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Sussan
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What ever happened with QFT? Heard so much about it years ago now only once in a while will a past Nobel laureate state it is real. I know string is the thing now. Any thoughts?
Sussan
Sussan
"Real"? Huh?? QFT is a framework, in which the Standard Model of Elementary Particles is formulated. The correspondence between quantities predicted by this model and actual experimental results are among the best (most accurate) in all of physics.Sussan said:What ever happened with QFT? Heard so much about it years ago now only once in a while will a past Nobel laureate state it is real.
Actually, for purposes of physics, it's becoming more and more of a sad joke.I know string is the thing now.
Sussan said:What ever happened with QFT? Heard so much about it years ago now only once in a while will a past Nobel laureate state it is real. I know string is the thing now. Any thoughts?
Sussan
strangerep said:Actually, for purposes of physics, it's becoming more and more of a sad joke.
That's a completely ridiculous and absurd statement. String theory is by far the most promising approach to a quantum theory of gravity. In fact, it provides a perfectly fine theory of quantum gravity (with a particular set of other particles) in 10 spacetime dimensions. Now, as it happens, we see 4 spacetime dimensions, not 10, and that set of particles is not the set that we see. But no other approach to quantum gravity has come anywhere close to achieving this level of success.strangerep said:Actually, for purposes of physics, it's becoming more and more of a sad joke.
Avodyne said:and there does not seem to be any principle that would select just one of these (let alone select the Standard Model as that one).
Avodyne said:That's a completely ridiculous and absurd statement. String theory is by far the most promising approach to a quantum theory of gravity. In fact, it provides a perfectly fine theory of quantum gravity (with a particular set of other particles) in 10 spacetime dimensions. Now, as it happens, we see 4 spacetime dimensions, not 10, and that set of particles is not the set that we see. But no other approach to quantum gravity has come anywhere close to achieving this level of success.
Furthermore, it is understood how to get from 10 to 4 dimensions, and how to get different sets of particles. The problem is that you can get many (possibly an infinite number) of different sets of particles in different numbers of dimensions, and there does not seem to be any principle that would select just one of these (let alone select the Standard Model as that one). So what we see may just be an accident, just like the orbits of the planets in our solar system are accidents (contrary to what Kepler wanted, that the orbital radii were fundamental numbers related to the platonic solids). Physicists who want to discard string theory because it seems to be telling us that particle types, masses, and couplings are like the orbits of the planets (just accidental numbers in our neighborhood) may find themselves sharing a room with Kepler in the halls of history.
strangerep said:"Real"? Huh?? QFT is a framework, in which the Standard Model of Elementary Particles is formulated. The correspondence between quantities predicted by this model and actual experimental results are among the best (most accurate) in all of physics.
Actually, for purposes of physics, it's becoming more and more of a sad joke.
Sussan said:Why such hostility between string theorist and OFT supporters? kinda shocked by the anger when I just asked a as it now appears a not so simple question.
Sussan
Sussan said:Why such hostility between string theorist and OFT supporters? kinda shocked by the anger when I just asked a as it now appears a not so simple question.
Sussan
atyy said:There is no hostility from string theory towards QFT. The standard model of particle physics is formulated in the language of QFT. The standard model has been standard for many years, having passed all experimental tests to date. When you hear of the Higgs mechanism or supersymmetry, those again are formulated in the language of QFT. Even quantum gravity at the low energies of our everyday world is described in the language of QFT. In other words, no one expects the language of QFT to fail except perhaps in the domain of quantum gravitational effects at very high energies.
What language is needed to describe quantum gravity at high energies is still unknown. String theory is certainly the leading candidate for a theory of quantum gravity at high energies. Even if it turns out to be experimentally false, it will hopefully help us learn the right language for quantum gravity. Remarkably, the language of QFT is thought to describe a sector of string theory, but holographically. Thus usually, a 4 dimensional spacetime is described by a 4 dimensional QFT. In string theory, a 4 dimensional spacetime is thought to be describable by a 3 dimensional QFT.
ZapperZ said:This is a very odd thread and a puzzling discussion. You might as well question what happened to Quantum Mechanics!
Please note that the physics that we use to describe the properties of the material you are using in your electronics often uses QFT! So you'll understand why many of us find your question to be unusually strange.
Zz.
Sussan said:Hi Zz,
I totally understand your concerns. Yes it is a “stupid” question for someone in the “field” and at times I have been called stupid, however as referring to this question I am more dumb than stupid. I did attend O.S.U. 1 year in honors level physics, however life had other plans thus married had children you know the movie. My IQ is around 135 (not the brightest bulb in this room for sure) did so-so in Calculus 1,2,3 (B average), so that being stated “should” be able to grasp the Higg’s concept if I just work at it with more diligence than most… which in turn led me here. After learning Hawkins was betting against the Higg’s Boson being found sparked my curiosity thus my layman (laywoman) journey as it were. Well I watched many YouTube videos about the Higgs and most stated analogies that to my mind does seem “stupid” snow, molasses, people in a room (please). I did come across Leonard Susskind’s (Demystifying The Higg’s Boson) an easy as pie to understand the “reasoning” for the understanding, however Susskind would make up names and events that threw my mind into confusion (not a hard thing to accomplish) so joined the forum to ask questions. The Higg’s field is that which actually “gives” in a sense matter weight not the boson which I kind of felt was the case. That led to Fields and that to QFT so watched several videos on QFT and though was ALL mathematical which was pretty easy to understand (means I actually could follow it to a degree) could feel that struggle between String Theorist and QFT Theorist were not commenting on both just their fields. Susskind String man would not say a word about QFT in his lectures and Michio Kaku another String man would not say anything of substance about QFT then I came across a video for QFT “Fields of Color” by Dr. Rodney A. Brooks that was “suppose” to give me a layman’s feel for QFT well in the video he talks about QFT as if it were a “lost” area of physics and went on to state Feynman was a particle man ONLY and did not believe in fields at all so here I am please help me understand.
Thanks Zz
Sussan said:I was asking because I just watched a video from YouTube about a book "Fields of color" from a Dr. Rodney Brooks about QFT and he implies that QTF is kinda a "lost" idea.
ZapperZ said:Say what?!
Zz.
ZapperZ said:Say what?!
Zz.
mitchell porter said:I think we're all somewhat perplexed by the claim that quantum field theory is a neglected theoretical framework, given that it is the bread and butter of high energy physics. There are two things that Brooks might be referring to.
First, in science popularization, you hear much more about quantum mechanics than you do about quantum field theory. But quantum field theory is just quantum mechanics applied to fields.
Second, a lot of QFT can be described in terms of particles. Perhaps you could say that Feynman invented much of the particle formalism of QFT, whereas Schwinger developed the field formalism, and Brooks is trying to evangelize Schwinger's perspective.
But the practical experience of most people who learn QFT is a hybrid of the two. They will start with field equations, interpreted quantum mechanically, but then quickly pass to the particle formalism. It's only for more advanced topics that the full field-theoretic picture becomes indispensable.
mitchell porter said:I think we're all somewhat perplexed by the claim that quantum field theory is a neglected theoretical framework, given that it is the bread and butter of high energy physics.
Sussan said:Thanks for the reply. I was asking because I just watched a video from YouTube about a book "Fields of color" from a Dr. Rodney Brooks about QFT and he implies that QTF is kinda a "lost" idea. He made me wonder so just asking.
Sussan
RogerWest said:In a recent letter that Rodney Brooks published in Washington Post, titled "Physics That Makes Sense," he says: https://www.washingtonpost.com/opin...c19f06-2ccd-11e6-b9d5-3c3063f8332c_story.html
RogerWest said:In a recent letter that Rodney Brooks published in Washington Post, titled "Physics That Makes Sense," he says: https://www.washingtonpost.com/opin...c19f06-2ccd-11e6-b9d5-3c3063f8332c_story.html
Wrong. What I have read about strings as a quantum theory of gravity, it is only a hope, based on some of the infinities not being present, that all the others may go away somehow too. Something reached for the numbers 1,2,3 when it would be necessary for all n. And, moreover, only for unbroken supersymmetry, which has nothing to do with the observed universe.Avodyne said:That's a completely ridiculous and absurd statement. String theory is by far the most promising approach to a quantum theory of gravity. In fact, it provides a perfectly fine theory of quantum gravity (with a particular set of other particles) in 10 spacetime dimensions. Now, as it happens, we see 4 spacetime dimensions, not 10, and that set of particles is not the set that we see. But no other approach to quantum gravity has come anywhere close to achieving this level of success.
Quantum Field Theory (QFT) is a theoretical framework that combines principles of quantum mechanics and special relativity to describe the behavior of particles at a subatomic level. It is a mathematical formalism that allows us to study the interactions between particles and their corresponding fields.
In classical field theory, particles are treated as discrete objects with definite positions and velocities. In QFT, particles are described as localized excitations in their corresponding fields, which are continuous and have infinite degrees of freedom. QFT also takes into account the principles of quantum mechanics, such as superposition and uncertainty, which are not present in classical field theory.
QFT has a wide range of applications in various fields of physics, including particle physics, condensed matter physics, and cosmology. It is used to study the behavior of fundamental particles and their interactions, as well as the properties of materials at a microscopic level. QFT also plays a crucial role in our understanding of the early universe and the current state of the universe.
Symmetries play a fundamental role in QFT. They are used to classify particles and their interactions, and they provide a powerful tool for understanding the underlying structure of physical theories. Symmetries also allow us to make predictions and calculations in QFT, as they can be used to derive conservation laws and other important quantities.
QFT is a highly complex and abstract mathematical framework, making it challenging to understand and apply. It also involves infinities and divergences in certain calculations, which require sophisticated techniques to handle. Additionally, there is currently no complete theory of quantum gravity, which is an important aspect of QFT that is yet to be fully understood.