General Definition and 1000 Threads

I where looking for elements that can absorpt neutrons without generating radioactive materials, and I found that most of them in Earth are suitable. I found that could work: C, O, Si, S, N, H The most common isotopes can receive one or two neutrons being stable, but if a neutron would be...

Are there a lot of theoretical research jobs in general relativity or would that be too hard to find?

Maybe I'm just being stupid, missing something simple ? How do you get from the top two equations to the second equation? Many thanks

Hi, Do we obtain the same escape velocity equation: Ve = sqrt(2GM/r) using both Newtonian and Relativistic approach?

I am collecting ways to visualize the curvature of spacetime -- and movement of objects affected by gravity -- as per Einstein's GR. Alternatives to the bowling ball / trampoline image so often used in the popular press. Images that show the similarities / differences between Newton & Einstein...

Background: I'm about to graduate with a mathematics degree(in the US), hence I have exposure to multivariable calculus, real analysis, abstract algebra, complex variables etc (no differential geometry however). I have also taken a class on QM(using Griffiths) and I saw some SR during a Modern...

I’ve already taken intro chemistry with a lab, and general chemistry 1. Unlike most universities, my college doesn’t require chemistry for physics majors. Should I take general chemistry 2? Would it really benefit me, or should I spend my time elsewhere? Edit: I’m referring to the standard...

I'm currently building a turbo-shaft engine and I am trying to find a good, yet simple to build free power turbine for extracting the exhaust energy of the jet engine. The Ljungström turbine seems promising as it is compact and easily machined from a 3 axis cnc machine. Does anyone know of the...

Is there a sensible way of defining a displacement vector in a general manifold? That is, the displacement vector being the difference between position vector at two different points... the problem is that these two different points have, in general, different tangent vector spaces. Never the...

Hi, I'm wondering if it is possible to measure radii of stars using general relativity, given its explanation of gravity as curvature of space. Thank you

I have little exposure to mathematics beyond high school algebra and physics, but I have become increasingly interested in physics, particularly its most towering achievements of modern times : Quantum Physics, as well as A. Einstein’s Special and General Relativity, the latter of a...

Hello! Thanks for your time reading my questions. When I was studying quantum statistical mechanics, I get so confused about the relations between Pauli's exclusion principle and the Fermi-Dirac distributions. 1. The Pauli's exclusion principle says that: Two fermions can't occupy the same...

High school student here... Recently, I've found an interest in topology and am trying to figure out the correct path for self-studying. I am familiar with set theory and some concepts of abstract algebra but have not really studied any form of analysis, which from what I've read is a...

There are two ways to revolve, around Y or X and the formulas are different. If I have something bounded by $$f(x) = x^2 + 1$$. I can write $$x = \sqrt{y - 1}$$. But, is it wrong to swap axis to show that I'm integrating dy, not dx?

$$4\frac{\partial u}{\partial t}+\frac{\partial u}{\partial x} = 3u$$ , $$u(x,0)=4e^{-x}-e^{-5x}$$ let $$ U =X(x)T(t) $$ so $$4X\frac{\partial T}{\partial t}+T\frac{\partial X}{\partial x} = 3XT$$ $$4\frac{\partial T}{T \partial t}+\frac{\partial X}{X \partial x} = 3$$ $$\left(...

If I am given the variable of time (observed), and diameter is it possible to measure the distance of a galaxy? Or do I need more variables? Just trying to figure out the most simple way to go about doing something like that.

This one may seem a bit long but essentially the problem reduces to some matrix calculations. You may skip the background if you're familiar with Lorentz representations. 1. Homework Statement A Lorentz transformation can be represented by the matrix...

I have a very general question... When labelling initial or final components on the x and y axes do you write, for example... Vxi OR Vix Is there a right or wrong answer? What is the convention?

Is the increase in mass/density of an object in motion purely relativistic? What I mean is if you were in a spaceship approaching the speed of light would you be able to measure a change in your mass/density or would the change only be observable to someone at rest. I'm aware of the Lorentz...

Hey guys! How do I derive the general expression for delta p times delta x which is the exception value in the harmonic oscillator. I am supposed to establish delta p and delta x as operators and the express those operators by raising and lowering operators.

I have Abstract Algebra Course, and my teacher is using the book, "Abstract Algebra" of David S. Dummit, and Richard M.Foote. This book, and other books which my teachers are using for the courses, seem to give definitions, theorems, and problems, in no historical order or are not mentioning the...

The question is not to distinguish space from time, but in general, what distinguishes a spatial dimension from other types of dimensions? For example, Hilbert space has an infinite number of dimensions, but they are not spatial; string theories add extra spatial dimensions. Is there a...

What tips should I follow to write a perfect essay?

Hi. I want to learn - amateurishly - Quantum Mechanics, and General Relativity, but my experience with Physics is very small. I want to ask, what should I learn - what books should I read - before I start to learn those theories? Sorry for my english.

Any one please refer some text for general theory of relativity, Also share some link of PDF about GTR

I'm trying to understand the BMS formalism in General Relativity and I'm in doubt with the so-called Bondi Coordinates. In the paper Lectures on the Infrared Structure of Gravity and Gauge Theories Andrew Strominger points out in section 5.1 the following: In the previous sections, flat...

On the one hand, the intuitive notion of a recurrence relation is clear from examples. On the other hand, what is the precise way to define it? The first interesting technicality is why should we call it a "relation" ? Is it, in general, a "relation" and not the more specific case of a...

I will be proceeding onto my masters degree in theoretical physics in about two months time. My goal is to learn as much as I can about quantum and statistical physics, as this is the field in which I would like to do my PhD. In my second semester, I have the chance to either study the...

Hi there. I am working with a problem where a sequence of numbers arises. This sequence reads: ##\{0,1,3,5,10,15,21,28\}## as far as I have worked it. I am trying to figure out the underlying relation that gives this sequence. These are related to indexes in a matrix, and I am trying to...

Hello! I solved the MIT physics graduate general exams (the Part 2 from http://web.mit.edu/physics/current/graduate/sampleexams.html) and they are super useful to consolidate your knowledge in the areas they cover. Does anyone know where (and if) I can find the exams between 2002 and 2012 and...

$\tiny{3.1.1}$ find the general solution of the second order differential equation. $$y''+2y'-3y=0$$ assume that $y = e^{rt}$ then, $$r^2+2r-3=0\implies (r+3)(r-1)=0$$ new stuff... so far..

Hi all, Only one is true at a time "general theory of relativity or Planetary orbits are elliptical...please clarify me I will thank full to you..

For this task i have to use differentiation to find a general expression for the rocket's velocity as a function of time. Q. A toy rocket has been launched straight upward. Altitude y as a function of time is given as y=bt−ct2, w b = 81 m/s , c = 4.9 m/s2 , t is time in seconds, y is in meters...

Could someone please provide guidance on how to begin this problem? I've attached the preface to the assignment question.Show that the general solution of the differential equation y″(x)=−y(x) is y(x)=Acos(x)+Bsin(x) where A and B are arbitrary constants. Hint: You'll need the Taylor series...

Homework Statement Homework Equations General Formula for Tan(a)=Tan(b) The Attempt at a Solution See the question I have uploaded. I have tried solving it this way, Firstly I applied the Quadratic Formula to get, Now we have two cases, CASE-1 When So General Formula here will...

Hello, How can I evaluate the following nested integral in MATLAB for a general value of ##K## {\int\limits_{u_1=0}^{\gamma}\int\limits_{u_2=0}^{\gamma-U_1}\cdots \int\limits_{u_{K}=0}^{\gamma-\sum_{k=1}^{K-1}U_k}}f_{U_1}(u_1)f_{U_2}(u_2)\cdots f_{U_{K}}(u_{K})\,du_1du_2\cdots du_{K} where...

Dear all I've been trying to work out the general solution to a 2nd order ODE of the form f''(x)+p(x)*f(x)=0 p(x) is a polynomial for my case. I believe series method should work, but for some reason I would prefer a general solution using other methods. I'll be much appreciative for any help...

hi everyone iam new here and i need help in general plane motion when we applied this eq aG=(angular acceleration)*r

\nmh{895} Find the general solution of the given differential equation $\displaystyle y^\prime - 2y =3te^t, \\$ Obtain $u(t)$ $\displaystyle u(t)=\exp\int -2 \, dx =e^{-2t} \\$ Multiply thru with $e^{-2t}$ $e^{-2t}y^\prime + 2e^{-2t}y= 3te^{-t} \\$ Simplify: $(e^{-2t}y)'= 3te^{-t} \\$...

Find the general solution of the given differential equation $\displaystyle y^\prime - 2y = t^2 e^{2t}$ Obtain $u(t)$ $\displaystyle u(t)=\exp\int -2 \, dx =e^{-2t}$ Multiply thru with $e^{-2t}$ $e^{-2t}y^\prime + 2e^{-2t}y = t^2 $ Simplify: $(e^{-2t}y)'= t^2$...

$\textsf{find the general solution}$ $$xy'+2y=e^x$$ $\textsf{divide thru by x}$ $$y' +\frac{2}{x}y=\frac{e^x}{x}$$ $\textsf{Find u(x)}$ $$\displaystyle u(x)=\exp\int\frac{2}{x} \, dx=e^{\ln x^2}=x^2$$ $\textsf{so far anyway..}$

So the other day I saw a YouTube video on how gravity works according to general relativity. From what I understand, objects bend space_time with their mass and create a shape which is close to a cone. Since objects only move forward in time through a straight line, the bent space_time makes...

<Moderator's note: Moved from a technical forum and thus no template. Effort in post #3.> What is the condition of tangency of a line y=mx+c on parabola with vertex(h,k) ,say for parabola (y-k)2=4a(x-h)? I could only find the condition of tangency on standard form of parabola, in the internet...

Hello everyone, I'll go straight to the question. The gravitational time dilation is equal to tearth = tspace*sqrt(1 - rs/r), with rs = 2GM/c2. However, the formula for speed of light in gravitational field is equal to v = c(1 - rs/r). My intuition tells me that these two formulas must be the...

So, if kinematics is the study of motion without reference to its causes (which is how it seems to be defined in many places), then here is my attempt to come up with a complete picture of motion without reference to its causes. This is just a summary to help me organize my thoughts (it is NOT...

Homework Statement The question I am working on is number 3 in the attached file. There are two initial conditions given: at time = 0, x(t) = D and x'(t) = v 'in the direction towards the equilibrium position'. Does that last statement mean that when I substitute the second IC in, I should...

I see this has been already discussed but the old threads are closed. EPR before EPR: a 1930 Einstein-Bohr thought experiment revisited "In this example, Einstein presents a paradox in QM suggesting that QM is inconsistent, while Bohr attempts to save consistency of QM by combining QM with the...

Hi everyone, I just created this account because it was actually the first time I wanted to ask a question myself, but this forum has helped me a lot in the past with my Physics and Maths related courses. So thank you for that. Going back to the topic...Now that I've completed some of the...

I came across a contactor catalog saying "Definite purpose". Then tried to figure out the types of contactor. Came across definite purpose and general purpose. What is meant by definite purpose contactor and general purpose contactor? On what basis can i choose definite purpose?

Homework Statement Question attached: Homework Equations see below The Attempt at a Solution [/B] my main question really is 1) what is meant by 'abstract tensors' as I have this for my definition: to part a) ##V^u\nabla_uV^a=0## but you do say that ##V^u=/dot{x^u}## ; x^u is a...