Weinberg Definition and 86 Threads

Editing... Please be patient! I came across this difficulty comparing several versions of the Feynman rules for QED. I traced the problem back to a statement of Weinberg's in "The Quantum Theory of Fields (Vol 1)", Chapter 5, page 195. Weinberg is busy setting up for deriving free field...

According to (5.1.6) $$U_0(\Lambda,a)\psi_\ell^+(x)U^{-1}_0(\Lambda,a)=\sum\limits_{\ell \bar{\ell}}D_{ \ell \bar{\ell} }(\Lambda^{-1})\psi^+_{\bar{\ell}}(\Lambda x+a).$$ (5.1.6) According to definition 5.1.4: $$\psi^+_{\bar{\ell}}(\Lambda x+a)=\sum\limits_{\sigma n}\int d^3{\bf p }...

Summary: Suppose that observer ##\mathcal{O}## sees a ##W## boson (spin-1 and ##m > 0##) with momentum ##\boldsymbol{p}## in the ##y##-direction and spin ##z##-component ##\sigma##. A second observer ##\mathcal{O'}## moves relative to the first with velocity ##\boldsymbol{v}## in the...

If ##\partial_{\alpha} J^{\alpha}(x) = 0## then ##Q \equiv \displaystyle{\int} d^3 x J^t(x)## is time-invariant. To show that if ##J^{\alpha}(x)## is a four-vector then ##Q## is also Lorentz-invariant, he re-writes it as \begin{align*} Q = \int d^4 x J^{\alpha}(x) \partial_{\alpha} H(n_{\beta}...

I saw a tweet from Lawrence Wright that Steven Weinberg passed away. I didn’t see any related news stories. Can anyone confirm? Not sure where to post this. Obviously he was one of the greatest of a generation.

Steven Weinberg wrote a book again. Did anyone read it? https://www.amazon.com/dp/1108841767/?tag=pfamazon01-20

https://arxiv.org/abs/2010.15621 Superselection of the weak hypercharge and the algebra of the Standard Model Ivan Todorov [Submitted on 29 Oct 2020] I haven't had time to study this paper yet. But a few curiosities: It talks about Clifford algebras. But in fact it builds on work due to...

I think Weinberg is quite clear about this: On p.87 of the second edition of his quantum mechanics book, he says, and on p.88: After having discussed decoherence, he says on p.92: For the instrumentalist approach (apparently your view of the matter), he states on p.92f this drawback: Then...

I have a lot of questions as usually, but must begin with the difficult to understand moment which have started my explorations of the Kepler's second law. In the book of Steven Wainberg "To Explain The World", in the technical paragraph twenty one I have found the next formula which represents...

Does someone know of an official or unofficial errata for the above book of Weinberg?

Recently I've started reading Weinberg QFT, Vol 1, to introduce myself better to quantum field theory, after finishing courses in qft at the university. Reading through the second chapter, I've found myself confused by his treatment of degenerate multiplets in Appendix C. Here is the equations...

Summary: A link to excerpts from a paper behind paywalls I just found this link featuring excerpts from a 2017 paper by Steven Weinberg on the measurement problem, which I couldn't read before, it being behind paywalls...

Hi, I stumbled upon an identity when studying tensor perturbations in cosmology. The formula states that $$ \int d^2\hat{p} f(\hat{p}.\hat{q})\hat{p}_i \hat{p}_k e_{jk}(\hat{q}) = e_{ij}(\hat{q})/2 \int d^2\hat{p} f(\hat{p}.\hat{q})(1-(\hat{p}.\hat{q})^2), $$ where ##e_{ij}(\hat{q})## is any...

in this equation ##J_{ \overline{ \sigma } \sigma }^{(j)}## what are they sigma bared ? Thanks <mentor edit Latex>

Hi, Two questions. Are Weinberg's "Lectures on Quantum Mechanics" a bridge to his QFT books? I read that his QFT volumes are excellent books, but not for the beginner. So, if I want to begin QFT, can I choose his "Lectures on Quantum Mechanics" for a graduate level QM book, and make the...

(Weinberg QFT, Vol 1, page 68) He considers Mass-Positive-Definite, in which case the Little Group is SO(3). He then gives the relations Is it difficult to derive these relations? I'm asking this mainly because I haven't seen them anywhere other than in Weinberg's book. Also, I'm finding...

Homework Statement specific lagrangian is defined. Have to get a equation of motion Homework Equations [/B] Lagrangian is defined as The Attempt at a Solution [/B] eq of motion that i drive like i guess term of f(x) have to vanish or form a shape of curl. but it didn't be clear...

I wondered if anyone might have something to say about how a 'Ray Transformation' should be defined and also point out what Weinberg means by his 'ray transformations T', see Weinberg, Reference 1, pg 91. Should a ray transformation be an equivalence class of operators? I have started to try to...

New member here, who decided four years ago to look into quantum gravity. My original intentions were pure: really, how hard could quantum gravity be? My current intentions are: to empathize with those who have approached this subject, spent hours, days, months pulling their hair out, yet...

The Weinberg angle ##\Theta_{W}## is commonly expressed as $$\cos\Theta_{W} = M_{W}/M_{Z}.$$ Can the Weinberg angle ##\Theta_{W}## be expressed in terms of the Higgs mass and the mass of the W boson as $$\sin^{2}\Theta_{W}= m_{H}/M_{W}?$$

Steven Weinberg has lately been critical of QM. He now also has a technical paper out called 'Lindblad Decoherence in Atomic Clocks', available on arxiv. Here is the abstract: It's a short paper (6 pgs of text), arguing for objective collapse (a la GRW/Diosi-Penrose/etc) instead of...

http://www.nybooks.com/articles/2017/01/19/trouble-with-quantum-mechanics/

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...

Hi all, and thanks in advance. I am an old guy learning GR for fun. Reading Weinberg's "Gravitation and Cosmology". PhD in math 1998, so I read all books like I read math books: every character, every word, every line, every page extremely carefully. I am stuck on the stupidest thing. On p.72...

Homework Statement Suppose that observer \cal O sees a W-boson (spin one and mass m \neq 0) with momentum \textbf{p} in the y-direction and spin z-component \sigma. A second observer \cal O' moves relative to the first with velocity \textbf{v} in the z-direction. How does \cal O' describe the...

Hi everyone, Weinberg uses spatial translation invariance to derive the momentum operator. But the way he does it puzzles me. Here is an excerpt of the book. Equation 3.5.1 is the definition of the unitary operator ##U(x)## for translation invariance: $$U^{-1}(x)XU(x) = X+x,$$ with...

Steven Weinberg has made what he calls a "modest proposal": http://arxiv.org/abs/1405.3483 Quantum Mechanics Without State Vectors Steven Weinberg (Submitted on 14 May 2014) It is proposed to give up the description of physical states in terms of ensembles of state vectors with various...

Hello everyone, I don't get how the second-order derivative ##\partial^2 S/\partial x_i \partial x_j## of the phase S arrives here. If one performs a power series expansion of the Hamiltonian around ##\nabla S##, then I do get where the first term ##A## comes from, but then adding higher-order...

Hi everyone, I'm a bit puzzled by the derivation of this formula, in particular since the definition of the "overbar" notation is a bit fuzzy (see Formula 6.4.1). Does anyone have a more formal definition of the correlation function in this setting (I know what a CF is, in general)? In this...

Hi, I don't get how one goes from 3.6.17 to 3.6.18 on Page 80 (Galilean invariance) regarding the zeroing of boost generator commutators. I do get that this is a special case of the Lorentz invariance (which I understand), but this particular step eludes me. Thanks for your help.

Weinberg 5.9.34 "[...] Using this together with Eq. 5.9.23 gives the general antisymmetric tensor field for massless particles of helicity ##\pm 1## in the form ##f_{\mu\nu} = \partial_{ [ \mu } a_{ \nu ] }##. Note that this is a tensor even though ##a_{\mu}## is not a 4-vector." Not a four...

In QFT vol 3 of Weinberg write:''For d=11 the spin 2 graviton representation of little group O(9) is a symmetric traceless tensor with 9x10/2-1=44 independent components:there is one 2+(-)i3,2+(-)i3 component with J23=+(-)2, seven2+(-)i3,k components with J23=+(-)1; and twenty eight k,l...

http://www.andyross.net/weinberg.htm In number 4 Steven Weinberg said that Traditional religions generally rely on authority, such as a prophet or a pope or an imam, or a body of sacred writings. Scientists rely on authorities of a very different sort. If I want to understand some fine point...

I have just finished reading (devouring) Steven Weinberg's _The First Three Minutes_ 1988 update, Basic Books. http://search.library.duke.edu/search?id=DUKE000806677 I found it both enjoyable and edifying. Clearly there has been a lot of water over the dam since its 1977 publication and 1988...

I'm having problem in deriving 23.6.11 from Weinberg's-Quantum Theory of fields... We have: \psi_f \rightarrow \exp (i a_f \gamma_5) \psi_f, f denoting the flavor. Then for the mass term lagrangian he writes: L_m = - \frac{1}{2} \sum_f M_f \bar{\psi}_f (1+ \gamma_5) \psi_f - \frac{1}{2}...

hi guys, this is the first time i post a thread. I have an issue on proving the scalar products for arbitrary momenta. Can anyone help me ? I always end up with N(p)N*(p')(D(L^-1(p)L(p'))_rowrow'detla I have been spending hours on proving this..still i can't prove it...

Is it a good choice to read these books first or there's a better way. My professor recommended me these books but as I started them they had bulk of maths and really matter was not that understandable on my first try. I am an engineer. I read physics in free time I can get , so shall I go ahead...

Homework Statement Basically I wanted to see if anyone would be willing to give me the solution to the 4th problem of the Weinberg textbook on quantum field theory. The exact question in the book is "Derive the perturbation expansion (3.5.8) directly from the expansion (3.5.3) of old-fashioned...

I am planning to start self studying GR and, before choosing a better book to use, I have been flipping through an old copy of Weinberg's book (Gravitation and Cosmology) and came upon something that is not making sense to me. I assume that I am missing something obvious. When he talks about...

Please demonstrate for me that: In any theory,the propagator \Delta_{f}(k) of a field of type f has asymptotic behavior: \Delta_{f}(k)~k^{-2+2sf} where sf is ''spin'' of the field.For massive fields of Lorentz type (A,B) then sf=A+B. (However,dropping terms that because of gauge...

This is discussed in Weinberg's Quantum Theory of Fields, in the chapter on Relativistic Quantum Mechanics. The point I am somewhat confused about occurs on page 63 - 64, if you have the book. He operates on a single particle state with the unitary homogeneous lorentz transformation...

I am following up Weinberg Cosmology book, but I have one question. In chapter 3.1, we have Eq (3.1.3) and (3.1.4) s(T) = \frac{\rho(T) + p(T)}{T} T\frac{dp(T)}{dT} = \rho(T) + p(T) In Eq (3.1.5), we have the Fermi-Dirac or Bose-Einstein distributions. n(p, T) = \frac{4 \pi g...

Author: Stephen Weinberg Title: Lectures on Quantum Mechanics Amazon link: https://www.amazon.com/dp/1107028728/?tag=pfamazon01-20

Author: Steven Weinberg Title: The Quantum Theory of Fields Amazon Link: https://www.amazon.com/dp/052167056X/?tag=pfamazon01-20 Prerequisities: Contents:

I have been following Winberg Book, volume I. I am currently working on chapter 5.8, the CPT theorem. I have two questions in this chapter. First one is, why can we choose the phases so that all particles \zeta \xi \eta = 1 I tried to solve this problem by assuming that this is...

Hello ! My books defines the photon and Z0 boson as: for the short read : I have 3 questions Are B0 and W0 orthogonal or the photon and Z0? How do you derive that tg(t) = g'/g (with g' corresponding to B0, g to W0) How do you derive that e = sin(t) ? The long read: Also W0 couples with g...

Hi All, I've been watching the Weinberg youtube video: and I have two questions. 1) He says at some point that although there is a symmetry which wants the standard model particles to be massless (and which is then spontaneously broken by the Higgs mechanism), this symmetry does not...

Homework Statement In a population on fish, 40 have red eyes and 260 have blue eyes. Allele for red is dominant over blue alleles. Use hardy Weinberg principle to calculate the frequency of the white and red allele. Homework Equations p2 + 2pq + q2 = 1 q + p = 1 The Attempt at a...

Has anyone studied the book "The First Three Minutes" written by Steven Weinberg? In this book the author stated the early universe conditions as: "At about one hundredth second after the big bang, the temperature of the universe was about a hundred thousand million degrees Centigrade. As the...

Hi, I've read a lot of posts about how Weinberg describes the S-matrix invariance in his book, but none of theme answered my questions. At page 116, sec 3.3 - "Lorentz Invariance" of Quantum theory of fields vol.1 Weinberg says: "Since the operator U(\Lambda, a) is unitary we may write...