Interesting Definition and 754 Threads

So today I noticed something pretty weird on an exit sign above a door in my school, looking somewhat like this: http://www.examiner.com/images/blog/wysiwyg/image/exit_sign.jpg The effect is pretty difficult to describe by words, since I didnt expect to see anything like that on it. But it...

Check this out: Violation of a temporal Bell inequality for single spins in solid by over 50 standard deviations, G. Waldherr, P. Neumann, S. F. Huelga, F. Jelezko, and J. Wrachtrup (2011) "Quantum non-locality has been experimentally investigated by testing different forms of Bell's...

Are they allowed? (funny ones didn't last long) of PF members also?

when a material becomes charged due to static electricity how come it does not stay charged or how come the atoms of the material do not become ions

As some of you may know, I'll graduate next Spring with a B.S. Mathematics and Physics minor. From my perspective, I wanted to gain a broad and fundamental technical education in undergrad. I view grad school as career training. Applied math is an option at my university. It would be the easiest...

A general question I came up with and it might be trivial, but I'm not entirely sure what the answer is. Does there exist a function analytic in the upperhalf plane that is unbounded and all of its derivatives are bounded but not identically zero? or equivilently does d^n/(dz)^n(f)<M for...

Just looking for some links to sites with guidelines for a quick chemistry demonstration. No particular topic, just nothing overly simplistic. I'd like it to be "visually entertaining" though - it's being done as a presentation, and frankly I'm not sure that the most interesting...

I am studying orbitals at school. They are very interesting and strange at the same time; they seem to be very similar to a planet in orbit around a black hole. However I am not here for that. I was wondering if you knew a good and short reference in order to understand E,Shrodinger's equation...

Imagine for a moment a steel core with no air gap, that is driven to saturation by a powerful permanent magnet. Imagine next that a coil is wrapped around some section of that core some distance away from the magnet, such that their only flux linking is through the saturated core. The magnet...

So basically I need to do a project on a topic in "beyond standard model" can anyone give me any theoretically interesting topics? I know this is a very loose question, but .. p.s I am a 3rd yr undergrad so nothing to crazy Only topics i can think of are just a standard search for a...

A conductive plate with no initial charge is put between two identical positevily charged plates. Is it possible that the plate which is put between those two plates configures a situation where the net force acting upon each plate is zero? (the third plate could have different dimensions then...

I want to find a function describing the motion of the particle undergoing the type of motion depicted. Basically it is a particle on a rotating vane (constant angular speed) and at some time it is released. The particle will move along the edge to the tip of the vane (and eventually fall off)...

(AB+1)/(ABC+A+C)=0.138, Find values of A,B,C.

Hello,I just discover a interesting phenomenon at lunch time when I drink a glass of water: When I hold a glass in my hands, If I look from above at the innerwalls of the glass, we can see a very bright and clear image of patterns on your fingertips through the glass. But when I use...

Harvard professor of history Niall Ferguson gave an interesting talk on history at the Australia Center for Independent Studies http://fora.tv/2010/07/28/Niall_Ferguson_Empires_on_the_Edge_of_Chaos His main point was that empires die fast.

I've got to do a talk for part of my physics degree and I'm trying to think of subject ideas. It doesn't have to be physics exactly, but must be scientific in some way. I was wondering if anyone had any ideas for quirky subject matter. To give you an idea, my favourite talk from the year...

So I'm really interested in the field of wave optics, and luckily for my undergraduate program, we get to do a measurement project on any area of our choosing. I was looking up topics and there are some interesting ones such as the luminous fountain where they use the idea of fiber optics to...

Hey all, I am currently looking to build something for fun, and to add to my college application/resume. I was thinking about building a particle accelerator, and did a good amount of research into that, and it seems like it would be expensive and complicated. However, I am still open to that...

What spacetimes do you consider to be important or interesting? Important or interesting as solutions to the Einstein field equation, or important or interesting geometrically. I'll start the list. Minkowski Schwarzschild (including extended) Kerr(-Newman)...

So I was trying to sleep last night but I had a random thought of a function that would be very very painful to graph. I am currently out of town and don't have access to a graphing calculator. Plus I kinda wanted a logical answer before seeing the graph to it. Perhaps some of you have seen it...

I was checking out a developing blizzard forecast for the northeast US today when I saw this interesting fog feature over the South Dakota, Nebraska, Oklahoma area. http://www.weather.com/maps/maptype/currentweatherusnational/uscurrentweather_large.html EDIT: The image is changing. It was the...

He once had a difficult moment, just to see what it was like. https://www.youtube.com/watch?v=L-4zfsy6rsM What else can be said about the most interesting man in the world? Stay thirsty my friends.

What does everyone think about this? http://www.fordham.edu/academics/programs_at_fordham_/mathematics_departme/what_math/index.asp

For the sake of doing it, I'm trying to factor a quintic polynomial over the reals using a cool technique I found a few days ago. It involves stenciling out the general form of the expression you want and then solving a nonlinear system in which there are more variables than there are...

Hi, I'm trying to understand spinors better, and I seem to be getting stuck on understanding the reason they're said to transform differently from vectors, and I'd appreciate any help with a justification for that. I'm sure I'm missing something pretty simple, but here goes; Here's what I've...

I just realized a Van de Graaf generator around 400...500 kV might be easily doable, by an average amateur working in a garage. I was also thinking these days about a DYI cyclotron project, which I scrapped because the magnet is just too hard to make and feed. But then I figured the Van de...

Homework Statement points A and B are on the parabola f(x)=4xsquared + 7x-1, and the origin is the midpoint of AB, find the length of AB Homework Equations The Attempt at a Solution I have spent time drawing out graphs and such but I am totally lost as to where to begin

I plan to take Engineering as a second degree since I haven't had much luck with my BSc. I'm considering Biomedical (somewhat high paid but jobs are seem to be rare), Chemical (twice as many employed and slightly higher pay) or Mechanical Engineering (highest number employed by a long shot). I...

This just hit me: there is a high probability my family and I will be alive to witness several key events in human history. Just think about it: there are at least 10,000 years of recorded human history but only in the last 150 of those people have experienced the most amazing things any human...

I was thinking about how big the universe got after inflation occured. Then I thought about Hubble's parameter. Ho = V / d (At the big bang, the distance between the two edges of the universe were zero) Ho = V / 0 Ho = ∞ km*mpc / s Therefore, the rate of the expansion must have been...

I request you all to perform this activity now (it will take less than a minute)- 1)Take a rectangular piece of paper. 2)Make two holes of the size or your fore-finger in it - equidistant from the edges (refer the figure attached. 3)Insert the fore-fingers of your two hands in the holes...

Homework Statement Prove or dispove T:R^n \rightarrow R^n is a linear transformation if for every u \in R^n and for every v \in kerT , T(u) \cdot v=0 then KerT = (ImT)^{\perp}The Attempt at a Solution True. since it was given T(u) \cdot v=0 and we are dealing with all of R^n then...

Homework Statement lim (x,y)→(3,1) | (x2y - 6xy - x2 + 6x - 9y - 9) / ( (x-3)4 + (y-1)2 ) Homework Equations none The Attempt at a Solution Since we have the indeterminate form '0/0' when we simply substitute (x, y) = (3, 1) we need to show the limit Does Not Exist. we will show...

Hey guys, if the function f(x) has a special property that; f'(x) = f(x) g(x) Whats the easiest way to find the nth derivative of f(x) in terms of f(x), g(x) and g'(x)'s derivatives? The same problem rephrased is if q(x) is the logarithmic derivative of f(x), then what's the nth derivative...

Homework Statement ~ Homework Equations center The Attempt at a Solution i can do part a. can you give me hints on part b and c?

On a test in multivariable calculus I came across, what I thought, was an interesting parabola. Figured I'd ask the forum because my professor is pretty unavailable. In parametric form it is, x=t+4 , y = (1/2)t^2 + 2 The reason I found it interesting is because t is always equal to...

So I've read the highest skydive occurred from a balloon and the entire jump lasted on the order of 10s of minutes. Heres my question: How the do you know where your going to land? The Earth rotates at ~1000mi per hour that's 12 mi per minute or 2.7 miles per 10 secs. So did these people use...

Comparing the average speed of a bunch of points with the individual points' speeds, I came across the following equation: \left(\frac{dx(t)}{dt}\right)^2 = \frac{1}{N^2} c^2 \sum_{i\neq j} \left(1-\frac{v_i(t) v_j(t)}{c^2}\right) where the v_i are the velocity vectors (3 dimensions) of the...

I found a pretty interesting question on the net. Can anyone please attempt at answering it? This is NOT a Homework question. I haven't reached this portion in my school, but I'm pretty interested in solving it. A German childrens' book, "Der Struwwelpeter" show as humor various misbehavior...

I've been working on this problem and would like some help or any hints. Give an example of a nonempty set A subset of R such that A = br(A) = Lim(A) = Cl(A), where br(A) denotes the boundary points of A, Lim(A) denotes the limit points of A and Cl(A) denotes the closure of A. I've tried...

I've been working on this problem and would like some help or any hints. Give an example of a nonempty set A subset of R such that A = br(A) = Lim(A) = Cl(A), where br(A) denotes the boundary points of A, Lim(A) denotes the limit points of A and Cl(A) denotes the closure of A. I've tried...

Homework Statement From 52 cards we draw one .Whats the probability that the drawn card is divisible by 4 Now : in my notebook its 12/52=3/13 .But shouldn't it be 13/52 ? BECAUSE clearly if we multiply 13 *4=52 Same problem : Whats the probability that of 52 cards I draw one that is...

[FONT="Arial"][SIZE="2"]Is there a proof or way of proving that all even numbers (taking into account the definition of an even number as n=2k) end in 0,2,4,6, or 8?

Take a prime[n] and double it, i.e., e.g., Pn (n=7) so prime[7] is 17, doubled to 34. Take all unique arrangements of two primes from P2 (3) to P7 (17): {3,3}, {3,5}, {5,5}, ..., {13, 17}, {17,17} Add the pairs together, e.g., {3,3} = 3 + 3 = 6 Now eliminate duplicates, i.e., {5,5} and {3,7}...

Stuff i find interesting in some way! K this is a thread I'm making to show u some things that i find interesting and hopefully some of u will find it interesting too.. It will be updated on regular basis with new interesting articles from various sources so stay tuned.. First article is...

So I'm thinking that for grad school I might like to get into some computational simulations and modeling. The reason for this is I'm not sure if I'll want to stay in Physics after grad school and being good with computers and modeling and such I think will give me a lot of options outside of...

Hi guys, Homework Statement how do i solve (or approximate if not solvable) this integral \int\int e^{-\alpha(|\vec{r}_1-\vec{r}_2|-r_0)^2} d^3\vec{r}_1 d^3\vec{r}_2 \alpha>0 Homework Equations none The Attempt at a Solution none

Linear Polarisability \alpha_{ij} is the amplitude of the electric field induced in the molecule in the i direction given a unit amplitude field in the j direction, hence E_i^{induced} = \alpha_{ij} E_j^{incident} (observing summation convention) Extending this physical...

I have spent hours and hours trying to solve a problem until reaching a dead point. I don't know how to solve, simplify, or proceed next with the following PDE: m \frac{\partial^2 x}{\partial t^2} + 2 \frac{\partial m}{\partial t} \frac{\partial x}{\partial t} + x \frac{\partial^2...

Well since we will never see something go into a black hole, won't we see everything the black hole tries to swallow around it? So wouldn't it be possible to see a black hole since a bunch of things would be around the event horizon. Answers are appreciated.