10
votes
4answers
652 views
Energy Measurements in a Two Fermion Double Well System
This question is related but my question here is much more elementary than discussions of the Pauli principle across the universe.
There has been a fair amount of discussion around at the moment on ...
2
votes
1answer
313 views
How can I subtract Spectra?
I am writing an application that should allow to view and manipulate spectra (Raman).
I am only given one normal spectrum consisting of 1024 coordinate points. Plus I have a background spectrum that ...
6
votes
3answers
747 views
On what basis do we trust Conservation of Energy?
I'm happy to accept and use conservation of energy when I'm solving problems at Uni, but I'm curious about it to. For all of my adult life, and most of my childhood I've been told this law must hold ...
2
votes
3answers
192 views
Are electrons in different energy levels considered identical?
In QM we require that the state that describes the system, an atom say, be symmetric or antisymmetric under permuting the identical particles.
What identical particles are we talking about here, all ...
2
votes
1answer
120 views
Can unbound electrons jump energy levels?
If an unbound electron (or indeed any charged particle) is moving through free space, is there a probability that it can spontaneously change energy by emitting a photon, or does this require the ...
2
votes
3answers
971 views
Newton's corpuscular theory
Where did Newton get the idea that light had a particle nature and not a wave nature? At those times, AFAICT there were no phenomena that showed particle nature. But wave nature is much easier to ...
7
votes
0answers
98 views
Measure of Lee-Yang zeros
Consider a statistical mechanical system (say the 1D Ising model) on a finite lattice of size $N$, and call the corresponding partition function (as a function of, say, real temperature and real ...
0
votes
1answer
114 views
Question about interaction between three objects
I have been thinking of Newton (insert bad words because of frustration) laws for hours and hours today, and I'm not going anywhere. I'm going insane! So, I made up this question.
Object A | ...
1
vote
1answer
209 views
How to find the value of the parameter a in this transfer function? [duplicate]
Possible Duplicate:
How to find the value of the parameter $a$ in this transfer function?
I am given a transfer function of a second-order system as:
$$G(s)=\frac{a}{s^{2}+4s+a}$$
and I ...
4
votes
1answer
129 views
The difference between projection operators and field operators in QFT?
Is there a good reference for the distinction between projection operators in QFT, with an eigenvalue spectrum of $\{1,0\}$, representing yes/no measurements, the prototype of which is the Vacuum ...
1
vote
1answer
83 views
How to find the value of the parameter $a$ in this transfer function?
I am given a transfer function of a second-order system as:
$$G(s)=\frac{a}{s^{2}+4s+a}$$
and I need to find the value of the parameter $a$ that will make the damping coefficient $\zeta=.7$. I am not ...
3
votes
0answers
94 views
Can you safely draw sparks from the nose of an electrified boy?
From Purcell's Electricity and Magnetism
A spectacular conclusion of one of the popular exhibitions of the time
was likely to be the electrification of a boy suspended by many silk
threads ...
0
votes
2answers
622 views
Two objects exert forces on each other, will the reactions affect them?
Two objects go in against each other, and then they collide, will object 1, exerting force 1, necessarily get on it a reaction equal in magnitude and opposite in direction?
EDIT:-
In my book it only ...
1
vote
1answer
773 views
Can we determine the force an object exerts by its mass and acceleration?
I understand that the objects acceleration is determined by the force exerted on it, and that the force exerted on it is determined by its acceleration.
But, does an object's (named A) acceleration ...
5
votes
2answers
79 views
Have scientists been able to find an example of a possible White Hole?
We went to a planetarium last night last night and watched "Black Holes" narrated by Liam Neeson. If I recall correctly, he said that scientists believe that they have identified a number of Black ...
1
vote
1answer
441 views
How does smoke move in the air and how can I direct it so it will go to a place I want it to go?
Let's assume a close room with 1-2 people who only one of them smoking cigarette.
What is the equation describe the smoking spreading? is it diffusion? what are the parameters is so?
Is there a ...
5
votes
1answer
94 views
Renormalization of the R-charge?
In general I would like to know as to known or what is/are the standard references about R-charge renormalization in supersymmetric theories. When does it do so and what is expected or known to be ...
3
votes
2answers
142 views
Thought experiment with entangled electrons
Suppose we start out by having two entangled electrons. We separate them by some distance and we put one electron inside a thin loop of wire connected to an extremely sensitive voltage measuring ...
3
votes
1answer
524 views
Angular momentum coupling-calculation of Clebsch–Gordan coefficients
I am facing problem in calculating the value of given Clebsch–Gordan coefficients representing the coupled angular momenta of two-particle system. For example
$$\begin{pmatrix}2 & 1 & 2 \\ 1 ...
4
votes
2answers
139 views
What are the lines visible between two cards held edge-to-edge?
Hold two cards (say credit cards) edge to edge, anything from a very slight
touch to about 1/3 mm separation, in front of any ordinary light
source. When I do this I see several
fine dark parallel ...
2
votes
2answers
111 views
How fast can toy helicopters change the turning direction of their propellers?
I saw someone do some tricks with a toy helicopter where he would turn it upside down for a while and it would still stay in the air. I thought it should have crash or at least not fly for very long ...
5
votes
2answers
210 views
What should be the equation satisfied by The Momentum commutators in a curved background?
This may be obvious but I have limited experience in physics , The generators of Spatial translation symmetry commutes with each other i.e [P(i),P(j)] = 0 but if Spacetime is a curved manifolds then ...
2
votes
2answers
1k views
Magnetic field in a cavity
We are given an infinitely long cylinder of radius $b$ with an empty cylinder (not coaxial) cut out of it, of radius $a$. The system carries a steady current (direction along the cylinders) of size ...
8
votes
3answers
364 views
Whether $m$ in $E=mc^{2}$ and $F=ma$ are both relativistic mass?
I know that $m$ in $E=mc^{2}$ is the relativistic mass, but can $m$ in $F=ma$ can also be relativistic? If the answer is yes, then can you tell me whether this equation is valid $E=\frac{F}{a}c^{2}$? ...
5
votes
3answers
323 views
Is there such a thing as “North” in outerspace?
On Earth, North is determined by the magnetic poles of our planet. Is there such a thing as "North" in outerspace? To put it another way, is there any other way for astronauts to navigate besides ...
1
vote
2answers
368 views
Sign of Velocity for a Falling Object
I'm working on a homework problem in Mathematica. We have to graph the height and the velocity of a function given an initial height and initial velocity. However, when I do the graph for the velocity ...
1
vote
2answers
90 views
Origin of field deduced from potential
Related: Tubelights+power lines pictures?
I would've edited this into the above question, but I realized that there' enough to it to qualify as a new one. Plus this seems to be a confusion of ...
4
votes
2answers
215 views
Can an Electromagnetic Gauge Transformation be Imaginary?
The Hamiltonian of a non-relativistic charged particle in a magnetic field is
$$\hat{H}~=~\frac{1}{2m} \left[\frac{\hbar}{i}\vec\nabla - \frac{q}{c}\vec A\right]^2$$.
Under a gauge transformation ...
4
votes
3answers
438 views
Assumptions in Bell's Theorem
It is often Stated that Bell's Theorem is equivalent to the statement: No theory of Local Hidden Variables can reproduce all of the predictions of quantum mechanics. I see nowhere in Bell's Theorem ...
3
votes
1answer
123 views
In a Sterling Engine, does heat from the hot side transfer to the cold side?
A Sterling Engine is a closed system. The "hot" side oscillates between higher temperature with higher pressure and lower temperature with lower pressure. Does Nature switch back and forth between ...
6
votes
2answers
310 views
Have red shifted photons lost energy and where did it go?
I think the title says it. Did expansion of the universe steal the energy somehow?
3
votes
3answers
297 views
Is there more energy in the collapse of a cavitation bubble than the energy required to create the bubble in the first place?
The following does not include all scientific details and parameters, only a common summary of "thoughts". What is scientifically wrong with this summary?
When you take your beer and tap the top ...
3
votes
3answers
269 views
The Asymmetry between Real and Imaginary in the three Pauli Spin Matrices
The Pauli spin matrices
$$
\sigma_1 ~=~ (\begin{smallmatrix} 0 & 1 \\ 1 & 0 \end{smallmatrix}),
\qquad\qquad
\sigma_2 ~=~ (\begin{smallmatrix} 0 & -i \\ i & 0 ...
2
votes
1answer
861 views
In what position can a current-carrying loop of wire be located in a magnetic field so that it doesn't tend to rotate?
I understand that if the wire is not aligned with the magnetic field, it won't rotate, but I'm still confused on how so.
Also, which direction is the current flowing?
3
votes
2answers
318 views
Is the electron wave function defined during photon emission
I have heard the term quantum leap to describe the (instantaneous?) transition from a higher energy orbital to a lower energy orbital. Yet, I understand that this transition time has now been ...
8
votes
1answer
300 views
Kramer's-Kronig relations for the electron Self-Energy Σ
I'm currently studying an article by Maslov, in particular the first section about higher corrections to Fermi-liquid behavior of interacting electron systems. Unfortunately, I've hit a snag when ...
4
votes
1answer
191 views
What is the mathematics behind artificially generated plasmas via electric fields?
The ionization degree of a plasma is given by the Saha equation, which depends on the temperature and the particle specific ionization energy. In thermal equilibrium, the relation between ionization ...
2
votes
1answer
46 views
Unknown quantum state with promise of classical data
I am trying to solve a problem in the measurement and identification of quantum states with a promise as to what states it could be. Here is the problem. Imagine a system that produces qubits in ...
1
vote
1answer
75 views
Formula for potential for 2 coaxial tubes
Could someone remind me of the formula for potential function for a system consisting of 2 coaxial tubes maintained at a fixed potential difference and the in between medium has uniform conductivity ...
3
votes
1answer
309 views
Double image in binoculars
How can I reduce the double image seen when looking through binoculars? I recently got a new pair, but have been having troubles using them because I am seeing double...
3
votes
1answer
38 views
A nice overview (and maybe derivation) of the Poincaré transformations of the Vector Spherical Harmonics
With $Y_{lm}(\vartheta,\varphi)$ being the Spherical Harmonics and $z_l^{(j)}(r)$ being the Spherical Bessel functions ($j=1$), Neumann functions ($j=2$) or Hankel functions ($j=3,4$) defining ...
0
votes
2answers
340 views
Question involving Vectors and Forces
This is a question I found in Mechanics for Engineers by Beer & Johnston.
A 600-lb crate is supported by the rope and pulley arrangement as shown below.
Write a computer program which can be ...
2
votes
1answer
2k views
Why is oxygen in a triplet state and what are the consequences?
From Wikipedia here and here:
''Almost all molecules encountered in daily life exist in a singlet state, but molecular oxygen is an exception.''
''The unusual electron configuration prevents ...
3
votes
3answers
344 views
Quantum perpetual motion
Perpetual motion describes hypothetical machines that operate or produce useful work indefinitely and, more generally, hypothetical machines that produce more work or energy than they consume, ...
5
votes
2answers
364 views
What's the importance of Noether's theorem in Physics
The Noether's theorem that I want to mention is the following: Noether's theorem.
I know the importance of Noether's contribution to modern algebra. Can anyone write about Noether's theorem in ...
2
votes
2answers
3k views
Are all metals good conductor of electricity?
I am writing an article for kids, which is on conductors and insulators of electricity.
If I make a statement that "All metals are electrical conductors and all non-metals are electrical insulators" ...
1
vote
1answer
526 views
Oil drop experiment--How was the result so accurate?
I remember while learning about Millikan's oil drop experiment and being pretty skeptical about the setup. I know that there is a lot of controversy regarding manipulation of data, but the fact is; he ...
5
votes
0answers
471 views
Good theoretical physics introduction for 6 year old very advanced in math? [duplicate]
I think now is a good time to introduce my son to theoretical physics. He asks so many questions about the universe, black holes, gravity, atoms, molecules, light, etc. He's borderline obsessed with ...
2
votes
2answers
210 views
Correlation Functions, Symmetries and Measurements
Is there a book that goes deep into correlation functions? What I'm interested in a book/article that explains in the detail the relation of the correlation functions with symmetries and how one can ...
1
vote
1answer
302 views
Bra space and adjoint vectors
If I'm not wrong, a bra, $ \langle \phi_n | $, can be thought as a linear functional that when applied to a ket vector, $| \phi_m \rangle$, returns a complex number; that is, the inner product it's a ...
