Theory Definition and 1000 Threads

Hello! PS. This is not a Homework question, I am asking about a concept. I am a Physics teacher from Brazil and last week one of the biggest Engineer universities here applied its entrance exam. However, a lot of teachers (including me) don't agree with one of the answers. Can you guys help...

If I plug the solution into the Schrodinger equation I get $$(i \hbar \partial_t - H)\ket{\psi} = 0$$ Since I know that the zeroth-order expansion is lambda is already a solution I think this is equal to $$(i \hbar \partial_t - H)e^{i\phi} e^{-i\gamma}\ket{\delta n} = 0$$ If now I carry on with...

In quantum chemistry, the MP rows (MP2, MP3, MP4, etc) can converge both quickly and slowly, and for some cases (e.g. CeI4 molecule) they even diverge instead of converging. My question is quite philosophic: what is the “mathematical cornerstone”, or “philosophical cornerstone” of the...

Moderator's note: Spin off from previous thread due to advanced nature of topic. There is classical field theory too, and GR is a relativistic classical field theory of the gravitational interaction. It's ironic that you fight for a geometrical-interpretation-only point of view and at the same...

I'm reading the https://www.phys.uniroma1.it/fisica/sites/default/files/DOTT_FISICA/MENU/03DOTTORANDI/TesiFin26/Urbani.pdf at paragrph 4.6.2 "The interaction term". They write a right hand side: < f(na,nb) f(nc,nd) f(ne,nf) > and they want to use a symmetry, for example they assume that...

Are there any QFT books that use little to no math? If there is a little math that is okay. I don't know much about math. I am looking for good explanations on how it works without math. Any help would be great!

Hi, Folks,...new around here. Please excuse my naivete, but-- I have a problem with the physics behind GHG Theory/GW. Most discussions seem to center around absorbtion/transmission spectra of gases, their correlation with temperature, ala' Black Box radiation and such, and the fact that GHG...

It is often said that one of the drawbacks of the standard model is that it has many free parameters. My question is two-fold: What exactly is a free parameter? My understanding is that the free parameters of a model/theory are the ones that cannot be predicted by the theory and need to be...

A lot of people say that Quantum Field theory (QFT) an Quantum Mechanics (QM) are equivalent. Yet, I've found others who dispute these claims. Among the counter-arguments (which I admittedly do not have the expertise to pick apart and check their validity in full) are the following: 1) While QFT...

-1st: Could someone give me some insight on what a ket-state refers to when dealing with a field? To my understand it tells us the probability amplitude of having each excitation at any spacetime point, but I don't know if this is accurate. Also, we solve the free field equation not for this...

It came to my attention yesterday this, from my ignorant point of view, amazing paper that describes what it looks as another Theory of Everything: https://arxiv.org/abs/2110.02062 If I didnt understand incorrectly, from first principles / a pre quantum theory (Trace Dynamics, 8D octonionic...

Homework Statement:: Mathematics to understand Quantum Scattering Theory Relevant Equations:: Suitable math book to understand Quantum Scattering Theory I need to study Scattering theory from Introduction to Quantum Mechanics by David Griffith. But I think I need to study mathematics first...

Let's say we have a big object like chair. According to Objective-collapse theory, is the wave of the chair collapsing and spreading out so fast we see it in one definite position or, does the chair collapse and it remains in this collapsed state longer than microscopic objects like atoms?

I was reading in the Book: Introduction to Quantum Mechanics by David J. Griffiths. In chapter Time-Dependent Perturbation Theory, Section 9.12. I could not understand that why he put the first order correction ca(1)(t)=1 while it equals a constant.

In This wikipedia article is said: "If the quantum field theory can be accurately described through perturbation theory, then the properties of the vacuum are analogous to the properties of the ground state of a quantum mechanical harmonic oscillator, or more accurately, the ground state of a...

Let ##\phi## be a scalar field and ##g_{\mu \nu} = \eta_{\mu \nu}+h_{\mu \nu}/M_p## where ##M_p## is the Planck mass (so we assume we deal with perturbations). Let ##\Lambda_2,\Lambda_3## be energy scales such that ##\Lambda_2 \gg \Lambda_3##. These are defined by ##\Lambda^2_2 = M_p H_0## and...

When trying to explain from where did all the laws come from, John Wheeler proposed the anaphorism of "Law without law". He proposed that at the "beginning" there were no laws whatsoever, only pure chaos, and that they emerged from randomness and chaos when our universe was created. In his own...

(Sorry about writing a book! But I felt more information was the better mistake.) Okay, here's the deal. I have been teaching myself Physics and Math beyond my MS in QFT. I have been doing this for the last 20 or so years and I've gotten reasonably decent at it but String Theory is a bit...

Hi, All. In searching for images related to the introduction of band theory in solid sate physics I found this one: I would like to ask you if I am correct in thinking the increase in the number of splittings (in b) is misleading to students. Thank you all DaTario

Which is the mathematical procedure to obtain ##\delta r = \frac{GM}{3c^2}## from ##\nabla^2 V = R_{00} = 4\pi G\rho## where ##\nabla^2 V## is volume contraction of a spherical mass of density ##\rho## and ##R_{00}## is the 00 component of Ricci tensor ##R_{ij}##?

Hello! I saw in many papers people talking about the effects of a time dependent perturbation (usually an oscillating E or B field) on the energy levels of an atom or molecule (for now let's assume this is a 2 level system). Taking about energy makes sense when the hamiltonian is time...

Hi, I am back yet again with another problem I was reading the following question and attempting it. It was an interview problem, so it isn't technically homework, but I don't know where else to post it. I think there are elements of game theory involved, but I have no academic background in...

Non-critical string theory, on Wikipedia it says: Has it been experimentally disproven or are other reasons for its apparent obscurity?

Hi, I was attempting the following question and would appreciate any insight on how others would approach this game theory/probability-type question. Question: You have been chosen to play a game involving a 6-sided die. You get to roll the die once, see the result, and then may choose to...

From what I understood Supersymmetry means there are more particles than we currently know about and they are predicted by (some/all, I do not know) versions of String theory. Is it so important to String theory or can it work without SUSY? Thank you!

Is it easy to combine them or impossible? Is there a tension due to the non-locality found in Bohmian mechanics? Thank you!

The title is my question, and this post is meant to be a place for discussions. I think it is somewhat related to game theory and microeconomics, but I am not sure how to accurately categorize it. Let me give you an example. Let us suppose that Mr. Goose, an ideal person with a national average...

I had been studying this topic from various textbooks and review articles and I am confused about some terminologies and concepts. The question I have typed in this PDF. [Mentor Note -- Added screenshot of PDF contents]

According to Michio Kaku, Nobel laureates have taken both sides towards string theory since some of them accept it and some of them reject it, as he says here (https://www.snowboundbooks.com/book/9780385542746): “Kaku also explains the intense controversy swirling around this theory, with...

I read that he admitter having lost his bet with Preskill when he discovered the ADS/CFT equivalence. I can understand that because CFT is a quantum theory in which evolution is unitary (but there is the problem of measurements). so the black holes can be described with unitary tools. On...

I'm looking for complete and detailed references on constrained Hamiltonian systems and Dirac brackets. While my main interest is electrodynamics, I would prefer a complete exposition of the theory from the ground up. So far, my knowledge about the topic comes from books in QFT, like Weinberg...

The observed diffraction patterns in slit experiments are held up as proof of wave-particle duality. But wave theory diffraction (borrowed from optics - Kirchoff's Laws, Fresenel & Fraunhofer diffraction) don't quite fit the experimental results. There is always some tinkering to get theory to...

https://www.cs.bham.ac.uk/~mhe/papers/omniscient-journal-revised.pdf Might be my favorite article I’ve ever came across I would like to see some interpretations on it to broaden my currently very narrow point of view… Have fun! -oliver

I would like to know if any of you think there's any sort of connection, analogy, or common features between, sets in set theory and wave functions in QT? Wave functions lack trajectories, so do sets. Wave functions also distribute over areas, as sets can do. To my understanding, wave...

Hello, I am looking for a reference which describe perturbation theory with two parameters instead of one. So far, I did not find anything on the topic. It might have a specific name and I am using the wrong keywords. Any help is appreciated. To be clear, I mean I have ##H =...

I know that studying QFT requires understanding Lie Groups and infinitesimal generators as they correspond to symmetry transformations. I want to study or take a course (offered by my university) in QFT in the coming academic year and I have the option to take a abstract algebra course offered...

I read somewhere that Morse originally applied his theory to the calculus of variations. I'm wondering, is this application useful in physics and mechanics, like maybe it sheds light on lagrangian mechanics? Does anyone know?

I was reading brief history of time by hawking and there I stuck on this line “A theory is a model of universe or a restricted part of it and a set of rules that relate quantities in the model to observations we make.” What is it saying? Please elaborate. What are rules and quantities ? Also...

I am not able to understand the following paragraph from my Physics textbook; "The velocity of an object, in general, changes during its course of motion. Should it be described as the rate of change in velocity with distance or with time? This was a problem even in Galileo's time. It was first...

This is the article. This is not the usual sort of study I read but given the last 16 months, I thought I would post and see what pf guys thought of the method and conclusions. The line of best fit in the results seemed a bit random to me but let's see what you make of it...

The astronomer Stacy McGaugh has become the most prominent public promoter of MOND (modified Newtonian dynamics) in recent years, on the grounds that it makes many successful predictions, yet according to the standard "LambdaCDM" (dark energy plus cold dark matter) paradigm, there's no reason it...

Hello everybody! I have to implement a sudoku solver in C ++ taking advantage by graph coloring theory, where each number to insert is a color of the associated graph node. In particular I would like to use the Welsh-Powell algorithm. I find myself in trouble starting with this project and I...

Hello everyone! This is my first post here. I am trying out an argument that I've been sculpting, and I thought this might be a good community where I can get some good feedback. My work is in data driven methods for dynamical systems, and in particular, I am an operator theorist. I have been...

In Sydney Coleman Lectures on Quantum field Theory (p48), he finds : $$D\mathcal{L} = e^{\mu} \partial _{\mu} \mathcal{L}$$ My calulation, with ##\phi## my field and the variation of the field under space time tranlation ##D\phi = e^{\mu} \frac{\partial \phi}{\partial x^{\mu}}## ...

How can i find the angle that a projectile is fired where the maximun height is the same as the traveling distance? I need to find this first in a theoretical way, then i need to confirm this with a simulation. And i need to use only this y=yo+Voyt+1/2gt^2 x=Voxt

The author start of with $\frac{1}{(y+\sqrt{3})^2} - 2 \cdot \frac{1}{1 + y^2} \left( \frac{y}{\sqrt{1+y^2}} \right) = 0$ and arrives at the equation $y = \frac{(1+y^2)^{3/2}}{2(y+\sqrt{3})^2}$ The solution is merely by iterating (use an initial guess value of y, calculate the RHS, then use this...

In the famous book, Gravitation, by Misner, Thorne and Wheeler, it talks about the stress-energy tensor of a swarm of particles (p.138). The total stress-energy is summed up from all categories of particles. Is summation meaningful in the non-linear theory of Einstein gravitation? Thanks.

Summary:: recommend learning materials Although I took galois theory as an undergraduate, I never really studied it. Any recommendations for good resources?

This is purely a historical question that came up in another thread. I always thought LET was the theory put forward by Lorentz that said the Lorentz-Fitzgerald formula contracts objects moving through the aether. Clocks slowed down due to a shortening of their components. Light was an...

Does the law of conservation of mass fail to meet the first postulate of the special theory of relativity(the laws of physics are the same in all inertial frames of reference)?