Theory Definition and 1000 Threads

Homework Statement Spaceship A, traveling past us at 0.7c, sends a message capsule to spaceship B, which is in front of A and is traveling in the same direction as A at 0.8c relative to us. The capsule travels at 0.9c relative to us. A clock that measures the proper time between the sending and...

This is a bit of a philosophical/conceptual question. I've done tons of reading on it, of course, but haven't found anything that makes me go 'ah ha'! I am working steadily through the mathematical formalism of differential geometry, but am struggling to grasp how the things we say in this...

why is the general theory of relativity is so complicated i feel that it's very simple no thing hard in it there is a whole website to make people understand it i read the articles and i didn't found any thing complicated knowing the i am 13 so it should be very hard to understand

Greetings, I'm not a physicist but I have a general interest in physics and cosmology. I was watching the following video where they were talking about how an electron behaves like a wave and its position is not know until it is measured. Then it was explained how the probability of the...

What's the main reason that we cannot unify QED and Gravity or with other foces ?

I would like to know where one may operate with tensor quantities in quantum field theory: Minkowski tensors, spinors, effective lagrangians (for example sigma models or models with four quark interaction), gamma matrices, Grassmann algebra, Lie algebra, fermion determinants and et cetera. I...

I have read about general relativity, quantum mechanics, and physics is general, but I'm looking for a book that goes a little bit more in depth with the math behind the theories (I understand a lot of those equations are going to be complicated). I'm in 10th grade so I'm doing Algebra II this...

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

I was thinking about the immediate ways that physicists had for checking the validity of Newton's theory of gravitation in the time Newton published it. An obvious way would be to check if it predicts what is stated by Kepler's laws. Does anyone know if this was made? Do you know of other tests...

Hi everyone, I am working on a second bachelor's degree in Computer Science, and am hoping to enter a Phd program in fall of 2019. Recently, I have taken an interest in Chaos Theory and was wondering if it is possible to do research in the field in the Computer Science department, or if it is...

The Scientific Method says that if a theory disagrees with observations, it has been falsified (according to Karl Popper). String theory predicts that spacetime is 10-D, but it is observed to be 4-D. This is a wrong prediction by the theory. So string theory is falsified. String theorists then...

bosonic string theory requires 26 dimensions superstring theory requires 10, 9 spatial 1 dimension of time Witten has researched twistor string theory has there been any serious research with (super) string theory written on 4 complex -valued dimensions of spacetime? the additional dimensions...

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

"... quantum mechanics isn’t a complete physical theory in its own right, but rather a framework for the construction of physical theories." I found this in Michael Nielsen's blog and elsewhere. I am perplexed. In what fundamental way does it differ from Newtonian Mechanics (Theory) in not...

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

I am reading "Introduction to Set Theory" (Third Edition, Revised and Expanded) by Karel Hrbacek and Thomas Jech (H&J) ... ... I am currently focused on Chapter 1: Sets and, in particular on Section 3: The Axioms where Hrbacek and Jech set up an axiomatic systems (which they do NOT call ZFC ...

Hi pf, I was wondering about a bubble moving with constant velocity in a liquid, and how the motion affects the mass transfer. Since the viscosity of the gas is significantly smaller than the viscosity of the liquid, the condition ## \tau_{gas} = \tau_{liquid} ## tells me that $$ \mu_{gas} (...

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

What do MHB members think are the best books at an undergraduate or senior undergraduate level on set theory ... Further what are the best books on set theory at a graduate level ... ... Peter

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

Hi! Sorry for my bad English! I don't know much of physics, I know some experiments that show that relativity is real, quantum entanglement, particle and wave duality and so on... So, the only theory that explain all of it mathematically is M theory and the strings, but we can never test it to...

Hey, Theory: The voltage of a thundercloud is too low to ionize air particles and to produce a thunder. Particles of cosmic radiation are the trigger. I calculated whether the voltage of a thundercloud is enough to ionize air particles but the voltage was always to low. So I wanted to know...

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

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

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

How is chaos incorporated into quantum gravity theories, or in theories that incorporate all the known 4 interactions? I don't believe I've seen a thread where chaos theory is discussed in relation to superstring theories or LQG. I've seen some papers and dissertations on quantum chaos and...

I understand that in group theory, a group consists of a set and a binary operation for the elements in the set, and of course all the group axioms. But if we move away from set theory into category theory, is a group defined on a category?

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

https://www.ma.utexas.edu/users/dafr/OldTQFTLectures.pdf I'm reading the paper linked above (page 10) and have a simple question about notation and another that's more of a sanity check. Given a space ##Y## and a spacetime ##X## the author talks about the associated Quantum Hilbert Spaces...

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?

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...