Weak Definition and 503 Threads

If you need to cross a bridge and you have reason to worry about its load-bearing capacity, do you choose to drive across it fast, or slow, or does it not matter? What are the considerations?

Hi people: I keep reading one day that weak isospin is exactly conserved by all interactions; other days that sometimes weak isospin is *not* conserved. Can anyone clear this one up?!

What are the weak and strong forces? I'm trying to understand what are the strong and weak forces and more importantly what is its role (if any) on the architecture of the atoms. Thanks!

Hi guys, Could someone with a better understanding of the standard model answer a question about the weak force? In a class I'm teaching, a question in the textbook asks if photons feel the weak force. My first thought was that it's fermions that feel the weak force and therefore the...

Hello! I have a question that has been bothering me for some time, and I thought this would be a good place to ask. This is my first posting on PF as well, so I hope this is well placed. There are force laws for the coulomb attraction and gravity. Are there similar force laws that can be...

After talking with students from other schools and looking around at "typical" physics curricula, I can't help but wonder whether mine is a bit weak... I go to a large state school with a relatively tiny physics department and part of me thinks they have condensed the workload in order to...

Hi; In chapter 9 of Solid state physics of Ashcroft&Mermin(Electrons in a weak periodic potential), there is a General Approch to the Schrodinger Equation when the Potential is Weak. i can't understand what is meant by the term DEGENERACY? or what does "nearly degenerate free electron...

The leptons and hadrons carry the weak isospin charge. What allows the weak bosons do carry the charge? Is it because they have a mass?

Hi, I don't know very much about the weak force, but gravity, EM and the strong force all seem to apply an actual F = ma type of force (at least, I think the strong force does). But my limited knowledge of the weak force is just that it is involved in radioactive decay. Maybe this is why some...

Anyone have an idea when/where there might be accessible draft of the paper, or want to share any insights beyond the press: http://www.scientificamerican.com/article.cfm?id=first-proof-that-infinite-many-prime-numbers-come-in-pairs Terry Tao has an initial comment...

Hello. I am a high school level student and I had a question about weak acids/bases and why they wouldn't work as a buffer on its own. If the dissociation of a weak acid is HA \rightleftharpoons H^{+} + A^{-}, then when we add OH^{-}, it will react with the H^{+} to form water. Because the...

Homework Statement Find the pH in 50.0 mL of 1.00M HCl + 50.0 mL of 1.00M HF Homework Equations None to speak of really... The Attempt at a Solution I figured out [HCl] and [HF] in the solution: they're both 0.5M. I have absolutely no idea what to do at this point... Thanks.

In Deep Down Things, an excellent book of B Schumm, at page 288, he explains that the weak force is short range because the Weak quanta have a large mass. Using de Broglie wavelength relation: Lamda = h / p, he gets a wavelength of 10 ** -18 m, and he concludes that this is the W quanta range...

The W couples to left-handed particles only. What about the Z? Is it the same? Thanks in advance!

Homework Statement So I'm looking at the spectrochemical series of ligands which has that I- < Br- < Cl- < F- < OH- < ox2- < H20 < NH3 < en <bpy< phen <CN- Where the left side are weak field ligands and the right side are strong field ligands. A lot of my homework problems involve...

So according to the rules of solubility all ionic compounds containing acetate are soluble in water. However acetic acid is a weak acid. Why is this if acetate is dissolved in water?

Well, I was looking at the beta decay of neutron, and I thought that the weak interaction can be seen in analogue to QED, where you have an electron that emits(or absorbs) a photon and gets scattered. In the same way, couldn't we say that a Neutron is scattered to a Proton (I see them as the...

Homework Statement Let ##U\subset\mathbb{R}^n## be a bounded open set with smooth boundary ##\partial U##. Consider the boundary value problem $$\begin{cases}\bigtriangleup^2u=f&\text{on }U\\u=\frac{\partial u}{\partial n}=0&\text{on }\partial U\end{cases}$$where ##n## is the outward pointing...

Apologies if this is rather trivial. I'm having a hard time wrapping my mind around the mathematics of energy bands and periodic potentials. I understand that an electron in a periodic potential will be of the form \phi_k(r) = e^{ik.r}u_k(r) . This wavefunction has periodicity of the...

I am confused about when and to what extent parity is violated in weak decays. On the one hand, there's Wu's famous experiment where electrons are emitted preferentially in one direction. This parity violation can be said to be maximal, since all electrons are emitted in one direction...

Homework Statement I am confused about parity violation in weak decays. I learned about Wu's famous experiment and how it demonstrates that parity is violated in weak decays. However, when I am doing a course problem on nuclear β-decay, then it still necessary to conserve parity...

Buffer (pH of a weak acid decreases when we add NaOH! Yes, really.. This is not homework, but just something that I find not following general rule. Just wondering why. So We have the titration of 20.0 mL of .100M HF with .100M NaOH With 0mLof NaOH, the pH=2.08 (by calculating) But...

That is if a tissue paper is wet,it is easier for us to "separate" into many small portions than in dry condition does. Why? Sorry for my poor english,i don't know how to express it well, but i hope it is understandable.

Homework Statement Recall that log 2 = \int_0^1 1/(x+1) dx. Hence, by using a uniform(0,1) generator, apprximate log 2. Obtain an error of estimation in terms of a large sample 95% confidence interval. If you have access to the statistical package R, write an R function for the estimate and the...

Provided they aren't in an excited state (which would allow a decay via EM or strong). I had a question asking why the neutral lambda particle, consisting of uds quarks, has a lifetime characteristic of the weak. The answer being that it must decay via the weak to change the s-quark flavour into...

I know there are four different forces in the universe and they all affect us. I know that gravity is the force of objects' mass interacting I know electromagnetic is the force carried by photons and is the cause of electromagnetic waves I know that the strong nuclear i responsible for the...

I just came across the following Quote in an introductory Quantum physics book"There are certain experiments in which behave differently in their mirror image form, this is called the Parity Violation in." Can anybody explain in detail what parity violation is and what mathematical description...

A long wavelength light has too little energy to knock out electrons, so how do scinetists detect them? and how does a light with low energy ever cease to exist since it can never be absorbed?

Homework Statement Determine the pH at the equivalence point after 20.00mL of a 3.75 M NaF(aq) solution is titrated with 3.25 M HI(aq) Homework Equations ##k_a = \frac{[A^-][H^+]}{[HA]}## The Attempt at a Solution The first thing I noted was that NaF ##\rightarrow## Na+(aq) +...

Hello, I have to calculate the gravitational field strength g given by the De Sitter-Schwarzschild spacetime. If G=c=1 I get: R_{00}\simeq -kT_{00}+\frac{1}{2}kT\eta_{00}+\Lambda \eta_{00}\simeq -kT_{00}+\frac{1}{2}kT_{00}\eta^{00}\eta_{00} +\Lambda \eta_{00}\simeq...

Since the hurricane has killed school for awhile, I was working on some stuff that I knew we would not cover in class any more, but could end up on a test and I got to this question. It seems like it should be simple, but I have been stumped all day. Don't know if anyone here will have the...

1. Yukawa Potential So reading about the yukawa potential I notice that the constant k is related to the inverse of the effective distance of the force from what I've been reading. Thing is everything I read about the strong force states it has infinite range but simply has a maximum potential...

I just read some basic concepts on General Relativity, and this idea pops up: I know we should use variations of metrics for gravitational field in the Lagrangian. But considering the resemblance of gravitational field(weak-field) to electromagnetic field, can we construct a 4-potential similar...

I read in a paper http://nngroup.physics.sunysb.edu/~nngroup/misc/Documents/NeutrinoReactionsAtAcceleratorEnergies.pdf that delta_I = 1/2 rule of the strangeness-changing weak current implies the ratio of cross section of proton->Ʃ0 process to neutron->Ʃ- process to be 1/2. The delta_I = 1/2...

I read in a paper that delta_I = 1/2 rule of the strangeness-changing weak current implies the ratio of cross section of proton->Sigma0 process to neutron->Sigma- process to be 1/2. I do not understand what is this selection rule and how does it effect the cross section ratio of the 2 processes...

The strong interaction has color ''charge'',the electromagnetic interaction has electric charge,the gravity interaction has mass ''charge'',then what is the charge in weak interaction? Each interaction corresponds to a symmetry.Symmetry SU(3) for strong interaction, SU(2)xU(1) for...

I ran across the following passage in the Wikipedia article on mass-energy equivalence: This level of physics is way over my head, but I'm wondering: "What happens to the quarks that comprise the protons and neutrons?" Are they conserved in the neutrinos and antielectrons? Chris

Hello, I'm looking to amplify a very weak AC signal using op-amps. The problem I'm running into is that I can only operate using a +5V supply voltage, no negative voltages. My AC signal is about 5mV and I need it to be about +2.5V. The AC signal is initally DC baised and is at +3.5V, so I put a...

Folks, I am struggling to see what is happening here particularly when ## \displaystyle \sum_{i=1}^{n-1}## transforms into ##\displaystyle \int_{x_1^e}^{x_{n}^e}## ##\displaystyle 0=\sum_{i=1}^{n-1} \left [ \int_{x_i^e}^{x_{i+1}^e} (a \frac{dw}{dx} \frac{du}{dx}+cwu-wf )dx- \left [ w(x)...

Homework Statement Folks, determine the weak form given Navier Stokes eqns for 2d flow of viscous incompressible fluids ##\displaystyle uu_x+vu_y=-\frac{1}{\rho} P_x+\nu(u_{xx}+u_{yy})## (1) ##\displaystyle uv_x+vv_y=-\frac{1}{\rho} P_y+\nu(v_{xx}+v_{yy})## ##\displaystyle u_x+v_y=0##...

Is the weak force really a "force"? I have seen that gravity, electromagnetism and the strong force are described by physicists in detail in the sense that specific things can be said about what is attracted and/or repulsed and under what circumstances these forces are manifested. All we ever...

Does anybody could help me to state if the following particles experience strong interactions, weak interactions, both interactions or neither of the two interactions? This is what I think: electron = strong interactions and weak interactions boson = weak interactions down quark = strong...

I'm still highly confused about the weak force. Every time I read about it I get something along the lines of it is responsible for beta decay which to my understanding is when a proton or a neutron exits from the atom's nucleus. One thing I have trouble understanding is that if the strong...

1. Homework Statement and attempt at a solution Considering that the ground state of the beryllium atom is 2s^2 and the first excited state is 2s2p, I was wondering in how many lines would the emission/absorption spectrum be modified in a weak magnetic field. I know that if there's no...

Homework Statement Weak Duality Theorem. If x ε ℝn is feasible for P and x ε ℝm is feasible for D, then cTx ≤ yTAx ≤ bTy. Thus, if P is unbounded, then D is necessarily infeasible, and if D is unbounded, then P is necessarily infeasible. Moreover, if cTx = bTy with x feasible for P and y...

With beta decay a down quark turns into a up quark + W- results in e- and (anti-neutrino) and up quark turns into a down quark + W+ produces e+ + (neutrino), does the W- and W+ get emitted and then turn into e- + (anti-neutrino) or e+ + (neutrino) or do they stay in the nucleus? How does the Z...

Hi all, For my studies I'm currently looking into Weak anti localisation. I've come across a lot of articles making use of this effect, but none of them describe the concept of WAL. So far I've been unable to find it in my books. I hope one of you can help me with this.

So I am wondering about one thing. The charged propagators in weak theory are W+- bosons. The mathematical expression for them, while drawing the Feynman diagrams is: -i\frac{g_{\mu\nu}-\frac{q_\mu q_\nu}{m_W^2}}{q^2-m_w^2}. The problems that are usually given to me are simple and involve...

Compared to, for example, electromagnetic interactions. Are the "weakness" and "slowness" perhaps somehow related? Perhaps both "weakness" and "slowness" can both be reformulated as "having a low probability of occurring", making the "slowness" apparent, and making the "weakness" a...

the spin orbit coupling removes the degeneracy but not completely, should we still use the degenerate perturbation theory. is it because of relativistic corrections? Thanks!