1
vote
0answers
29 views

Is the expanding of the universe also a cause which can induce gravitational waves from mass?

Gravitational waves arises when mass is rotating in another mass'orbital, in explosions and of course in case of colliding black holes. But are they also created when mass is moving and speeding ...
-2
votes
0answers
30 views

Observer inside Schrodinger's box

Let's place a human observer with Schrodinger's cat inside the box. After some time, the inside observer finds out that the cat is dead. For an outside observer however, the state is a superposition ...
0
votes
2answers
32 views

microstates and internal energy

Consider a system having an internal energy U. The internal energy U is a macrostate parameter but has many microstates. What is the difference between 2 microstates for a given internal energy U?
0
votes
0answers
26 views

Why is it said that the cosmic censorship hypothesis depends on the future evolution of the spacetime?

I am reading a bit about the cosmic censorship hypothesis and I came across the following statement: Cosmic censorship is precisely a statement on the global future evolution of a spacetime. My ...
-1
votes
0answers
5 views

Analysis of molecular properties of Polyatomic systems using Raman Spectroscopy

I have been working on the Raman Spectrometer for fast 1 week. I have been trying to figure out the title of my project work and things I would do. However, the title as stated above looks mostly like ...
0
votes
1answer
31 views

Schwarzschild manifold

I am given the following metric $$g = \frac{dr^2}{1-2m/r} + r^2dS,$$ where $dS$ is the standard metric on the sphere $S^2$. I am told that this is isometric to $\mathbb{R}^3$ or (taking its ...
4
votes
3answers
73 views

String models of particle physics

What general features of particle physics are derived/replicated by constructing string models of particle models? How do such models address the fixing of free parameters like the masses and the ...
0
votes
1answer
31 views

Exercise 18b in Schutz's First course in GR

The question is as follows: Show that a timelike vector and a null vector cannot be orthogonal. So we have a timelike vector $\vec{A}$, s.t $\vec{A}^2<0$; and a null vector, $\vec{B}$ s.t ...
0
votes
1answer
32 views

Is the cosmological time grosso modo isochrone?

Is the cosmological time grosso modo isochrone? by analogy with space isotropy. Or else do we have possibly great differences by analogy with great voids in the space. We know that it's not strictly ...
0
votes
0answers
24 views

Question on Law of Conservation of energy? [on hold]

A body of mass $m$ is thrown upwards with a velocity $u$. At a point $x$ metre above the ground, the ratio between kinetic energy and potential energy is 1:5. What will be the new ratio at $x$, if the ...
0
votes
1answer
25 views

Kronig Penney Model [on hold]

Why can't we solve the two differential equations obtained $$\dfrac{d^2\phi}{dx^2}+\dfrac{2mE}{h^2}\phi=0$$ and $$\dfrac{d^2\phi}{dx^2}+\dfrac{2m(E-V)}{h^2}\phi=0$$ .... By the same method by which ...
4
votes
1answer
38 views

Black hole singularity from collapsing light vs dust

Consider two black holes, one formed from a spherical cloud of electromagnetic radiation, and one formed from a non-interacting dust solution. The stress energy tensor is traceless for ...
0
votes
4answers
49 views

Are there any known non-zero mass objects travelling at almost $c$ observed in the universe so far?

Have we ever observed a body or particle with non zero mass traveling at almost $c$? I'm asking this because according to relativity as an object approaches light speed it's mass approaches infinity, ...
1
vote
1answer
35 views

$F\cos\theta$ is not proportional to $d\cos\theta$?

If I’m working in two dimensions and I wanted to calculate the net electrostatic force on charge C, where charges A and B are stationary, of the same charge, and placed on the y-axis equidistant ...
1
vote
0answers
47 views

How could a heavy manhole cover jump out of the ground, fly through the windshield and hit a driver in a car?

Today (12 of Feb), there was this accident in Boston where a driver was killed because a manhole cover (~200lbs) had somehow become airborne and struck her. The car looks like an SUV, so her head must ...
0
votes
1answer
32 views

Tensor product distributive property?

Is it true that for vectors $a$, $b$, $c$, $d$ we have $$|a\rangle \otimes |b\rangle \langle c| \otimes \langle d|= |a \rangle \langle c| \otimes |b \rangle \langle d|?$$ So does this kind of ...
0
votes
1answer
30 views

Reference point for U tube question

Referring to the following diagram, I am expected to pick out the one case where the fluid in the tube is not in static equilibrium. They are in the other three cases. The answer is that situation 2 ...
0
votes
0answers
13 views

What's the simplest, first order way to calculate the temperature change in this scenario?

I am trying to model this experiment in a simple (i.e., relatively analytic, non-computational) way. I have a little square of a thin film (10s of nanometers thin) of material A, on a relatively ...
-1
votes
0answers
19 views

Electric flux boundary condition

I dont' get why following equations hold isn't equation (3-121b) should be $D_{2n} - D_{1n} = \rho_s$ instead? Since $D_{2n}$ is going outward of the gaussian surface whereas $D_{1n}$ is ...
3
votes
1answer
56 views

Heisenberg Uncertainty Relation and Relativity

It's well known that in QM the position and momentum of a particle cannot be known simultaneously. It's also well known that in special relativity the idea of simultaneity loses its meaning. Would it ...
0
votes
0answers
25 views

Graphic analysis of sound wave acceleration

I'm working on a lab involving measuring the velocity of various sound waves, done by dropping a bowling ball with accelerometers lined up in a certain position nearby. Each accelerometer is a fixed ...
1
vote
2answers
46 views

Are gravitational waves effected by the curvature of space time (gravitational lensing)?

I have a basic question I can't seem to find anything on (I keep hearing about how gravity waves and gravitational lensing were both predicted by Einstein). We all know about the gravitational ...
3
votes
1answer
58 views

How did LIGO detect the source of the gravitational waves?

I read the newspaper today and I found that LIGO had detected gravitational waves. This is from their official website: For the first time, scientists have observed ripples in the fabric of ...
0
votes
2answers
60 views

What is the amount of dark energy in the Universe, in joules?

I'm toying with an idea, and need absolute amounts of dark energy. I'd also like the same for dark matter. If these values are not estimated, why not?
-1
votes
0answers
28 views

Physics specific heat question [on hold]

The instructions below outline the procedure for a demonstration. Materials: four 100 g metal blocks, each of a different metal, four polystyrene foam cups, each containing 150 g of 10°C water ...
0
votes
0answers
20 views

Time-coherency of “incoherent” light

Even "incoherent" light as the one of a light bulb has some coherency, and would interfer in the double-slit experiment (even if more blurry because the different wavelengths don't trigger the same ...
0
votes
2answers
27 views

Proving charge on outer surface of parallel plate capacitor must be zero

If we have two conducting plates, with charge $Q$ and $-Q$, why is the charge on the outer surfaces of each conductor zero? I've been trying to wrap my head around the problem. Firstly, don't excess ...
4
votes
0answers
59 views

How does LIGO reduce noise below what it is detecting?

LIGO is designed to detect changes in length on the order of 10,000ths the scale of a proton. I know they are extremely well isolated from their surroundings, but how could we even approach isolation ...
-2
votes
2answers
54 views

Why didn't 0.2A at 2V kill me?

I was recently connecting a circuit together like here: and I had the voltage set at 2V, with a 10Ω resistor. By Ohm's law, there was a current of 0.2A (and was confirmed by my multimeter). I ...
0
votes
0answers
41 views

Are gravitons affected by the force of gravity?

Every particle, including photons, is affected by gravity. Would this be true for gravitons as well? Gravitons should always move at the speed of light, so, if photons are red-shifted while moving ...
-1
votes
0answers
15 views

Capacitor charge [on hold]

It takes 14.8 J of energy to move a 13.0-mC charge from one plate of a 17.0-μF capacitor to the other. How much charge is on each plate? Assume constant voltage.
0
votes
1answer
23 views

Direct vs. indirect CP violation: theoretical foundations

I know very little about the difference between direct and indirect CP violation. I've been studying QFT from Peskin and Schroeder's "An Introduction to QFT", and they don't seem to address this ...
0
votes
0answers
13 views

Can I determine the maximum acceleration with frequency and magnitude?

Consider a mass oscillating up and down on a spring with negligible energy loss. If only the frequency and magnitude of the oscillation is known, how can one determine the maximum acceleration of the ...
0
votes
0answers
21 views

Higgs mechanism preserving supersymmetry

It is said that if supersymmetry was unbroken, masses of the superpartners would be equal. But at least for MSSM there are no SUSY-invariant terms that would allow the electroweak SSB, as far as I ...
0
votes
0answers
22 views

simulation probabilistic classical computation on quantum computers

Given an $N$-level quantum system with computational basis $\{|1> ,|2> , \cdots, |N> \}$, if we perform an unitary operation $U$ on a computational basis state $\{|j> \}$ and then measure ...
1
vote
0answers
24 views

Acceleration 4-vector in Schwarzschild metric [on hold]

I am working on A note of a paradoxical property of the Schwarzschild solution by Abramowicz M. A. and Lasota J-P It is a note on surprising cases in the context of the standard Schwarzschild ...
0
votes
1answer
46 views

Which requires less energy, complete mechanical breaking or vaporization of matter?

Let's say we have a one kilogram piece of rock. Now if we want to separate each molecule from the other molecules making this piece of rock, which method requires the least energy while neglecting ...
1
vote
0answers
63 views

Why are the arms of the LIGO interferometer so long?

The LIGO experiment consists of two interferometers, where each one of them has two 4 km long arms. Within these, light is further trapped via Fabry-Pérot cavities to achieve a total path length of ...
0
votes
0answers
14 views

Resonant Scattering and the Breit-Wigner Formula

Most of what I ask relates to the derivation found here: https://farside.ph.utexas.edu/teaching/qm/lectures/node91.html The basic idea is that we first consider zero energy s wave scattering from a ...
0
votes
2answers
33 views

Question about limit cycles and linear systems

In here http://users.isy.liu.se/en/rt/claal20/SysBio2015/Notes_SysBio_2015_partC.pdf it says: A limit cycle is however an intrinsically nonlinear concept: a linear system cannot have a limit ...
0
votes
2answers
58 views

Information can't travel faster than $c$

When we say that information cant travel faster than light, we mean that phase velocity can go beyond $c$ but the group velocity can't. Hence, we say that a plane wave carries no information. What I ...
0
votes
0answers
11 views

Can Obstruction of EM waves itself obstruct change in field?

Let us continue to accelerate a particle P, up and down: between two points X,Y in space(and, say, always in a symmetric manner relative to X,Y). Now, as I know, we'll be continuously dragging the ...
1
vote
0answers
27 views

Two Dimensional Momentum [on hold]

[2] []3> A tennis player receives a ball of mass $60\ \mathrm g$ travelling horizontally at $55\ \mathrm{ms}^{-1}$ perpendicular to the net, and returns it at $28\ \mathrm{ms}^{-1}$ in a direction at ...
3
votes
0answers
71 views

Are gravitational waves dissipated and what is the mechanism?

I was amazed by the fact that we have been able to detect gravitational waves created thousands of year before they were observed. My surprise is that any wave phenomena I know it is always ...
0
votes
1answer
53 views

How much time distortion was caused by GW150914?

I understand (at least I think I understand) that LIGO used distortion of space to detect GW150914 (one arm grew longer, the other arm grew shorter, causing interference in the returning laser-pulse ...
-2
votes
0answers
17 views

Is wormhole time travel possible? [on hold]

I'm a student in the UK, doing an EPQ, I was wondering what your views are on wormhole time travel. Do you think it's possible, I understand that forwards time travel is more likely than backwards ...
-1
votes
1answer
14 views

Proper significant digits in terms of a characteristic scale

Suppose I have a defined quantity in a paper $$g = 20\ \mathrm{meV}$$ and I wish to express the following equivalence (where $k_{B}$ is the Boltzmann constant which easily has more than 3-digit ...
0
votes
0answers
6 views

Two-particle correlation function for Slater determinant

In a paper by Peschel, http://arxiv.org/abs/cond-mat/0212631, he writes: Consider first a system of free fermions hopping between lattice sites. The one-particle correlation function is ...
-2
votes
0answers
27 views

Can something made of atoms be subatomic? [on hold]

Let's say there is an object made of atoms, this object is subatomic in scale. Can such a thing exists?
0
votes
0answers
28 views

Has Jaynes' argument for quantum mechanics as a possible theory of inference been debunked?

To my understanding, there is currently no scientific consensus on which interpretation of quantum physics is the correct one, if any. The most famous one, perhaps for historical reasons, is the ...

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