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Link between photon helicity and polarization of $A^\mu$ electromagnetic potential

From Wigner theorem we know that the irreducible unitary representation of the Poincarè group for massless and spin 1 particle is labelled by the momentum $p_\mu$ and the two possible helicity $+1,-1$ ...
Andrea's user avatar
  • 593
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0 answers
6 views

Physical meaning of Cahn-Hilliard boundary conditions

Consider the 1D Cahn-Hilliard equation for a two-component mixture, on an interval $x\in[a,b]$: $\frac{dc}{dt} = -\frac{d}{dx}j(x)$ where the flux $j(x) = -\frac{d}{dx}\left(c^3 - c - \gamma\frac{d^2c}...
C.M.O.B.'s user avatar
1 vote
0 answers
19 views

$\phi^4$ quantum fields theory with vanishing physical mass

Let us consider the $\phi^4$ theory, where $\phi$ is a real scalar field, such that the physical mass vanishes. Is it true that the bare mass also vanishes?
MKO's user avatar
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14 views

What's the difference between electrical induction and chemical batteries

I'm new in physics/chemistry and i'd like to know what's the difference between both of them and how do they affect the electromagnetic field and move electrons. Also I'd like to know how does a ...
Psi's user avatar
  • 11
1 vote
0 answers
24 views

A list of failed attempts towards a proof of confinement [closed]

Can one give a list of failed or open attempts (not necessarily Supersymmetric) towards a proof of confinement in 4d regarding YM or QCD?
Bastam Tajik's user avatar
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1 vote
1 answer
18 views

A capacitor partially filled with dielectric

Assume a parallel plate capacitor that was charged up to $Q_0$ from a source $U_0$ and then disconnected from the voltage source. The plates have an area $A$ and the distance between the plates is $d$....
Ilia's user avatar
  • 21
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0 answers
26 views

Gravitoelectromagnetism (GEM) and Planck's constant [closed]

I've studied physics mainly on my own, having earned a degree in geology (in Italy). Almost by chance, I realized that applying the GEM equations (gravitoelectromagnetic; an approximation of the ...
Arcangelo Recchia's user avatar
0 votes
0 answers
10 views

How to calculate the amount of diopters to shift focused point closer to an eye?

In case a human eye has "good enough" focused objects in 1.5 meters and when getting closer, the quality of image loses, how to calculate the amount of diopters to get focused picture (let's ...
Damir Tenishev's user avatar
4 votes
0 answers
33 views

Confinement, Holographic QCD, Seiberg-Witten Theory

I have seen a bunch of articles that all try to show confinement using AdS/QCD or Holographic QCD method. I pretty much know that the lastest attempt to prove confinement based on breaking SUSY even ...
Bastam Tajik's user avatar
  • 1,272
0 votes
1 answer
21 views

How to calculate the amount of diopters needed to get focused point closer to an eye?

As far as I know a human eye has approximately 19 diopters and this could be used to calculate the focal point when the observed object is placed in infinity and incoming lights are parallel. How can ...
Damir Tenishev's user avatar
1 vote
0 answers
25 views

Nuclear (astro)physics for relativists and field theorists

Lately I've become interested in compact stars and I would like to learn a bit about the nuclear physics that goes into them. However, I don't know anything about nuclear physics, except for a few ...
Níckolas Alves's user avatar
4 votes
0 answers
41 views

Are de Sitter, Anti-de Sitter and Minkowski spaces spatially infinite?

I am not someone who has studied general relativity, however have recently developed an interest in it. From what I have seen online, de Sitter, Minkowski and Anti-de Sitter spaces are often compared ...
Aradhya Jain's user avatar
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0 answers
21 views

Canonical Variables in Dirac Spinor Field Theory

In S.Weinberg [QFT V1][1] section 7.1, in eq (7.1.15) and (7.1.16), he states that in order to be consistent with the previous-derived anti-commutator relation, we should take $\psi_{\text{n}}$ and $\...
Ting-Kai Hsu's user avatar
1 vote
0 answers
8 views

Larmor frequency in NMR for nucleus with spin greater than 1/2

I'm reading the theory about NMR and in most textbooks I can see that the Larmor frequency achived as follow: on the one hand from QM we know that $$\Delta E = \hbar \omega $$ on the other hand, if ...
Sagigever's user avatar
  • 555
0 votes
2 answers
44 views

Do conductors have bound charges?

In Griffiths, the total charge density of a dielectric is: $\rho$ =$\rho_b +\rho_f$. I have several questions: Can the total charge density of a conductor be written as the equation above? Do the ...
Felix wong's user avatar
1 vote
2 answers
33 views

Vertical Circular Motion ($u$ minimum)

In vertical circular motion, when we consider motion of a pendulum bob, while finding minimum velocity to complete VCM, we take Tension=0 at highest point and velocity at highest point is not equal to ...
Navs's user avatar
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-2 votes
0 answers
40 views

$i\epsilon$ prescription for finite systems [closed]

What is physical interpretation of path integral for finite time and finite epsilon (i.e without taking limits time->+-inf, epsilon->0)? Does it mean you are doing some finite temperature qft ...
Peter's user avatar
  • 343
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0 answers
30 views

How to derive Smarr formula for Kerr Black Hole?

Following is the Smarr formula for Kerr Black Hole $$M=\frac{\kappa A}{4\pi}+2 \Omega J $$ where $\kappa, \Omega$, $J$ and $A$ are surface gravity, angular velocity, angular momentum and surface area ...
Talha Ahmed's user avatar
0 votes
2 answers
17 views

Granular Material Piles on an Inclined Plane

Consider a conical pile of sand (or any other granular material) that is placed on a flat surface. This conical pile has a given radius and height (r and h, respectively). What would the effect be on ...
K.R.'s user avatar
  • 1
0 votes
1 answer
23 views

Ampere's law on solenoid, using a circular loop

Suppose we take a long and tightly wound solenoid with current I going in it. We can find the field inside, by ampere's law, taking a rectangular loop and assuming the magnetic field just outside the ...
EagerToLearn's user avatar
-2 votes
0 answers
19 views

Need help with SMRs and nuclear reactors [closed]

I'm writing my IB extended essay on SMRs and how they might be useful for energy generation in Singapore but I don't quite understand a couple things. How do their passive safety systems work and ...
aaron's user avatar
  • 1
0 votes
0 answers
14 views

Bayesian distribution for the rotated qubit example

If say we consider a spin-up qubit having undergone some Pauli-Y rotation $\theta \in [0, \pi]$, and further consider discretizing the rotation range $[0, \pi]$ such that $\theta_j \in [0, \pi]$ where ...
John Doe's user avatar
  • 297
4 votes
2 answers
113 views

Meaning of general Lorentz transformations

According to Wikipedia, the Lorentz transformations for two inertial frames are written:$$\begin{cases} t'=\gamma(t-\frac{\mathbf {r}_{\parallel }.\mathbf{v} }{c^{2}} )\;\;\;(*)\\\mathbf {r'...
The Tiler's user avatar
  • 1,400
-1 votes
0 answers
35 views

Relativity problem about light signals and rockets equipped with mirrors [closed]

I find in a relativity book a problem that states: "A rocket with its own length $L$ moves away from Earth at a constant velocity $v$. A radar signal emitted from a ground station is reflected ...
idefix's user avatar
  • 1
0 votes
0 answers
16 views

"Linear independency" of Lie Brackets [migrated]

I was watching this eigenchris video. At 21:49, he says: $$[g_i, g_j]=\Sigma_k {f_{ij}}^{k}g_k$$ for $\mathfrak{so}(3)$. Does this mean $[g_i, g_j]$ and $g_i, g_j$ can be linear independent? What ...
Cro's user avatar
  • 137
0 votes
0 answers
21 views

Insertions of the action inside correlators

Suppose I have a scalar field theory described by an action $S[\phi]$ that can be massive $\lambda\phi^4$ theory, what is the effect of inserting a power of the action inside of correlators? Like: $$\...
Fra's user avatar
  • 2,263
0 votes
0 answers
16 views

Different coupling to different kinds of sources?

Context: 1+1 dimensional scalar field coupled to a background electromagnetic field generated by two charges, q and -q situated at the points 0, a, respectively. This article studies the effect of the ...
dolefeast's user avatar
  • 170
1 vote
0 answers
28 views

On time arrow and coordinate change in General relativity

This may be a silly question but I would like to have things cleared up once and for all in my head. I will take the example of a Schwarzschild black hole as a solution to vacuum Einstein Field ...
Jeanbaptiste Roux's user avatar
3 votes
2 answers
210 views

Physical meaning of symmetric and antisymmetric wavefunction

On describing Bosons and Fermions, the symmetry of wavefunction is introduced first. Here, If two particles a and b, are in two states n and k respectively, we get the wavefunction individually. On ...
Rajesh R's user avatar
1 vote
2 answers
55 views

Conservation of linear vs. angular momentum in two similar cases

I have a question that eludes my understanding: Imagine we have a bullet of mass $m$ and a rigid pendulum with a bob of mass $M$ hanging from a rigid rod of negligible mass hanging from the ceiling ...
Giovanni Piacentini's user avatar
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0 answers
12 views

Two cylinders rolling without slipping on planks

I am struggling with the following setup. This setup consists of three massless planks and two massive cylinders, as can be seen from the figure. The lower plank is pulled with a force $F$ that ...
Bml's user avatar
  • 439
1 vote
0 answers
45 views

Lagrangian of a multi-dimensional scalar field

We know that the Lagrangian has to be a scalar. Would it be possible if this scalar is multi-dimensional (for example $m\times m$)? Let's say a field $\phi$ is represented with an $m\times m$ matrix ...
physics_2015's user avatar
1 vote
0 answers
20 views

Thermal flunctuations of density in thermal equlibrium? [closed]

According to physics a fluid or gas in thermal equilibrium is not exactly homogeneous. Locally its density undergoes random fluctuations which are small compared to the corresponding equilibrium value....
stackdk93's user avatar
-2 votes
1 answer
44 views

Are there any experiments that examine Hamilton's Principle directly?

Or can it be examined? I 'd glad if you can share some ideas about "principles" in general.
Toboraton's user avatar
  • 109
1 vote
0 answers
61 views

Necessity of Singularity in General Relativity

The Schwarzschild solution is the standard example used to describe a black hole, its important points being the event horizon and the central singularity. But this solution is derived by assuming an ...
RC_23's user avatar
  • 9,481
-1 votes
1 answer
47 views

A Force Perpendicular to the Velocity changes only the direction of motion?

Why does a force that remains perpendicular to velocity alaways only change the direction of the motion(circular) and not induce a velocity in the perpendicular direction???
Atharva Thakur's user avatar
0 votes
2 answers
51 views

How to understand gyroscopes by using vectors?

I’ve seen plenty of videos explaining how gyroscopes work, but almost non of them why they are constrained to work in such way. From seeing only angular momentum vectors, how could one predict ...
Alexander Djurovich's user avatar
-2 votes
0 answers
25 views

Is the energy spectrum of molecules of an ideal gas at equilibrium in an isolated system the Maxwell-Boltzmann distribution? [closed]

The energy spectrum of an ideal gas at equilibrium in a closed system at thermal equilibrium with its surroundings is described by the Maxwell-Boltzmann distribution. If the system is then isolated ...
Arthur Goldman's user avatar
1 vote
0 answers
39 views

Coulomb gas correlators on the sphere

I am trying to understand Appendix B.2 of Nakayama's notes (https://arxiv.org/abs/hep-th/0402009), wherein he derives the correlation functions of the following action (Coulomb gas) on the sphere: $$ ...
Jay Padayasi's user avatar
0 votes
3 answers
98 views

My ionizing smoke detector fell a month ago. Is it possible I've been irradiated?

My ionizing smoke detector is from Kidd, it's written it produces 0.6 microCuries in nominal conditions but a) It's expired since 2010 (I'm renting, just realised this), and b) It fell out of nowhere ...
Mister Mystère's user avatar
-2 votes
3 answers
43 views

How can a non-derivative interaction involve the derivative of a scalar field?

I was reading up on the paper "The Fate of the False Vacuum" by Sidney Coleman and the claim is made that a scalar field with standard Lagrangian density: $$ L = \frac{1}{2} \delta_{\mu} \...
Adam P's user avatar
  • 1
0 votes
0 answers
30 views

How quickly can you reduce temperature of content in a jar by running cold water over it? [closed]

If I have a glass jar with a metal lid that contains 24floz of water @ 70F and I continuously run 45F water over the top of the closed jar, how long will it take for the 24fl oz to reach 45F?
Eric Shanfeld's user avatar
0 votes
0 answers
33 views

Does detailed balance apply if electrons and ions have different temperatures

Suppose I have a plasma where the ion temperature $T_i$ is different from the electron temperature $T_e$. Does detailed balance still exist between recombination and ionization?
S.T. Zweig's user avatar
7 votes
1 answer
341 views

Jellium Hamiltonian in the thermodynamic limit

In Fundamentals of Many-body Physics by W. Nolting, 1e, the author arrives at the following formula for the electron-electron contribution to the Hamiltonian of Jellium: $$ \hat{\mathcal{H}}_{ee}=\...
CW279's user avatar
  • 349
1 vote
0 answers
62 views

Discovery of a Formula for Geostationary Orbit Distance: Seeking Expert Feedback [closed]

I’m an amateur enthusiast without a formal academic background in mathematics or science. Recently, I stumbled upon an idea and derived a formula that I believe calculates the distance traveled along ...
Luca Blonda's user avatar
2 votes
1 answer
26 views

Energy in Dielectric Medium as a Sea of Dipoles

Simply, why is the energy density in a dielectric medium = $\frac{1}{2}K\epsilon_oE^2$ where K is the dielectric constant of the dielectric medium? Working proof Consider a capacitor that is charged ...
Kayen Jain's user avatar
0 votes
2 answers
81 views

The usage of temperature in quantum mechanics

This is a follow up question for my previous question, because now I am more confused than I was before. In a regular quantum mechanics course, temperature plays no role as it does not appear in the ...
MathMath's user avatar
  • 1,131
0 votes
0 answers
27 views

The total horizontal distance traveled by a bouncing ball nudged off a table of height $H$ [closed]

Suppose a ball gently rolls off a flat surface of height $H$ and free falls to the ground subject only to the law of gravity. Once the ball hits the ground, it rebounds as shown in the figure. When ...
user42700's user avatar
  • 101
0 votes
0 answers
20 views

How to count simple resistor circuit configurations? [closed]

Really stumped by this one (I'm not an EE!). Suppose we are given 1, 2, 3, 4, 5, and 6 one-ohm resistors. They can be arranged in series, parallel, bridge, and so forth circuits. No dangling resistors ...
Ken Bannister's user avatar
3 votes
0 answers
44 views

Non-crossing approximation (NCA) in 'Large-$N$ expansion' (Altland & Simons CMFT)

I have a question about non-crossing approximation (NCA) stated in Condensed Matter Field Theory by Altland & Simons1. It is on page 200-203 for the 3rd edition (on page 223-227 for the 2nd ...
Jinu.P's user avatar
  • 31

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