2
votes
0answers
408 views

Nonlinear refraction index of vacuum above Schwinger limit

This question is more about trying to feel the waters in our current abilities to compute (or roughly estimate) the refraction index of vacuum, specifically when high numbers of electromagnetic quanta ...
0
votes
2answers
2k views

What is Curie-Weiss temperature?

What is Curie-Weiss temperature? What is the difference between Curie-Weiss temperature and Curie temperature?
1
vote
2answers
1k views

about waveplate and polarization

I have a throlabs half- and quarter-wave plate with rotation plate. There shown the angle scales and a line denotes the fast axis. But what does the angle mean? I do some research and someone said the ...
1
vote
0answers
93 views

How does a lens affect the field of view in a mirror?

If one looks into a mirror, he can see a certain field of view. If he places a convex lens that magnifies (or a concave lens that does the opposite) in front of the mirror, but so that he can still ...
0
votes
1answer
955 views

Can I use Newton's second law to solve what seems to be a torque problem?

The Problem: An 8-m-long beam, weighing 14,700 N, is hinged to a wall and supported by a light rope that is attached 2.0 m from the free end of the beam. If the beam is supported at an angle ...
1
vote
1answer
233 views

About Efimov States and Halo-Nuclei

I read that Halo nuclei could be seen as special Efimov states, depending on the subtle definitions. (The last sentence in the second to last paragraph of this Wikipedia article.) This does ...
0
votes
2answers
325 views

Impedance Matching

When viewing fast pulses on an oscilloscope, why is impedance matching required? I'm not totally clear on why. I'm guessing it is because I don't want 'ringing' and because I want signal integrity.
6
votes
2answers
196 views

Mean of a measurement on periodic data: what is the use of the inverse of correlation length?

Correlation and autocorrelation is something that in my Bachelor's programme in physics has been somewhat overlooked, so I'm in trouble understanding their use in this paper (The prisoner’s dilemma on ...
0
votes
0answers
63 views

Quantum Mechanics Text for Electrical Engineers [duplicate]

Possible Duplicate: What is a good introductory book on quantum mechanics? What is a good introductory text on quantum mechanics that could be used to train electrical engineers in device ...
1
vote
0answers
90 views

Determining Water Level

Given a cylinder of a constant shape and size, how can the water level be calculated using the inside surface of the container? For instance, could the inside lining of the container be a pressure ...
0
votes
1answer
287 views

Morse potential and chaos

I have heard that the Morse potential equation $$\tag{1} -\frac{\hbar ^{2}}{2m} \frac{d^{2}}{dx^{2}}y(x)+ae^{bx}y(x)-E_{n}y(x)=0 $$ is related to the two dimensional equation on the Poincare half ...
0
votes
1answer
295 views

Spectrum of quantum fluctuations in a harmonic oscillator

If we have a harmonic oscillator and look at it on small scale the energy is quantized and we can calculate the different eigenstates. In general the energy eigenvalues are given by $$E_n = ...
0
votes
1answer
633 views

What is the importance of electrodynamics and magnetism in physics as a whole? [closed]

At my university the second half of a year long sequence in basic calculus based physics focuses on electrodynamics and magnetism. I am wondering what is the significance of these topics to physics in ...
5
votes
1answer
246 views

What happens when a piezo crystal is exposed to a vacuum?

Application of mechanical stress to a piezo crystal generates a charge. Quoting from wikipedia, a 1 cm3 cube of quartz with 2 kN (500 lbf) of correctly applied force can produce a voltage of 12500 ...
4
votes
1answer
418 views

About the gauge invariance of Chern-Simons' theory (in local coordinates)

I am aware of the differential form language proof of the fact that for arbitrary gauge transformations the Chern-Simons' term shifts by a WZW term (on the boundary). But I am getting confused if ...
3
votes
1answer
138 views

An issue about the compactness and the existence of CTCs

There is a well known fact that a compact spacetime necessarily contains a closed timelike curve (CTC). Proof can be found in several books on GR (e.g. Hawking, Ellis, Proposition 6.4.2), and in ...
2
votes
1answer
813 views

Potential Energy in General Relativity

I often hear about how general relativity is very complicated because of all forms of energy are considered, including gravitation's own gravitational binding energy. I have two questions: In ...
4
votes
1answer
5k views

Is it possible to have a Gas heavier than a liquid?

Does such a pair of substances exist, that in certain physical conditions (temperature, pressure) when both are placed in the same conditions, one will be a liquid, the other - a gas, and the gas ...
1
vote
2answers
148 views

A problem concerning the force between currents or moving electrons

Concerning two identical wires carrying the same current (same direction, speed and magnitude), they will be attracted because of the Ampere force. But when I was in the frame moving with the same ...
10
votes
1answer
724 views

How or why is fractional quantum mechanics important?

I read about Fractional Quantum Mechanics and it seemed interesting. But are there any justifications for this concept, such as some connection to reality, or other physical motivations, apart from ...
3
votes
1answer
129 views

Confused over the presence of 2 expressions for $\Psi(x,t)$

I'm following Griffiths' Introduction to Quantum Mechanics, and I see that he's got 2 different expressions for $\Psi(x,t)$. One of them is ...
2
votes
1answer
406 views

If we have a current $I$ flowing down a wire, why must the net bound current be zero?

Say we are dealing with a wire that has a current $I$ flowing through it, i.e. $I$ is the free current. Why must it then hold that the net bound current, that is, the bound volume current, $J_b$, and ...
1
vote
2answers
2k views

Why are different frequency bands used in different countries?

Why are different frequency bands used in different countries despite ITU's effort for a common frequency band use? There's got to be a reason behind this. For instance, U.S.-based Verizon Wireless ...
2
votes
2answers
538 views

What's the difference between two Hydrogen atoms?

If we are given two Hydrogen atoms, would the only difference between them would be their quantum state (Energy level or eigen value, and the corresponding Orbital or eigen state) and their location ...
2
votes
1answer
503 views

Velocity of real gas molecules?

It is known that the velocity of ideal gas molecules can be computed using Maxwell-Boltzmann law of distribution of molecular velocities, with average velocity given as: ...
2
votes
1answer
2k views

Application of diffraction problem!

Here is a problem that I am working on, which is the applying the concepts of diffraction to the setting of the sun: Air has a small, usually negligible index of refraction. It is 1.0002926. This ...
1
vote
2answers
7k views

Torque And Moment Of Inertia

I am reading the two concepts mentioned in the title. According to the definition of torque and moment of inertia, it would appear that if I pushed on a door, with the axis of rotation centered about ...
1
vote
0answers
33 views

Half-Life Question [duplicate]

Possible Duplicate: How do we know that some radioactive materials have a half life of millions or even billions of years? I understand how to calculate decay, but it seems to me that the ...
3
votes
1answer
1k views

Why do some metal containers not conduct heat, while some do?

Some metal containers such as the Nissan Thermos ones, even if 100 C water is filled inside, the container is still cold to the touch on the outside. It won't be even warm: At the same time, some ...
11
votes
1answer
759 views

Why does my natural whistle have a maximum volume

When I whistle, I find that I can vary the volume by pushing more or less air through my mouth at once. However, when I increase volume past a point, I start to hear a blend of rushing air and a ...
14
votes
3answers
6k views

Does Fire Conduct Electricity? Why?

Recently, I have stumbled upon a YouTube video by Veritasium describing the conductivity of fire. My question is: how exactly does fire conduct electricity? I am a high school student; therefore ...
2
votes
2answers
2k views

Poisson brackets: prove that they are canonical invariants

EDIT: I haven't forgotten to accept answer, the question is still open.. I need a clarification about Poisson brackets. I'm studying on Goldstein's Classical Mechanics (1 ed.). Goldstein proves ...
1
vote
1answer
686 views

Derivation of the self gravitational potential energy of a sphere

I have been searching on the Internet but have not found a derivation of the formula for the self gravitational potential energy of a sphere. Can someone show how to do this? I assume it involved 6 ...
2
votes
0answers
476 views

Simple model of edge states for a two-dimensional topological insulator

Quantum spin Hall states or, topological insulators are novel states of matter that have insulating bulk and gapless edge states. Are there any simple models that show these features? See e.g. the ...
4
votes
1answer
250 views

Probability in Quantum Mechanics

Do you need to take a probability/statistics course for Quantum Mechanics, or is the probability in quantum mechanics so rudimentary that you can just learn it along the way? I'm in doubt as to ...
6
votes
0answers
147 views

Gauge-invariance of pole mass using Ward Identity

I am able to explicitly verify to one-loop order that pole masses are independent of the choice of gauge paramter. But how do I use the Ward-Identity/Taylor-Slavnov identity show that the position of ...
0
votes
1answer
6k views

Calculating Moment Of Inertia

The problem I am working on is: A uniform, thin, solid door has height 2.10 m, width 0.835 m, and mass 24.0 kg. (a) Find its moment of inertia for rotation on its hinges. (b) Is any ...
0
votes
1answer
880 views

Two Different Sorts of Inertia: Inertial Mass and Moment of Inertia

There are two different sorts of inertia: inertial mass and moment of inertia. I am currently reading about moment of inertia. Now, I know inertia is an important concept; with it, we can determine ...
2
votes
1answer
193 views

Fractal Cosmology and Misner's Chaotic Cosmology

I have a question pertaining to the ideas behind the considered homogeneity and isotropic nature of the universe (at a grand scale) versus the theory of a chaotic and anisotropy structure of the ...
-1
votes
1answer
200 views

Direct nuclear reactions problems [closed]

can anyone explain Multi-step nuclear reactions in terms of direct nuclear reactions .
2
votes
0answers
34 views

One dimensional motion with changing acceleration. Falling to a large body from a great distance [duplicate]

Possible Duplicate: Radial fall in a Newtonian gravitational field My math and physics are rusty. I am trying to calculate the time an object takes to fall to a large body. Before you ...
0
votes
1answer
282 views

Direct nuclear reaction in nuclear physics

Time taken to occur a direct nuclear reaction is very low $10^{-22}$sec . I want to know the Importance of direct nuclear reactions.
5
votes
1answer
229 views

Hawking Radiation from the WKB Approximation

Reading this paper which is itself an exposition of Parikh and Wilczek's paper, I get to a point where I fail to be able to follow the calculation. Now this is undoubtably because my calculational ...
2
votes
1answer
112 views

A problem with supersymmetry transformation invariance

Consider the following transformation of the integration measure $dX d\psi_1 d\psi_2$: where $\psi_1$ $\psi_2$,$\varepsilon^1$, and $\varepsilon^2$ are Grassman variables. $\delta_\varepsilon X= ...
2
votes
1answer
757 views

What is different between resolvent and green function

I bumped into a book, where Resolvent $R^{\pm}(E)$ is defined as $e^{\mp iHt/\hbar}=\pm\frac{i}{2\pi}\int_{-\infty}^{\infty}dER^{\pm}(E)e^{\mp iEt/\hbar}$ and $R^{\pm}(E)=\frac{1}{\pm ...
5
votes
5answers
7k views

How far can water rise above the edge of a glass?

When you fill a glass with water, water forms a concave meniscus with constant contact angle $\theta$ (typically $\theta=20^\circ$ for tap water): Once you reach the top of the glass, the water-air ...
6
votes
1answer
3k views

Momentum as Generator of Translations

I understand from some studies in mathematics, that the generator of translations is given by the operator $\frac{d}{dx}$. Similarly, I know from quantum mechanics that the momentum operator is ...
3
votes
1answer
291 views

Hubbard Model Hamitonian

$H = -\sum\limits_{i,j} A_{ij} c_i^{\dagger} c_j + \frac{U}{2} \sum\limits_i(c_i^\dagger c_i)(c_i^\dagger c_i -1)$ is defined to be a Hamiltonian for modeling quantum random walk of identical ...
1
vote
4answers
893 views

Hamiltonian in position basis

Let $ H = \frac{-h^2}{2m}\frac{\partial^2 }{\partial x^2}$. I want to find the matrix elements of $H$ in position basis. It is written like this: $\langle x \mid H \mid x' \rangle = ...
7
votes
1answer
459 views

The cleverest way to calculate $\left[\hat{a}^{M},\hat{a}^{\dagger N}\right]$ with $\left[\hat{a},\hat{a}^{\dagger}\right]=1$

Who can provide me some elegant solution for $$\left[\hat{a}^{M},\hat{a}^{\dagger N}\right]\qquad\text{with} \qquad\left[\hat{a},\hat{a}^{\dagger}\right]~=~1$$ other than brute force calculation? ...

15 30 50 per page