Theory Definition and 1000 Threads

What is the best theory why our vacuum may be in the edge of metastability? Is it possible there are many false vacuum separated by energy barriers and the reason why our vacuum may be metastable is so that it is easier to cross the different false vacua (not necessarily to the true vacuum)?

I believe this could be interesting to many people here who are interested in quantum theory but are not (yet) professional physicists: http://lanl.arxiv.org/abs/1803.07098

The theory of electroweak temperature says that when you have a plasma of particles at energy above the electroweak phase transition (100 GeV). The Higgs field would turn from nonzero vev to zero and the electroweak forces would unite and the electroweak bosons would become massless. What...

Hello! I am reading some things about representation theory for SU(n) and I want to make sure I understand it properly. I will put an example here and explain what I understand out of it and I would really appreciate if someone can tell me if it is right or not. So for SU(2) we have ##2 \otimes...

Could someone please check if these are right?

I'll start by saying I'm posting this in Beyond the SM just because we have no elementary spin-3/2 particles in the SM as far as we know, though I was also considering posting it elsewhere. If you feel it's more appropriate in another area just let me know. As for the question itself, I'd like...

Homework Statement : [/B]This is a general conceptual doubt, not a numerical based doubt. We were taught that when an electron(or any charged particle) moving with uniform velocity enters a magnetic field(perpendicular to its direction of motion), then a force acts on the electron which makes it...

In his second lecture of the QED series (see below), Prof. Richard Feynman explains the phenomenon of reflection from a plane mirror, and then the working of a diffraction grating with his theory of arrows (probability amplitudes), and we see that how the new theory, which is much moved from the...

Can someone at least gives a summary of the constrains in the E8xE8 heterotic superstring theory? Many sources are mostly outdated that was written decades ago when not much research were done yet in superstring theory. So is E8xE8 already refuted? Or to what degrees and what constrains? I need...

By "The Force" I mean from "Star Wars". https://aeon.co/essays/cosmopsychism-explains-why-the-universe-is-fine-tuned-for-life The author seems to say that the Universe is an active sentient agent that has fine-tuned itself so as to make the fundamental forces of nature be such as to allow for...

The Godel theorem shows that the standard Peano axiomatization or arithmetic is undecidable. However, there is an alternative Presburger's axiomatization of arithmetic, which is decidable. Similarly, the standard ZFC axiomatization of set theory is undecidable. For instance, the continuum...

Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Renormalization Continue reading the Original PF Insights Post.

Hello, I have begun to teach myself Control Theory. I am looking for a book that is focused for mechanical engineers. I do not mind examples in electrical engineering, but they bore me (no offense). Also, I find some books begin with Laplace Transforms. Yet I found this online lecture...

So if string theory is to be correct it must be able to come up with the observed value for the energy density of empty space which is pretty close to zero? A naive understanding of the compact spaces of string theory tells me that an "energy audit" of the highly curved compact manifolds of...

Homework Statement Derive, using the canonical commutation relation of the position space representation of the fields φ(x) and π(y), the corresponding commutation relation in momentum space.Homework Equations [φ(x), π(y)] = iδ3(x-y) My Fourier transforms are defined by: $$ φ^*(\vec p)=\int...

Hi! Can anyone recommend a good introductory book for measure theory? I've found Terence Tao's online book to be a good start, but would I be asking too much if I wanted something even more introductory? Ultimately I'm working toward Ergodic theory (and probability theory along the way) with...

Hello, everyone! My name is Hannah Taylor and this is my first time contributing to a forum so bear with me while I figure everything out. In the meantime let me share a few facts about myself with all of you.. I was born and raised in a small village called Cowden, we have about 650 people &...

I am practicing for my math exam next week and I came across this problem: A set has 200 elements in it. It is partitioned into three subsets so that the second and third subsets have the same number of elements. If four times the number of elements in the second subset is three times as many...

Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Interacting Quantum Fields Continue reading the Original PF Insights Post.

I have been reviewing GR lately because as a mentor I find myself now answering more of those questions. I learned GR years ago from Wald and other sources, but since then have been exposed to the symmetries of the Standard Model. What struck me during this review is I now have a different...

Hi. Maybe you can help me clarify the ideas a little. I've put in google the following. rebuilding.quantum It seems that there are scientists interested in founding quantum theory on bases that harmonize with simple criteria. After more than 100 years of elaborating and debugging quantum...

Hi, I was watching a really interesting old video from Richard Feynman who was talking about how precise/accurate the predictions of quantum theory agree with observation. The number of decimal places it agrees he said is astounding. He likened it to measuring the circumference of the Earth to...

Hello everyone. I have a question about the fact that there is no drag in the thin airfoil theory. I have read that it comes from inviscid and incompressible flow (potential flow) but what i can not understand is why there would be no drag from pressure differences ? The skin drag is of course...

http://arxiv.org/abs/1801.04083 UV completion of a theory of Superfluid Dark Matter Andrea Addazi, Antonino Marciano (Submitted on 12 Jan 2018) We show that a model of superfluid dark matter, modifying the Newtonian potential and explaining galactic rotational curves, can be unitarized by the...

There is a relationship between each of the mathematical values in each of the paradoxes with regard to each observers. There is obviously also a relationship between every situation we study in the Special Theory of Relativity. The Lorentz Transformations obviously prove this. So, I began to...

Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Free Quantum Fields Continue reading the Original PF Insights Post.

I'm currently applying for grad schools in string theory with an interest in AdS/CFT but am open to fundamental formalisms in string theory. I was trying to decide on a few universities to apply to. I am currently considering University of California Davis and University of Illinois Urbana...

This is probably extremely wrong I just want to know how. If photons don't experience time doesn't that mean they are every where at once, and if that is true doesn't part of quantum physics say before a particle is observed its in all the states it can be in? So doesn't that apply in that sense...

So in string theory at each point of Minkowski spacetime we might have a 3 dimensional compact complex Calabi–Yau manifold? We can have curved compact spaces without complex numbers I assume, what is interesting or special about complex compact spaces? Thanks!

Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Quantization Continue reading the Original PF Insights Post.

A scalar field theory with potential $$V(\phi)=-\mu^2\phi^2+\lambda \phi^4$$ is spontaneously broken and as a consequence, for the ground state, $$\langle \phi(x) \rangle \neq 0$$. However, the path integral, which should give ground state expectation values, looks to be zero by oddness of the...

<< Mentor note -- posts broken off from an Insights comment thread >> [/color] Ok, this is where I show my ignorance, but all this is theoretical and why I get lost with these academia discussions. Time is just a mathmatical construct to measure the motion of two or more objects relative to...

Einstein's theory states that curvature of space (created by a celestial body around itself) determines the orbital path of other celestial bodies around it within that curved space by a constant lateral force acting towards the centre upon that revolving body. Then why is that a similar force...

I wondered if anyone might know of any open access materials, possibly lecture notes, on the content of the following papers or books. P.A.M Dirac, 1950, Can. J. Math. 2,147 "Generalized Hamiltonian Dynamics" P.A.M Dirac, 1933, Proc. Camb. Phil. Soc., 29, 389 "Homogenous variables in classical...

I just finished reading Walter Isacson's Einstein. I note that Einstein's motivation for Special Relativity was the constant speed of light as shown by Michelson and Morley, and his motivation for General Relativity was the equivalence of gravity and acceleration as experienced, for example, in...

Ten mutually distinct non-zero reals are given such that for any two, either their sum or their product is rational. Prove that squares of all these numbers are rational. I tried using 3 of those numbers - a, b and c. And I checked each of the possible situations but I'm not sure if my maths...

Hi, I have a blog oriented on computational physics: https://compphys.go.ro For many posts I have a GitHub project. Lately I started some DFT oriented ones, the latest being a DFT (with plane waves basis) project for a 'quantum dot'. Currently I started working on a project that will use the...

What are the books that speak about string theory you would suggest me? And the book against this theory? (I'm an undergraduate physics student) Thanks!

Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Gauge Fixing Continue reading the Original PF Insights Post.

If question isint allowed please delete and let me know. I'm just wondering what the general consensus is about M theory?

How far ahead are we in Grand Unified Theory? Are we still searching for proton decay?

Why does max tegmark's and brian greene's levels of multiverses consider as the highest level the mathematical multiverse hypothesis if other authors like David Lewis consider that there could be also universes non described by maths? Why does it stop at level iv (mathematical universes...

"There are various theories about how the solar system formed, but scientists haven't been able to agree on a single model that explains all the quirks of our corner of space as it exists today. Now, scientists at the University of Chicago have...

Homework Statement The time (minute) that it takes for a terrain runner to get around a runway is a random variable X with the tightness function fX = (125-x)/450 , 95≤x≤125 How big is the probability of eight different runners, whose times are independent after 100 minutes: a) Everyone has...

I've always read that these two theories are incompatible, and how General Relativity works for large scales while Quantum Theory represent reality in extra-small cases. So my question is where is the limit where General relativity ceases to exist and Quantum Theory gives a better portrait of...

Homework Statement Homework Equations Reduce the matrix to reduced matrix by removing 1 row completely Number of trees = determinant of [ Ar times ArT ] The Attempt at a Solution I removed 4th row to get Ar(reduced matrix) Then I did Ar times Ar (transpose) And found it's determinant but I...

What does it means for a physical theory to have hamiltonian, if it is formulated in lagrangian form? Why doesn't someone just apply the lagrangian transformation to the theory, and therefore its hamiltonian is automatically gotten?

Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Reduced Phase Space Continue reading the Original PF Insights Post.

Quantum mechanics does a good job in describing the hydrogen atom. Are there any views either mathematically or conceptually in describing the hydrogen atom?

Homework Statement In a vessel is a 5 cent coin and two 1-cent coins. If someone takes up two randomly chosen of these coins, and we let X be the total value of the coins taken, what is the probability function for X? Homework Equations I know that X has a value {2,6} The Attempt at a...