0
votes
0answers
9 views

What is the shape of a band electron in momentum space?

Band electrons occupy adjacent sharply defined momentum states that in xyz space take the form of a spectrum of wave functions. These wave functions span the entire xyz volume of any compact unit of ...
-1
votes
0answers
12 views

Why we have to sum in all final states of hadrons

Correct if i am wrong. In deep inelastic scattering have to sum in all final sates hadrons because we do not want to detect the hadrons. all we want to detect is the electron. Am i right?
-1
votes
2answers
10 views

Pressure exerted by a gas and the ideal gas equation

While determining the pressure exerted by any gas at a temperature why do we not consider the surface area of the container in which it is kept? We say that : P=nRT/V, where, n is the no. of moles, R ...
1
vote
1answer
19 views

deriving Bio-Savart law in QFT

It's so important and meaningful that a new theory of physics contains main equations and results of previous related ones. Maxwell theory and QFT both have explanations on electromagnetic phenomenon ...
0
votes
1answer
9 views

Which timestep should I use for a n-body simulation of the Solar system?

I am trying to implement a n-body simulation of the Solar system and I am stuck on the issue of the simulation timestep size. At first I would like to use a simple Euler stepping scheme. Knowing that ...
1
vote
0answers
25 views

Usage of tensors in physics

As I understand it, tensors are multi-linear maps that map vectors (and dual vectors) to real (or complex) numbers, but I'm hoping to gain some intuition as to why they are useful in physics. Is it ...
0
votes
0answers
13 views

Why does time-independent Hamiltonian not depend on angle variable?

In Landau and Lifshitz Mechanics, $\S50$ Canonical variables a time-independent Hamiltonian is considered, and a canonical transformation is done such that adiabatic invariant $I$ becomes the new ...
0
votes
1answer
11 views

A Formula for the Phase Difference Between the Eelectric and Magnetic Wave Oscillations?

A) Is there a formula for the phase difference between the electric and magnetic field oscillations, in vacuum, in an electromagnetic wave emitted from an antenna, as a function of the frequency the ...
0
votes
0answers
11 views

Why would two inertial frames be distinguishable, if the coordinate of an evenet perpendicular to the motion would be different?

This question arises from the classical example: imagine a laboratory frame, and a space shuttle frame, the space shuttle moving in the laboratory frame with a constant velocity, let's say in the $x$ ...
0
votes
0answers
9 views

Conserved quantity in a spacetime with Killing vector

I am trying to prove that that the expression $Q=-\frac{1}{\kappa}\int_{S_\infty} \nabla^i \xi^k \mathrm{d}\sigma_{ik}$ is a conserved quantity for a spacetime with Killing vector $\xi^i$ where ...
0
votes
1answer
18 views

Can/will a proton escape the nucleus when a force is applied?

Protons are contained within the nucleus of an atom. Protons carry a positive charge. With an electric field, we can exert a force on the proton. Is it possible for the proton to escape the nucleus? ...
0
votes
0answers
15 views

normal force on a physical pendulum

I have read and understood that a normal force has got nothing to do with torque on a physical pendulum. But I can't understand in which direction the normal force points to. Can someone help? This ...
0
votes
1answer
17 views

Why can the dispersion relation for a linear chain of atoms (connected by springs) be written as $\omega(k)=c_s \lvert k\rvert$?

On the german wikipedia site (right under "Akustische Moden"), the dispersion relation for a linear chain of atoms (connected by springs): $$\omega(k)=2 \sqrt{\frac{K}{M}} \left \vert ...
2
votes
1answer
18 views

Which 'annihilation' processes dump energy to the cosmological plasma?

I have been considering a generalisation of the cosmological process involved in computing the temperature of the cosmic neutrino background. It is well-known that (simplistically) this temperature ...
0
votes
0answers
20 views

Heisenberg uncertainity principle is valid in the case of QFT? [duplicate]

The Heisenberg uncertainty principle is valid (or taken into account) in the case of QFT?
0
votes
0answers
8 views

Fluctuation theorem - Tasaki Crooks

The Tasaki Crooks relation connects forward and backward evolution of a system which is initially in equlibrium: $$ \frac{P_F(W)}{P_B(-W)}=\mathrm{e}^{\beta(W-\Delta F)} $$ If the system would ...
0
votes
0answers
25 views

How to explain the AdS/CFT correspondence to scientists but non-physicists?

I need to convey to idea and foremost the enthusiasm in our field for the AdS/CFT correspondence during a presentation of five minutes to an audience of scientists but non-physicists and corporate ...
0
votes
1answer
13 views

Question about levers

Suppose we have a lever $AB$ of length $1m$ and that the fixed point is $O$ and $AO=0,3m$. If in $B$ I have a down vertical force of $F_1=5N$, find the force $F_2$ applied in A that guarantees the ...
-6
votes
0answers
23 views

~9586 digits of Vacuum permeability

Hello i wanted to know the Vacuum permeability which is 4π×10−7 but that wouldn't work for my java program so I made a program to calculate some digits of the Vacuum permeability and I wanted to share ...
-5
votes
0answers
16 views

MOS junction physics

Why when apply a voltage $V>0$, the acceptor ions tends to appear at junction though the electrons and holes are changing at the same rate? assume it to be p channel MOS junction
0
votes
1answer
21 views

Do air particles always rush to fill a container?

I'm sitting here in the metro station, drinking a bottle of water, and watching how the flow of water out of my mouth changes as air rushes into the bottle. My questions is: in space, obviously the ...
1
vote
1answer
34 views

Question about inertial mass and gravitational mass

I know that inertial mass $m_i$ is the quantity that appears in Newton's second law: $F=m_ia$ and that gravitational mass $m_{g_1}$ is the quantity that appears in Newton's gravitational law: ...
1
vote
2answers
22 views

Low density black holes and singularity

According to wikipedia "... the average density of a supermassive black hole (defined as the mass of the black hole divided by the volume within its Schwarzschild radius) can be less than the ...
0
votes
0answers
9 views

Wind turbine impact on cars fuel consumption

I have question that I still can't resolve. How much cars fuel consumption rises(l/100km) if I attach 1 kW wind generator to cars body? How can I calculate that and what do I need to know? ...
0
votes
1answer
27 views

If there are two conserved quantities that do not commute, why is there typically another?

I have come to the following conjecture: Consider two observables $A,B$ that do not commute and represent conserved quantities, there is typically a third conserved quantity. E.g. for some ...
0
votes
0answers
22 views

Calculating rocket thrust

for my recent project I'm trying to compute somewhat accurate rocket physics (although approximations are good enough - for example for aerodynamics). The project is about making "game-like" ...
-2
votes
0answers
13 views

Adiabatic approximation with scaled time?

A car is sent to take a student from coaching every day. The car arrives at the coaching 15min before the time. One day coaching gets closed one hour before the usual time. Then the student without ...
0
votes
1answer
26 views

Representing Hamiltonian in discrete position basis

I am trying to numerically find eigenstates of an Hamiltonian. Let $V(x)$ be some potential. Suppose my space is between $-L,L$ and that the allowed positions are every $\Delta x$, such that ...
1
vote
0answers
15 views

Adiabatic approximation with scaled time?

In this article (page 3) they have following expression for the coefficients in the adiabatic approximation: $$\dot a_k(t)=-a_k(t) \langle k| \dot k \rangle -\sum_{n\ne k} a_n(t) \frac{\langle ...
0
votes
1answer
22 views

As hot air rises is the cold air that rushes in pushed in or sucked in?

I seem to remember from high school, the state of equilibrium. Volumes of more molecules wanting to get to a volume of less molecules and causing a state of equilibrium. From this I believe cold air ...
1
vote
0answers
8 views

Heating of mixture of gases with one gas barely above its boiling point

What happens when mixture of two gases is heated in a closed container? If one gas expands faster than the other and increases pressure of the container enough so that the boiling point of the other ...
0
votes
1answer
16 views

Critical Value for Dispersion of light

If there is a ray of light moving from $n_1$ to $n_2$ you can get dispersion if $n_1$ is a function of wavelength. What angle of incidence ($\theta_1$) will maximise the dispersion? My solution so ...
0
votes
1answer
14 views

The direction of electric field in a thin hollow cylindrical insulating shell

Consider a thin hollow cylindrical insulating shell like the one above draw in 3D-coordinate with Z-axis going out of page and is centered at the origin of XYZ axis. It has electric charge +Q ...
0
votes
0answers
16 views

How to obtain the Klein Gordon equation for DBI action?

The action for DBI field is given by $$S=d^{4}x\,\sqrt{-g}\left[- V(\phi)\sqrt{1-g^{ij}\partial_{i}\phi\partial_{j}\phi}\right]$$ And the required Klein Gordon is given by $$\square ...
0
votes
2answers
18 views

Beam of light from glass to air

I am reviewing some concepts on light and came across a question that puzzled me. A beam of light is incident from a glass into air. The incident ray is 60 degrees to the normal. The question actually ...
0
votes
1answer
11 views

Translational Velocity

Is the translation velocity equivalent to its real velocity or radial velocity? Online sites and textbook are saying different things, So Im not too sure what is going on
5
votes
2answers
123 views

Damped oscillator: time-reversal, time-translation and dissipation

The equation of motion of a damped oscillator $$\frac{d^2x}{dt^2}+\gamma\frac{dx}{dt}+\omega_0^2x=0$$ which is invariant under time-translation $t\rightarrow t+a$, but not under time reversal ...
-4
votes
0answers
19 views

Floating of a dead body [on hold]

Why does a dead body float on water? And why does it float by making head downward? The dead body floats due to the production of gases. But how are the gases produced? And which gases are produced? ...
-1
votes
1answer
32 views

Unification of Newtonian gravity and electrostatic force

Can we not unify Newtonian gravity & electrostatic force? All properties are almost same. We can imagine the atoms of the Earth's core to become dipoles when a body is freely-falling. Thus, due to ...
1
vote
0answers
11 views

Can charged scalar have non zero vev?

In Higgs-Kibble mechanism, if we consider a SU[2]_L doublet of complex scalar fields, then one of them is charged and the other neutral. Why does the neutral field acquire vev and not the charged one? ...
-2
votes
0answers
11 views

The state below has non-zero entanglement, but why is its discord zero? [on hold]

|ψ⟩=(|00⟩+|11⟩)/√2. after calculation, I get $\delta=cos^2(\theta)\log cos^2(\theta)+sin^2(\theta)\log sin^2(\theta)$, Its minimum value is 0, therefore the discord of the state is zero. But there is ...
0
votes
0answers
5 views

Relation between phase of dark field and bright field images

I am trying to understand how the super-resolution technique based on Fourier Ptychography 1. In the paper, we run phase retrieval algorithms using images captured using illumination at different ...
0
votes
3answers
22 views

Ohm's law and an ideal voltmeter

In an ideal voltmeter there is infinite resistance so because of which no current is flowing through it and the voltage reading is not affected. The ohm's law stated that V = I * R In an ideal ...
3
votes
0answers
22 views

${\cal N} = 4$ supersymmetry, reference request

I am looking for references for the following questions for the purposes of doing something with $S$-duality and AdS/CFT, of which I couldn't find adequately addressed in Wess and Bagger. What is ...
2
votes
1answer
22 views

What does a one-photon state look like as a wave functional?

According to a post on a mailing list here: https://groups.google.com/d/msg/sci.physics.research/n7Ao7N9aeq0/wqgj20-jBQAJ In general, quatum states |Psi> of the electromagnetic field, no matter ...
0
votes
0answers
40 views

Has Rovelli proven that time doesn't exist? [on hold]

Has Rovelli proven that time doesn't exist? See this paper on the Arxiv for a description of his ideas. I am reading some people argue at length, and inauspiciously, that he has. I am entirely ...
-1
votes
1answer
62 views

Does Newton's third law apply to fundamental forces?

The acceleration between two electrons A, B at 1 cm distance is a = 2533 km/s^2, therefore each of them will experience it, so they will distance each other with an acceleration of 5066 Km/s^2, ...
0
votes
0answers
11 views

What is the size/mass of largest metal plate that was moved by casimir effect?

I learned about Casimir effect recently. Is it applicable only on very light/thin metal plates( in terms of micro/nano meters) or is the effect large enough to be noticed on mili meters scale? What is ...
0
votes
0answers
12 views

Could science still exist if the nature of events in the universe would be truely random? [on hold]

Most of the science is based on the study of how something behaves in a well defined pattern. Everything follows a rule. Which is the base of all scientific studies. So, in case if there won't be any ...
0
votes
0answers
13 views

Find the Work Done in this system [on hold]

In Inclined plane if friction force = the weight of the object. What is the total work done by this system?

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