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<?xml version="1.0" encoding="utf-8" standalone="yes"?><rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom"><channel><title>Home on Georgios Varnavides</title><link>https://gvarnavi.github.io/</link><description>Recent content in Home on Georgios Varnavides</description><generator>Hugo -- gohugo.io</generator><language>en</language><lastBuildDate>Tue, 19 Dec 2023 14:00:00 +0600</lastBuildDate><atom:link href="https://gvarnavi.github.io/index.xml" rel="self" type="application/rss+xml"/><item><title>About</title><link>https://gvarnavi.github.io/about/</link><pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate><guid>https://gvarnavi.github.io/about/</guid><description>I&rsquo;m originally from Cyprus where I grew up and studied before moving to the US to obtain my BS in materials science &amp; engineering and BS in civil &amp; environmental engineering from MIT in 2017. Enamored with the Boston weather, I decided to stay at MIT to pursue my graduate studies in the department of Materials Science, where I recently defended my thesis entitled &ldquo;Electron Hydrodynamics in Crystalline Solids&rdquo;.
Currently, I&rsquo;m a postdoctoral Miller research fellow at the University of California, Berkeley &ndash; co-hosted by Prof.</description></item><item><title>MRS Fall 2023 - 3D Inverse Scattering Problems</title><link>https://gvarnavi.github.io/presentations/mrs23-inverse-scattering-problems/</link><pubDate>Tue, 19 Dec 2023 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/presentations/mrs23-inverse-scattering-problems/</guid><description>Georgios Varnavides, Stephanie Ribet, Reed Yalisove, Joel Moore, Colin Ophus, Mary Scott.
2023 Nov 29, Interactive presentation link
Abstract Accelerated electrons passing through a thin sample acquire Aharonov-Bohm phase shifts due to sample interactions which scatter the incident electron wavefunction. These include coherent sources such as electrostatic scattering off atomic columns and scattering against a magnetic vector potential, as-well as incoherent sources such as thermal diffuse scattering and plasmon excitations. Despite the large mechanistic differences between these scattering sources the fact that they are simultaneously collected as far-field diffraction intensities, as-well as the large order of magnitude difference in the acquired phase shifts, suggests the signals are hard to deconvolve.</description></item><item><title>IMC23 - 3D Imaging of Antiferromagnetism</title><link>https://gvarnavi.github.io/presentations/imc23-imaging-magnetization/</link><pubDate>Tue, 12 Sep 2023 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/presentations/imc23-imaging-magnetization/</guid><description>Georgios Varnavides, Stephanie Ribet, Reed Yalisove, Joel Moore, Colin Ophus, Mary Scott.
2023 Sep 14, Interactive presentation link
Abstract An electron beam passing through a thin sample acquires an Aharonov-Bohm phase shift due to the electrostatic potential, V(r), and magnetic vector potential, A(r), of the sample:
\[ \phi(\vec{r}_{\perp}) = \phi_e(\vec{r}_{\perp}) + \phi_m(\vec{r}_{\perp}) = \sigma \int V(\vec{r}_{\perp} + l \hat{\omega}) dl - \frac{e}{\hbar} \int \vec{A}(\vec{r}_{\perp} + l \hat{\omega})\cdot \hat{\omega} dl, \] where \( \sigma \) is the interaction constant, \( e \) is the elementary charge, \( \hbar \) is the reduced Planck&rsquo;s constant, and \( \vec{r}_{\perp} \) denotes the position vector lying in the plane perpendicular to the beam projection direction \( \hat{\omega} \).</description></item><item><title>Miller Institute 2023 Introductions</title><link>https://gvarnavi.github.io/presentations/mf23-introduction/</link><pubDate>Mon, 04 Sep 2023 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/presentations/mf23-introduction/</guid><description>Georgios Varnavides
2023 Sep 04, Interactive presentation link
A short 3-min presentation given to the Miller Institute community as a way to introduce myself to new members.</description></item><item><title>MM23 - Simultaneous Reconstructions</title><link>https://gvarnavi.github.io/presentations/mm23-simultaneous/</link><pubDate>Thu, 27 Jul 2023 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/presentations/mm23-simultaneous/</guid><description>Georgios Varnavides, Stephanie Ribet, Reed Yalisove, Joel Moore, Colin Ophus, Mary Scott.
2023 Jul 24, Interactive presentation link, Conference proceedings link
Abstract While the observation of magnetic structure with nanometer spatial resolution has been successfully achieved with various transmission electron microscopy (TEM) techniques such as Lorentz TEM, off-axis electron holography, differential phase contrast (DPC), and more recently, Lorentz scanning TEM, atomic-scale imaging of magnetization remains challenging. This can be traced back to the extremely small phase-shifts acquired by the electron beam due to the magnetic vector potential, \( \boldsymbol{A}(x,y,z) \), compared to those acquired due to the electrostatic potential of the sample, \( V(x,y,z) \):</description></item><item><title>Interactive Presentations Workflow</title><link>https://gvarnavi.github.io/presentations/interactive-presentations-workflow/</link><pubDate>Sun, 23 Jul 2023 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/presentations/interactive-presentations-workflow/</guid><description>Observable Notebooks First things first: if you want an interactive presentation you need to create (or re-use!) interactive components or widgets. These need to run client-side and would ideally be packaged as react components. I like using observablehq to do this, a reactive notebook environment for javascript code.
Admittedly, coding in javascript is a bit of a learning curve but I have found the scijs family of packages as-well as numjs to be a fairly good numpy replacement for N-dimensional array scientific computing.</description></item><item><title>Tilings and Projection Set Algorithms</title><link>https://gvarnavi.github.io/musings/tilings-and-projection-set-algorithms/</link><pubDate>Thu, 02 Feb 2023 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/musings/tilings-and-projection-set-algorithms/</guid><description>Introduction As part of my postdoctoral Miller fellowship, I have been developing computational imaging algorithms to recover the phase of an object from diffraction intensity measurements, using a technique called &ldquo;electron ptychography&rdquo;. One of the earliest and most successful algorithms for such phase retrieval is based on projection onto (non-)convex sets, which turns out to also be able to solve a variety of non-convex problems. Perhaps the most fun application is solving a Sudoku puzzle.</description></item><item><title>Counting Digits of Pi</title><link>https://gvarnavi.github.io/musings/counting-digits-of-pi/</link><pubDate>Mon, 25 Jul 2022 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/musings/counting-digits-of-pi/</guid><description>Introduction As part of the MIT course 3.029 I taught in the spring of 2022, we held optional coding &ldquo;get-togethers&rdquo; once a week, alternating between &ldquo;Data-Visualization Hour&rdquo; and &ldquo;Code Show and Tell&rdquo;. In particular, the week of Pi day happened to fall on &ldquo;Code Show and Tell&rdquo; and the students thought it&rsquo;d be fun to code up one of the craziest Pi-related phenomena I know.
This is very beautifully explained in the 3Blue1Brown video below:</description></item><item><title>Generative Art</title><link>https://gvarnavi.github.io/musings/generative-art/</link><pubDate>Sun, 24 Jul 2022 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/musings/generative-art/</guid><description>Together with some friends in the DMSE department, I&rsquo;ve been teaching a generative art workshop during MIT&rsquo;s Independent Activity Period (IAP) for the past 5 years. IAP 2022 was the fifth* iteration of the workshop (previously taught in 2017 and 2018 with Emma Vargo, 2020 with Amina Matt, Jovana and Nina Andrejevic, and 2021 with Jovana and Nina).
The 4-day workshop walks through python and Wolfram Language notebooks, covering the following broad topics:</description></item><item><title>Geographic Map Distortions</title><link>https://gvarnavi.github.io/musings/geographic-map-distortions/</link><pubDate>Sat, 29 Jan 2022 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/musings/geographic-map-distortions/</guid><description>I’ve long been fascinated with transportation maps, and in particular the revolutionary re-design of the london-underground map by Harry Beck in 1933. In his iconic design, which has since been adopted by most transportation maps, Harry Beck deliberately sacrifices geographic accuracy for visual clarity of information - by using equally-spaced stations on straight lines with only 45/90 degree bends.
In this Wolfram Community post, we investigate how the local coordinate system is additionally distorted through the years as more stations get added to display the information more clearly.</description></item><item><title>Yoga Poses Constellations</title><link>https://gvarnavi.github.io/musings/yoga-poses-constellations/</link><pubDate>Sat, 05 Jun 2021 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/musings/yoga-poses-constellations/</guid><description>At its first meeting in 1922, the International Astronomical Union (IAU), officially adopted the list of 88 constellations that we use today. These include 14 men and women, 9 birds, two insects, 19 land animals, 10 water creatures, two centaurs, one head of hair, a serpent, a dragon, a flying horse, a river and 29 inanimate objects. As many of us have (frustratingly) witnessed first hand while star-gazing - most of these bear little resemblance to their supposed figures.</description></item><item><title>Electron Hydrodynamics</title><link>https://gvarnavi.github.io/research-topics/electron-hydrodynamics/</link><pubDate>Fri, 04 Jun 2021 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/research-topics/electron-hydrodynamics/</guid><description>In most conductors at room-temperature, electron collisions are akin to billiard balls, resulting in the macroscopic observation of diffusive flow (Ohm&rsquo;s &ldquo;law&rdquo;). Recently, spatially-resolved transport measurements have revealed electrons in strongly-interacting materials can behave akin to classical fluids, confirming theoretical predictions over fifty years old.
I study these &ldquo;hydrodynamic&rdquo; electron flows across various length scales, from their microscopic origins, to mesoscopic finite-size effects, and to their macroscopic observables. Recently, I was part of a team which imaged these flows in a 3D conductor for the first time, corroborating a newly-proposed electron interaction mechanism mediated by lattice vibrations.</description></item><item><title>Advanced Characterization</title><link>https://gvarnavi.github.io/research-topics/advanced-characterization/</link><pubDate>Thu, 03 Jun 2021 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/research-topics/advanced-characterization/</guid><description>I have long been fascinated by materials characterization, and in-particular the ability to image atoms and nanoscale phenomena at high spatial resolution. One of the most versatile instruments to achieve this is the scanning transmission electron microscope (STEM).
In my PhD work, I have collaborated with experimentalists to directly image moirè superlattices at the interface of 2D/3D materials and investigate phonon localization at the interface between two 2D materials with high-resolution STEM-based techniques.</description></item><item><title>Spatially Resolved Transport</title><link>https://gvarnavi.github.io/research-topics/spatially-resolved-transport/</link><pubDate>Wed, 02 Jun 2021 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/research-topics/spatially-resolved-transport/</guid><description>During the course of my PhD, I developed an open-source software package called SpaRTaNS to perform spatially-resolved transport by solving the steady-state Boltzmann transport equation in three real-space and three momentum-space dimensions.
SpaRTaNS is &ldquo;carrier-agnostic&rdquo; with applications in phonon (heat) transport (e.g thermal interface resistance of semi-coherent interfaces), as-well as electron (charge) transport (e.g the importance of microscopic interactions in electron hydrodynamic flows). SpaRTaNS can be run on anything from a laptop to high-performance computing systems, and provides a flexible API for specifying custom boundary conditions, collision operators, geometries, state spaces, and more.</description></item><item><title>Materials Science Pedagogy</title><link>https://gvarnavi.github.io/research-topics/materials-science-pedagogy/</link><pubDate>Tue, 01 Jun 2021 14:00:00 +0600</pubDate><guid>https://gvarnavi.github.io/research-topics/materials-science-pedagogy/</guid><description>I spend a great deal of my time thinking about pedagogy and the role visualization and computation can play in education. Currently, I am co-authoring an open-source materials science textbook with long-time friend and mentor Prof. W. Craig Carter. The idea is to curate some of the content we&rsquo;ve developed teaching through the years, into a cohesive collection of computational notebooks which would guide undergraduate and first-year graduate students in materials science and engineering programs.</description></item><item><title>Search</title><link>https://gvarnavi.github.io/search/</link><pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate><guid>https://gvarnavi.github.io/search/</guid><description/></item></channel></rss>