Pair Definition and 379 Threads

What are your favourite pair of shoes? What are the coolest shoes you've ever seen? Do you care about shoes at all? Does someone spend all of your money on shoes? Tell us all about it... Personally I usually just where black leather boots. It's hard to find normal looking boots anymore...

I freely admit that I am notationally challenged, so please help me out with this: (from Enderton, A Mathematical Introduction to Logic) I'm baffled. Since \{x,y\} = \{y,x\} how does <x,y> = \{\{x\},\{x,y\}\} define the ordered pair <x,y>?

can some one help me out wit this it says to squeeze them a little bit but i have no idea what they are saying i have a pair just like em but i can't make em do anything this site says, can anyone offer any help? http://scientificsonline.com/product.asp_Q_pn_E_3101302

When an gamma foton interacts with matter it can produce an Electron-pisitron pair. Why don't lower energy fotons sometime's produce an neutrino-antineutrino pair. Lepton number and charche wil be concerved (please forgive me for me bad english)

In Chapter 6 of M. Kaku's book (QFT), he wrote (p184) "...by rotating the diagram around, we can convert bremsstrahlung into pair creation." Bremsstrahlung, as far as I know, involves atoms. Does this mean that when bremsstrahlung with >1.2 MeV strikes an atom we will get an electron and a...

Am I right in understanding that Gamma Rays can decay into an electron-positron pair without interacting with any matter as indicated by Bubble Chamber results?

Hi All :smile:, I have a question which is at least partly one of believe but I would be interested in your opinion. We know that there is some problem with the black hole's entropie. If some object with entropy S collapses and it evaporates completely via Hawking Radiation, then where has...

Can someone check this for me? Two point charges, Q1 = + 5.00 nC and Q2 = -3.00 nC, are separated by 35.0 cm. (a) What is the potential energy of the pair? What is the significance of the algebraic sign of your answer? (b) What is the electric potential at a point midway between the charges...

This isn't really a brain teaser as much as a game. I have a Five Crowns deck at home. This consists of a deck of 55 cards (well, two decks of cards) with five suits. 3 is lowest and King is highest. You can't do 3-King in a straight. There are jokers, but I'm not using them --...

In pair production, an nucleus is needed to take away some momentum from the photon so momentum conservation is respected. correct?

How can a photon knock an electron from a shell, entirely out of the atom? (i.e PhotoElectric Effect) Photons have 0 rest mass, and little relativistic mass? For force, F = ma For example, let m = negligable (like the photon's mass is) mass so = mn If F = (mn)a and mn is small...

Is there a short answer why pair production can not happen in empty space, but that photons must interact with an external field? thanks and a nice weekend oh, just saw someone asked the same question in the nuclei section today and answers already there

if you want to show or prove that pair production cannot occur in empty space, why do you have to use the relativity equation?

Hi, I have heard someplace in my graduation course that two gamma photons are not allowed to yield a pair of particle anti-particle unless there is some material agent nearby. I remember also that this result was told to be very easy to demonstrate. Unfortunatelly there is no room for that in...

hi, this is about particle antiparticle pairs being produced outside the event horizon of black hole. this is what i know about it: we know that a black hole has entropy. it therefore must have temperature and hence must radiate. however, a black hole is defined as a body which pulls in...

I read a book and there it is written something as following: "By the lifetime of a virtual pair (e-e+) (that is given by the HUP) a virtual e- can remove with the distance s from the e+ that is given by: s=c*d(t) (d(t) from HUP)." My question: How can they annihilate if they are away at a...

"lensed" quasar pair Here is a paper about a purportedly lensed quasar. http://xxx.lanl.gov/abs/astro-ph/0505248 Has anybody notice how "lensed" quasars, like those comprising the Einstein cross, seem to manage to retain their point-like appearance instead of exhibiting arc-like...

Hi. Can pair production happen in vacuum? I had this question for a test. And the answer is: no, it cannot because it would violate the conservation of momentum, since you can't have a momentum zero photon. But i seem to recall that pair production happen in space (?). Due to...

1. A coin is located 19.6cm to the left of a converging lens (f = 16.5cm). A second, identical lens is placed to the right of the first lens, such that the image formed by the combination has the same size and orientation as the original coin. Calculate the separation between the lenses...

Suppose in general that we have two functions F(x)= \int_{0}^{cos x}e^{xt^2} dt G(x)= \int_{0}^{cos x}\(t^2e^{xt^2} dt H(x) = G(x) - F'(x) Where, I need to prove that H(\frac{\pi}{4}) = e^\frac{\pi}{8}/\sqrt{2} Okay, so far I have computed the integrals of both of...

I'm looking for a 21 letter word for my crossword puzzle, couldn't find it on google, I knew where to go. "two or more pairs of allels segregate independently"

This should be so easy but I'm having trouble understanding why {{x},{x,y}} defines an ordered pair (x,y). I'm trying to work through the following problem from the Zakon Series pdf textbook: If (x,y) denotes the set {{x},{x,y}} prove that, for any x, y, u, v, we have (x,y) = (u,v) iff x=u...

Does anyone know how to solve a pair annihilation problem ( positron and electron), for the energy of the resulting particles, in this case photons?

How far apart in space are these electrons? Are the spins truly up and down or do they have the same spins (parallel)? If they are up and down paired, then what causes that orientation?

The water and sedimentary cycles are interrelated in many ways, Would you please help me to identify the interactions between : sedimentary and tectonic, sedimentary and igneous, igneous and tectonic, water and tectonic ? Thank you very much in advance,

It seems rather odd to me energy mass equivalancy of pair creation would be the same as for the the energy mass equivalancy of direct conversion of energy to mass with increased velocity. In the first case you are not only creating mass but you are also creating particles.In the the...

Imagine a two dimensional universe, a plane. We take two perfect circles on this plane; they are uncompressable, being elementary particles or some such thing (whatever they are, the important thing is that they cannot be compressed). We take these two circles and set them on a collision...

I'm pretty much okay with pair production but in the eqt we have that a photo gives an electron and a positron. If we do it the other way round we have an electron and a positron giving 2 photos in order to conserve momentum. Why do we not have 2 photos of energy for pair production ir order...

Problem: A photon of energy E strikes an electron at rest and undergoes pair production, producing a positron and another electron. photon + e- --------> e+ + e- + e- The two electrons and the positron move off with identical linear momentum in the direction of the initial photon. All...