Local Definition and 521 Threads

I'm reading wald page 85, and he defines a stress-energy tensor for the linearized gravitational field. he mentions that it not gauge invariant as a problem. but isn't that a general property of any tensor (except scalars). so any stress-energy tensor will not be gauge invariant (change of...

Plenty of Dark Matter Near the Sun http://www.sciencedaily.com/releases/2012/08/120809090423.htm Evidence for dark matter near the sun "We are 99% confident that there is dark matter near the Sun," says the lead author Silvia Garbari. In fact, if anything, the authors' favored dark...

Very cool! I just started using my new femtocell connection from AT&T. It provides a cell connection for a range of about 10 meters, using an internet connection. It seems to work great. The connection is solid with 5 bars, and the sound quality is excellent. I have been playing dueling phones...

So I am participating in a program that allows me to take classes at a local university and the counselor suggested that because I plan to go into physics when I go off to college (I will be a high school senior next year) it would be a good idea to take the honors introductory course that is...

How do I find the extrema using Taylor Series?? I am so used to find extrema just by finding the first derivative (make it =0) and then finding the second derivative and then just use the formula f_xx.f_yy - f_xy and just look at the sign but this time I need to use taylor expansion. I hope you...

Dear all, Sorry to post this question in this section again. I am currently looking into few static analyse algorithms. I noticed that they are analysing with different order moments or cumulants to analyse the data. I guess it is because these algorithms are focus on different aspect of...

Homework Statement I'm trying to figure how to to determine if a function is Locally Asymptotic Stable or Instable. I also need to know if the approach of the function is monotone or oscillatory. Homework Equations Non-linear dierence eq. model : xn+1 = f (xn) (1) Linear dierence eq...

Hi All, First off, thanks to all the old hands at physicsforums, you guys are truly an amazing resource. I was thinking about a system today that at first glance, appears to violate local conservation of energy for two mechanical wave pulses interfering with each other. Consider a...

My favorite food is the peanut butter cookie. I get them every single time I go grocery shopping. Today, I was hit with bad news. They did not have any cookies, and they would not be making any more, ever! :cry: The baker told me that it's due to so many people having peanut allergies and...

Local oscillators that is used in RF transmitters for AM modulation.Any help is appreciated. Thanks !

Critical Points, intervals, local max/min help! Calculus. 1. I need help with a homework problem that I just cannot get right. It asks: Answer the following questions about the functions whos derivative is given below. f'(x) = (sinx +1)(2cosx +\sqrt{3} ), 0\leqx\leq2∏ a. what are the...

Homework Statement A Pitot is used to measure the air speed of a light aircraft. The pressure difference recorded by the tube in flight was 3300 N/m^2. The local air pressure was 950 kN/m^2 and the temperature was 7 Degrees (280K). Calculate the local air density and the speed of the aircraft...

Weih's data: what "ad hoc" explanations do local and non-local models give? From the thread on Nick Herbert's proof: harrylin: The more I become aware about the tricky details and the impressive experimental attempts to disprove "local realism", the more I am impressed by - to borrow some...

Hi all Suppose for a dynamical system \dot x=f(x) , x \in \mathbb R^n there exists finite number of isolated equilibria, each of which is locally stable (i.e eigenvalues of the associated Jacobian have negative real parts). My question is: Can this happen for more than one equilibrium...

Homework Statement http://img13.imageshack.us/img13/5793/84188411.jpg Homework Equations Find a condition on b such that x = 0 is a local minimum of the potential function. The Attempt at a Solution To find local minimum, potential function (V) of the system should be written. V...

Hi, I have been going over past papers and i found this question. Find any local maxima or local minima of the functions g(x) = |f(x)| and h(x) = +√f(x) in the interval, −∞ < x < ∞. How Would I go about solving this?

How do I find the local minimum of z=sqrt(x^2+y^2) I know its simple, but I'm stuck on it. I've tried using the second derivative but it just goes exponential. Then I tried using the second derivative test but did'nt succeed. And kindly could someone solve it step by step as it makes it much...

Homework Statement f(x,y)=5xy-7x^2+3x-6y+2 [b]2. Homework Equations (f_xx)(f_yy)-(f_xy)^2 the hessian or discriminant of f The Attempt at a Solution i arrived at a solution but i don't think its correct, and the answer isn't in the back of the book, so i just wanted to ask if i did...

Homework Statement F(x)=(x^2)/(x+1) Find critical points Find local maxima & minima Homework Equations None The Attempt at a Solution F'(x) = x(x+2)/(x+1)^2 crit points: -2,0,-1 f(-2) = -4 f(0) = 0 f(-1)=undef My book is telling me that f(0) is the minima, and f(-2) is the...

Homework Statement ## f\left( x,y\right) =x^{2}-4xy+6x-8y+2y^{2}+10 ## ## f_{x}=2x-4y+6=0 ## ## f_{y}=-4x-8+4y=0 ## ## f_{y}=-4\left( x-y+2\right) ## -2=x-y, then solving fx and using this equality ## f_{x}=0=2\left( x-2y+3\right) =0 ## 2(-2 -y+3)=0 2(1-y)=0 y=1, then pluggin...

Hey forum I got to submit this in a few hours so if anyone could help me with this quick times, you would really be saving me :P Homework Statement Given the following graph of h(x) I only need help with part b) which asks for the local minimum or maximum points of the graph...

what does it mean.

Homework Statement see attachment The Attempt at a Solution I don't understand how they found fxy = 1 I understand how they found fxx, they used simultaneous equations, but I don't understand that notation.

I was wondering if anyone knows whether there exist strictly local interpretations of quantum mechanics. I understand that Bell's theorem tells us that any hidden variable theory must be non-local if it is to give QM. But what about other interpretations such as many worlds? It is obvious that...

According to this, if someone spins around at 2 revs per second when the moon is in the horizon, the moon seems to move at 4 times the speed of light. And this implies the moon is not in our local reference frame. And per this, local inertial frame applies to "small regions of a gravitational...

At the time Schwarzschild derived his solution (1915) he only had a version of the EFE that was not fully coordinate free, he used the equations in unimodular form, and therefore he could only consider the "outside of the star" part of the fully general covariant form we know now. So does a...

Consider an analytic function $f$ and non-constant defined on a set $\mathcal U\subset\mathbb C$ open and connected. Prove that the real-valued functions $|f|,\,\text{Re}(z),\,\text{Im}(z)$ can't achieve local maximum. This one looks hard, how to do it?

As I understand in SR light is always c in it's local reference frame regardless of a present gravitational field. Light would appear to be traveling slightly less than c in a gravitational field otherwise known as the Sharpio Delay in all non-local reference frames. Now, light must be traveling...

Homework Statement Theorem: Let f: M->R where M is a open subset of Rn Suppose f is C2(M) Let x E M such that "gradient of f at x" = 0 and the Hessian of f at x is positive definite Then x is a strict local minimum point of f. The above theorem is given in my textbook. If instead...

Hi all, I don't know if this is the right section, but I really need to solve this problem. I've been searching for the correct formula for two days. OK, here's the picture: The global rotation of all objects (rot_x, rot_y, rot_z): red object (0.00, 45.00, 0.00), blue object (45.00, 0.00...

Say I have an invertible partial differential operator P:H1(Rn) -> L2(Rn) where H1 denotes the first order L2 Sobolev space. I know |u|H1(Rn) ≤ |(P-z)u|L2(Rn) for certain z. Can I somehow obtain |u|H1(U) ≤ |(P-z)u|L2(V) for subsets U, V of Rn where V is only "slightly" larger than U...

Dear all, I would like to know from you the solution about this problem (which is not a homework, but a topic of my Master thesis!): I need the strain energy density related to a circle of radius r0 centered in an arbitrary point of a square plate, under the boundary conditions described in...

hi suppose i run Two notebook and in each of them i have matrix A and Constant B and a function C in each notebook these things have the same name. if in notebook 1 i assign B=10 then in notebook 2 B is 10 too , which is not my desire. how can i define these constants and matrices and...

What is the relevance of Local Lorentz Invariance Violations if they would be detected in any future experiments? Does it mean there is absolute space and time in the microscopic sector below where current experiments can't probe or other absolute parameters since there would be preferred frame...

Bonjour, I need to numerically compute the net electrical resistance of a given geometry. I know the shape of my object, it is relatively simple. It's close to this: http://2.imimg.com/data2/QX/UC/IMFCP-3019296/i-shape-big-1-250x250.jpg Actually my shape is even simpler because it's a...

I've learned Kg to Kgf this time I got another question.. I think it's another way around.. "The weight of an object is 25kgf. What is it's mass if local gravity is 9.6m/s^2" Tried this.. 25/(9.6)(9.8)= 25.5kg

Okay, so I have an astronomy/astrophysics exam tomorrow and I understand everything except for the local standard of rest. Could someone please explain it to me? Thanks!

Homework Statement The question provides a graph and asks for the local minimums. I attached a picture with the graph. 2. The attempt at a solution I said the local minima are when x=0,2,5. However the answer key suggests they are at 1,2,5. Could someone please explain why 1 is a...

what did bell show concerning the existence of a local hidden variable model for quantum physics?

Hi Say I have two expressions of the form F(r, t) = \int{dr'\,dt'\,\,x(r,r',t,t')g(r',t')} and F'(r, t) = \int{dt'\,\,x'(r,t,t')g'(r, t')} It is clear that F' is local in space, whereas F is non-local in space. Is it correct of me to say that F' describes an isotropic...

Homework Statement f(x,y)=(1+xy)(x+y) Homework Equations The Attempt at a Solution I started out by expanding and got: x+y+x^2y+xy^2 Then I found all my partial derivatives and second derivatives: f_{x}=1+2xy+y^2, f_{y}=1+2xy+x^2, f_{xx}=2y, f_{yy}=2x, f_{xy}=2(x+y)...

It is an old idea that, at least in principle, hidden variables could be local if they are superdeterministic. However, so far this idea seemed too speculative for highly respectable journals such as Physical Review Letters to publish research on it. But now it seems that it has changed. The...

Please bring me out of my state of confusion if I need to be... The question is how to calculate the rate of an atomic clock (a pendulum clock may work otherwise) on board a vehicle traveling along the surface of the Earth at constant altitude, like a bus, a train or an aeroplane. This was first...

I heard in a conference that gravity forbids to construct local gauge invariants like Tr-\frac14 F^{\mu\nu}_aF_{\mu\nu}^a and only allows non-local gauge invariant quantities like Wilson Loops: Tr P e^{\oint_{\gamma} A_a dx^a}. Could someone explain me where does it come from? I have a basis...

I have a question I wanted to clear up. According to the definition of a "local inertial" frame in GR, you must use a coordinate system that locally looks Cartesian, right? I mean if you had a coordinate system with a basis that wasn't orthogonal, then it would not be considered a local inertial...

Hi, Let f :X-->Y ; X,Y topological spaces is any map and {Ui: i in I} is a cover for X so that : f|_Ui is continuous, i.e., the restriction of f to each Ui is continuous, then: 1) If I is finite , and the {Ui} are all open (all closed) , we can show f is continuous...

Hi everyone, Recently I faced a problem in calculating bending stress in a long UPN profile "flange" due to concentrated force. It seems that the regular/familiar formula for bending stress in a finite/short element does not applicable in local bending of long/infinite beam. See sketch...

I chanced upon an argument in Misner, Thorne and Wheeler to the effect that the energy/momentum of the gravitational field cannot classically be localised. Basic idea: you can make the Christoffel symbols vanish at any point, and hence the gravitational field at that point will vanish, taking...

One term I fully understand yet I have never seen how one actually does the calculation is the local gravity a particle feels in a gravitational field. Now, I honestly feel this is as stupid of a question as they come, but intuitively I'd say, if I wanted a(r), the acceleration as a function...