0
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0answers
2 views

Clarification regarding atmospheric opacity

I have taken a look at the related questions Can someone explain to me the concept of atmosphere opacity? and Why can spacecraft observe terrestrial gamma rays, but terrestrial observers not ...
0
votes
0answers
4 views

Could a pocket universe be birthed out of the negative pressure in our universe?

I have just recently started learning about inflationary cosmology so I don't know much about it. But from my understanding, the theory says the big bang was started by the expansion of a small region ...
0
votes
0answers
7 views

Is there a way to strip all the electrons from single atom with atomic number greater than 2

Please explain by what means electrons extraction can be done. How person can focus activity on single atom (from precision point of view) to do so? How at each step person can know how much electrons ...
-3
votes
0answers
17 views

Special Relativity Problem: What's wrong here?

Two 1 kg blocks float in space. After an explosion, they move left and right at 0.6 c. Consider their momentum relative to a frame of reference moving a 0.6 c to the right relative to their center of ...
5
votes
2answers
566 views

Are there weak force waves?

In the same way as there are electromagnetic and gravitational waves that update the information on their respective field, is there an analogue for the weak and strong forces?
5
votes
1answer
181 views

Near Energy In the Null of a Hertzian Dipole

Since $\mathbf E = -∇Φ - ∂\mathbf A/∂t$ one expects an oscillating $\mathbf E$ field even in the null of a Hertzian Dipole unless the two right hand side terms cancel -- which they do in the far field ...
3
votes
2answers
45 views
+50

Determining Mass of Spectroscopic Binaries

I know that the mass of a binary star system is given by Kepler's Law: $$\mathrm{m_1 + m_2 = \frac{4 \pi^2 r^3}{GT^2}}$$ Further we know that: $$\frac{r_2}{r_1} = \frac{v_2}{v_1} = \frac{m_1}{m_2}$$ ...
5
votes
1answer
59 views

Why does wet hair keep its shape when it dries?

When I wash my hair and go to sleep, my hair is impossible to comb in the morning, stubbornly sticking to the shape it assumed during the night. The only way to get it right is to wet it again and ...
1
vote
2answers
36 views

Force of water hitting a wall

If you had a 8" pipe with 500psi stream of water exiting it and hitting a wall at 90 degrees 8 feet away, what would the force of the water on the wall be? Thank you all. Non-mathematician.
-1
votes
1answer
122 views

What's my $\mathrm dM$? Gravitational Potential inside a circle of mass

I'm trying to find the gravitational potential for an arbitrary point within a ring of uniform mass density. The point is constrained to be in the same plane as the ring. So we start with: $$\Phi=\...
1
vote
3answers
37 views

How does an hydraulic ram pump work?

Hydraulic ram (wikipedia)(youtube) uses the water hammer (wikipedia) to pump water. Please help me understand how it works. I understand that the check valve catches the pressure from the water ...
-3
votes
0answers
34 views

Why does the Microwave disturb the Internet Signal?

I have no back round in physics but was wondering how come every time the microwave is turned on, the internet slows down dramatically?
0
votes
1answer
18 views

Any good statistics books under the context of astronomy?

I just started a position as a research aide with the cosmology group at Argonne National Lab, and am working on creating and finding correlations within velocity dispersions of galaxy clusters. After ...
-1
votes
1answer
39 views

Competition Physics Book for High School Physics

I am currently a high school physics student who has recently started participating in some physics competitions. Although I have an alright understanding of the physics and mathematics and can ...
1
vote
2answers
66 views

What is the meaning of the size of an elementary particle in QFT? What is the meaning of a point particle?

I think I have often seen people refer to the size of a particle being at most a given value, or a particle being a point particle, in the context of quantum field theory. However from what I ...
6
votes
3answers
4k views

What does the phrase “limb of the earth” or “atmospheric limb” mean?

What does the term limb of the earth (see this question, for example) or atmospheric limb mean? The phrase strikes me as very odd, since earth is nearly spherical. Do other planets with atmospheres ...
3
votes
2answers
1k views

Average Force vs Net Force

The F in $$Impulse = F*t$$ is said to be the average force. For a ball dropped vertically onto a horizontal surface, the average force, F, on the ball from the floor is: $$F = \frac{\Delta{p}}{t}$$ $$\...
8
votes
3answers
125 views

'Slapping' sound when trains pass each other

I have noticed that when riding in a train travelling at over 100 kmh$^{-1}$, a loud 'slap' can be heard when another train travelling at a similar speed passes in the opposite direction, followed by '...
1
vote
0answers
15 views

Functional Differetiation of a complex functional

Suppose I have a simple functional $$S=\int{dx\;\phi^{*}(x)\phi(x)}\tag{1}.$$ Assuming $\phi(x)$ and $\phi^{*}(x)$ are independent and I take a functional differential with respect to $\phi(x)$ and $\...
1
vote
1answer
134 views

Nature Of Bulb Glowing In Parallel LR circuit with bulbs

In the given circuit the switch is initially closed and then opened after some considerable time.Then which bulb will stop glowing first? Which bulb will glow more brightly?Why ? .After opening ...
2
votes
0answers
77 views

What is the geometric explanation for why the interior angles of a triangle sum to 180 degrees in both Euclidean space and Minkowski spacetime?

Four-dimensional Euclidean space has the same topology and affine structure as Minkowski spacetime, though the two have different metric structures. Given that the interior angles of a triangle ...
0
votes
0answers
22 views

Statistics: combining independent observables for the same quantity, how to check independence? [on hold]

Let's assume we have a set of observations $\{x_i\}$ and that I have a physical models aimed to describe the observations, and that this model has a parameter $y$. Let's assume that I have two ...
2
votes
2answers
91 views

Physics without math [on hold]

If anybody could imagine an advanced civilization with advanced knowledge of the universe(s) but without a mathematical language, how would they use their knowledge? How could it be possible to ...
0
votes
2answers
27 views

Friction, Dynamics question

In the given question $F=2t$ where $t$ is time in seconds for which the force has been applied. Friction exists only between $A$ and $B$ with coefficient of friction $\mu=1/2$. Here we can easily see ...
1
vote
1answer
32 views

Electric Field of a Disk an Infinite Distance Away

The electric field of radius $R$ and a uniform positive surface charge density $\sigma$ at a distance $x$ from its center is given as $$E = \frac{\sigma}{2 \epsilon_0}\left( 1 - \frac{1}{\left(\frac{...
3
votes
1answer
97 views

Physics of detection of coherent light in an incoherent background using the more compact Fabry Perot interfeometer?

I read University Of California Berkeley Professor J. Bokor's Chapter 7 course notes , shown below as an imgur image , on Temporal Coherence tonight. I am sending an email to Professor J. Bokor ...
3
votes
1answer
44 views

On LOCC operations

I am trying to learn quantum information theory. Suppose we have a bipartite (as well as multi-partite) quantum system $H_A \otimes H_B$. What is a LOCC map $\phi: \mathcal{B}(H_A \otimes H_B) \...
1
vote
1answer
137 views

The Fermi Surface of the Free Electron Model for T>0K

For the Free electron model, we can easily describe the Fermi surface at T=0 due to the uniqueness of the Fermi-Dirac Distribution at T=0; below the Fermi-level, a state is definitely filled, above, ...
5
votes
1answer
64 views

What happens to the electric field lines when an electron and positron collide?

A month back I began my course in classical electrodynamics. I know about the field lines of moving charges. But I have this question that if an electron and a positron are situated some distance ...
1
vote
0answers
28 views

Are Fock spaces just a special type of tensor algebra?

Are Fock spaces just a special type of tensor algebra? The definitions I am using: http://en.wikipedia.org/wiki/Fock_space http://en.wikipedia.org/wiki/Tensor_algebra From what I can tell, the ...
1
vote
0answers
34 views

Detecting supersymmetry

What would scientists in particle colliders look for as evidence of supersymmetry?
0
votes
1answer
25 views

Situations in which there is path difference interference or formation of standing waves

I came up with a doubt about standing waves and path difference in general. Consider these two different cases as examples. If I have a rope fixed at one end and I make the free end oscillating, I ...
1
vote
2answers
53 views

Horizontal rolling without slipping

I'm trying to find the friction coefficient that makes the body roll without slipping but I just can't reach a value. The force is applied on a small central disk of radius $r=0,03\, m$ and mass $m=0,...
7
votes
1answer
408 views

Adiabatic approximation

The adiabatic approximation for solid state systems is rather radical. I was wondering in which cases it breaks down. As it is based on the idea of the nuclii being much heavier than the electrons I ...
2
votes
0answers
23 views

Is there a block spin renormalization group scheme that preserves Kramers-Wannier duality?

Block spin renormalization group (RG) (or real space RG) is an approach to studying statistical mechanics models of spins on the lattice. In particular, I am interested in the 2D square lattice model ...
-3
votes
3answers
45 views

Average speed without given distance [on hold]

Here is the problem where the speed is given but not the distance and need to find the average speed.
2
votes
0answers
12 views

Have the BaF2 scintillators a strong correlation with the alimentation current that cause the shifting of the centroids in the distribution?

In gamma gamma correlation I suspect the presence of systematic error maybe caused by a non optimal alimentation voltage according to someone there is a quadratic correlation between centroids ...
5
votes
1answer
143 views

How to calculate the ground states' Berry phases with doubly degeneracy, such as that due to the particle-hole symmetry or time reversal symmetry?

Suppose the ground states of a system are doubly degenerate due to an anti-unitary symmetry $K$, which are $|\psi>$ and $|K\psi>$. If the system is an one-dimensional Fermion system and anti-...
1
vote
0answers
30 views

Proof of two Lorentz-algebra identities

I am currently working through the QFT introduction text by Peskin and Schroeder and try to fill in two identities that I wasn't able to prove (it should be fairly simple, but my experience with this ...
1
vote
2answers
269 views

Mechanics Landau Galilean Principle

I started reading Landau's Mechanics book and was having some trouble understanding the Galilean Relativity Principle. What does Landau mean by saying space to be homogenous and isotropic and time is ...
0
votes
2answers
119 views

Speed of light and relativity [duplicate]

Suppose there are two observers $A$ & $B$ both are in motion, now $A$ sees $B$ is moving with speed $'u'$. A says that another object $'d'$ is moving with speed $c+u$ w.r.t. A in the same ...
8
votes
8answers
270 views
+50

How to pour water from a bottle as fast as possible

When one pours water out of a bottle, it first flows smoothly but then a pressure 'blockage' develops and the pouring becomes interrupted and turbulent, so that the water comes out in splashes. This ...
0
votes
2answers
27 views

Torque on electric dipole placed in non uniform electric field

When electric dipole placed in non uniform electric field, what is the approach to calculate torque acting on it? Can it be zero?
1
vote
0answers
23 views

Why does AC Conductivty in Drude Theory have an Imaginary and a Real Part?

In the Drude Model the direct current (DC) conductivity is given by the following formula: $$\sigma_0=\frac{ne^2 \tau}{m}$$ where $\tau$ is the relaxation time. Furthermore, the AC conductivity in ...
0
votes
0answers
21 views

Eigenkets in matrix representation

We use base kets in matrix representation of an operator $X$. Could the base kets be possibly be eigenkets also, of operator X? (Here, I'm taking X as a general operator , not only observable,i.e. ...
1
vote
4answers
2k views

If electromagnetic fields give charge to particles, do photons carry charge?

As I understand these two statements: An electromagnetic field gives particles charge A photon is a quantum of electromagnetic field It must mean that a photon carries charge. But I guess it isn't ...
2
votes
1answer
22 views

How to calculate absorbed dosage

Lets say you have some unstable isotope which decays via beta decay. For example, lets say you want to calculate the amount of beta radiation that is emitted from the decay of $^{87}\textrm{Kr}\to ^{...

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