Theory Definition and 1000 Threads

I am retired from a major railroad co. where I worked on electronic weighing equipment. I have an associate of applied science degree from a local university. I have a basic understanding of dc and ac electricity but the explanation I recently read on this forum was the easiest to understand...

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

Looking for a good quantum field theory book. Any suggestions?

I asked my question in overflow, so far with no answers. Perhaps here, I'll get an answer. https://mathoverflow.net/questions/282048/a-lemma-on-convex-domain-which-is-a-lipschitz-domain [admin edit: Below is the actual question posted, so our community doesn't have to follow multiple links:]...

Greg Bernhardt submitted a new PF Insights post A First Idea of Quantum Field Theory - 20 Part Series Continue reading the Original PF Insights Post.

The term 'phase space' is often used in the study of nonlinear dynamics.What is it.

Why there must be a way of including gravity into a quantum theory? What leads scientists to believe that ultimately all the interactions must be subjected to quantisation? Would that be because we describe all other interactions in quantum theory and so we must include gravity on this...

latest paper Ghirardi-Rimini-Weber model with massive flashes Antoine Tilloy (Submitted on 12 Sep 2017) We introduce a modification of the Ghirardi-Rimini-Weber (GRW) model in which the flashes (or collapse space-time events) source a classical gravitational field. The resulting semi-classical...

Homework Statement Anyone know anything about queueing theory? would really appreciate some help. the question goes as follows: The annual S&C Christmas sale is so popular that it is necessary to limit the number of customers who can be inside the store simultaneously; this limit is set at 60...

So Heisenberg's Uncertainty says that we can't know both the position and the velocity of a particle accurately, because measuring one will disturb the particle enough that it's no longer possible to accurately measure the other as it was. So one or the other has to remain unknown to us. This...

I need good books on Molecular Orbital Theory. The book(s) should have the basics, and the level should not be less than graduation. I have Quantum mechanics books, but they don't throw any light on this. My course books are rubbish, only mentioning the name of the theory and some illogical...

This question is more about the maths than the physics. So I am reading the textbook by Bergersen and Plischke, and they get the following: $$m= \tanh [ \beta (qJm+h)]$$ where ##m## is the magnetization, ##q## is the number of nearest neighbours of site ##0##, ##J## and ##h##are the...

Hi, How do you differentiate between fields from a new theory or new fundamental forces? For example. If QM is replaced with a new theory, would the extra dynamics and degrees of freedoms be new forces of nature or can they be non-force or field related, can you give some examples to...

in question 10.19 , i use equation 10.26 to do the question . I have all the values of all variables , except q ( load per unit area) ... Homework EquationsThe Attempt at a Solution How to get q ? It's not stated in the textbook . Is there something to do with the homework =4m ?? I assume q =...

Dear All Can anyone explain for me what is meant by gravitational anomalies in gauge theory? What is the difference between it and gauge anomalies? Thank you

So a gluon in string theory may be an open string whose ends live on one or two branes? These strings have an orientation along the string? Does the orientation change direction if we reverse time, some where I thought I read that one can think of a flow along the string so if you reverse...

I used Newtons method and taylor approximations to solve this equation $$f'''+\frac{m+1}{2}ff''+m(1-f^{'2})=0$$ It solves for velocity of air over a flat plate. The velocity is a constant ##u_e## everywhere except in a boundary layer over the plate, where the velocity is a function of distance...

My son is taking a chemistry class in high school, and he was telling me this morning that their teacher had taught them there was some kind of fundamental distinction between scientific laws and theories. He said the teacher had told them that laws are just fundamental regularities observed in...

Homework Statement ca(0)=1, cb(0)=0 zeroth: ca(t)=1, cb(t)=0 1st: ca(t)=1, cb(t)=i/hbar*integral(H'(t) exp(iwt)) dt ca^2+cb^2=1 to 1st order of H'.: What does it mean? it is evidently not 1 at all. Homework EquationsThe Attempt at a Solution

In quantum gravity, I get 'mixed signals' as regards renormalizability. My state of confusion is being caused, I suspect, by an incomplete understanding of what is covered under t'Hooft's 1972 proof that non-Abelian gauge theories are renormalizable. ( = Nobel Prize 1999). Specifically, some...

Hi everyone, I am trying to learn the underlying number theory concepts behind cryptography, and I was wondering if anyone knows of good resources for learning about number theory as applied to cryptography. I was hoping to practice writing proofs as well. Thanks!

Back in the 1960s, Richard Feynman worked on quantum gravity for a few years, and most of his notes are collected in the 'Feynman Lectures on Gravitation'. His approach was that of a particle physicist applying the principles of QED to GR, notably the concept of gravitons mediating the force of...

Hello, I am studing theoretical physics and i would like to focus my work in string theory, but my fellows say that is a waste of time. ¿Do you think that is worthwhile to spend my time and effort un string theory? Greetings

My main question is regarding whether the membership relation is taken as an undefined concept (as is usually hinted in set theory books) or if the membership relation can be defined within the language of first order predicate theory. Let me describe a method to define the membership relation...

I want to discuss about two apparent contradictions that are on my mind for awhile. 1st: General Relativity predicts no radiation out of black holes. Quantum Mechanics does. If we perform an experiment and see that say, black holes radiates outwards, does that mean General Relativity is wrong...

I get a gist of how electric charge comes about in string theory here, https://physics.stackexchange.com/questions/5665/electric-charge-in-string-theory How much needs to be amended to the above answer to understand how color charge comes about in string theory? I assume there are interesting...

I'm studying Dynamo Theory, and have just a few questions. Today's theory says that currents in the molten outer core of the Earth give rise to magnetic fields. Now it would seem that the theory does not mean "molten iron currents", since together that is an electrically neutral substance, but...

Hi. Is there some kind of measure theory generalized to uncountable unions? Of course one needs to take care how to make sense of sums over an uncountable index set. I was thinking about following formulation of the additivity property of the "measure": $$\mu\left(\bigcup_{i\in\ I}...

I'm curious about something. And most of you are probably going to click away as soon as I say, or type this, I guess. But for those of who haven't, thanks. In the Iron Man comics, movies and tv shows the arc reactor keeps Tony Stark from lethal heart damage and keeps the Iron Man Armour...

What is the force acting on an object according to general theory of relativity? If there is a such a force, can we predict the motion of an object in general relativity just using the modified Newtons laws of mechanics i.e using relativistic mass of an object instead of rest mass ?

Hey there! I just want to ask if there are any books you would like to recommend that helps in studying high energy physics and HEP data analysis? Also can you recommend a good book for group theory and symmetry? I would be glad if you have links to free downloadable books. Thanks in advance!

What if the mystery of unified theory is solved (i.e we found a TOE)? What would be the next mystery in physics(will their be any or will the context of physics would be completed(i don't think so,what do you think?).

Urs Schreiber submitted a new PF Insights post Introduction to Perturbative Quantum Field Theory Continue reading the Original PF Insights Post.

Homework Statement Prove that if ##A \subseteq B##, then ##\bigcup A \subseteq \bigcup B##. Homework EquationsThe Attempt at a Solution This is a simple problem, but I just want to make sure I am writing out the proof correctly: Suppose that ##A \subseteq B##. We want to show that ##\bigcup A...

Does General Relativity predicts that in the early universe vacuum energy was converted into matter? How does it relates to the Inflation Theory by Allan Guth? I'm asking this because I remember reading in a book on GR that there are ways of calculating the total amount of energy in the...

Hey so from my understanding of Einsteins theory of relativity the closer you travel to the speed of light the slower time is for you, is that right? if it is right does that give to reason that there could be a critical speed past the speed of light for which time for the object traveling at...

Homework Statement Assume that ##x## and ##y## are members of a set ##B##. Show that ##\{ \{x\}, \{x,y\} \} \in \mathcal{P} \mathcal{P} B## Homework EquationsThe Attempt at a Solution I know that ##\{ \{x\}, \{x,y\} \} \in \mathcal{P} \mathcal{P} B## iff ##\{ \{x\}, \{x,y\} \} \subseteq...

Physicists had success in developing a relativistic quantum mechanics, also Quantum Field theory. I wonder why it's not the same with a quantum gravity theory. I suppose this is mainly because we do not have good emphirical information from a place where Einstein's theory fails: black holes...

Is there any theory law explaining the nature of space and describing what is space and what happens to space when some event take place in space.

Hello, I have read somewhere that the next major step in physics will be unifying general relativity with the quantum theory. Does anyone know about such? I wanted to know a bit more. I have read about such in the book by Stephen Hawking "A Brief History of Time". Thanks, I. P.S. My apologies...

Homework Statement Show that ##\bigcup \{\mathcal{P} X : X \in A \} \subseteq \mathcal{P} \bigcup A## Homework EquationsThe Attempt at a Solution Suppose that ##c \in \bigcup \{\mathcal{P} X : X \in A \}##. Then by definition this means that ##\exists a \in A## such that ##c \in \mathcal{P}...

I know two essential points where General Relativity plays a central role in String Theory: i) definition of the theory using a target spacetime with some Riemannian background metric in the Polyakov action and ii) recovery of the Einstein field equations as conditions regarding conformal...

Homework Statement In analogy to the Bohr theory of the hydrogen atom, develop a quantum theory of Earth satellites, obtaining expressions for the orbit radius, r_n, and the energy, E_n in terms of the quantum number n and other relevant parameters. Use the "Old" Quantum Theory. A satellite of...

Just out of curiosity, what would a proof of ##a^m a^n = a^{m+n}## amount to? Of course obviously if you have n of one thing and m of another you get m+n, but I am wondering if this is rigorous enough, or if you need induction.

Hello all; this my first time ever taking physics, and I am in dire need of some help with homework. I've had an attempt at part A (please take a look and provide feedback), but have no clue where to even begin on part B (how would I go about calculating questions 5, 6, and 7, to be precise?)...

What's the difference between relativistic quantum mechanics and quantum field theory? In principle, my guess is that to do the former, one needs to express the Hamiltonian in a relativistic, Lorentz invariant, form, because it seems to be the only frame-related term in the wave equation. (Is...

I have some questions about scalar field Lagrangians, using the box notation defined as \Box \equiv \frac{\partial^2}{\partial t^2} - \nabla^2 . It's a basic, perhaps silly issue, but somehow I've managed to sweep it under the rug for a long time. So, usually, the Lagrangian of a free scalar...

Hello! Recently I found this article: http://quantum-journal.org/papers/q-2017-07-14-13/pdf/ Being familiar with some basis of quantum formalism, I, nevertheless, experienced several difficulties with understanding of the theorem described in this paper. I would really appreciate if someone...

And if I can extend this further, for liquids?

In the multiverse theory, I keep on hearing that our observable universe is one of many universes. Is that saying that our universe ends at the point we can no longer see it - at the end of the observable universe. That would mean that the Earth is the literal centre of our universe. Am I...