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    A Is this system of equations (numerically) solvable?

    Hi, In a project of mine I've encountered the following set of equations: $$ \sum_{i=1}^N \left(\frac{1}{M}\sum_{\alpha=1}^Mg_{ij}^\alpha - u_{ij}^* \right) = 0 \qquad \forall: 1\leq j \leq N$$ $$\sum_{i<j}\left( (u_{ij}^*)^2 - \frac{2}{M^2}\sum_{\alpha < \beta}^Mg_{ij}^\alpha g_{ij}^\beta...
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    Solving a system of nonlinear equations

    This is actually not a homework problem, but a problem I'm encountering while working on a little project and I'm not sure if it's even solvable or if it makes sense what I'm doing 1. Homework Statement First, I have the equation $$p_{ij} = \frac{1}{2}\left( \tanh{(-\frac{\theta_i +...
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    Other Books on history of physics?

    I realized that I know nothing about the history of physics! Does anyone have any good recommendations on this topic? For example I'd like to have a clear timetable in my head about what was discovered at what time? by who? what were the methods/thoughts that went into it and what did the rest...
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    Evaluating partition function (stuck for weeks)

    Hi, I'm trying to calculate the partition function for a certain system and I arrived at an expression for the partition function $Z$, and have been stuck here for two weeks at the least. This is not a homework problem. If this is the wrong place to post a question like this, could you please...
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    Quantum Computing presentation ideas

    Hey everyone, I'm sorry if this is not the right place to ask this, but here it goes: I have to do a presentation on a topic on quantum computing. Does anyone know any cool doable topics? We have been working through Ballentine's quantum mechanics book, to give you an idea of the level. Thanks!
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    Switching from physics to finance

    Hey everyone. I'm currently doing my Master in Theoretical Physics, because I like to study physics, but I don't want to have a career in physics. Right now I'm looking at a career in (quantitative) finance. I don't have any knowledge of it yet. Does anyone have any tips on making this switch...
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    Question about the metric tensor

    Hey, I have not done any proper differential geometry before starting general relativity (from Sean Carroll's book: space time and geometry), so excuse me if this is a stupid question. The metric tensor can be written as $$ g = g_{\mu\nu} dx^{\mu} \otimes dx^{\nu}$$ and its also written as...
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    I want to learn general relativity

    hello, I would like to learn general relativity. To understand general relativity, do I need to understand the math on a rigorous level? (the way mathematicians understand the math) . What math do I need? Can you suggest me some math/general relativity books? Thanks and sorry if my english...
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    Feeling like I forget everything I learn

    hey, I'm a 3rd(last) year physics student. I have the feeling that I am forgetting everything that I learn very rapidly. For example, in my 1st year I had things like classical mechanics, optics and classical electrodynamics. At the time I understood these subjects pretty well, and aced them(I...
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    2D fermi gas

    Homework Statement Show that PV = E Homework Equations E= \int^\infty_0 D(\epsilon)n_{FD}(\epsilon) \epsilon \cdot d\epsilon n_{FD}=\frac{1}{(1+ e^{-(\alpha +\beta \epsilon_k)})} \psi(\alpha ,\beta, V) =\beta PV =\sum_\vec{k} \ln{(1+e^{-(\alpha +\beta \epsilon_k)}) } and in an...
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    Lagrangian Mechanics, bead on a hoop

    Homework Statement This is the problem: http://i.imgur.com/OJyzfhz.png?1 Homework Equations $$\frac{dL}{dq_i}-\frac{d}{dt}\frac{dL}{d\dot{q_i}}=0$$ $$ L=\frac{1}{2}mv^2-U(potential energy)$$ The Attempt at a Solution This is my attempt at question A): http://i.imgur.com/IeJVGm3.jpg...
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    Evaluating a line integral

    Homework Statement P is the part of the curve 9y²=4x³ between the points (1,-2/3) and (1,2/3). Evaluate the integral $$\int_P x ds $$ Homework Equations The Attempt at a Solution $$\int_P x ds = \int_P x |r'(t)| dt $$ My problem is that I cannot find a right...
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    Electric field along the y-axis of a charged semicircle

    Homework Statement Find the electric field along the y-axis of a charged semicircle (with the center of the circle in the origin) with radius R, with a uniform charge distribution $$ \lambda$$ ...
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    Can't solve this difficult definite integral for the life of me

    Homework Statement Definite integral: \int \frac{\ln(x+1)}{x^2+1} dx from x=0 to x=1 (sorry I don't know how to do integral boundaries with tex) The Attempt at a Solution I just am clueless on how to do this, I'm almost 100% sure you are not supposed to find the anti-derivative...
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    Special relativity problems

    Homework Statement Two planes are flying (one behind the other) with the same speed v with respect to the ground, and they have two identical clocks on board. The distance between the planes is determined on x_1 (they don't mean the distance measured is equal to x_1 do they..?). On t=0...
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    Atwood machine acceleration

    Homework Statement I'm trying to find the acceleration of the masses in an atwood machine, the pulley has a rotational inertia I. The pulley has a radius R Picture : http://en.wikipedia.org/wiki/File:Atwood.svg But I made it accelerate the other way, so the equations from newtons 2nd law are...
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    Number minus sum of digits is dividable by 9

    Hello! Why is it so, that if you have a number, for example 183, you take the sum of the digits of that number, so 183-(1+8+3), u get a number that is always dividable by 9? I'm sorry if this is a dumb question, I'm not very good at math but still curious to know.
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    Find the pattern

    Which one do you think is next?
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    Average induced voltage

    Homework Statement A coil with 10 windings(radius 0,07m) is inside a homogenous magnetic(B=0,050T) field, it makes an angle of 90 degrees with the field lines so the magnetic flux is at it's max. Over a period of 0,050 seconds it gets turned by 180 degrees, what is the average induced...
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    Air pressure of guy jumping

    Hello, I don't need help solving a problem, but need help explaining why the given answer is true because I don't understand. A guy is jumping from something(outside) and I need to calculate the air pressure at a certain height. Given is that the temperature on sea level is 1,013*10^5 Pa, and...
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