Weinberg Definition and 86 Threads

Weinberg in his 1st book on QFT writes in the paragraph containing 2.5.12 that we may choose the states with standard momentum to be orthonormal. Isn't that just true because the states with any momentum are chosen to be orthonormal by the usual orthonormalization process of quantum mechanics...

I have a few questions about the contents in Weinberg, the Quantum Theory of fields Vol1. First one : At the end of page 77(Sec 2.6), we got -ζ_σ=ζ_σ±1. From this, we could refer that ζ_σ should be proportional to (-1)^σ. But, in the next page, Weinberg concluded that ζ_σ =ζ(-1)^(j-σ). As I...

Alright, so excuse my ignorance, but I have no idea why the choice he uses for boosts is "convenient" Just to make sure everyone is on the same metric etc etc. Weinberg uses (-,+,+,+) with gamma defined traditionally and God-given units He requires that transformations..(oh my,,,how...

Homework Statement He says "choose the states with standard momentum k to be orthonormal", does he mean for example state with momentum (0,0,0,M1) and with momentum (0,0,0,M2) to be orthogonal or states with the same k^2 to be orthogonal if they have different k? Also where he calculates in...

Hi, a few lines below equation (3.1.5) Weinberg writes: "The transformation rule (3.1.1) is only possible for particles that for one reason or another are not interacting." I thought a lot about it, but don't see any possible reason. Can you help please? After a few lines he defines...

In <Cosmology> written by Weinberg, in page 109, it says that \epsilon=\alpha_{B}T^4+\frac{3}{2}n_{B}Nk_{B}T p=\frac{1}{3}\alpha_{B}T^4+n_{B}Nk_{B}T \alpha_{B}T^4is the average energy density of black-body radition, then what does \frac{3}{2}n_{B}Nk_{B}Tmeans? the energy density of...

In Weinberg QFT vol 1, page 69, when deriving the little group structure for the case of zero mass can anyone explain the following: The transformation W by definition leaves k^{\mu}=(0,0,1,1) invariant, i.e. W^{\mu}_{\nu}k^{\nu} = k^{\mu} . Why can you immediately deduce from this that for...

I'm trying to understand induced representation / little group stuff in Weinberg QFT vol. 1 chapter 2 (around page 64, 65, 66). So is this the correct way of thinking about it: We have the Poincaré group of symmetries; we wish to know how to represent operators (derived from these symmetries)...

Homework Statement the frequency of the dark form (dominant) of mice is =.15 and the light form has 10% more mortality rate than the dark form mice. find the frequency of p and q for the next generation Homework Equations i am stuck here because i don't know the original number or i...

Is there any cosmology book out there that is up to date, more substantial than Linder, but less so than Weinberg? I own Linder and have read it, and it's fine, but it only goes so far. I have a pretty firm grasp of GR, but if I bought Weinberg I think the chances I'd wade through it are slim...

Hi, and thanks in advance for reading this. I've been bashing my head on my desk for days on this now. My problem is the first sentence of the paragraph after equation 32.1.5 in Weinberg III: "... note that for a given $Z_{nm}$ to be non-zero, since it is a scalar all of the $\sigma$s in...

The title is my question. What are the relative merits of the two books? I've only read part of Peskin & Schroder, and one of my complaints is that the book doesn't cover canonical quantization of QED which I need for my course. I don't know much about Weinberg's book, but it seems to be have...

Until recently, I thought that any theory that contains non-renormalizable interactions in the power-counting sense (i.e. those whose couplings have negative mass dimension) must be an 'effective' theory that necessarily breaks down at some energy. However, I've been looking at Weinberg's QFT...

Hello ! In an article (Einstein's mistakes) published in 2005 in "Physics Today" by Steven Weinberg, he says: """""" even so, einstein would still probably be unhappy with today's theories, because they are not unified with gravitation and because matter - electrons, quarks and so on...

First off I am a physics instructor at a local school and am trying to learn QFT from books. So this is not homework for a class at all. I am trying to re-derive Eq. 2.5.14 from the above equation to it and it is in fact that "above" equation which is my hurdle. It is on pg. 66 for those of...

I have been able to read through up to here (middle of pg. 60). The instructions given are not clear: (I arranged the text so as to be easier to read on the page here.) "Next, let's apply rules (2.4.8), (2.4.9) Eq. (2.4.8): U(\Lambda,a)J^{\rho\sigma}U^{-1}(\Lambda,a) =...

Mtd2 spotted this paper by Steven Weinberg that just went on arxiv. http://arxiv.org/abs/0911.3165 Asymptotically Safe Inflation Steven Weinberg 13 pages (Submitted on 16 Nov 2009) "Inflation is studied in the context of asymptotically safe theories of gravitation. It is found to be possible...

Excellent talk at clear basic level. To save time, one can start at minute 7:00. That's where he discusses the standard model and then the Higgs, and then moves on to what else might be found. http://www.ustream.tv/recorded/2384517 I gather the talk was given this morning, 19 October, at a...

Can anyone explain to me why in going from (2.4.7) to (2.4.8) the indices on the LT are arranged in the way they are. Why is mu the first index (lower) and rho the second (upper)? Could they have been arranged in any other way? From the rules that I know, they can.

The link to the video is here: http://motls.blogspot.com/2009/07/cern-weinberg-about-asymptotic-safety.html

Interesting that Steven Weinberg should cite Asymptotic Safety work by Martin Reuter and Frank Saueressig. And another UV-safety article by Roberto Percacci, that appears in Oriti's new book Approaches to Quantum Gravity: Towards a New Understanding of Space, Time, and Matter. Here's a bit...

Hi there, I'm giving lectures on SUSY following Weinberg III. Here's my problem: Is (27.1.12) correct? I mean, shouldn't the \Omega dependent factors be swapped? Otherwise \Phi^\dagger \Gamma is not gauge covariant! My understanding is that the extended gauge transformations of (27.1.11)...

Hardy Weinberg problem please help If 4% of a population in Hardy Weinberg equilibrium expresses a recessive trait, what is the probability that the offspring of 2 individuals who do not express the trait will express it? I did what I could and got an answer. My work is below. Could you...

I'm completely confused by page 202 of Weinberg's QTF, Vol.I. In particular: I can't find "Hankel" anywhere on PF, and wikipedia is no real help. Surely integral (5.2.8) doesn't converge (the integrand oscillates between ±1)? In fact, I think it's -∞. :redface: So how can it be a...

HELP on Hardy Weinberg Problem! Homework Statement the allel for unattached earlobes is dominant over the allele for attached earlboes. in a population of 500 individuals 25% show the recessive pheontype. how many individuals woul you expect to be homozygous dominant and heterozygous for...

Alright, I'm trying to follow Weinberg's derivation of the matter part of the Lagrangian for electroweak theory, and I am all confused. This is equation (21.3.20) in volume II. He writes: iL_e = - \left( {\begin{array}{*{20}c} {\bar \upsilon _e } \\ {\bar e} \\...

Greetings everyone, I have to give a lecture about supersymmetry, so I started reading Weinbergs quantum theory of fields vol 3, which is quite of a task. Sometimes I've trouble with some of his conclusions, and I hope you could help me there. I really do not understand how he got to the...

I am trying to study QFT from Weinberg's Vol. 1. I am at the moment stuck at the path integral quantization of QED (Weinberg's treatment). I am not sure how he integrates out the matter field momenta (for the spinor field) in eq. (9.6.5). I thought for spinor fields you don't do that...

https://www.amazon.com/dp/0198526822/?tag=pfamazon01-20 I wonder if this is an update of his book Gravitation and Cosmology.

From 1980 onwards a lot of people have been operating under the misconception that gravity, by itself, is UNRENORMALIZABLE. People have tended to suppose that it could only be handled within a unification context, where the Einstein-Hilbert action is abandoned for dreams of more complex...

Homework Statement The frequency of PKU in european populations is about 1/10000. What is the frequency of the allele for PKU? The attempt at a solution I know PKU is an autosomal recessive disorder so does that mean q^2=1/10000? I'm not quite sure where to go from here :bugeye:

Newsweek had an article earlier this month (10 November) about a conference on Science and Religion attended by many top scientists including Nobel laureate physicist Steven Weinberg. Weinberg said something that was both poignant and apt. I never heard anyone use this figure of speech...

https://www.physicsforums.com/showthread.php?p=811631#post811631 see page 13 of the paper: "As for me, I have just enough confidence about the multiverse to bet the lives of both Andrei Linde and Martin Rees’s dog." haw haw a Steven Weinberg position paper on the string theory...

Nice lecture by Steven Weinberg "Where Do We Stand? This is the 2004 KITP Future of Physics Symposium. I highly reccomend Weinberg's lecture. You may also want to listen to Leonard Susskind, who promises not to mention the Anthropic Principle in his talk, then flogs it mercilessly. As...

"The bones in our throat" (Weinberg) http://online.itp.ucsb.edu/online/kitp25/weinberg/ Steven Weinberg gave an interesting talk about the current situation in particle physics yesterday (7 October) called Where Do We Stand? Audio is available----as well as slides and video. Around minute...

Which book on general relativity is better to start with? "Gravitation" by Misner, Thorne and Wheeler, or "Gravitation and Cosmology" by Weinberg ?