@paulbalduf@mathstodon.xyz
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paulbalduf

@paulbalduf@mathstodon.xyz

Theoretical physicist
Postdoc in Combinatorics&Optimization at U Waterloo
Associate postdoc at Perimeter Institute for Theoretical Physics
I work with Feynman graphs, combinatorics of power series, resurgence theory, and do a lot of C++ programming.
My goal is to understand the physical properties of renormalized Green functions in quantum field theory.
What, actually, is an instanton?
#quantum #physics
#math

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paulbalduf, to physics
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In , scattering amplitudes can be computed as sums of (very many) s. They contribute differently much, with most integrals contributing near the average (scaled to 1.0 in the plots), but a "long tail" of integrals that are larger by a significant factor.
We looked at patterns in these distributions, and one particularly striking one is that if instead of the Feynman integral P itself, you consider 1 divided by root of P, the distribution is almost Gaussian! To my knowledge, this is the first time anything like this has been observed. We only looked at one quantum field theory, the "phi^4 theory in 4 dimensions". It would be interesting to see if this is coincidence for this particular theory and class of Feynman integrals, or if it persists universally.
More background and relevant papers at https://paulbalduf.com/research/statistics-periods/

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paulbalduf,
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@johncarlosbaez These are primitive (=subdivergence-free) graphs for the 4-point function. Hence, these numbers are independent of the chosen renormalization scheme (this is one reason we concentrated on this class).
These observations are contained in https://link.springer.com/article/10.1007/JHEP11(2023)160
We have since made the complete data set available, it can be downloaded from
https://borealisdata.ca/dataset.xhtml?persistentId=doi:10.5683/SP3/NLEDGH

danie10, to HomeAutomation
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You can automate much of your home and devices with a Raspberry Pi and open-source Home Assistant

This article is a worthy reminder that are already many things in your home which you can automate from garage door openers, to your home router, to a solar system, to lights, to speakers, and so much more.

Home Assistant has hundreds of ready to ...continues

See https://gadgeteer.co.za/you-can-automate-much-of-your-home-and-devices-with-a-raspberry-pi-and-open-source-home-assistant/

paulbalduf,
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@danie10 Amazing to see that more and more home automation tasks can be done open source and on private hardware.
Putting all this data in "the cloud", who might sell it to third parties, can have unexpected consequences. I recently discovered that knowing the data series of my indoor room temperature (not any home automation data, just the temperature in one room) is already enough to give away the city I live in. https://paulbalduf.com/blog/room_temperature/

kaffeeringe, to opensource German
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Einen kostenlosen Unlimited-Account für bekommen alle mit einer E-Mail-Adresse der Universitäten in Nebraska!

Lehrkräfte können dann einfach eine Literatursammlung für ein Seminar an die Studierenden freigeben. Lerngruppen können Quellen miteinander teilen. Ein super Service, der es ermöglicht, dass alle Studierenden und Mitarbeitenden den gleichen Zugang bekommen.

Vielleicht ist das ja auch eine Idee für Universitäten in Deutschland.

https://news.unl.edu/newsrooms/today/article/libraries-upgrade-to-zotero-institution-citation-management-tool/

paulbalduf,
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@kaffeeringe In Waterloo haben wir auch eine Campuslizenz für Zotero. Allerdings kann man es auch sehr gut ohne Lizenz benutzen, das eigentliche Programm ist ja open source. Wenn man entweder die Online-Synchronisation nicht braucht oder einen eigenen Server dafür hat, kostet es nichts.

paulbalduf, to physics
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Here is a curious finding from our statistical analysis https://arxiv.org/abs/2403.16217 :
A is a graphical short hand notation for a complicated integral that computes the probability for scattering processes in field theory.
An electrical circuit can also be described as a graph. What happens if we interpret the Feynman graph as an network, where each edge is a 1 Ohm resistor? We can then compute the resistance between any pair of vertices and collect all these values in a "resistance matrix", as shown below. The average of all these resistances is called "Kirchhoff index". Now it turns out that this average resistance is correlated fairly strongly with the Feynman integral of that graph: A graph with large contribution to quantum scattering amplitudes on average also has a large electrical resistance. Isn't that a nice connection between two seemingly distinct branches of theoretical ?

Correlation between average resistance and Feynman period

paulbalduf, to random
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Hi all!
I'm Paul, a theoretical physicist currently based in Waterloo/Canada.
I work in combinatorics, graph theory, and renormalization of quantum fields. Effectively, that's half of the time pen and paper calculations, the other half C++ programming 😁! And another half is teaching calculus at the moment...
I did my in Berlin, and my Bachelor's in the beautiful city of Jena.

In my free time, I do all sorts of other physics related things (it seems I have turned my hobbies into my job -- like the Pokemon professors back in the day). Currently, I am trying to get a Raspi-based ventilation system in a summer cottage to measure the amount of beverages present from the building's heat capacity.
Also, I like biking and hiking and dogs.

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