

An Introduction to Quantum Field Theory - simulate
http://www.ribbonfarm.com/2015/08/20/qft/

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danbruc
Obligatory link for those that want to go a bit deeper into the rabbit hole -
The Theoretical Minimum, a collection of physics lecture by Leonard Susskind.

[http://theoreticalminimum.com/](http://theoreticalminimum.com/)

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bostonpete
Into the rapid hole??

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danbruc
Fixed.

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bostonpete
OK, I thought maybe I was missing a physics pun or something... :-)

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timelined
This is a pretty good introduction. I highly recommend Feynman's book "QED:
The Strange Theory of Light and Matter" as an excellent in-depth work that
does not sacrifice accuracy for the sake of making difficult ideas
understandable. It is both very clear to the layperson and accurate to the
physics.

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Steuard
Wholeheartedly seconded. This book occupies a nearly unique position in the
physics literature: it is neither a textbook nor a popularization. It assumes
little more knowledge (of math or physics) than the typical popularization,
but it explains what is very nearly the true, complete structure of its
subject matter (quantum electrodymanics). Now, the methods that it teaches are
absolutely unwieldy: it would be hopeless to do any real, meaningful
calculation by drawing countless little arrows! But (as I think Feynman says)
you can go to grad school to learn the _efficient_ tricks. The underlying
concepts will carry through essentially unchanged.

I wish I could write like that.

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lobster_johnson
An interesting and surprising fact about Feynman's books is that he never
_wrote_ any of them, as such; he famously disliked writing. QED is essentially
a transcript of a lecture (although I don't know how much polishing and
editing was done by Feynman himself; probably some). Same with his collection
of physics lectures. His most popular book, "Surely You're Joking, Mr.
Feynman", was transcribed from a series of interviews, pretty much verbatim.

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613style
This is a great article. One thing I don't understand: the author says:

> If you want to create something heavy like the Higgs boson, you have to hit
> the > Higgs field with a sufficiently large (and sufficiently concentrated)
> burst of > energy to give the field the necessary one quantum of energy.)

So when the LHC creates a spike of energy at a point large enough to create a
Higgs boson, why does that energy interact with the Higgs field and get "used
up" by other fields? In other words, if Higgs requires 100 units of energy and
electrons require 1, why do we get 1 Higgs boson and not 100 electrons?

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danbruc
Not a physicist, but that actually happens. Depending on the coupling
strengths between the various kinds of particles respectively fields and the
amount of energy they have, different particles get created with different
probabilities. That is why the Higgs is so hard to detect - for every Higgs
you produce billions and billions of other particles that are easy to create
and you have to look for the one Higgs in all this mess. Physicists calculate
the expected amounts of other particles with incredible precision, subtract
that from the experimental results and if they are successful they end up with
a tiny amount of unexplained stuff.

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danbruc
Are quantum fields actual elements of reality or just a convenient
mathematical tool to deal with many particle systems?

One of the questions I am struggling to find a satisfying answer for for quite
some time. Depends on whom you ask? We can't tell because both ways of
thinking are completely equivalent? Fields are real! No, they are just a tool!
Are there issues with real fields forming a preferred reference frame? Does
somebody know? (My current understanding seems to suggest that fields are just
a tool.)

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xlm1717
The way I've understood it is, particles are localized excitations of fields.
You know of the Higgs boson. It is the excitation of the Higgs field, which
exists through all space. Similarly, an electron is an excitation of the
electron field (not electromagnetic field), which exists through all space.
Every single electron is a localized excitation of the same, single field.

I don't know how to answer the relativistic questions of fields yet. For that
one would need to learn a lot of Quantum Field Theory.

For the layman, however, these two links are very informative:

[http://www.symmetrymagazine.org/article/july-2013/real-
talk-...](http://www.symmetrymagazine.org/article/july-2013/real-talk-
everything-is-made-of-fields)
[http://www.pbs.org/wgbh/nova/blogs/physics/2013/08/the-
good-...](http://www.pbs.org/wgbh/nova/blogs/physics/2013/08/the-good-
vibrations-of-quantum-field-theories/)

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danbruc
I understand that, but is it just a neat mathematical model to treat particles
as excitations of fields because it makes calculations especially easy or is
there really a field out there?

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MisterMashable
Fields are real because perturbation theory (Feynmann diagrams) is unable to
describe solitons, vorticies, monopoles and bound states.

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selimthegrim
Sounds like the best argument I've heard on this thread yet.

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mudil
Ether is back!

Well, somewhat. Now it's in the form of Higgs field. Unlike ether, Higgs field
does not interact with uniformly moving particles, only those that are
accelerating.

Here's a great book I just recently listened: [http://www.amazon.com/The-
Black-Hole-War-Mechanics/dp/031601...](http://www.amazon.com/The-Black-Hole-
War-Mechanics/dp/0316016411)

It's by Leonard Susskind from Stanford. The thoughts experiments in the book
are just terrific. Loved it.

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w0000t
I wouldn't call it Ether, since that would imply some absolute reference
frame.

