Symmetry Definition and 907 Threads

O.K. , this question is inspired by a physics class I'm taking where we're working out the expectation values of wave functions, but I think the question really belongs in the math section. Thank you in advance for any help. Here goes nothing... We have a function ψ(x,y,z) = x e\sqrt{}x2 +...

Suppose that on a Riemannian manifold (M,g) there is a killing vector such that ##\mathcal{L}_{\xi} g = 0.## How would one then characterize the group of diffeomorphisms ##f: M \to M## such that $$\mathcal{L}_{f^* \xi} (f^*g) = 0?$$ How would one describe them? Do they have a name...

If I understand correctly, conservation of baryon and lepton numbers imply that quarks and leptons are "basic" i.e. non-interchangeable particles? What happens when one such particle is annihilated, can the energy produced be used to "generate" the other type, or do some additional particles...

The Fourier transform, wrt to angular frequency, needs of a factor (1/2π) for get f(t) or F(ω), actually, this factor is broken in 2 factors (1/√2pi) and each kernel, direct and inverse, receives one factor for keep the symmetry in equation. F(\omega)=\int_{-\infty }^{+\infty }\frac{e^{-i\omega...

Typically a symmetry is taken to be something that leaves the action invariant. However, on a classical level, isn't that asking way too much? To match what we conceptually mean by symmetry, we only need something that maps solutions to solutions, so something which leaves the action invariant...

Symmetry is an important way to find new physical laws according to Feynman. The equation that describes the electric field and the gravitational field are quite similar. Since the electric and magnetic fields are well defined by the Maxwell equations could it be possible, by symmetry, that...

I am trying to understand a little further how software such as ANSYS implements cyclic symmetry in an analysis. A colleague of mine spoke to a support engineer and I think that he may have misinterpreted what was said. He is now under the impression that when we invoke a cyclic symmetry...

We know that observables correspond to hermitian operators on the Hilbert space of physical states of the system. We also know, via Wigner theorem, that for each symmetry there is a linear unitary operator (or anti-linear and anti-unitary). In the case of a continuous symmetry, that is in the...

Can someone explain why the answer is D a < 0 because it finishes downwards e < O because the y-intercept is in the negatives. b, & d = zero (but i don't get this) c is supposedly > 0 (nor do i get this) According to the solutions the graph is an even function, and symmetrical about the...

Hey, I have been doing a few proofs and stumbled across this little problem. Trying to show the symmetry of the Ricci tensor by using the Riemann tensor definition ##R^m_{\ ikp} = \partial_k \Gamma^m_{\ ip} - \partial_p \Gamma^m_{\ ki} + \Gamma^a_{\ ip} \Gamma^m_{\ ak} - \Gamma^a_{\ ik}...

##H=-\frac{\hbar^2}{2m}\frac{d^2}{dx^2}+\frac{1}{2}m\omega^2x^2## Parity ##Px=-x## end ##e## neutral are group of symmetry of Hamiltonian. ## PH=H## ##eH=H## so I said it is group of symmetry because don't change Hamiltonian? And ##e## and ##P## form a group under multiplication. Is there...

I have a question about allowed transitions and molecular states. For an electric dipole transition between two states (say molecular or atomic) to have a non-zero probability of occurring, the transition dipole moment \langle \psi_{f}|\textbf{μ}\left|\psi_{i} \right \rangle must be non-zero...

I have a question regarding symmetry groups. I've often heard that the Standard Model is a SU(3) x SU(2) x U(1) theory. From what I understand these groups contain the symmetries under which the Lagrangian function is invariant. If so, what does every one of the 3 groups above contain (what...

Homework Statement Find the resistance across AB. Use symmetry to determine currents. Homework Equations Please see diagram. The Attempt at a Solution I really don't seem to understand symmetry in circuits. What is the link between the geometrical symmetry of the situation and...

Homework Statement An element is taken from the wall end of the cantilever beam that is loaded as per the diagram. What are the stress components of the element, taken at x=0, y=h/2, z=0 Homework Equations σ=My/IThe Attempt at a Solution So from the shear moment diagram, the moment and shear...

I have a question about symmetry energy in semi-empirical mass formula, According to semi-empirical mass formula as follows: E=avA-asA2/3-acZ(Z-1)/A1/3-asym(N-Z)2/A why in the symmetry energy only squared parameter symmetry are exist and there is not the first power of asymmetry parameter?

Homework Statement http://i.imgur.com/d4ViHux.png Homework Equations The Attempt at a Solution The author writes: "Now, using symmetry, we have..." But what symmetry does the author use? Also, I got the integral as shown in the remark but why is it wrong?

If function is ##f(-x,-y)=f(x,y)##, is then ##\int^{a}_{-a}\int^{a}_{-a}f(x,y)dxdy=0##? Thanks for answer.

Hello, I have read that above a certain temperature, the weak bosons become massless and become indistinguishable to the photon. Is the idea simply that at high enough energies, the Higgs field can sit on top of the peak in the mexican hat potential? I.e. at high enough energies, it's vacuum...

"..his equations indicated that atoms could indeed form a regularly repeating lattice in time, returning to their initial arrangement only after discrete (rather than continuous) intervals, thereby breaking time symmetry..." I was wondering about the theory's validity and if you had heard of...

So, I have a basic/general question here. I understand that, for example, the QED Langrangian has U(1) gauge symmetry. I also understand that this means (when you have written the Lagrangian with the covariant derivative) that if you transform the wavefunction (\psi \rightarrow e^{i \theta (x)}...

Problem: Consider the planar urea molecule. i) Determine the point Group, as well as the symmetry of the x,y and z coordinates. ii) Consider the following atomic orbitals: C : 2s; 2p N : 2s; 2p O : 2s; 2p H : 1s Determine the equivalent sets of orbitals and the symmetry of each set...

Homework Statement Evaluate the double integral of (2+xy^2) over dA (dxdy) using symmetry where R = [0,1] x [-1,1] Homework Equations The Attempt at a Solution I don't know how to use symmetry to evaluate this.. However if I integrate this integral normally i first get...

Homework Statement 1) Which U(1), SU(2) and SU(3) gauge invariances are implemented in nature according to the Standard Model? What are the related quantum numbers? 2) The SU(2) symmetry is referred to as a non-abelian symmetry. What does this imply for the interactions between the force...

Suppose we have a Lagrangian \mathcal{L(\phi, \partial_\mu \phi)} over a field \phi, and some variation on the field \delta \phi. If this variation induces a variation \delta \mathcal{L} = \partial_\mu F^\mu for some function F^\mu, then Noether's Theorem tells us that if we construct the...

In almost every QFT or particle textbook we learn that complex scalar fields or spinor fields (or even multiplets of spinor fields) have a phase symmetry (global gauge symmetry.) You can append to these fields an exponential with a complex phase in the Lagrangian and the dynamics remain the...

Hi. I'm working through one of my first problems on sets and relations, and I need some help understanding if I'm getting this right. Any help/suggestions on my through process is greatly appreciated. The question is: Determine whether the relation R on the set of all real numbers is...

I have a question that I have approached, but want to check if I'm on the right track. Let G denote the group of symmetries of a circle. There are infinitely many reflections and rotations. There are no elements besides reflections and rotations. The identity element is the rotation by zero...

Find the electric field for a non-conducting sphere of radius R = 1 meter that is surrounded by air in the region r > 1. The interior of the sphere has a charge density of ρ(r) = r. The answer is k(pi)/r^2, but I can't seem to get that. My problem is with finding the enclosed charge. I've tried...

Hi, I've seen pictures like this one: http://www.lcst-cn.org/Solid%20State%20Physics/Ch25.files/image002.gif Is there any good explanation somewhere on this subject? I'm using Kittel's book but there's nothing in there on this.

I've been thinking about chapter 11 of Griffiths' Introduction to Elementary Particles. In section 11.7, he gives the Lagrangian density \mathcal{L}=\frac{1}{2}(\partial_{\mu}\phi)(\partial^{\mu}\phi)+\frac{1}{2}\mu^{2}\phi^{2}-\frac{1}{4}\lambda^{2}\phi^{4} and shows that the minimum...

Hello, Can anybody please explain what is super symmetry and what is special unitary group? I read Wikipedia but could not understand the entire story. I have done liner algebra and matrices. U(n) is the unitary group. Special unitary group is a sub-group of unitary group U(n). But...

In Quantum Mechanics, when we exchange identical particles the physics doesn't change. I wonder what stuff is conserved when this symmetry is demanded. I asked my professor but he didnt/couldnt answer. Google is no help either.

Hello, I am quiet new to this subject. I am just repeating in a few words, what I have learned so far: The 4 fundamental forces of nature, strong, weak, electromagnetism and gravity. Physicists are trying to re-generate a condition, a very high temperature during the Big Bang, to find out...

Say we have two inertial observers Bob and Alice moving relative to each other at a significant fraction of the speed of light c (say 0.5c). Bob is moving to the left relative to Alice and Alice to the right relative to Bob. When their origins cross, a pulse of light is emitted to the right...

Homework Statement Your supposed to set up the integral and do it from the calculator. y = , y = (cosx)^2, -pi/2 <= x <= pi/2 a. x axis b. y axis Homework Equations I = ∏∫(cosx)^4 dx = 3.70110 and for part b I = ∏∫((1)-(cosx)^2)^2 dx = 3.70110 The Attempt at a Solution Did...

Hello, I am quiet new to this subject. I am reading over grand unified theory and found that there are quiet a number of Symmetries, like U(1) and SU(2)..... Can anybody help me in finding all the types of symmetries and how it evolved and what are they basically are? Thanks

Hello, PF have helped me a lot understanding a lot of important things in physics, I hope you guys can help me with this too :). I have problems understand the symmetry groups. I know there are groups like SU(2), O(3).. etc. But I have no idea how they represent certain particles.So particles...

\renewcommand{\vec}[1]{\mathbf{#1}} Here is an excerpt from the text: "[...]Theorem 12.5 The only finite symmetry groups in ℝ^2 are \mathbb{Z}_n and D_n. PROOF. Any finite symmetry group G in \mathbb{R}^2 must be a finite subgroup of O(2); otherwise, G would have an element in E(2) of...

From looking at the Wikipedia entry on string theory I gather that it is found that any given physical model implies two Calabi-Yau spaces. Perhaps one space gives rise to a sector of particles with left-handed weak interactions and the other gives rise to a sector with right-handed weak...

I wonder if symmetry breaking of the U(1)SU(2)SU(3) symmetries of the standard model have anything to do with the calculation of the cosmological constant. Do we assume that the symmetries are broken or unbroken in the current calculation of the CC? As I recall, one way symmetry is broken in...

Hi there, I've done some searching around on the forums and in the library, but I haven't found what I was looking for - some information of symmetry violation in the early universe. I know some small pieces of information but I'm currently trying to consolidate that so that I have an actual...

Hi there, I've done some searching around on the forums and in the library, but I haven't found what I was looking for - some information of symmetry violation in the early universe. I know some small pieces of information but I'm currently trying to consolidate that so that I have an actual...

I am entranced. I mean There are so many thing which seem to deal with skew symmetry, like the skew anti-symmetric matrices of Electromagnetic 4-tensor, I have this thing, a question. And it is stated as: " if you take the inner product of the rows of a skew symmetric matrix would it be equal to...

What is the general method for finding symmetry in molecules which would allow you to find which nuclei are equivalent in an NMR spectrum? I know it sounds vague but it seems inevitable. Any good guides on the Internet would be great. My main issue is with larger molecules whose structures are...

Greetings, Can someone give a detailed explanation of why the expectation value of z coordinate in the ground state of hydrogen atom is zero due to parity symmetry? In addition how do you represent parity inversion in spherical coordinates and how do spherical harmonics behave under this...

In peskin at page 319 right above equation (10.6) he writes "If the constant term in a taylor expansion of the self energy were proportional to the cutoff ##\Lambda##, the electron mass shift would also have a term proportional to ##\Lambda##. But the electron mass shift must actually be...

Hi I am looking at the contours of the following function f, which trace out an ellipse: f(x, y, z) = \exp(-x^2a)\exp(-y^2b) Here a\neq b are both positive, real constants. The axis of these ellipses is along z. Now, I am wondering how to generalize the function f such that the symmetry...

Homework Statement This is the second part of a question I asked earlier. I tried to figure it out but was having trouble even with 4 of my peers. PART 1 (SOLVED) A function f is said to symmetric about a point (p,q) if whenever the point (p-x, q-y) is on the graph of f, then the point...

Homework Statement A function f is said to symmetric about a point (p,q) if whenever the point (p-x, q-y) is on the graph of f, then the point (p + x, q - y) is also on the graph. Said differently, f is symmetric about a point (p,q) if the line through the points (p,q) and (p+x, q+y) on the...