All Questions

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0answers
2 views

Feeling sound; frequency and volume

How loud and "low" must a sound be in order for one to feel some physical sensation in response? I've read that below certain frequencies humans can be expected to "feel" sounds in their chests, and I ...
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0answers
3 views

Charge of Universe

The charge of the universe is said to be zero. The most general argument I hear about this is that: since there was no net charge before the universe there must not be any after. Hence the universe is ...
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0answers
5 views

How to determine exchange particle of two-to-two process?

For the process, $e^+e^- \rightarrow e^+e^-$ I know that the exchange particle is a photon and for the process $\gamma\gamma \rightarrow e^+e^-$, the exchange particle would be an electron but I'm not ...
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1answer
10 views

How was Maxwell able to derive velocity distribution?

Did he assume that their velocities follow some kind of statistical distribution and fit the parameters accordingly. Or did he mathematically prove it?
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0answers
9 views

European XFEL : TDS strutures

Can someone explain whats the difference between fill time, accelerator fill (Ta) time and cavity fill time(Tc)? Is fill time and acellerator fill time the same ?
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0answers
4 views

Bond Nature of a comound

How can we determine the type of Bond in LiBaPO4? can we find out the nature of bond through charge transfer values of these elements? if yes then how?
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1answer
13 views

How does thermal energy in a system do mechanical work?

Explain that a system with thermal energy has the capacity to do mechanical work. Also, in addition to this what are the differences between work and mechanical work?
0
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1answer
24 views

How far can you pee on the moon vs. mars?

Let's suppose you are at Elon Musk's Future Mars colony and you drank too much beer, how far can you pee on Mars if you can pee one meter on earth? If the next day you get on the shuttle to the ...
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0answers
16 views

Don't matter-antimatter annihilate each other completely releasing energy as photon?

Matter and antimatter should annihilate each other completely releasing energy in the form of photon, however it is discovered that smashing electron and positron together can also spew out higgs ...
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3answers
29 views

If a wavefunction is normalized at $(x,t)$, is it also normalized at $(x\!-\!ct,t)$?

If $\Bigl( \Psi(x,t),\Psi(x,t) \Bigr) =1$, I want to find out if $\Bigl( \Psi(x-ct,t),\Psi(x-ct,t) \Bigr) =1$. My attempt was $\Bigl( \Psi(x-ct,t),\Psi(x-ct,t) \Bigr) = \int_{-\infty}^\infty |\Psi(x-...
0
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1answer
13 views

Relative energy

Suppose a ball is travelling at 5km/h, person A is travelling at 2km/h and person B is travelling at 5km/h in the opposite direction. The ball is travelling at 3km/h relative to A and at 10km/h ...
1
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1answer
15 views

Molecular model of liquids

The macroscopic behavior of gasses and solids follow very intuitively from the description of matter as quasi-spherical molecules interacting with each other with attractive and repulsive forces. ...
2
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0answers
22 views

What is so topological about topological phase transitions?

I am studying the KT-transition, which is called a topological phase transition. The phase transition is driven by vortices in a 2-D superfluid, where it is shown that at a critical temperature $T_c$ ...
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1answer
23 views

In static fluid, pressure at same heights are equal. Is this applicable to the oceans?

Generally we consider the reference as horizontal line. But if we consider a vertical water column in the ocean. Then, if we want to consider the reference it should be a circular not a horizontal ...
0
votes
2answers
16 views

Can I make an inductor coil from covered cables?

I have huge amounts of wires, and it's impossible to remove all the plastic cover off of them. I thought of making the coil just like that, as they are, will it have the same magnetic field or at ...
0
votes
1answer
19 views

Imaginary part of vacuum polarization tensor

I deal with vacuum polarization diagram calculation with help of QED by Landau et al. and I would like to understand one interesting statement. I know how to compute $\Pi_{\mu\nu}(k)$ via dimensional ...
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0answers
21 views

What kind of integration is used in different areas of physics? [on hold]

I'm aware that there are multiple types of integration in mathematics, e.g., there's the Riemann integral, the Riemann-Stieljes integral and the Lebesgue integral, but I'm not privy to their ...
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0answers
8 views

With respect to which system are accelerations written in a non-inertial frame?

If $\vec{a}=\vec{a_0}+\vec{a_r}+\vec{\omega}\land(\vec{\omega}\land\vec{r})+\frac{d\vec{\omega}}{dt}\land\vec{r}+2\vec{\omega}\land\vec{v_r}$ being $\vec{a}\to$ absolute acceleration of the ...
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0answers
3 views

Strategy for finding flow field for steady, incompressible flow in 2D based on density information

I'm working on a simulation where we wish to determine the flow field for an incompressible fluid based on known values for density at each point. The only outside force is gravity. (Density is not ...
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2answers
27 views

Lorentz transformation of vector field

Under a Lorentz transformation, a vector field transforms as: $A'_{\mu}(x')=\Lambda^{\nu}_{\mu}A_{\nu}(x)$ My question is, why is the Lorentz transformed vector field evaluated at $x'=\Lambda x$, ...
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0answers
14 views

Determining the pseudo-time period of a system of $n$-pendulums via Kane's method in Python

We can use Kane's method to integrate the equations of motion for a system of $n$ pendulums with arbitrary masses and lengths (see derivation). In particular, if $(x_i,y_i)$ denotes the Cartesian ...
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0answers
8 views

Potential from scattering matrix [duplicate]

Given a scattering matrix, is there a procedure to find the potential from the scattering matrix? I think there should be a way as the scattering matrix holds the information of the boundary ...
0
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1answer
16 views

Skin effect prevailing the drift velocity effect

In general, an electron will propagate randomly in a conductor at the Fermi velocity( produced due to thermal energy of the conductor). An applied electric field will give this random motion a small ...
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0answers
5 views

What is permittivity at infinite frequency in cole-cole equation?

I am working with estimating the dielectric constant as a function of frequency. I did calculate the S-Parameters from Agilent VNA. The study is similar to this paper When working this, i came across ...
0
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1answer
10 views

Principle of Energy Dispersive x-ray Spectroscopy

I have a question about the EDS I don't understand how the detector can differentiate the Energy of incident x-ray simultaneously. In my thought, the emitted x-ray from the sample have different ...
0
votes
1answer
26 views

Radial vs tangential component of electrical field due to dipole

I was wondering that why should the maximum magnitude (with respect to $\theta$) of radial component of electrical field of an electric dipole, $$E_r=-\partial V/\partial r=\frac{2p \cos\theta}{4\pi\...
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0answers
7 views

How are fluid membranes stretchable?

The Poisson's ratio of fluid lipid membranes is exactly $\nu=0.5$, because fluids can flow. As answered in this question, under the assumption of a finite bulk modulus $K$, this is the value of $\nu$ ...
0
votes
1answer
29 views

Proof that electrostatic self-force is zero

Suppose there is a charge distribution in region V and zero charge density outside V such that electric field goes to zero infinitely far away. How to prove that this charged body does not exert an ...
0
votes
1answer
15 views

Does the distance between the slits, in the double slit experiment, affect the pattern displayed?

Does the distance between the slits affect the pattern displayed? I want a pattern where light parts and dark parts are equal, and I don't want the light parts to be bigger than dark parts.
-3
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0answers
43 views

What would happen if the universe had no gravity? [on hold]

My question is what would the universe be like without gravity.
-1
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0answers
16 views

Pendulum moving in linear motion

Given a diagram below, the linear velocity of the point of rotation is v_linear and the angle that the tension line makes with vertical axis is theta, and its angular velocity theta dot. Assuming ...
-1
votes
0answers
10 views

What is the variance of |S| in Bell's inequality (CHSH inequality)

I found an online exercise that begins with: So far so good. I also found a standard proof of equation (3), but what I did not find is a proof for its variance/standard deviation. The CHSH value |S| ...
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0answers
7 views

Statistical model for local polymer concentration

I'm trying to describe the local constraining of two points located on a 2-part DNA polymer (double and single stranded), with respect to one fixed end. See the schematic below: Here I would like to ...
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0answers
19 views

Computing Hamiltonian from a matrix formed Lagrangian

I tried to use the fact that Hamiltonian is a Legendre transformation of Lagrangian and thus, H= pq'-L. But I don't understand how to use the fact that Tij is a symmetric matrix, to compute the ...
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0answers
14 views

How does an object's volume affect its gravitational pull?

Two instances. An object is in front of two different planets with the same masses, but two different volumes. How does the gravitational pull vary from each planet? I am thinking with more given ...
0
votes
1answer
16 views

What is the least energy trajectory in Astronomy?

Hi I wanted to know what the least energy trajectory is in relation to astronomy as I can't seem to find a good answer on Google. I want to know because I am trying to answer this question: A ...
0
votes
1answer
44 views

How much harder is a proton theoretically speaking than a diamond?

It's generally said that a diamond is the hardest substance known to man (apparently there are a few materials known to be harder). However, one ought to expect that a proton or neutron should be ...
-1
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0answers
30 views

Where is the present moment in physics?

In an essay in the book, On Space and Time, with contributions by Connes, Majid and Penrose, John Polkinghorne writes in the final essay, titled The Nature of Time: The equations of physics do not ...
1
vote
1answer
25 views

How can one the find normal force of a block resting on a pool floor underwater?

There is the force of gravity on the block, the atmosphere, the water pressure o top of the block, but how about between the block and the floor? Would we calculate water pressure pushing up from the ...
1
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0answers
18 views

What are soft theorems in context of scalr fields

What are soft theorems ? I tried reading Weinberg’s paper but couldn’t understand it, are there any resources on this ? I am very interested in the case of scalars.
0
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1answer
19 views

If an electron is in an infinite potential well, would it emmit photon when it bounces off the wall?

Let say there is an electron in an infinite potential well. Since it's trapped in the well, I assume (which I'm not sure of whether it's valid to assume such thing) that it will bouce off the wall and ...
-2
votes
2answers
22 views

How does thermodynamics affect our lives? [on hold]

How does the second law of thermodynamics affect our lives? Could we live without the second law of thermodynamics? What is the whole purpose of thermodynamics affecting our lives? I know this is a ...
0
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0answers
13 views

The rate of expansion right after inflation ended

Before inflation occurred, the expansion of the universe was non-inflationary (expanding slower than inflation). What happened to the rate of expansion right after inflation ended? $~$Did ...
0
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0answers
5 views

Calculation of time-ordered propagations and correlators

I am reading the following paper M. H. S. Amin and D. V. Averin, “Macroscopic Resonant Tunneling in the Presence of Low Frequency Noise,” Phys. Rev. Lett., vol. 100, no. 19, p. 197001, May 2008. I ...
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votes
2answers
36 views

Could we use experimental evidence of micro black holes to prove the existence of additional spatial dimensions?

They are planning to create a new particle accelerator that can smash particles together at a much higher energy than the LHC. If in the process we observe the decay of a micro black hole, would that ...
0
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0answers
8 views

How to Find Jerk from Discrete Velocity Data?

I have measured the velocity of an object at discrete intervals. I want to find the corresponding acceleration and jerk of the object. How do I do this with discrete values rather than continuous ...
0
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0answers
9 views

Deconstructing harmonics

If I am firing a burner into a cylindrical chamber with a flat rear refractory wall, and we are experiencing constructive amplitude because of a coincidence of sound frequency and vessel length - can ...
0
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0answers
19 views

negative unity matrix not hermitian?? (stabilizer formalism)

I read the section in the attached picture about the stabilizer formalism and was wondering about the last sentence in the pic. It says that all operators of the stabilizer group are hermitian, ...
0
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2answers
47 views

These terms are so foreign to me that they feel like unnecessary jargon; what do these terms mean, and are they relatively common?

No pun intended in the title. ;) I am having trouble understanding this sentence on Wikipedia's page for Unified Field Theory: Governed by a global event $\lambda$ under the universal topology, ...
0
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0answers
27 views

Perpetual Motion and Thermodynamics [duplicate]

How does the second law of thermodynamics disprove all perpetual motion machines?

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