Local Definition and 491 Threads

I spent days trying to find this information on the internet, but i think i will never find it, so i came here looking someone who knows it. The Mystery is : Where is the Gravitational center of the Local SuperCluster (Also known as Virgo SuperCluster) ? Some Usefull information that i...

The equivalence principle implies that it's always possible, by an appropriate coordinate transformation, to locally transform away the effects of gravity by going into a freely falling frame. Furthermore the local flatness theorem implies that it's always possible to but the metric ##g_{\mu...

Hey guys. I'm having doubts about something in a GR text I read (Gravitation - T.Padmanabhan). In general, for Lorentzian 4-manifolds, we call a basis of smooth vector fields ##(e_{\mu})^{a}## (that is, a set of smooth vector fields that define a basis for the tangent space at each event of...

As the only thread I've ever started before (https://www.physicsforums.com/showthread.php?t=369328 ) attracted a lot of interest, became one of the most viewed threads in the forum, and was closed :-), I'd like to make a short update here. I have published a new article on the topic: "No...

Hi All, I am interested in the discussion in section 10.5 of Schutz's First Course in GR book. Specifically, the conditions at r = 0 of a static, spherically symmetric interior star (or whatever) solution e.g. Schwarzschild interior solution. He argues that by enforcing local flatness one...

Homework Statement ds^2 = g_{tt} dt^2 + g_{tx} (dt dx + dx dt) with g_{tt} = -x and g_{tx} = 3 "Show that this is indeed a spacetime, in the sense that at every point, in any coordinates, the matrix g_{\mu \nu} can be diagonalized with one positive and one negative entry. Hint: You...

Jacobi identity in local coordinates?!? Apparently (i.e. according to an article written by physicists), the Jacobi identity for the Poisson bracket associated to a Poisson bivector \pi = \sum\pi^{ij}\partial_i\wedge\partial_j is equivalent to...

Also how can local causality be violated?

Greetings Physicists, I've been accepted to study at my state University for my Ph.D in Physics. I reticent to accept however for two reasons; 1. They are not offering me a TA'ship immediately. This means I would have to finance at least my first year with student loans and work study...

Say Alice gives Bob the wave-function, a momentum eigenstate, of a charged particle. Bob then makes a local gauge transformation on the wave-function, ψ --> exp[iqθ(X,t)]ψ. Can Alice now undo the local gauge transformation with the right addition (or subtraction?) of electromagnetic...

Hi I have some function f = f(x1,x2,...xn) over some domain [0,1]^n, and I'd like to find the global minimum. The function is *highly* non-linear and takes about 1 second to evaluate. I know it's positive because it's the sum of squares of about 1,000,000 arguments, each of which pretty much...

Here is the question: Here is a link to the question: Calculus homework help?!? - Yahoo! Answers I have posted a link there to this topic so the OP can find my response.

How to do local Physics Analysis ?? You Know all the LHC machine at CERN, and the CMS detector (Compact Muon Solenoid) This detector run a CMSSW ( CMS Software ) on CERN machines, can i download that software on my local machine, run it and do physics analysis? if yes how to download it, and...

Homework Statement A person whose mass is 150lb weighs 144.4 lbf. Determine a) the local acceleration of gravity, in ft/s2, and b) the persons mass, in lb and weight, in lbf, if g = 32.174 ft/s2 Homework Equations F=ma The Attempt at a Solution A) Using F=ma I got 144.4 lbf =...

These are notes I made when I was studying the subject 20 years ago. They seem fine considering that I was student then. I believe they can be useful for those who are studying Yang-Mills and other related material. Sam

I have recently read a few things about the local interstellar clouds and while I am by no means a science expert, math and science were my strong points. After reading about this a few things occurred to me, and they seem to be bad for our solar system. The clouds are ~10,000° C, our solar...

Let me start this off by informing you a little about myself. I am a Freshman at my local community college. I am majoring in Biological Science (that's the only science major of study here; kind of covers it all.) I am majoring in Physics as my field of study, however. Physics has always...

Homework Statement Which of the following sets of equipment cannot be used to measure the local value of the acceleration due to gravity (g)? (A) A spring scale (which reads in force units) and a known mass. (B) A rod of known length, an unknown mass, and a stopwatch. (C) An inclined...

I've been working on a decentralized algorithm for finding local minima. Can anyone give me a few examples of mappings of the form F:R→R that have multiple local minima. I'm having problems defining neighbourhood on mappings from R2→R, so I thought I'll test it out on single variable functions...

Knowing the dielectric constant of a medium we can earn the electric field at any point in that medium which is deferent from the applied external electric field. So why do we use the Local field correction?

Homework Statement Find the local extrema of the function f(x)=(x^3-2x-2cos(x))Homework Equations derivatives, some algebra The Attempt at a Solution Well, the concept is simple. Solve for the first derivative and set it equal to zero: dy/dx=2sin(x)+3x^2-2=0 and Next, solve for x to...

The coordinate speed of light relative to its speed at infinity is calculated as (1-2M/r)c (at infinity) yes?? SO it makes sense that local measurements made with local rulers and clocks which are contracted and dilated respectively would still be c for radial measurements. But how does that...

Hi everyone! :smile: I'm newbie in this forum, please help me for my question. In differential equation we know that the differential equation has a solution and uniqueness. which is usually called the existence and uniqueness theorem. my question, what is the difference of local existence...

Homework Statement Why is 'a' not a local maximum? Homework Equations The Attempt at a Solution According to the definition of a local maximum, I have to take an open interval around 'a' so it seems like 'a' is a local maximum. I don't understand why it isn't.

Homework Statement Assume that the polynomial P(x) has exactly two local maxima and one local minimum, and that these are the only critical points of P(x). Sketch possible graphs of P(x) and use them to answer the following. (e) What is the sign of the leading coefficient of P(x)? positive...

Homework Statement Find the local max/min or saddle points of f(x,y) = (x-y)(1-xy) Homework Equations The Attempt at a Solution I expanded the equation to f(x,y) = x-y-(x^2)y+xy^2. Then I found the partial derivatives of the function. fx = 1-2xy +y^2 fy = -x^2-2xy I'm...

Hi guys. Today was my last day of Calculus I class, and I’ve had this question simmering in my mind for some time now. Perhaps you guys may enlighten me or point me in the right direction? Consider the Weierstrass function, which is continuous everywhere but differentiable nowhere. We know that...

hi everyone, I have been trying to understand gauge theory. I am familiar with the Noether's theorem applied in the context of simpler textbook cases like poincare invariant Lagrangians. This is my question: Are there Noether currents corresponding to the local gauge symmetries too and would...

General relativity says that nothing can go faster than the speed of light when measured against local landmarks. What counts as a local landmark? What is the boundary between a local and distant landmark?

Pretty elementary question here, but I'm new to astronomy and I'm having trouble estimating LST. Online sources give me the exact formula, but this doesn't really help me on the fly. My location is 97.7-ish degrees W of Greenwich, which I know means I can subtract roughly 5.5 hours from Sidereal...

Homework Statement f(x)={0 for x<0, \sqrt{x} else} a) Is f(x) globally Lipschitz? Explain b) Find the area for which f(x) is locally Lipschitz. Homework Equations The Attempt at a Solution a) f(x) is not globally Lipschitz in x on [a,b]xRn since there is a discontinuity at x=0. b) I would...

Can somebody explain in layman's terms the connection between local flat space (tangent planes) on a manifold and the Riemann tensor.

I am familiar with basic calculus of variations. For example, how to find a function that makes some integral functional stationary (Euler-Lagrange Equations). Or for example, how to perform that same problem but with some additional holonomic constraint or with some integral constraint. The...

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...

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...