General Definition and 1000 Threads

Recalling my reading on a variety of physical systems solutions were always defined for some time after the system is energised. For example circuits, waves... For these systems a whole lot of complex, "stuff" eg sloshing around of energy, occurs to result in a stable value in time, stable...

Hello, If I have an x^2 graph that goes from 0 to a point a. Is there a general solution to where the area of the left side is equal to the area of the right?

Hello, I am new to this forum, but have read a lot of posts and it seems really cool. I am 38 and have a B.S. in mathematics (from many years ago). I work in insurance, so I am pretty far removed from acedemia now. I have kept up my math studies as a hobby. After studying a lot of theoretical...

Homework Statement Attached Homework EquationsThe Attempt at a Solution So the question says 'some point'. So just a single point of space-time to be isotropic is enough for this identity hold? I don't quite understand by what is meant by 'these vectors give preferred directions'. Can...

Forgive me if this question is a bit amateurish but i am no physicist. I know in general terms that GR and QM aren't compatible with one another, but my question is...Do they even need to be? can it not be a handoff scenario? why can't GR govern what it is supposed to govern and QM govern what...

Hi all, I'm working through chapter 2 of Michael Tinkham's Introduction to Superconductivity. On page 40, he asserts that the skin-depth for a general complex conductivity is (In Gaussian units) $$\delta = \frac{c}{\sqrt{2\pi\omega\left(|\sigma| + \sigma_2\right)}}$$ where $$\sigma = \sigma_1...

The conservation of probability says: $$\partial_t J^{0} + \partial{i}J^{i} = 0$$ Use the Schrodinger equation to obtain$$ J^{i} (\vec r)$$. I have no idea where to start this kind of problem because the notation makes no sense to me. I would appreciate a hint or nudge in the correct direction.

I don't know much about general relativity, but I'm curious if Zeno somehow foresaw the reallty of the universe many many years before Einstein did(without any rigour ofc, but still the idea holds?). Understanding the Zeno's arrow paradox, stating that an arrow is motionless at a certain moment...

What are the pros and cons between choosing Computational Physics vs choosing Gen Physics? I want to make the best choice I can but I want to move on to a masters in physics but I'm not sure if Computational Physics will have me ready for the masters degree.

Hi, I am wondering why every general solution to Schrodinger equation can be built from separable solutions. In other words, I don't follow that why every solution to Schrodinger equation can be written as $$\Psi(x,t) = \sum c_n\Psi_n(x,t)=\sum c_n\psi_n(x)\phi_n(t)$$ I know that the right hand...

Homework Statement "By choosing the lower limit of integration in Eq. (28) in the text as the initial point ##t_0##, show that ##Y(t)## becomes ##Y(t)=\int_{t_0}^t(\frac{y_1(s)y_2(t)-y_t(t)y_2(s)}{y_1(s)y_2'(s)-y_1'(s)y_2(s)})g(s)ds## Show that ##Y(t)## is a solution of the initial value...

Hello. Resistive Ohm's law is famously known as V = IR. We can derive its microscopic version as being followed. V = El, where E and l are, respectively, an electric field and a resistive load length over which a voltage drop V is developed. I = JS, J and S are a current density and a...

Hi everyone! I wanted to put a quick post up on the forum! I'm a final year undergraduate chemistry student, and my dissertation topic involves using molecular quantum dynamics to simulate charge-transfer at a solar cell heterojunction. My knowledge of quantum mechanics is acceptable, but I'm...

Homework Statement I just can't seem to get the right answer. z^4+80i=0 looking at the complex plane u see the radius=r=80 (obviously) using De Moivre extension: z^n=(r^(1/n))(cos((x/n)+k2pi/n)-isin((x/n)+k2pi/n)z1=((80)^(1/4))(cos(3pi/8)+isin(3pi/8) shouldnt this be a root?z2=...

I'm reading a very general definition of parameter on this site Parameter definition - Math Insight. I didn't understand why we call the variable $t$ of the curve $\alpha(t)=(\cos t,\sin t)$ a parameter. For me $t$ in this case is a variable too according to the definition of the site I...

Is the Hubble's law(recessional velocity linearly proportional to distance) valid for all cases even when the spacetime is curved? Is there a nonlinear model for Friedman models or it's always linearly proportional?

< Mentor Note -- thread moved to HH from the technical forums to use a scpecific schoolwork problem to illustrate the general concept of torque in a FBD > I'm writing up a lab report for Physics class and I have to draw FBDs for torque being applied to a ruler resting on a pivot point. I've...

Moderna Therapeutics has apparently been working on developing RNA for drug uses with a minimum of publicity, publishing mostly just patents and getting a lot of investment capital. Their goal is to make injectable RNAs that will be translated into specific proteins. This approach could be...

Has anyone heard of "Bauer's Paradox" in Einstein's working out his equations for General Relativity? The description I came across was extremely fuzzy (something about an expression for a certain tensor adding up to be zero when it shouldn't, or vice-versa), so I am looking for a better...

So I'd like to say sorry if this has been posted before, or I'm placing it in the wrong area... After taking several months off (which I probably shouldn't have done) I am going to start self teaching myself, some subjects will be easy, but what I'm wondering is how can I properly test myself...

Had to find the general formula for the gradient of a function r^n. r is the length of the vector connecting (x,y,z) with (x',y',z') I took the gradient of r^n and simplified it. If I plug in any number for in in r^n and go through the process, I will get the same result as if I take this...

I am thinking about taking GR as an elective,but I have no plans on going into cosmology or any related field.I wanted to know if when applying for graduate school,whether it is a positive for them to see you have taken a "high level" course,such as GR. I know that the best thing is to have...

Let us assume that a spacetime has a global time-displacement symmetry described by a timelike Killing vector field ##\xi^\mu=(1,0,0,0)##. Further assume that we have a particle with four-momentum ##P^\mu=m\ V^\mu##. It is well-known that a stationary observer with four-velocity ##U^\mu##...

Homework Statement An equation of motion for a pendulum: (-g/L)sinΦ = Φ(double dot) Homework Equations L = length g = gravity ω = angular velocity Φο = initial Φ The Attempt at a Solution The solution is Φ=Asinωt+Bcosωt solving for A and B by setting Φ and Φ(dot) equal to zero respectively...

Last year I finished the undergraduate course in Mathematical Physics. This year, more precisely in March, I'm going to start the graduate course to acquire a master's degree in Physics. Now, for this course I must choose a research topic and find an advisor. This is being a little bit...

Homework Statement Hello gentlemen! I came across a real challeging problem about static, which states the following: assume a force system is equivalent to a force \vec{F}_{1} and a couple M_{1}\vec{k} acting at a point \vec{r}_{1}. Find some point \vec{r}_{2} and a force \vec{F}_{2} so that...

Conceptual question here: In the case of something that dissipates energy, how do we describe the transition between the range along which the system can continue to dissipate energy more or less in the same way and the point at which, given increasing temperature, the system can no longer...

Homework Statement I have ##R^{u}_{o b u } F^{o}_a - R^{u}_{oau}F^{o}_{b}## and I want to show that this equal to ##2R_{o[aF^{o}_b]}## where ## [ ] ## denotes antisymmetrization , and ##F_{uv} ## is a anitymstric tensor Homework Equations Since ##F_{uv} ##is antisymetric the...

Consider: 1. Energy is a system's ability to do work. 2. Work is force over a distance. 3. A force is applied over some distance. 4. All physical change (i.e. all change in a system through its phase space) is the result of force. ∴ Therefore, energy would seem to be a system's ability to...

Homework Statement Calculate the circumference of the circle θ = θ0 (a constant) in the spatial geometry \begin{eqnarray*} dS^2 = a^2(d\theta^2 + sin^2\theta cos^2\theta d\phi^2) \end{eqnarray*} Hence, (by finding R(z)) sketch the cross section of the surface embedded in three dimensions via...

Hi, I'm developing a data structure to represent 3-D meshes for numeric simulation. I want those meshes to be able to handle any type of polyhedron (not only the classic tetra and hexahedron). The best data structure that I could find was one based on half-edges (or darts), such as this one...

Hello everybody, I'm currently helping a friend on an assignment of his, but we are both stumbled on this exercise, I'm posting it here We define a function ##f## which goes from ##\mathbb{R}## to ##\mathbb{R}## such that its argument maps as $$ x \mapsto...

I've volunteered for a project at my uni in which the objective is to develop a "green wave" system to sync traffic signals for cyclists. We have a specific location, but the idea is to build a general case that can be applied to any stretch of road. The brief is super vague and we didn't...

Homework Statement In is more acidic than but In (para nitro phenol) is more acidic than (ortho nitro phenol) why? Homework Equations in ortho nitro benzoic acid due to -I and -M effect it is more acidic than it's para species (-I effect more in ortho position) . The Attempt at a...

Homework Statement In pyrrole the electron density is maximum on which carbon atom? so if the numbering starts from nitrogen, the carbon on the right side of nitrogen let it be numbered as 2 and the next one as 3 and so on... which of the following options will have the carbons of maximum...

Is it correct, at least in the context of general relativity, to say that in a coordinate basis, the inner product between space-like basis vectors will be 1, and in a non-coordinate basis the inner product will be defined by the corresponding component of the metric? Can I take this conditions...

1.- The hilbert space approach does not include distributions (free particle, for example) nor mixed states. 2.- The C* algebra approach does not account for unbounded operators. 3.- Rigged Hilbert space approach does not include mixed states. I'm not sure about path integral formulation... so...

I don't quite get this question, how is it done ?

I understand that General Relativity can make a difference between a spinning and non spinning mass thus can make better prediction for planetary orbits for example. The effect is frame dragging. However if we simulate a Newtonian gravitation and instead of representing a planet as a sphere...

Hello all, I'm an undergraduate at a large research university in Massachusetts working in a lab where my group contributes to the Muon g-2 experiment at Fermilab in chicago. Essentially what I'm working on is optimizing an optical rotation (Faraday) magnetometer system for use in magnetic...

Hey guys, I am teaching general physics (among other things) at an international school. The general physics course is designed as a introduction to all students to physics. These students could be interested in physics-career or not. My principal has given me a lot of leeway in designing my...

In my Google searchs and by reading threads on this forum I've seen that the books people most recommend on general relativity are Graviation, by Thorne, Wheeler and Misner, Wald's book and Weinberg's book. I'm in the first year to get a bachelor degree on physics and I could read any of these...

I've heard that unlike Special Relativity, General Relativity claims that you can' say any reference frame is better than another frame, including frames in which Newton's Laws don't hold. I've seen debates about this specifically in the context of geo/helio-centrism. From what I understand...

Hi. (I'm sorry for my poor English.) I'm looking for a good book on General Relativity, specially on Black Holes and Graviational Waves. I got Schultz book once ago, but it has a fuzzy notation and does not deal with the math as I suppose to. I know the basics of Differential Geometry, Topology...

In Schutz says When we have weak gravitaional fields then the line element *ds* is $$ ds^{2}=-(1+2\phi)dt^{2}+(1-2\phi)(dx^{2}+dy^{2}+dz^{2}) $$ so the metric is $$ {g_{\alpha\beta}} =\eta_{\alpha\beta}+h_{\alpha\beta}= \left( \begin{array}{cccc} -(1+2\phi) & 0 & 0 & 0\\ 0 & (1-2\phi) & 0 &...

I'm trying to understand how the various EM tensors work in General Relativity. The only source I've found is https://en.wikipedia.org/wiki/Maxwell%27s_equations_in_curved_spacetime, but there are two things I don't get. Why do they use ordinary partial derivatives instead of covariant ones...

I have spent hours on the web and in libraries to obtain a general and careful approach to the notion of capacitance, without success. Please, read carefully the question: I already know the usual blabla about capacitance. Also, I appologize in advance for the length of this question. I...

Hello I have not understand this.

Hello, I am currently in my third year of study in the honors bachelor of applied physics program at my university. At the beginning of this semester I was placed on academic warming. I need to get my GPA up in a few key physics courses to solve this problem. I have a few question however. I...

Hi guys, I need to design a transistor switching circuit to switch two channels on a tube/valve amp without adding noise or altering the sound of the tube channels. What issues am I likely to have to deal with? Thanks, Billy