- Today Google turned 21!
- MeerKAT Telescope Discovers Giant Radio ‘Bubbles’ At Centre Of Milky Way
- Analysis is based on correlating massive amount of radio interferometry data

- Ortvay Institute Seminars are open and highly recommended for students
- On every 2nd Thursday 3PM, ELTE Lágymányos Campus, Northern Building, 0.81 (Ortvay lecture hall) Check schedule!
- Yesterday: Mate Nagy about tracking and simulating collective behaviour

**2019 Phisics Nobel Prize****James Peebles’**insights into physical cosmology have enriched the entire field of research and laid a foundation for the*transformation of cosmology*over the last fifty years,*from speculation to science*. His theoretical framework, developed since the mid-1960s, is the basis of our contemporary ideas about the universe.- In October 1995,
**Michel Mayor and Didier Queloz**announced the first discovery of a planet outside our solar system, an exoplanet, orbiting a solar-type star in our home galaxy, the Milky Way. At the Haute-Provence Observatory in southern France, using custom-made instruments, they were able to see planet 51 Pegasi b, a gaseous ball comparable with the solar system’s biggest gas giant, Jupiter. - This year’s Laureates have transformed our ideas about the cosmos. While James Peebles’ theoretical discoveries contributed to our understanding of how the universe evolved after the Big Bang, Michel Mayor and Didier Queloz explored our cosmic neighbourhoods on the hunt for unknown planets. Their discoveries have forever changed our conceptions of the world.
- popular science summary

**Quantum Supremacy?***Quantum supremacy is the point at which quantum computers can solve problems that are practically unsolvable for “classical” (non-quantum) computers to complete in any reasonable timeframe. It is generally believed that at least 49 qubits are required to cross the quantum supremacy line.**Google’s ‘Sycamore’ quantum computer was able to achieve “quantum supremacy” — solving a complex problem that would otherwise be impossible for a classical computer to solve in its lifetime — in just three minutes and 20 seconds, compared to the estimated 10,000 years it would take the world’s most advanced classical computer, Summit.**To demonstrate quantum supremacy, we compare our quantum processor against state-of-the-art classical computers in the task of sampling the output of a***pseudorandom quantum circuit.***Due to quantum interference, the probability distribution of the bitstrings resembles a speckled intensity pattern produced by light interference in laser scatter, such that some bitstrings are much more likely to occur than others. Classically computing this probability distribution becomes exponentially more difficult as the number of qubits (width) and number of gate cycles (depth) grows.*- some explanation
- some more explanation
- original paper

**The fastest way to multiply integers and matrices**

**Identification of strontium in the merger of two neutron stars**(from yesterday’s Ortvay)*Half of all of the elements in the Universe that are heavier than iron were created by rapid neutron capture. … we report the identification of the neutron-capture element strontium in the spectrum of kilonova AT2017gfo—which was found following the discovery of the neutron-star merger GW170817 by gravitational-wave detectors.*

- Maximum Likelihood Estimation vs. Least Square Fit notebook
- Methods for differentiation and calculating gradients, on emphasis on neural network weight optimization
- Ordinary Differential Equations - explanation slides
- Predictor-Corrector Method explanation, local annotated copy
- Energy conservation notebook

- Project1 reflections
- Fermi-Ulam-Pasta-Tsingou system and original paper
- Mary Tsingou’s contribution to the Fermi-Ulam-Pasta study
- Logistic map (nice animations)
- In 1975, Dr. Feigenbaum, using the small HP-65 calculator discovered that the ratio of the difference between the values at which such successive period-doubling bifurcations occur tends to a constant of around 4.6692.
- Stretch-and-fold chaos and the horseshoe map
- Coupled chaotic maps
- Chaotic double pendulum notebook
- Lorenz attractor
- Dimensionality of the underlying dynamics: Taken’s theorem and the Grassberger-Procaccia algorithm
- Chaos in dripping faucet time series

- News: related to Grassberger-Procaccia algorithm and Takens theorem:
- Lotka-Volterra population dynamics model and original hare-lynx time series
- not only animal population
**predator prey like systems in chemistry**:- Briggs–Rauscher oscillating reaction (nice video)
- Belousov–Zhabotinsky reaction (with simulation demo) and experiment video1 , video2
- Examples of more complex systems: Citric acid cycle , Metabolic pathway, “Google map” of metabolic pathways

**Fractals:**- Mandelbrot set
- News: Onsager prize, Tamas Vicsek
- fractal dimension
- example fractal dimensions
- DNA fractal Peano-Hilbert globule article
- Hear rate fluctuation dynamics fractal

- genetic algorithm related to Barnsley’s fern and also evolutionary models
- Some fun with Diffusion Limited Aggregation
**Cellular automata:**- 1D
- NKS
- Golly
- Neumann universal constructor with a surprise
- Digits of Pi
- Gerard ‘t Hooft’s idea
- on general graph: Kauffman’s NK boolean network and some analysis

**Computer performance:****Thermodynamic simulations, Ising model:**- Simplest model of phase transition: Ising model, exact 2D solution, Onsager 1944 and a real life 2D ferromagnet (2018)
- Faster dynamics, spin clusters: Swendsen-Wang algorithm, visualization
- Metropolis algorithm and simulated annealing
- Hopfield model
- Neural nets have similar complex energy landscape: visualizations , article
- Numerical optimization and stat phys.: Moore & Mertens: The Nature of Computation , short summary
- NP-hardness concept, list of problems ; protein folding is NP-hard? or not

- New aspects: Adiabatic quantum computation
- Simulated bifurcation
- the Feynman path integral is based on variational principle like Fermat’s optical principle

**Molecular dynamics**- long range force cutoff, Ewald: link link2
- initial transient. Start with Maxwell distr. but since the coordinate-velocity correlations are not correct, temperature rescaling needed: link
- protein folding link
- energy landscape: link
- badly folded proteins: prions
- protein folding with machine learning: alphaFold
- hoomd-blue open source molecular dynamics simulator program
- argon with Hoomd
- two/three component mixing with Hoomd
- interesting problem: tetrahedron packing theoretical limit and hoomd simulation

**Partial differential equations**- classification and boundary conditions and explanation of names
- Finite element method and comparision to Finite difference method link
- FTCS and Crank-Nicolson methods as stepping examples
- von Neumann stability analysis link
- openFOAM open source computational fluid dynamics program

- (gravitational problems, slingshot) Grazing fireballs, “near-hit” asteroids that approach and leave Earth: https://arxiv.org/abs/1912.01895