Theory Definition and 1000 Threads

Urs Schreiber submitted a new PF Insights post Why Higher Category Theory in Physics? Continue reading the Original PF Insights Post.

Hello Please see attached page from a textbook. Can someone explain why H = 4f.le.vo^2/2d.g and why delta H is given by the expression in the book? Note that the figure it mentions is on the top of the page. I have tried for days here. Thanks

Are there any good examples of how group theory can be applied to solve multivariate algebraic equations? The type of equations I have in mind are those that set a "multilinear" polynomial (e.g. ## xyz + 3xy + z##) equal to a monomial (e.g. ##x^3##). However, I'd like to hear about any sort...

Hello, I would appreciate it if someone would suggest some Quantum Field Theory books that an advanced undergraduate could read. Thank you!

Dear all, recently I'm reading up some string/M-theory, especially the role of branes, because I'm writing a popular science book in Dutch. Every textbook states the issues one encounters when you try to quantize p-branes for p>1, as is discussed e.g. here...

I read Lucien Hardy's paper whose tittle was "Quantum Mechanics, Local Realistic Theories, and Lorentz Invariant Relativistic Theories". There, he argued that lorentz invariant observables which involved locality assumption contradict quantum mechanics. I tried to follow his argument, but got...

Homework Statement If someone on a spaceship looked at a clock on Earth traveling at 99.5% the speed of light what would they notice? Homework EquationsThe Attempt at a Solution Would they notice that time is faster on earth? Is my assumption correct

can string theory reproduce hawking radiation in non-extremel black holes in 4D? i.e physically realistic black holes. do they exactly match hawking's calculations? what is the interpretation of hawking radiation in string theory?

I was quite distraught knowing that chegg.com has no textbook solutions for "measure theory" even though it has four for abstract algebra. Could it be that the textbooks are called something else?

Why do we need perturbation theory in quantum mechanics?

Hi all. I am looking for a book in Quantum Field Theory, not for the first read. I have already studied it for university purpose, but now i would like to study the subject again from a book to cover holes and have a deeper understanding before starting a possible PhD. I heard about Srednicki...

I'd really like some help in answering the next question...anything that might help will save my life: F is defined this way: F:A→B where A,B⊂P(N) and P(N) is the power set of the naturals. Let S,R∈A such that S is a proper subset of R if and only if F(S) is a proper subset of F(R) My question...

Any pointers about where to get information and perhaps pictures of the different whiteboards shown in Big Bang Theory? I am particularly interested on the season where Sheldon abandons string theory; the boards for this chapter (155, season 7 ep 20, aired 10th April 2014) seem to show some...

I was under the impression (false one appraently (I read Lubos Motl answer in stackexchange)) that Schwinger's theory which is covered in his three volumes called "Particles, Sources and Fields.", is really only a different interprataion to QFT, but the end results are the same. Now I read the...

hi, initially when I saw these statements , I got really amazed, and now I endeavor to find the proofs of these statements, bu I would like assure you of the fact that there are very very very few sources which evaluate M/G/K or M/G/infinite queue, mostly sources prefer to handle the subject of...

Homework Statement Consider the 3 following Scenarios: 1. 2. rms value of line voltage is 208 V Three equal impedances, 60 +j30 W each, are delta-connected to a 230-V rms, three-phase circuit. Another three equal impedances, 40 +j10 W are wye-connected across the same circuit at the same...

Note this isn't actually a homework problem, I am working through my textbook making sure I understand the derivation of certain equations and have become stuck on one part of a derivation. 1. Homework Statement I am working through my text (Quantum Mechanics 2nd Edition by B.H Bransden & C.J...

Homework Statement Let S= {e^2*i*pi/n for all n in the natural numbers} and let F=Q Is F:Q 1) algebraic? 2) finite? 3) simple? 4)separable? Homework EquationsThe Attempt at a Solution 1) Every element in S is a root of x^n-1 and every element of a in Q is a root of x-a, and thus I think...

Homework Statement Let K be the splitting field in C of the polynomial g(X) = x^3 + 4 over Q a) determine the degree of the extension K:Q, b) determine the structure of the galois group Gal(K:Q) c) Using the Galois correspondence, determine all subfields of K d) Let r be an element of K and let...

Homework Statement Let's look at Q(a,c):Q where a is the third real root of 2 and c is a primitive cube root of unity. Then this extension is Galois and it's Galois group is isomorphic to ##D_3=S_3##. The proper subgroups of the Galois group are thus <(12)>,<(23)>,<(23)>,<(123)>. Let (12)...

I've recently read (portions of) the paper "QFT as pilot-wave theory of particle creation and destruction," available here: http://xxx.lanl.gov/pdf/0904.2287v5 This paper has been mentioned in a number of other threads, but I have a different question (not as an expert, unfortunately). The...

Classical fields are usually constructed using a collection of classical harmonic oscillators, e.g. masses connected to springs. The energy of a classical harmonic oscillator is proportional to the amplitude squared. QFT uses quantized versions of those same classical fields. But, in the...

Hi all, I'm about to buy the first volume of the series by Weinberg, but I'm a little worried about the edition, see I have a lot of requisites for a book before buying it. I've seen in the library the old hardcover edition and it looks fine for me: it's not written too small and the book even...

Could someone explain or point me in the right direction on how string theory explains the leptons? TIA, Kevin

Surly the variable speed of light is a dead dog, this article says it is not, and the theory can be tested But some researchers have suggested that the speed of light could have been much higher in this early universe. Now, one of this theory's originators, Professor João Magueijo from Imperial...

I was doing some reading on String Theory...I'm not a scientist, but i enjoy it (so forgive me if my question is stupid) and i was wondering: Being time a dimension, could it be the dimension the strings exist in? And interaction between all particles and all forces determine how they vibrate...

Wick's theorem allows one to write a free theory time-ordered ##n##-point correlation function as a product of free theory time-ordered ##2##-point correlation function. The procedure involves the pairwise Wick contraction of fields such that external fields are not paired up each...

Hello I have not understand this.

Consider the following time-ordered correlation function: $$\langle 0 | T \{ \phi(x_{1}) \phi(x_{2}) \phi(x) \partial^{\mu}\phi(x) \partial_{\mu}\phi(x) \phi(y) \partial^{\nu}\phi(y) \partial_{\nu}\phi(y) \} | 0 \rangle.$$ The derivatives can be taken out the correlation function to give...

What knowledge based are needed in relativity theory, not general public science education level, but true and mathematically. I have calculus and linear algebra education in university, Chinese engineering degree, quite rigorous in math education. Can I actually pick up relativity theory myself...

Hi :) Does the 'inner space' and 'inner particle physics' which Mr. Lisi refers to in his TED Talk at Maui in 2013 refer to the 8 dimensional maximal tori within E8 and how they function? TED Talk at Maui in 2013 (video): Thanks.

Greetings all :) I would like to know please how antiparticles fit into Garrett Lisi's E8 Theory. Thanks!

Hello, I have a question about the the difference between mathematical physics and theoretical physics in general and about the difference between the MSc Theoretical and Mathematical Physics courses at Edinburgh in particular. I am planning to apply, however I am not sure which of the two...

Hello I am interested in the Frenet-Serret Formulas (theory of curves?) relationship to theory of surfaces. 1) Can one arrive to the Frenet-Serret Formulas starting from the theory of surfaces? Any advice on where to begin? 2) For a surface that contain a space curve: if the unit tangent...

This is going to sound really strange, but I don't want to have this question inside of me and never ask it. I love business/economics/game theory. However, the subject I've studied the most in my life at this point is physics. The question of what I want to write about for my PhD thesis is...

I have read Average translation kinetic energy is 1/2RT per degree of freedom and Average translation kinetic energy for an ideal gases is 3/2RT.How? Does it imply f=3 for all ideal gases?

Homework Statement I wanted a proof that an object's center of gravity is the same as the center of mass by breaking the object into tiny pieces and then integrating over them. Homework Equations Well, the gravitational equation g=Gm1m2/r^2 The Attempt at a Solution I tried using some calc...

Hi I'm in high school but what I'm going to ask you is probably being teached in college. General formula: p=(2/3)*(N/V)*Ek p- pressure N- amount of molecules V- volume of the container Ek - AVERAGE kinetic energy I've been told by my physics teacher, that 2/3 constant factor in kinetic theory...

The theory of a complex scalar field ##\chi## is given by $$\mathcal{L}=\partial_{\mu}\chi^{*}\partial^{\mu}\chi-m_{\chi}^{2}\chi^{*}\chi.$$ Why is it not common to include a factor of ##\frac{1}{2}## in front of the complex ##\chi## kinetic term? What is the effect on the propagator of...

Given the theory $$\mathcal{L}=\frac{1}{2}(\partial_{\mu}\phi)^{2}-\frac{1}{2}m_{\phi}^{2}\phi^{2}+\partial_{\mu}\chi^{*}\partial^{\mu}\chi-m_{\chi}^{2}\chi^{*}\chi+\mathcal{L}_{\text{int}},\qquad \mathcal{L}_{\text{int}}=-g\phi\chi^{*}\chi,$$ the time-correlation function ##\langle \Omega |...

Hello. I'm studying a course of the Quantum Field Theory and I got a question in a canonical quantization of a scalar field. I don't write a full expression of the field quantization here but the textbook said terms with ei(p⋅x - Ept) are associated with an incoming particle and terms with...

http://mathhelpboards.com/pre-algebra-algebra-2/find-value-squareroot-3-using-graph-drawing-suitable-straight-line-19973.html I guess I found a method to obtain the square root of any number using the above graph. $x^2-2x-3$ What I did to find the square root of 3 was replace $x^2$ with the...

An interesting paper has appeared on nature.com: http://www.nature.com/articles/srep32815 The abstract: I expect this to spawn plenty of pop science claims about "scientists say we can reverse entropy". But the paper itself looks like a good discussion of how the second law actually works...

I am reading D. J. H. Garling: "A Course in Mathematical Analysis: Volume I Foundations and Elementary Real Analysis ... ...At present I am focused on Chapter 1: The Axioms of Set Theory and need some help with Theorem 1.2.2 and its relationship to the Separation Axiom ... ... The...

I am reading D. J. H. Garling: "A Course in Mathematical Analysis: Volume I Foundations and Elementary Real Analysis" ... ... At present I am focused on Chapter 1: The Axioms of Set Theory and need some help with Theorem 1.2.2 and its relationship to the Separation Axiom ... ... The...

Let's consider superstring theory on a 10 dimensional Minkowski background. And assume there is a D3-brane on which the open strings end and closed strings wander around freely in the background. I want to know, in what limit this gives a supergravity theory in which I can study it by using the...

I am new to this forum. I am an electrical engineer designing frequency synthesizers for electronic test and measurement equipment. I have a design problem and I think that number theory could help me solve it. I'm not a mathematician, so I will state the problem the best I can. Definitions...

Hello I am little bit confused about one topic on theoretical Physics and that is If we want to describe our Quantum world (example atoms in metal) then should I use Quantum field theory or Quantum mechanics?

Is supersymmetry part of string theory or does it have a place in the standard model

In another math thread https://www.physicsforums.com/threads/categorizing-math.889809/ several people expressed their opinion that, while statistics is a branch of applied mathematics, the probability theory is pure mathematics and a branch of analysis, or more precisely, a branch of measure...