Symmetry Definition and 907 Threads

here is what I am doing. I am trying to argue that the electric field is zero at the center of the sheet using only symmetry arguments. consider an insulator in the shape of infinite sheet of thickness 2a and with uniform charge density \rho. Now let me specify the coordinate system. The...

I hear the statement that global symmetries in the boundary field theory corresponds to gauge symmetries in the bulk. 1) Is this a generic statement that is expected to hold for all holography pairs? (Maldacena states this towards the end of his first lecture at PiTP2010, which was supposed to...

in a nutshell

Lets us say we are doing a vibration analysis of a structure with cyclic symmetry In very brief (as pointed out by AlephZero in one of his excellent reply) the whole motion can be represented by complex numbers which describe the motion of one segment. Now, my question is: 1)Is it...

Please teach me this: Does a symmetry of Lagrangian be reserved in each Feynman diagram of perturbative QFT,because even Ward Identity still deduces from U(1) symmetry that we consider each diagram has?. By the way, does effective action reserve the symmetry that Lagrangian has?. Thank...

The setup: I am reading the review: arXiv:hep-th/0004098 (page 9-10). In Einstein-Maxwell theory, the gravitational field equations read: \begin{equation} R_{\mu \nu} - \frac{1}{2} g_{\mu \nu} R = \kappa^2 \left( F_{\mu \rho} F^{\rho}_{\;\;\nu} - \frac{1}{4} g_{\mu \nu} F_{\rho \sigma}...

Talking about charges. If someone claims that in his work time reversal symmetry is conserved, does that equal to say he/she is not imposing a magnetic field?

Please teach me this: Why do we only consider symmetry group(Lie group and Lie algebras) but not general symmetry(the transform that keeps Lagrangian invarian) in QFT?Is it because the symmetry group is more simple and more beautiful and in reality the forces of Nature obey the symmetry...

What law of nature says that electroweak symmetry must be broken? Is it possible that in other parallel Superstrings (or others) universes.. electroweak symmetry were not broken and even after temperature of the Big Bang decreased to what is like ours, electroweak symmetry still existed in that...

Hi, Please can anyone explian what is cyclic symmetry? I'm new to this term and have encountered this in jet engine example Vishal

Here and then I read gauge symmetry makes theories renormalizable. Unfortunately I could not find a satisfactory explanation why that so is. Could someone shed some light? thanks

I have read Einstein's 1905 paper and a number of other explanations and have a question I can't resolve. The basic problem was that the mathematics differed between the case of a conductor moving relative to a magnet vs. a magnet moving relative to a conductor. Einstein used the Lorentz...

Starting with the D-dim. harmonic oscillator and generators of SU(D) T^a;\quad [T^a,T^b] = if^{abc}T^c one can construct conserved charges Q^a = a^\dagger_i\,(T^a)_{ik}\,a_k;\quad [Q^a,Q^b] = if^{abc}Q^c satisfying the same algebra and commuting with the Hamiltonian H =...

Please teach me this: Can we deduce Ward Identity in QCD from U(1) symmetry of QED?Because QCD is a theory of quarks and quarks have electric charge.So we need not deduce the Ward Identity from SU(3) symmetry,but we can be able to demontrate the Ward Identity( considering gluons)with U(1)...

Homework Statement is the function f(x) = (2x^2-x)/(x^2+x) even, odd, or neither?Homework Equations f(-x)=f(x) = even f(-x)=-f(x) = odd f(-x)≠f(x)≠ -f(x) The Attempt at a Solution f(x) = (2x^2-x)/(x^2+x) f(-x)=(2(-x)^2+x)/((-x)^2+(-x)) f(-x) = (2x^2+x)/(x^2-x) i think that's the right way to...

Let X = { a, b, c } X x X = { (a,a), (b,b), (c,c) } { (a,b), (b,a), (a,c), (c,a) } { (b,c), (c,b) } 1. Symmetric but not reflexive or transitive: R = { (a,b), (b,a), (a,a), (b,c), (c,b) } How come this is right? Isn't aRb, bRa imply...

Does anyone know how to derive the Ward-Takahashi identity for a field starting from a known conserved Noether current (or equally helpful, from a known symmetry transformation of the Lagrangian)? It'll probably be enough to allow me to do it for myself if you could explain quantitatively what...

Homework Statement I'm struggling to understand the concept of symmetry in quantum mechanics. My notes state "In general if the probability density has lower symmetry than the hamiltonian, the wavefunction will be degenerate". I don't really get the connection with the hamiltonian. It...

http://pirsa.org/11100056/ Can Lorentz Symmetry be Emergent? Speaker(s): Ted Jacobson Abstract: I will begin by discussing some of the strongest observational evidence for Lorentz symmetry, and the essential role that Lorentz symmetry appears to play in the consistency of black hole...

I would like to ask if anybody knows about some analysis of this part in Einstein's derivation of SR where he gets rid of unknown scaling function φ(v): "From reasons of symmetry it is now evident that the length of a given rod moving perpendicularly to its axis, measured in the stationary...

A few of the books and magazines I have read talk about maintaining CPT symmetry, but I can't see why it should be the case. What is the evidence, theoretical or experimental, of CPT symmetry?

Homework Statement Let M be a differentiable manifold, p \in M. Suppose A \in T_{1,p}^1(M) is symmetric with respect to its indices (i.e. A^i_j = A^j_i) with respect to every basis. Show that A^i_j = \lambda \delta^i_j, where \lambda \in \mathbb{R}. Homework Equations The Attempt at a...

I've been reading an <URL=http://www.nybooks.com/articles/archives/2011/oct/27/symmetry-key-natures-secrets/> article </URL> by Steven Weinberg on symmetry, written for laymen, in the New York Review of Books. Weinberg describes as simply as he can how symmetry lies at the heart of the Standard...

Is anyone in PF reading the titled book? For me, it is slow work because I have not done physics for a while - decades! I am retired and read some old physics books just for challenge. Mueller gives me that, but also reward. From time to time, I find little stumbling blocks, sometimes a...

Please teach me this: It seem to me that lepton manifests broken symmetry SU(2) with couple electron and neutrino(electron is a state with mass,neutrino is a state with nearly zero mass).Similarly for 2 other families of lepton,we have a state with mass and a state with nearly zero mass.But I...

Homework Statement Prove that symmetric and antisymmetric matrices remain symmetric and antisymmetric, respectively, under any orthogonal coordinate transformation (orthogonal change of basis): Directly using the definitions of symmetric and antisymmetric matrices and using the orthogonal...

I thought I had a good understanding of transistors, but I have seen articles on how to tell the collector from the emitter. I had always pictured transistors as a perfectly symmetrical device. Either side could be the collector, and the opposite side was the emitter. Clearly, there is some...

Hi there. I have this simple conceptual question, I'm studing electrostatics, and the book speaks about azimuthal symmetry. The doubt I have is, what's the difference between azimuthal symmetry and cylindrical symmetry? I mean there is any difference between those symmetries? it looks like the...

Homework Statement A wire of length L and negligible transverse dimensions, made of an insulating material, is placed on the x-axis between the origin and the point (L,0). The wire has a uniform line charge density lambda. using Gauss' theorem and exploiting the cylindrical symmetry of...

Hi, I am interested in grand unification with extra dimensions. Especially the case when extra dimensions are broken by orbifolding. Now I am trying to understand how the Goldstonebosons appear in the spectrum of a theory with global (for example SU(N)) symmetry. From the...

I know that the physical meaning of SU3 and SU2 - you can change the places of the quarks or/and leptons and you will get the same results. What is the physical meaning of U1, and O3,1 (Lorentz group if I am not wrong)? I know U1 is connect with the Polarization of the light. Thanks...

Homework Statement Consider the study of the motion of a two bodies system interacting with only gravitational forces. If the two bodies (or even one of them) has not spherical symmetry, how will you proceed? Indeed the Earth and the moon does not have spherical symmetry mass distributions...

For spin 1/2 particles, I know how to write the representations of the symmetry operators for instance T=i\sigma^{y}K (time reversal operator) C_{3}=exp(i(\pi/3)\sigma^{z}) (three fold rotation symmetry) etc. My question is how do we generalize this to, let's say, a basis of four...

Hello again! Say I have a potential well, between 0 and a. I also know how the wave function looks like for (t=0): \psi(x,0)= \frac {2bx} {a} for 0<x<\frac {a} {2} and \psi(x,0)= 2b(1- \frac {x} {a} ) for \frac {a} {2} <x<a Now, I wish to find the wave function of a general time...

Hi I have a problem that i couldn't solve by myself with my little background. I want to plot the bandstructure for a GaAs superlattice, the z-axis is the 111 direction. The structure is non periodic in the z direction and periodic in the x and y direction. The process is totally different then...

Hi I have a problem that i couldn't solve by myself with my little background. I want to plot the bandstructure for a GaAs superlattice, the z-axis is the 111 direction. The structure is non periodic in the z direction and periodic in the x and y direction. The process is totally different then...

Hi how, in my master project I am working on extra dimensions and I am asking my self why is it common to start most of the theories with a space time symmetry given by SO(n,1) (n>4) and then compactify the obtained spectrum to SO(3,1)xG (where G is an abitrary symmetry group). Because...

hi, i need to calculate the killing vector fields for axial symmetry for a project so i can study the galaxy rotation curves. i am assuming the galaxy to be a flat disk, in addition to being axially symmetric. so i figured that the killing vector fields with respect to which the metric...

Does anybody know what kind of geometrical symmetry FRW metrics present? I know it's not spherically symmetric, but I think I recall having read it shows radial symmetry.

I am extending the standard model symmetry group by introducing discrete symmetry (Z2). The group could be (I, G) or (I, -G). Is that called even and odd Z2 symmetry? What is the difference of considering either of them?

I'm trying to get a basic picture in my head of particles having mass. I always seem to come across the ridiculously vague statement that "the Higgs mechanism gives particles mass", and a passing mention of "spontaneous symmetry breaking". There is a lot of stuff confusing me at the minute so...

Gauss' shell theorem states that if given a spherical shell of charge such that the charge is uniformly distributed on the surface, the net electric field anywhere inside the sphere is zero. But I'm wondering (and turns out this was on a past exam), what happens if the charge is not uniformly...

Homework Statement Hi, I have a problem connected with time dilation symmetry, which is supposed to be explained in a following example: A rocket traveling at 0.8c starts from station P and is directed to station Q 864 million km away. Time taken to travel as measured by space station clocks...

Ok so, I have a few question regarding the symmetry and other properties of the magnetic monopoles. I see how they actually arise from a mathematical symmetry of Maxwell equations, but my first question is: if they were discovered to exist (experimentally speaking), would there be no need in...

In my lecture notes the symmetry elements for XeF4 are listed as: [PLAIN]http://img690.imageshack.us/img690/7216/syms.png but nowhere does it explain what 2C2 or σh means. What are these symmetry operations?

Hi, i want to ask about the basic explanation of twin paradox. In the explanation it says one twin has to accelarate to come back and the symmetry is broken and so one twin is older than other. Could you explain this symmetry and aging relation?

I have run into a problem where I have a frieze pattern F, the frieze pattern has horizontal refelctive symmetry, glide reflective symmetry, but does not have 180 degree rotation and does not have vertical reflective symmetry. G represents the symmetry group for F. G={reflection symmetry...

Homework Statement Let A and B be symmetric n x n matrices. Determine whether the given matrix must be symmetric or could be nonsymmetric. F=ABA Homework Equations (AB)^T=B^T A^t The Attempt at a Solution So if it's symmetric, that means (ABA)^T=ABA. I decided to make A one...

The question is: for a gas of weakly interacting molecules show that <v_x>=0 where <v_x> is the average velocity in the x direction. the probability of a molecule having a velocity v is given by: p(v_{X})=\sqrt{\frac{m}{2\pi kT}}e^{-\frac{mv_{x}^{2}}{2kT}} The above is a Gaussian...

I am having some trouble understanding particle exchange symmetry and I'm working on the most basic problem with 2 spin-1/2 particles in a 1D infinite square well. I understand that a singlet state requires a symmetric spatial wave function and a triplet requires an antisymmetric wave...