Quantum Fields: The Most Beautiful Theory in Physics!

BACKGROUND VIDEOS:

CHAPTERS:
0:00 - Historical perspective of modern physics
1:50 - The advent of Quantum Mechanics
5:00 - The problems with quantum mechanics
6:52 - What is Quantum Field Theory?
9:25 - How QFT explains force mediation and decay
10:53 - How QFT is also incomplete
11:44 - The most beautiful theory in the universe!
12:41 - Further study with Brilliant

SUMMARY:
Quantum field theory or QFT is the basis of the best theory we have in physics today to explain nearly everything, called the Standard Model of particle physics. What is Quantum Field theory? Why is it necessary? How is it different than quantum mechanics?

Classical mechanics indicates that an orbiting electron creates electromagnetic radiation which means that it would constantly lose energy, and fall to the nucleus. This does not happen. Quantum Mechanics solved this problem by showing that electrons travel in quantized orbits at their lowest energy state, and that they do not orbit but exist as a clould around the nucleus.

In quantum mechanics, objects are wavefunctions described by the Schrodinger equation. The location of a particle is unknown until the moment of measurement. We cannot know where it is beforehand, only the probability of finding it at any specific location.

This is a great model but it also has some problems. First of all, quantum mechanics is not relativistic. It will give you the wrong result if the quantum object is moving close the speed of light. The practical result of this is that as it doesn’t incorporate a speed limit, the speed of light, needed to make causality work. It allows for two measurements to influence each other faster than light. This would mean that there would be some reference frame in which the future could influence the past, breaking causality.

A second problem with quantum mechanics is that it only tells you how a particle evolves over time. It does not tell you how it is created or annihilated. So it can’t account for things like beta decay, due to the weak nuclear force, where a neutron transforms into a proton, an electron and an antineutrino.

This is where quantum field theory explains things that quantum mechanics cannot explain on its own. So what is quantum field theory? QFT a mathematical framework that combines classical field theory, special relativity, and quantum mechanics There is a field for every particle of the standard model.

All of these fields extend out in all of spacetime. The fields are always there and exist everywhere including inside your body. Although they exist everywhere and you can’t see them, they are not nothing. They are teeming with virtual particles. These are particle-antiparticle pairs that get created and destroyed constantly.

We can visualize these fields as a kind of ocean. Just like the ocean always has some turbulence, the fields always have a kind of turbulence even in their ground state of minimal energy. This turbulence is due to virtual particle creation and annihilation. In these turbulent seas, if there is enough energy, a larger wave can be created which CAN be measured. These are the real particles.

Energy can be transferred between two fields via a mediating boson field. This is considered an interaction or a force. Matter particles can’t interact on their own without a mediating boson.

So while in quantum mechanics there is no way for the neutron to split its energy into 3 different particles – a proton, electron and antineutrino, in quantum field theory this can be done via energy exchange between the fields. Although the number of particles may change, the total energy is always conserved. In other words, the energy of the fields is the same before and after the energy exchange. So by having quantum fields we can mathematically account for and model creation and annihilation of particles, as well as the mechanism of force exchange.
#quantumfieldtheory
#QFT
The icing on the cake is that the theory is fully relativistic, and free of causality violations. But even this modification of quantum mechanics is not perfect. For example, QFT is still missing gravity. We do not have a quantum field theory for gravity. So even QFT which is extremely accurate for the forces and particles we know of in the standard model, remains as yet incomplete.

[SabineHossenfelder]

Best brief QFT intro I've come across!

[david_melech]

My physics teacher once asked me where my home work was. I told him it was part of a home work field. With my home work popping in and out of existence almost instantaneously. And there always being an uncertainty of where the home work actually is. He laughed, and I got off easy that time.

[Fundawonder]

The lucidity of your presentation and explanations makes what appears complex simpler to understand. Much appreciated!

[GeezerBoy]

Many real science explainers and demonstrators on youtube are excellent: Sabine, Sean Carroll, Don Lincoln, many others, and especially this channel should have several million subscribers. Arvin is a superb explainer with team behind him. This is like Feynman brought back to life. Not a single filler word and each thought leads to the next. And without silly sound effects. Superb.

[dgsean]

Dude, this explanation is probably the best I have ever seen for QFT. Thank you

[Liamvanvugt]

Hey Arvin, after binging all of your video's I have become so increadibly intersted in physics, you are one of the main reasons for me choosing to study physics. So I want to thank you for making seemingly impossible to understand subjects intuitively availible to all of us :)

[baivulcho]

As always, Arvin makes a highly complex concept really approachable and brings it closer to our limited minds. Thank you for that, every time you create a new video I watch it with confidence that I will be able to grasp the concept behind it. The only thing that I know I will be missing by the end is simply more on the subject. It's like a window to a new universe which is shortly opened for us.

[fjdarling]

Certainly changes the way I think about Matter and Energy and their complex interactions. Thanks Mr. Arvin.

[AdityaChaudhary-oopr]

What an amazing episode. Amazing visuals with outstanding explanation. 🙏

[vincentjoyhere]

12:40 - When he said “I find this to be beautiful” - his smile was one of the most beautiful, meaningful things I’ve ever seen. Incredible theory and incredible presentation!! ❤

[terrifictiger]

Arvin Ash's videos make complex concepts so appealing and intuitive. Highly recommend this channel. Thanks so much Arvin

[laioren]

Another great video, Arvin! I also really appreciated your framework of using classical physics to "explain" electron behavior in an atom, and how that doesn't work, so it led to quantum mechanics. Like 99% of science communication is finding a way to make unintuitive concepts more intuitive for people, and I think using that historical parallel really does a great job of showing that we had a tool, it didn't work to explain this behavior, so we observed that behavior and it helped us create another tool, that then led us into that same situation again, and tada, QFT. Really well done.

[while.coyote]

I can't wait until amplituhedrons get explained on this channel. You're so good at explaining!

[micronda]

That's incredible that the fields extend in time as well as space. The best news I have heard in the 13 billion years I have existed. Well done man!

[Naturamorpho]

Great graphics for the interaction and mediation between fields! Thanks again for the great content! See you in the next video, my friend!

[glyphix]

You are becoming my favorite over PBS spacetime!!! don’t get me wrong. I still love that show but I feel like your last couple videos, you have given me “aha" moments, both on explaining in a layman friendly way, but also love how are you tie it together with the we are all one thing!!! I always wondered if it was just me or if there were people who understood it much better than me who also got the feeling that the things we learn from quotum mechanics seem to jive with a lot of the eastern philosophy about we are one… you are the universe… etc

[enlilannunaki]

Arvin, you are astonishingly good at what you do. Please never stop. Thank you.

[jessiejamesferruolo]

I found my connection with everything around me when I realized that we are the universe that has become aware of itself.

"We are made of starstuff. We are a way for the cosmos to know itself." - Carl Sagan

[bryanchambers]

Great thing about physicists like you is they can step aside from the math and actually explain whats going on. An oft overlooked aspects of explaining physics. I'm a physics teacher myself and I teach this way also.

[ygzbqig]

With such an immaculate explaining method, we had no issues in understanding everything you explain to us , , many thanks .