingly complex. This complex picture is valid even in very simple cases, for random homogeneous polynomials of degree p larger than 2. This has important consequences. For instance trying to find the minimum value of such a function may thus be very difficult.
The mathematical tool suited to understand this complexity is the spectral theory of large random matrices. The classification of the different types of complexity has been understood for a few decades in the statistical physics of disordered media, and in particular spin-glasses, where the random functions may define the energy landscapes. It is also relevant in many other fields, including computer science and Machine learning. I will review recent work with collaborators in mathematics (A. Auffinger, J. Cerny) , statistical physics (C. Cammarota, G. Biroli, Y. Fyodorov, B. Khoruzenko), and computer science (Y. LeCun and his team at Facebook, A. Choromanska, L. Sagun among others), as well as recent work of E. Subag and E.Subag and O.Zeitouni.
Presented on August 31, 2016 at 4:00 p.m. in the Klaus Computing Building, room 1116.; A specialist of probability theory and its applications, Gérard Ben Arous arrived to NYU's Courant Institute as a Professor of Mathematics in 2002. He was appointed Director of the Courant Institute and Vice Provost for Science and Engineering Development in September 2011. Professor Ben Arous works on probability theory (stochastic analysis, large deviations, random media and random matrices) and its connections with other domains of mathematics (partial differential equations, dynamical systems), physics (statistical mechanics of disordered media), or industrial applications. He is mainly interested in the time evolution of complex systems, and the universal aspects of their long time behavior and of their slow relaxation to equilibrium, in particular how complexity and disorder imply aging.; Runtime: 79:00 minutes
Wed, 31 Aug 2016 00:00:00 GMThttp://hdl.handle.net/1853/558182016-08-31T00:00:00ZArous, Gérard BenA function of many variables, when chosen at random, is typically very complex. It has an exponentially large number of local minima or maxima, or critical points. It defines a very complex landscape, the topology of its level lines (for instance their Euler characteristic) is surprisingly complex. This complex picture is valid even in very simple cases, for random homogeneous polynomials of degree p larger than 2. This has important consequences. For instance trying to find the minimum value of such a function may thus be very difficult.
The mathematical tool suited to understand this complexity is the spectral theory of large random matrices. The classification of the different types of complexity has been understood for a few decades in the statistical physics of disordered media, and in particular spin-glasses, where the random functions may define the energy landscapes. It is also relevant in many other fields, including computer science and Machine learning. I will review recent work with collaborators in mathematics (A. Auffinger, J. Cerny) , statistical physics (C. Cammarota, G. Biroli, Y. Fyodorov, B. Khoruzenko), and computer science (Y. LeCun and his team at Facebook, A. Choromanska, L. Sagun among others), as well as recent work of E. Subag and E.Subag and O.Zeitouni.Near-field Microwave Imaging of Electrostatically Modulated Quantum Materials
http://hdl.handle.net/1853/55804
Near-field Microwave Imaging of Electrostatically Modulated Quantum Materials
Lai, Keji
Field-effect transistors (FETs) are the backbone of modern semiconductor devices. The same concept of electrostatic modulation of carrier densities has also been very fruitful for the exploration of electronic properties in advanced quantum materials. Using a non-invasive microwave impedance microscope with ~100nm resolution and ~1nS sensitivity, we have visualized the metal-insulator transitions of various materials in the FET configuration. The images acquired at different gate voltages of MoS2 and HgTe devices clearly show the spatial evolution of conductance at the edge and bulk of the sample. Strong electrical inhomogeneity is observed in the MIM images, revealing the fluctuations of disorder potential in the 2D layer. I will also discuss the conductance mapping in ion-gel-gated electric double-layer transistors and 2D devices under laser illumination. The combination of novel FETs and impedance microscopy paves the way to study phase transitions in complex materials induced by electrostatic field effects.
Presented on August 29, 2016 at 6:00 p.m. in the Instructional Center, room 105.; Keji Lai is an Assistant Professor in the Department of Physics at the University of Texas at Austin.; Runtime: 60:16 minutes
Mon, 29 Aug 2016 00:00:00 GMThttp://hdl.handle.net/1853/558042016-08-29T00:00:00ZLai, KejiField-effect transistors (FETs) are the backbone of modern semiconductor devices. The same concept of electrostatic modulation of carrier densities has also been very fruitful for the exploration of electronic properties in advanced quantum materials. Using a non-invasive microwave impedance microscope with ~100nm resolution and ~1nS sensitivity, we have visualized the metal-insulator transitions of various materials in the FET configuration. The images acquired at different gate voltages of MoS2 and HgTe devices clearly show the spatial evolution of conductance at the edge and bulk of the sample. Strong electrical inhomogeneity is observed in the MIM images, revealing the fluctuations of disorder potential in the 2D layer. I will also discuss the conductance mapping in ion-gel-gated electric double-layer transistors and 2D devices under laser illumination. The combination of novel FETs and impedance microscopy paves the way to study phase transitions in complex materials induced by electrostatic field effects.The stability of colloidal metallic nanoparticles in reactive chemical environments
http://hdl.handle.net/1853/55705
The stability of colloidal metallic nanoparticles in reactive chemical environments
El-Sayed, Mostafa A.
Issued as final report
Sat, 01 Jan 0007 00:00:00 GMThttp://hdl.handle.net/1853/557050007-01-01T00:00:00ZEl-Sayed, Mostafa A.