0
votes
1answer
8 views

Harmonic motion equation - non-null right hand side

Considering the following motion equation : \begin{equation} \ddot x + \frac{a^2 b^2}{c^2} x = -V \frac{a b}{c^2} \end{equation} where $a$, $b$, $c$ and $V$ are all constant. One can identify the ...
0
votes
0answers
6 views

How can I get the sensitivity of some eye cone at a specific wavelength?

The following graph shows the sensitivity for eye cones and rods, but I want to know e.g. what is the red cone sensitivity for a wavelength of 500 nm? How can I find an answer for questions like this?...
0
votes
0answers
9 views

Is my understanding of creation/annihilation operators' functional dependency correct?

I am trying to gain a little intuition about second quantisation, specifically about creation/annihilation operators. Lets say you quantise the free EM field (in 1d) and end up with the usual: $H=\...
-1
votes
1answer
18 views

Sending someone into the future using the sun?

Ok so for starters, i am not nearly as smart as the least-smart person on here, but I have been reading a lot about all sorts of stuff. We now know that the ability to "send" someone to the future is ...
1
vote
0answers
10 views

regarding the zero internal electric field in a conductor (electrostatic case)

Let's say we have a homogenous electric field in the z direction. For computational simplicity let's say we have a thin sheet of metal covering entire the x-y plane. The answer here is straight ...
-2
votes
0answers
13 views

Human Magnetic fields

What exactly causes a person to be extremely sensitive to static electricity? Is it caused from windy days or certain fabrics your body injesting various precious metals, and slowly discharged from ...
0
votes
0answers
6 views

Create spinning / modulating plasma effect without spinning the whole appartus

I'm trying to create a variable spinning / modulating plasma effect without turning the whole apparatus as seen in the video. https://www.youtube.com/watch?v=Wis_HEa3X84 Is it possible to just use ...
0
votes
0answers
17 views

How to intuitively understand susceptibility formula?

When calculating various susceptibilities, we get below formula again and again. $$\chi \left( {q,0} \right) \sim \sum\limits_{\bf{k}} {\frac{{{f_{\bf{k}}} - {f_{{\bf{k}} + {\bf{q}}}}}}{{{\varepsilon ...
1
vote
0answers
7 views

Plasma generated with gas and how far does it penetrate the skin

I know Far Infrared can penetrate the body’s tissues 1.5 inches (almost 4 cm) beneath the skin. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3699878/ But how far will a plasma field generated with ...
1
vote
1answer
50 views

Is $A_\mu A^\mu=0$ a good gauge fixing?

I am taking a course in classical electrodynamics and I am facing this problem Prove that $A_\mu A^\mu=0$ is a good gauge fixing or not. If it is, there are residual gauge freedom? I know that, ...
0
votes
1answer
15 views

Question on motion of vehicles

What slows us down while we are climbing in a sloped road, and what makes us faster while sliding down? Friction and what else?
0
votes
1answer
24 views

Are there any numerical predictions of the Newtonian gravitational constant $G$ from modern theories?

There are no established relationships between the Newtonian gravitational constant $G$ and other fundamental constants, so there is no way to derive its value from other quantities. Its value must be ...
0
votes
0answers
14 views

Is fluidic capacitance affected by the level of pressure

I am studying the bubble trapping by an active fluid inserted onto the channel. The equation for in and out flow is: q(t) = - dV/dt = -dV/dp * dp/dt = C*dp/dt. I have an exercise that asks what ...
4
votes
2answers
151 views

Is there any problem with the idea that gravity is repulsive at long distances?

If gravity is repulsive at long distances, would this suffice in explaining "dark energy"? Was there any reason why a new concept (dark energy) was introduced rather than just assuming that gravity ...
4
votes
2answers
55 views

Beyond Hamiltonian and Lagrangian mechanics

Lagrangian and Hamiltonian formulations are the bedrock of particle and field theories, produce the same equations of motion, and are related through a Legendre transform. Are there more such ...
0
votes
1answer
24 views

Composite materials

I'm reading about brake pad material. The paper said ...according to original equipment manufacturer (OEM) the pads are made by combining five types of materials: binders, abrasive, performance, ...
1
vote
0answers
20 views

Geometric (topological?) structure and consequences of the canonical hamiltonian method

(1) Even though (I think) I understand the concept of a tangent bundle, I have trouble assimilating the idea of the configuration space being one and in relation to what that is the case. How can I ...
1
vote
0answers
20 views

Correct terminology or way to refer to the 2 “types” of ice sublimation

I'm trying to get the right terminology for various forms of phase change. I am familiar with the phase change / triple point diagram for water, and we have various terms for the transition of a ...
-1
votes
0answers
27 views

Acceleration of particles, de Broglie wavelenght

I have an exam in two days and one of the questions I could get, that I cant find the answer to is: What's the point of accelerating particles based on the de Broglie Wavelenght? Is there some sort of ...
0
votes
3answers
45 views

Could dark matter possibly be anti-matter?

Considering the broken symmetry after the big bang - what I understand as there being a huge surplus of matter and a lesser presence of anti matter - is it possible that dark matter could be anti-...
0
votes
0answers
20 views

What is meant by interactions being mediated by force-carrier particles?

When a photon interacts with an electron, what is observed to happen? Force-carrier particles are described as the mediators of these interactions. What does this mean and how is this concluded?
1
vote
0answers
20 views

Simulating a noisy image: Poisson Noise Clarification

I'm currently working to simulate an image that mirrors the output of a CMOS camera we have in the lab. My images include Poisson (photon) noise as well as a gaussian (readout) noise. My issue is ...
0
votes
0answers
17 views

Magnetic field transformation under rotations

If you have magnetization vector in vertical magnetic field, it starts precessing. If you do a transformation to rotating coordinate system you obtain a stationary magnetization. Is there a direct ...
2
votes
1answer
21 views

Does the Bekenstein entropy bound present problems for unitarity in cosmological models that invovle a collapse or bounce?

If we expect the Bekenstein bound, or something like it, to hold in a collapsing universe, will that not eventually force us to accept some loss of information, or is there something I'm missing?
0
votes
0answers
14 views

A question about character table of the group Td. Field theory

I am trying to get the character table of the group Td using the basis functions already defined. I have a problem with the basis function (2z^2-x^2-y^2, x^2-y^2) because I don´t get the character -1 ...
0
votes
0answers
38 views

How to calculate possible spin of two photon system?

Photon hasn't well defined quantity such as spin. Instead of it, it is characterized by helicity $h$. Let's assume state of two photons in CM frame (with $\mathbf k$ being the momentum of one of ...
0
votes
1answer
54 views

Do photons interact with everything?

Suppose you shoot a beam of photons in a particle collider. Are there any particles in which the photons do not interact with? Q2: What is an interaction between particles?
-3
votes
0answers
22 views

Electrodynamics

I am having some trouble with this question. Why is there such a discrepancy? Is my reasoning correct? (this is my first time on such forums.. So kindly inform me if I am posting it at the wrong ...
4
votes
3answers
41 views

Why is there a matter-dark matter asymmetry?

It is said generally that nature is symmetric. For example if light behaves as both a particle and a wave, then matter must also do so, which turns out to be true. But we find that the Universe ...
1
vote
1answer
13 views

An approximation question from “Nuclear Models” by Judah Eisenberg and Walter Greiner

I'm looking at page 311 of the book "Nuclear Theory" by Judah Eisenberg and Walter Greiner. Now for identity (49) which is: $$\omega_{1,2}^2=\frac{\omega_\alpha^2+\omega_\zeta^2-2bc\omega_\alpha\...
0
votes
0answers
12 views

Explosion of a object into fragments and their position? [on hold]

While I was looking through my textbooks, I found a question: An isolated particle of mass $m$ is moving in a horizontal plane (the $x$-$y$ plane) along the $x$-axis at a certain height above the ...
-2
votes
1answer
34 views

Why speed of light is constant with respect to any inertial frame of reference? [duplicate]

Its getting too difficult to think.if we travel at the speed of light then will light will cross us at same speed or travel with us adjacent (special theory of relativity)
0
votes
0answers
39 views

Euler-Lagrange Equation in Quantum Field Theory

The quantum fields are operator valued distributions. In some sloppy books like Peskin and Schroeder the Euler-Lagrange equation are used to get the equations of motion. What does it mean to take a ...
0
votes
0answers
17 views

Which lightning (/physical phenomenon) did I witness to?

I witnessed a lightning at quite close distance, but since it was somewhat unusual, I was wondering what it was more exactly. I was on a pier on a small river; the weather was relatively clear - ...
0
votes
1answer
21 views

Multi-particle systems with different accelerations

While taking a system of multiple bodies under motion, is it possible to take those bodies in a system which have different accelerations? Say there are 3 particles having acceleration along x,y and z ...
0
votes
1answer
42 views

Physical meaning of enthalpy

I've been reading about thermodynamics and reached the topic about enthalpy . I've understood its derivation but I don't understand its physical meaning ... Also I don't understand why they have ...
0
votes
0answers
17 views

complete local thermal equilibrium and conserved quantum numbers

I am reading Weinberg's Cosmology book and I am confused of the statement "complete local thermal equilibrium in which all conserved quantum numbers vanish". My question is: How is complete local ...
-2
votes
0answers
30 views

what is the rough motion of an electron in an atom [duplicate]

If The Uncertainity principle is true,then how does an electron move ?if the motion cannot be random also,then how does it occur?
8
votes
4answers
331 views

Curvature of Hilbert space

That may appear as a dumb question, but: Does Hilbert space have curvature, or is it a flat space? How and why?
0
votes
0answers
21 views

Acceleration mass graph of constant force

If the same horizontal force is applied to objects of different mass. Which graph explains the experimental results. My logic was that since $$ f = ma $$ Is a linear equation it will be a straight ...
3
votes
0answers
15 views

Inflaton Decay Rate

After inflation, (p)reheating is supposed as the mechanism which is responsible for restoring hot Big Bang. Always the resulting decay rate of inflatons into bosons and fermions are mentioned without ...
-2
votes
0answers
21 views

Beats: frequency of resulting wave vs. beat frequency

The beats frequency heard from the interference of two sound waves with frequencies $f_1$ and $f_2$ is $$\nu=|f_1-f_2|$$ Nevertheless the frequency of the resulting wave is not $\nu$ but the mean ...
0
votes
0answers
16 views

Total dilation of a signal from Tau Sagittarii [on hold]

Please forgive my ignorance, but I'm attempting to figure out how to do this... I want to learn how to evaluate the total dilation of a signal (waveform) leaving Tau Sagittarii to us. This assumes ...
5
votes
0answers
31 views

How are coherent astronomical objects imaged?

I am studying astronomical imaging, and am curious about how to image astronomical objects which are coherent. Stellar interferometry measures the mutual coherence function of a star, and then uses ...
1
vote
0answers
36 views

Charged pendulum oscillations

Recently, a question was asked in our school, regarding the calculation of the time period of a charged pendulum bob suspended in an electric field with the help of an insulating thread(gravity also ...
-1
votes
0answers
29 views

Could Earth being multipolar 600 million years ago might have caused Cambrian radiation?

According to some of the latest research Earth might have been multi polar instead of being bipolar 650 million year's ago (http://phys.org/news/2016-06-earth-ancient-magnetic-field.html) Do you think ...
0
votes
0answers
18 views

Decomposition of the Time-Evolution Operator: Translationally Invariant MPO

Hello everyone myself Sudipto. Currently I'm learning the matrix product state technique in order to simulate 1d spin system and study different properties of the system form quantum information ...
-1
votes
0answers
24 views

how can I detect cosmic muons from background?

Is there anything I should be careful with if I would like to detect muon at sea level? Noise background? Threshold? Even signals from other particle with stronger flux rate?
-3
votes
0answers
32 views

use of earth magnetic field

If we use earth magnetic field as a big magnet and take earth opposite charged electromagnet than it is possible that earth opposite charged electromagnet repel from earth surface.
0
votes
0answers
34 views

What is the difference between the light coming from Moon and the Sun?

The moon surface is reflective so, we should have the same light spectrum. And yet there is a difference in the quality of these two lights.

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