Last time we figured out that when you start with a theory of noninteracting fields and quantized it, you could think of the result as a theory of noninteracting particles. Now we let those particles interact, and describe what happens using Feynman diagrams.
The Biggest Ideas in the Universe | 10. Interactions
And here is the associated Q&A video:
The Biggest Ideas in the Universe | Q&A 10 - Interactions
1. Who did the cool graphic behind you? I’d like to see it animated.
2. Can you write out an equation that corresponds to a very simple Feynman diagram?
3. Are “virtual particles” simply calculation devices or are they “real”?
Thanks as always!
Hi doctor Sean! Thanks a lot for the video! Really, a lot! =)
Please, I have a doubt about the superposition of fields… Let’s take the temperature field inside a car for example. If we were to consider it a quantum field, it would mean that we would have a function that would give the odds for all it’s possible configurations, like the odds of being 27 degrees Celsius in the driver seat and 25 degrees in the passengers seat, and a probability of being 30 degrees in one seat and 20 in the other… is this it? And there’s a complex number that represents all of this possible configurations?
Also, when the wave has an energy that means it behaves like two particles… Is this two particles at the same place at the same time?
Your explanation in the end about virtual particles were particularly awesome!
Also, shouldn’t an electron and a positron explode if they interacted, since they are matter and anti matter?
Didnt locality felt long ago, due to entanglement?
Thanks again!!!!
How is it possible that an electron going forward in time and a positron going back in time can collide is this proven by observations or is just part of a theory at the moment ? and secondly are the viritual particles in the diagrams the same or related to the virtual particles that are supposed to be popping in and out of existence in space?
Hey Sean! I have a question for the Q&A and this is actually a question that has been bothering me in physics for a while now so I’d love to get an answer from a real expert! So if antimatter is matter but with CPT reversal then why do people say neutrinos are their own anti particles? Sure the charge is 0 and the reverse of 0 is 0, but for anti neutrinos do the P and T get reversed relative to regular neutrinos? Or are there really no distinction from regular and anti neutrinos? This question isnt just for neutrinos too, I’m just using them as an example to hopefully get you to clarify some of my confusion dealing with antimatter. If this question is too much of a stretch from the topic of the video I would love if you could email me too, but I know you’re a busy man so I’d understand if this question goes unnoticed. Either way thanks for your time Sean! Great series!!!
could you kindly explain what it means to quantize a field. what is specifically the mathematically technique being applied when you quantize a field
You mentioned that virtual particles are not real – that they are not really a particle at all. But if this is the case how does Hawking radiation work? The idea that the vacuum of space generates virtual and real particles that annihilate almost immediately, but sometimes one of the two particles falls into the event horizon and thus the radiation from the black hole (the second particle being free to roam about, not having a virtual particle to annihilate). If these virtual particles are just a mathematical construct, what falls in to the black hole then? Or are these virtual particles a different thing altogether?
If you weren’t planning to do this later, could elaborate on a case where the ‘waviness’ of the field was important, as opposed to the collection of particles view?
Thanks!
Can you help us understand how the Bell Inequality discussion seemed to conclude that a consistent QM theory could not be local, yet in this lecture you state that the interactions of quantum fields must be local.
Dr. Carroll
This question involves trying to connect ideas covered in Something Deeply Hidden, as well as your great ideas videos. If Hilbert space turns out to be finite dimensional would that have any implications for the many worlds interpretation of QM? I understand that a finite dimensional wave function for the universe would still allow for an infinite number of values for the wave function, but might there be in some sense not enough “room” for all the different non interacting wave functions of the many worlds? Would there be at some point where no more branches would fit without forcing them to interact with each other in some way?
Feel free to ignore the question and just try ferret out the underlying misconceptions. Also, thank you so much for all the work you put into trying to educate the public (us).
Read a couple of your books a while ago. Can’t wait to dig into this series! Hope Entropy will be one of the Big Ideas.