Reference Definition and 1000 Threads

i would like to read some stories in Fermi's research

I have gone through two volumes of Cohen (Quantum Mechanics). Now I need a book on Quantum Statistical Mechanics. The book should use axiomatic formulation using density matrix. Please give me a suggestion. ( I'm also introduced with 2nd quantization slightly) Thanks for any help in advance.

hello, in relativity something can go faster than the speed of light as long as it is not in the observer's frame of reference which would say that a FOR has a size but i read that a FOR was infinite in all directions. Someone explain this contradiction please!

can inertial reference frame ever have "lenght contractions" in 3d or in rest? hi! thank you for all answers in this topic in previous threatin same topic. i open this new thread in same topic but here i try to keep the issue here very short and readable , with no speculation and concentrating...

We have a problem of perfect reference frames( according what we are taught in school) If universe is expanding, the so called fixed stars are also moving. According to the special relativity, the speed of light is constant in every reference frame, So if we let light as the perfect reference...

hi can inertial reference frame be in different sizes at least in theory? i mean that can there be two different frames of reference in same place at same time, where the observer in both frames observes physical laws to be normal in their own frame of reference, but the other frame appears to...

So, the gravitational potential energy of a mass "X" from the sun is, let's say, 100joules. Why is it that when we take the gravitational potential energy of the mass from the reference point of infinity that the gravitational potential energy is -100joules? I understand the negative...

Homework Statement Particle track detectors are used to measure the speed of particles if the lifetime of the particle is known. Particle X has a lifetime of 256.2 ps. These particles are created in an experiment inside the detector by a given reaction. The particles leave 21.8 cm long tracks...

Hi. In Apostol's book "Introduction to analytic number theory", Teorem 3.2(b), Apostol proves (1) \zeta (s) = \lim\limits_{x \to \infty} \left\{ \sum\limits_{n \leq x} \frac{1}{n^s} - \frac{x^{1-s}}{1-s} \right\} for s in critical strip. I know this translates to a Mellin transform...

I know the triple point of water is at 273.16K and atmospheric pressure But how are we going to make it as a reference when we measure temperature of something? Thank you

Hi! I think this should be a fairly easy question to resolve, but it's currently giving me fits... Suppose we consider a system of three interacting particles where we assume two of the particle (at positions r1 and r2) have infinite mass (such that we can ignore their kinetic energy) and do...

Homework Statement In a given reference frame, event 1 occurs at t1 = 0 s and position x1 = 0 m while event 2 occurs at t2 = 3.6 × 10^−4 s and x2 = 0.60 × 10^5m. Is there a second reference frame in which these events could be at the same place but different times? If so, specify its motion...

Recently learned about Special Relativity, so my brain is running perpetual circles around itself asking questions. So, I figured I would come here and ask where could I find out more information about the Lorentz Factor being undefined at a luminal velocity? Or more basically, where do I...

Homework Statement a)Suppose the chancellor of the university drops a 2.00 kg water balloon from the administration building balcony 10.0 m above the ground. The chancellor takes the origin of his vertical axis to be even with the balcony. A student standing on the ground below the...

I was working on some algebraic topology matters, thinkgs like the connected sum of some surfaces is some other surface. And for this study, I was using the Munkres's famous textbook 'Topology' the algebraic topology part. My qeustions are as follows: Q1) Munkres introduces 'labelling scheme'...

I'm interested in a serious discussion (at the level of Arnold's mechanics text) about the alleged connection between Boltzmann's H theorem and Poincaré's theorem (rumor has it Boltzmann was pretty upset with Poincaré's result). Could anybody help me ? Thank you!

Before I say anything, I don't really have any experience in physics. But this question just popped into my mind concerning cause and effect and I can't seem to find the answer to it on the web. Here it is...Are cause and effect the same thing if a frame of reference is not present? For...

I have a small intuitive issue with the idea. If you could humour me for a moment, imagine a particle moving at some velocity v. An observer sitting on an armchair at rest wrt the background stars, but far enough away from them to negate any gravitational effects, sees the particle moving...

Homework Statement The problem, basically, is very simple but, it is confusing me. It says: "There is block on a moving train, which is being pushed by a man. The man applies force F to displace the block by s wrt Train. The moves S in that period. Find work done on the block by the force wrt...

I've read all sorts of descriptions in textbooks and online, but I don't get the purpose of reference frames. Why can't you just put everything on the same set of coordinate planes? I don't see what difference it makes. There was an example with a car traveling alongside another car, and that to...

Homework Statement I am doing a problem involving a man dropping a ball from the top of a mast of a ship at t =0 a height h above the origin of a ship's coordinate system. In the sea's frame of reference, the ship is moving with velocity u\hat{i} . The origins of these two frames...

Homework Statement You are traveling in a car going at a constant speed of 100 km/hr down a long, straight highway. You pass another car going in the same direction which is traveling at a constant speed of 80 km/hr. As measured from your car’s reference frame this other car is traveling at...

Hi I have recently started GR and have found the mathematics to be quite easy (have encountered differential manifolds and tensor calculus in other subjects), but the physics is troubling me, allow me to elaborate. In special relativity, we have a very intuitive idea of how observations work...

hi i am study the optical effect of alpha radiation and gamma radiation on cr-39 detector i want good reference for uv/vis spectroscopy ( obsorption and Fluorescence) and any good reference alpha track effect

Homework Statement An observer in frame S standing at the origin observes two flashes of colored light separated spatially by Δx = 2300 m. A blue flash occurs first, followed by a red flash 5 µs later. An observer in S ' moving along the x-axis at speed v relative to S also observes the...

I understand perfectly how to find the reference angle for a degree, such as 150 degress = reference angle of 30 degrees, because the 2nd quadrant goes from 90 to 180 degrees, so you simply subtract 150 from 180 to come up with 30. I get that: 11pi/4 = 495 degrees. 495 degrees will give you...

Hi guys, when I was trying to post something in the H/W forum and tried to use the Latex reference I could press the tab, but nothing happened. Is this a bug? Thanks!

Homework Statement If you are in a noninertial reference frame, that means: Homework Equations The Attempt at a Solution I know that nonintertial reference frame is something that is moving. However, if I am in it, then should I be moving together with it?

This is something that interested me after reading about time dilation. For the point of making it simpler, ignore relativity relating to gravitational fields Lets say for example, that the Earth does not orbit the sun, and the solar system doesn't orbit within the galaxy etc (makes it easier...

I understand that the ~14.6 billion year age of the universe is in the cosmological frame, i.e., representing the coordinate time elapsed in a comoving reference frame. Of course this means (as has been discussed plenty of times here) observers in different frames would measure a different age...

I'm a bit unsure about the last couple of bits of this question, and I'm hoping someone might be able to help. Homework Statement a) Let a reference frame with origin O & Cartesian axes (x, y, z) be fixed relative to the surface of the rotating Earth at co-latitude θ (i.e. 0≤θ≤∏, where θ...

Why are reference angles necessary in trigonometry. I understand they are the acute version of an obtuse angle.

Hey, I'm wondering if there is a small reference book/sheet or so around for writing up experiments in undergraduate lab work, mostly in the error analysis? How did/do you go about deciding on how to calculate various errors? Thanks!

Hi to all, I am a new one to this physics forum and i have a doubt regarding Inertial Reference frames. In an article of IRF, it is given as "There is no absolute inertial reference frame, meaning that there is no state of velocity which is special in the universe." Can anybody please...

I'm writing a scientific paper and I'm basing it on a set of simulations that I carried out. I have generated some plots and I need to show that my generated plots are exactly the same as the ones on a reference paper. Obviously, I can't just copy-paste the plots from the reference. So how do I...

It must be, right? Obviously, if you're pushing a block by exerting a force F on it over a distance D on the ground, if you are in the frame of you or the block, your distance is 0 so it appears you're doing no work. I ask this question because I was doing a practice problem that should be...

Homework Statement A space traveler takes off from Earth and moves at speed 0.99c toward star Vega, which is 26.00 ly distant. How much time will have elapsed by Earth clocks when the traveler reaches Vega? 2. The attempt at a solution I looked at the problem solution, which...

In studying SR, I've been subscribing to a particular definition of a Frame of Reference that makes sense to me. Recently, I've been made aware by another PF member that there may be other, broader, definitions that are valid and that people use. I would like to know more about these broader...

Practicing Lorentz transformations but still not absolutely clear about conditions for observer's frame of reference. For example: Suppose that just as one of Einstein's long and surreally fast trains is passing a station platform, lightning strikes the platform at two points making scorch...

Hello I know that 5 volts in reference to ground (0 volts) is 5 volts as there is a potential differencce of 5 volts between 0 and 5 volts. Does this mean 5 volts in reference to 2 volts would be 7 volts as there is a potential difference of 5 volts between 2 and 7 volts? Thank you for...

One can easily prove that \nabla \cdot f is invariant under a rotation of the reference frame, however I would like to prove that the divergence operator itself is invariant (same principle, different approach). In other words I want to prove that \mathbf \nabla = \mathbf e_x...

hey guys , is there anybody here to give me a nice reference for f(R) gavity ? Regards thecoop

I'm looking for an elementary book that has no prerequisites other than calculus, differential equations and elementary number theory about hypergeometric series. If it has good exercises in the end of each chapter, that would be great. Any suggestions would be appreciated.

Homework Statement I wanted to know if I consider the frame of reference as a rotating body itself, then will the points lying on the body rotating be stationary with respect to the rotating frame of reference? Homework Equations None The Attempt at a Solution As per me, if I am...

Hi there. I need help to work this out. A particle with mass m is studied over a rotating reference frame, which rotates along the OZ axis with angular velocity \dot\phi=\omega, directed along OZ. It is possible to prove that the potential (due to inertial forces) can be written as: V=\omega...

Basically: I jump forwards, exerting an amount of energy enough to push me forward with some velocity. But in my reference frame, I exert the same force, except the entire universe moves backwards with that same velocity, where did that energy come from? I sort of know this has to do with...

It is my understanding that the faster an object moves, the more energy is required to accelerate it. As an object approaches the speed of light, an infinite amount of energy is required to further accelerate it, which is why no object can travel faster than the speed of light. But movement is...

I have a question (thought experiment) that pertains to the speed of light and point of reference. I'm just interested in thinking about this subject and I can't quite get my head around this. I'm sure the answer is probably simple. Thank you for your help. By the way, if the answer involves...

I have a device (fNIRS, though knowledge of fNIRS probably isn't necessary to help) which produces very noisy signals and a noise reference. The noisy signal consists of a combination of a desired signal, and a noise signal, which is a scalar and phase shift of the noise reference. However, I'm...

Is there any other object except photon which moves at the speed of light? Why can't an object moving at the speed of light be taken as reference frame? Can we use the equation m=m(0)/sqrt(1-v^2/c^2) for an object moving with speed of light?