Symmetry Definition and 907 Threads

When you add two angular momentum states together, you get states which have exchange symmetry i.e. the highest total angular momentum states (L = l1 + l2) will be symmetric under the interchange of the two particles, (L = l1 + l2 - 1) would be anti-symmetric...and the symmetry under exchange...

consider the following two graphs. I want to calculate the symmetry factors for them . I am using field contraction method for that. but I am getting 2 for the 2 vertex diagram and 1 for the zero vertex diagram where it should be 4 and two respectively. Can anyone do it for me. I am writing...

Hello. I need help with the following problem: I don't know where to start. I know that the frame can be split up into one symmetric part and one symmetric+assymetric part but i forgot the theory and rules on translation and axis etc. I hope someone can help as I have to hand in the...

I was thinking whether to ask this question or not because the mentor might not like it. Again it could be my misconception. But I think I should ask this question because it would help others who are at the same level of study as I am. So those people can just see this post of mine and clear...

The Polyakov action, S=\frac{1}{4\pi\alpha^\prime}\int d^2\sigma\sqrt{-h}h^{\alpha\beta}G_{ij}(X)\partial_\alpha X^i\partial_\beta X^j has the local symmetries, diffeomorphism on world sheet and the Weyl invariance. But is diffeomorphism on the target space also a symmetry? The target space...

Is there any simple justification about graphene having no band gap? How bout its linear E-K? Why bilayer graphene has a quadratic E-K and electric field can open a band gap there? I do not completely understand the broken symmetry argument? Also Why MoS2 which has similar structure, do not...

Homework Statement Take the action S = \int d^4x \frac{1}{2} \left( \partial_{\mu}\phi(x)\partial^{\mu}\phi(x) - m^2\phi^2(x) - g\phi(x)^p \right) , and consider the following transformations: x^{\mu} \rightarrow x^{'\mu} = \lambda x^{\mu} \phi(x) \rightarrow \phi^{'}(x) =...

I am reading Srednicki's book and I am stuck at this point of calculating symmetry factors for Feynman's Graph in the context of dealing with interacting scalar field. First of all my question is what is the standard procedure to calculate it. The way Srednicki has talked about it is that if...

It just occurred to me that induction can be seen as a statement quite analogous to that of "a function whose derivative is 0 on an interval is constant on that interval". Suppose there is a property P about the natural numbers that we want to prove. Then let P: N -> {0, 1} be a function for...

I am trying to understand the (possible) couplings between scalar chemical reaction phenomena and vectorial phenomena such as heat conduction and mass diffusion. It is argued in the literature that I have read that the usual assumption of cross coefficients for scalar+vectorial phenomena only...

Hello,I read an article about fo generating mass for the first two generations of quarks by breaking the flavour permutation symmetry S3. In the top of the page 5 of the following article: http://arxiv.org/pdf/hep-ph/9807214v2.pdf , they mention that "Mq1 transforms as the mixed symmetry term...

Hi all, Have anyone heard about a symmetry called " Z symmetry " . It's considered a discrete symmetry, in which terms at a Lagrangian for example can take "Z charges" 0, 1 or +1 to be invariant or non-invariant under this symmetry .. I heard about before, but I try to find any reference...

Homework Statement the question is that there is a particle in 3 spatial Euclidean dimensions in cylindrical coordinates. I want to find a symmetry for the lagrangian if the potential energy is function of r and k.theta+z V=V(r,k.theta+z) Homework Equations k is constant L=T-V...

We know how objects such as the metric tensor and the Cristoffel symbol have symmetry to them (which is why g12 = g21 or \Gamma112 = \Gamma121) Well I was wondering if the Riemann tensor Rabmv had any such symmetry. Are there any two or more particular indices that I could interchange and...

http://arxiv.org/abs/1409.0492 Is the Standard Model saved asymptotically by conformal symmetry? A.Gorsky, A.Mironov, A.Morozov, T.N.Tomaras (Submitted on 1 Sep 2014) It is pointed out that the top-quark and Higgs masses and the Higgs VEV satisfy with great accuracy the relations...

What are the high symmetry directions for a two-dimensional oblique crystal? Please provide a figure of the corresponding Brillouin zone with high symmetry points labelled.

Hi guys, I have a question about symmetry breaking in Susy, I hope it won't be so naive that I just started to study supersymmetry .. The question is that there are two Higgs doublets in Susy, H_u and H_d, how these two doublets first break supersymmetry at high energy scale and then make...

In the Dirac equation, the only thing about the gamma matrices that is "fixed" is the anticommutation rule: \gamma^\mu \gamma^\nu + \gamma^\nu \gamma^\mu = 2 \eta^{\mu \nu} We can get an equivalent equation by taking a unitary matrix U and defining new spinors and gamma-matrices via...

I have a homework problem where I have to solve for the displacements of the attached system using cyclic symmetry. To do this, I know that I have to find the harmonic load components of the system. One thing that my professor did not make clear (or if he did, I missed it) is how to determine...

First I want to consider an example of 1D motion. Lagrange equation: $$ \frac{d}{dt} \frac{\partial L}{\partial \dot x} - \frac{\partial L}{\partial x} = 0 $$ If we transform $$L \rightarrow L+a$$ with a is constant, the equation of motion remains unchanged. This is global symmetry. To obtain...

I have a few questions about the Pauli exclusion principle: 1. Why do physicists believe that the symmetry in the wavefunction we assign to particles (indistinguishability) is due to an actual restriction in the physical state space that the particles can occupy (the attributes following from...

Hi I am re-reading Srednicki's QFT. In chapter 58, he points out that the Noether current $$ j^\mu=e\bar{\Psi}\gamma^\mu\Psi$$ is only conserved when the fields are stationary, which is obvious from the derivation of the conservation law. Meanwhile he assumes that $$\partial _\mu...

Why is it so important to the universe that if you measure the spin of an entangled pair and its up then the other particle must be down. It seems to have no practical use so why does the universe enforce this rule, how would reality differ if it wasn't true. And is it a law of symmetry...

How do I calculate the symmetry axis of a Hyperbole ? Is there a formula? If the Hyperbole is formula : f(x) = a/(x-p) +q

I am wondering what kind of approaches people take to a cyclic symmetry analysis in FEM when you have multiple repeating features that don't divide to the same integer. Take the example below for example. I have a N_HOLES = 136 and I have N_SLOTS = 52. I am not sure what to do here. The...

I know about symmetry and antisymmetry and so on, but a thought that I had never considered just hit me. If we had two fermions in the triplet symmetric spin state and hence therefore an antisymmetric spatial state, for example a harmonic oscillator in the first excited state must be one in...

Homework Statement Is this relation, R, on ## S= \{ 1, 2, 3 \} \\ R = \{ (1,1), (2,2) , (3,3) \}## Symmetric? It is obvious that it is reflexive.

Hi, I'm just getting a little confused with all the definitions here and I need some confirmation on what I say is correct or not; Isospin symmetry: The property that an interaction is independent of the T_3 value? Isospin breaking: The property that it is dependent on T_3 ? Charge symmetry...

Homework Statement http://imgur.com/W4Ntkfb Homework Equations E=KQ/R2 e= electric field Q = charge R = radius from point to charge K is a constant, 9x109 The Attempt at a Solution http://imgur.com/4CTEwDw If my handwriting sucks, I basically did the standard integral of...

I am trying to understand the connection between symmetry and conservation. For the electromagnetic force, the conserved quantity is charge, the corresponding symmetry is the phase of the wave and the force carrier is the photon. For the electroweak force, the conserved quantities are the...

Can one set up a multiplication table for the symmetry group C3V of the equilateral triangle. Then show that it is identical to that of the permutation group P3. I need some clarification... What about a matrix representation (2x2) for these groups? → Here was thinking to use...

1. P. Marder ever said that there is no special symmetry results in two dimensional oblique lattice. But it still possesses inversion symmetry. r → -r How to understand r → -r? 2. Many book ever states that space symmetry broken by atomic displacement can bring ferroelectricity. But why...

If the probability for a state α prepared initially to be in a state β at a later time is given by: S_{\beta \alpha} S_{\beta \alpha}^* and for a state β prepared intitially to become a state α is: S_{ \alpha \beta} S_{ \alpha \beta}^* then in order for the two to be equal (by...

I know--because of Noether's theorem--that continuous rotational symmetry implies conservation of angular momentum, and that continuous translational symmetry implies conservation of linear momentum. It also turns out that the discrete translational symmetry exhibited by a Bravais lattice...

Hello, ∫|cos(px/2)|dx between [0,2] I encountered this rule. How does this apply to other intervals of say [3,4],[7,9] etc. Are the numbers both halved? so [3,4] becomes [1.5,2] etc? Also, does this rule apply to all symmetrical functions? Thank you, Tim

I am trying to derive the conserved charge from the symmetry of the action under Lorentz transformations, but I am doing something wrong. Noether's theorem states that the current is J^\mu = \frac{\partial \cal L}{\partial(\partial_\mu \phi)} \delta\phi - T^{\mu \nu}\delta x_\nu For an...

Why is the chiral symmetry breakdown determined for the vector/axial current as: V = \frac{m_{π^{+}}-m_{π^{0}}}{m_{π^{0}}+m_{π^{+}}}\approx 0.01 A= \frac{m_{π^{+}}-m_{f^{0}}}{m_{f^{0}}+m_{π^{+}}}\approx 1 ? why do we choose the difference between the pion+ (~140MeV) and pion0 (~135MeV)...

Homework Statement A horizontal 845.0 N merry-go-round with a radius of 4.3 m is started from rest by a constant horizontal force of 74.0 N applied tangentially to the merry-go-round. Find the kinetic energy of the merry-go-round after 2.2 s. Assume it is a solid cylinder. The...

Hi everyone. I don't know whether this is an advanced or introductory topic but I I've always wondered how to prove symmetry arguments in electrostatics, magnetostatics etc mathematically. Suppose you have an infinite line charge and you need to calculate the electric field at some distance...

I have several questions about symmetry in quantum mechanics. It is often said that the degeneracy is the dimension of irreducible representation. I can understand that if the Hamiltonian has a symmetric group G, then the state space with the same energy eigenvalue will carry a...

Hi, I am looking into symmetry breaking and how it (may have) affected the photon/baryon ratio in the primordial universe. I found this wonderful encyclopaedia of cosmology which relates the grand unified theory to an orthorhombic crystal, making analogies for symmetry, spontaneous symmetry...

I'm trying to understand inflation (in the cosmic sense). I know that ultimately that's a subject that involves both quantum field theory and General Relativity, but I'm wondering to what extent it can be understood from the point of view of classical (non-quantum) GR. If you have a classical...

For a given lattice, specifically a diamond, it has C3v symmetry and the symmetry operation in real space is easy to see, 2C3 around high symmetry axis and 3sigma_v. My question is, if the lattice is expressed in reciprocal space, (say wavefunction defined in momentum space), then how to define...

Homework Statement I haven't been assigned these questions, but I'm trying to trudge through them to better understand symmetry. This is for my inorganic class. It's just a series of short questions like: C3 – S56 = ? S4 + i = ? C3 + i = ? Stuff like this. And just looking at the...

Homework Statement I am going over a practice exam, and I need to find the FSS of f(x)=x(\pi^2-x^2) Homework Equations f(x) \sim \sum^\infty_{n=1}a_n sin\left(\frac{n \pi x}{L}\right) a_n=\frac{2}{L}\int^L_0 f(x)sin\left(\frac{n\pi x}{L}\right)dx The Attempt at a Solution I think I...

As far as I know identical fermions are antisymmetric under exchange. Identical bosons are symmetric under exchange. Is this fact blurred when we consider isospin? Considering the wavefunction of a proton-neutron system; \psi = \psi_{space} \psi_{spin} \psi_{isospin} I'm told this needs...

In the standard model, the Lagrangian contains scalar and spinor and vector fields. But when we consider spontaneous symmetry breaking, we only account for the terms contain only scalar fields, " the scalar potential", in the Lagrangian. And if the scalar fields have vacuum expectation value...

Consider any of the latest maps of the temperature fluctuations of the CMB. Such a map can be considered a 2 dimensional topographical map of the surface of a sphere, high points hotter, low points cooler. Consider the contours that divide such a map into the two regions, fluctuations hotter...

I am bit confused by how to approach this concept with mean field theory. As I understand a symmetry break (like a acquiring a finite magnetization) can happen if at low enough temperatures the Free energy decreases when breaking the symmetry. Normally this temperature is found by calculating...

I understand that the QED Lagrangian is invariant under the CPT transformation. Is it also invariant under C, P or T separately?