Theory Definition and 1000 Threads

<< Mentor note -- posts broken off from an Insights comment thread >> 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 each other...

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.

Homework Statement i am stuck on part d , see below Homework Equations parts a to c are fine polyakov action: ## \frac{1}{2} \int \frac{1}{e(t)} \frac{dX^u}{dt}\frac{dX_u}{dt}-m^2 e(t) dt ## EoM of ##e(t)##: ##\frac{-1}{(e(t))^2} \frac{dX^u}{dt}\frac{dX_u}{dt}-m^2=0## [1]you plug the EoM...

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...

Hi guys! My question is about the diffusion coefficient of the mixture of gases. Consider two gases in thermal equilibrium (Maxwell velocity distribution) having different densities n1 and n2. Let's suppose that the molecules are rigid spheres with diameters d1 and d2 and masses M and m...

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...

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...

hi, when we talk about heavy meson, its momenta is defined as label and residual momenta. if the second quark's mass is almost comparable to heavy quark, then would the scaly of residual momenta be changed? I mean can it be lambda instead of lamda square in case of comparable mass?

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.

Homework Statement I have the following definition of the space-time coordinates Homework Equations Working in a certain gauge we can also do: From which we can find: Where ##N_{lc} ## sums over the transverse oscillation modes only. The Attempt at a Solution [/B] MY QUESTION: I...

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?