1
vote
0answers
72 views

Suggestions contents for soliton theory [closed]

I have been studying solitons theory to make a note on dimension analysis for solitons At first I have derived one space dimensional kink solution for soliton theory. I want to go to higher ...
2
votes
2answers
535 views

Ricci tensor for a 3-sphere without Math packets

Let's have the metric for a 3-sphere: $$ dl^{2} = R^{2}\left(d\psi ^{2} + sin^{2}(\psi )(d \theta ^{2} + sin^{2}(\theta ) d \varphi^{2})\right). $$ I tried to calculate Riemann or Ricci tensor's ...
5
votes
1answer
241 views

How can an asymptotic expansion give an extremely accurate predication, as in QED?

What is the meaning of "twenty digits accuracy" of certain QED calculations? If I take too little loops, or too many of them, the result won't be as accurate, so do people stop adding loops when the ...
2
votes
1answer
136 views

Is it possible to have topological degeneracy in 1D ?

I mean to have q-fold degenerate ground states on a ring which could not be lifted by local perturbation. If the answer is no, then what is the physical (or mathematical) reason against having such ...
1
vote
1answer
598 views

Elementary question on pion-proton scattering cross-section

Is $E_k$ the energy of the outgoing or incoming pion? The first peak is supposed to be a delta baryon. What does the graph tell us, experimentally? A pion of kinetic energy x comes in, then we ...
0
votes
3answers
83 views

Interaction photons-matter and dimensional analysis

I know that when photons pass through matter, the law that describes the intensity in function of the thickness is: $$I(x)=I_0 e^{-\mu x}$$ where $\mu = \rho \frac{N_a}{A} \sigma$ and ...
3
votes
3answers
883 views

How do I determine the location of a free particle with Schrödinger's equation?

I'm trying to get to grips with the Schrödinger equation by looking at a free particle. I'm certain at some point I massively misunderstood something. According to a textbook and a lecture the free ...
2
votes
3answers
6k views

Rotating a stone with a string

Suppose we are given a stick and a stone tied to the stick by a string. Now if we rotate the stone around the stick the stone rises in height (see picture below). My question is which force accounts ...
5
votes
2answers
1k views

Translator Operator

In Modern Quantum Mechanics by Sakurai, at page 46 while deriving commutator of translator operator with position operator, he uses $$\left| x+dx\right\rangle \simeq \left| x \right\rangle.$$ But for ...
-1
votes
1answer
96 views

Charge gained due to photoelectric effect [closed]

Here I think, one beam will knock out just one electron. So, I am not able to even understand what the question says. Please someone give a hint as to what the question asks... As source of the ...
1
vote
1answer
3k views

Floating Objects and Weight

The Situation: A ball is placed in a beaker filled with water and floats. It is also attached to the bottom of the beaker via a string. The Question: The ball is attached to the beaker, thus ...
4
votes
1answer
102 views

Live feed from a Rocket traveling near the speed of light?

Okay, odd question popped up in my physics class today. If a rocket ship is traveling at .99c for 1 year, and is streaming a video at 30 frames/sec to earth, how would the earth feed be affected? ...
0
votes
2answers
255 views

Derrick’s theorem

Consider a theory in D spatial dimensions involving one or more scalar fields $\phi_a$, with a Lagrangian density of the form $$L= \frac{1}{2} G_{ab}(\phi) \partial_\mu \phi_a \partial^\mu \phi_b- ...
4
votes
1answer
352 views

Moyal Product in Non Commutative Quantum Mechanics

Can someone please explain me what is a Moyal product? Also, how does putting $$X_a(\psi) ~=~ x_a\star\psi$$ realise $$[X_a,X_b]=i\theta_{ab}{\bf 1}?$$ Ref: Quantum mechanics on non-commutative ...
1
vote
2answers
313 views

Doppler shift of radio signals to an accelerating observer

Suppose a man leaves from Earth to a star which is 1000 light years away. He accelerates to a velocity such that the entire trip lasts a year, from the reference frame of the rocket. Now lets pretend ...
2
votes
2answers
6k views

Area under a displacement graph

If the area under an acceleration-time graph denotes velocity and the area under a velocity-time graph denotes displacement, what exactly does the area under a displacement-time graph denote?
8
votes
3answers
1k views

How can neutrinos “beat light”?

Article in the CERN newsletter "symmetry breaking" has the following statement: "Neutrinos are often the first particles to bring news of events in space to Earth, beating even light.". What does this ...
4
votes
3answers
2k views

What does it mean for electric current to be a scalar?

After reading the reasons for considering electric current as a scalar quantity, I was confused at a point which read "The magnitude and direction of current does not depend upon the direction of the ...
1
vote
2answers
159 views

Could the outer structure of the Universe be made from Antimatter?

Cern recently stated that antimatter may be repelled by matter, much like the opposite effect of Gravity. So is it possible that antimatter is actually repelled to the edges of the Universe to create ...
4
votes
2answers
125 views

Is there a naturally occuring sound pressure level reference?

There are lots of devices that purport to measure the absolute value of sound pressure levels. Here is an example, here's another, there's also this iPhone App. Putting such devices side-by-side in ...
0
votes
2answers
2k views

How would you determine whether an object is at equilibrium? [closed]

How would you determine whether an object is at equilibrium or not? What is the definition of equilibrium?
5
votes
1answer
176 views

physical importance of regularization in QFT?

The standard lore in QFT is that one must work with renormalised fields, mass, interaction etc. So we must work with "physical" or renormalised quantities and all our ignorance with respect to its ...
0
votes
1answer
180 views

If a balloon is continuously filled with air and stays at a constant shape and size will there be any empty space in the balloon?

If a container like a balloon but with constant volume is filled, is it possible to pack air molecules so closely together that they don't have any empty space between them? If so, what would this ...
3
votes
2answers
138 views

Why does the quantum eraser seem to violate energy and momentum conservation?

In the literature of the quantum eraser experiment it is argued that the change in statistics of the system from non-interference to interference is due to the erasing of "distinguishing information". ...
1
vote
1answer
263 views

Additional boundary conditions for inclined flow?

I am solving an inclined flow problem, and am stuck. The problem is to find the volumetric flow rate of inclined flow in a square channel. Once I have the velocity profile, I can just integrate over ...
4
votes
0answers
66 views

Does the number of left handed chiral quark superfields always equal half the number of quark flavours?

In Weinberg's "The Quantum Theory of Fields Vol III" page 267 we're told that $n_f = 2N_f$. Where $n_f$ are the number of flavours and $N_f$ is the number of left chiral quark superfields (or the ...
0
votes
1answer
138 views

Creating a state of definite momentum and position(within uncertainty limit)

claim: $a^{\dagger}$= $\int d^{3}kf_{1}(k)a^{\dagger}(k)$ Creates a state with Localized momentum $k_{1}$and localized position near origin; where $f_{1}(k)$ $\propto ...
1
vote
1answer
463 views

Can false origin be anywhere in a graph?

Can I start labeling my $x$ and $y$ axes from non-zero values when drawing a graph? Or is there any convention to only label $x$-axis from non-zero value when using a false origin and not $y$-axis? ...
3
votes
1answer
181 views

Tension of rope in the gravitational field of earth

Two balls of mass $m$ each one are connected with mass-less rope with the same length as the radius of earth. The system is in free fall. Prove that the tension of the rope when the nearest (to ...
4
votes
5answers
6k views

Does the unit of a quantity change if you take square root of it?

For example, I have a mass, m = 0.1kg and I square root it, giving me m = 0.316 (3s.f.) does the unit still stay as kg, or does it change?
0
votes
1answer
128 views

How fair is it to say that all chemistry arises from failures of the ideal gas law?

I was reading here about how the ideal gas law assumes point masses and non-interaction. Is it fair to say that all chemistry arises from failures of that? Of course, such a sweeping generalization ...
3
votes
1answer
149 views

Has martian sunset same spectra than this earthly bluish-violet sunset?

Has martian sunset same spectra than this earthly bluish-violet sunset? What about sunset on Mercury?
0
votes
1answer
143 views

Vortex in D dimensions soliton

let us consider the two-dimensional configuration shown in Fig. 3.1a. The lengths of the arrows represent the magnitude of φ, while their directions indicate the orientation in the $φ_1 -φ_2$ plane. ...
0
votes
1answer
67 views

Electric Field in Dieletric

I have a simple doubt. The textbook I'm working with says that if $E_0$ is the electric field in some region without diletric, then if we introduce a dieletric of constant $k$ the new field will ...
17
votes
1answer
417 views

Where do high-energy neutrinos come from?

Last week the IceCube South Pole Neutrino Observatory published a press release reporting the possible discovery of two neutrinos with energies of over 1 PeV. Would anyone here be willing to help me ...
1
vote
1answer
683 views

Mathematical explanation of quantum teleportation

I am now studying quantum teleportation. I get what the process is like but I'm wondering why it happens this way. You've got two entangled particles A and B whose wavefunctions are entangled. You ...
1
vote
1answer
534 views

What is the work done by an ideal gas?

What is the work done by an ideal gas when final pressure and volume are both different from its initial pressure and volume or when both pressure and volume changes ?
1
vote
1answer
183 views

What is a good reynolds number for this process?

I’m trying to convince my boss that the mixers we are using are too much. I’m trying to prove that we are over-mixing our product. Our product is ink…just your basic ink found in your printer at home. ...
1
vote
1answer
446 views

Finding the Steady State Charges

Here the problem states to find the steady state charges on the condensers.<<<< According to me the charges on second at steady must be ...
3
votes
2answers
196 views

Phys.org Spectral geometry to unite relativity and quantum mechanics, restate in laymens terms?

Lingua Franca links relativity and quantum theories with spectral geometry Could someone give me a short synopsis of this article in laymens terms? What implications does this have in the physics ...
1
vote
0answers
88 views

What is the difference between Cramer and Vaidman?

Two very interesting new papers on arXiv last night by Lev Vaidman and friends lead me to ask about the differences between Cramer's transactional interpretation of quantum mechanics (TIQM) and the ...
-2
votes
2answers
293 views

A question to the theory of multiverse

Guys I couldn't catch a point of multiverse theory.. Theory: If space-time goes on forever, then it must start repeating at some point, because there are a finite number of ways particles can be ...
-1
votes
1answer
333 views

Acceleration, velocity and speed

It is given that acceleration is constant, so can we infer that average speed and velocity are the same?? Moreover, circular motion is out of the question, as the function of x(t) where ...
1
vote
1answer
296 views

Volume of gas at which relative fluctuation of gas density occurs

I have the following question: In what volume of gas occurs 10 % relative fluctuation of gas density under pressure of $10^5\text{ Pa}$ and temperature of $293.15\text{ K}$? I don't understand ...
6
votes
2answers
537 views

First and second fundamental forms

I'm writing notes about the 3+1 formalism in general relativity, for myself. Inevitably I came across the notions of first and second fundamental forms. Mathematically, it is clear how these objects ...
2
votes
1answer
73 views

CMB anisotropies and tightly coupled limit

Sorry if this is a technical question. I am studying the origin of CMB anisotropies and the tightly coupled limit of the Boltzmann equations. We have a fluid composed of ionized electrons and photons. ...
2
votes
1answer
218 views

Are $A$ and $J$ in Black's equation (for electromigration reliability of wires/interconnections) independent?

Black's equation is an empirical model to estimate the MTTF (mean time to failure) of a wire, taking electromigration into consideration. Since then, the formula has been getting popularity in ...
1
vote
2answers
1k views

Confused about the electric field at the surface of a conductor

We know that the electric field at the surface of a conductor only have a normal component equal to $\rho/\varepsilon$ (finite number). But let’s consider the point $\text{P}$ (at the surface of a ...
2
votes
0answers
138 views

Lecture Notes confusion: Constructing the Einstein Equation

This question is on the construction of the Einstein Field Equation. In my notes, it is said that The most general form of the Ricci tensor $R_{ab}$ is $$R_{ab}=AT_{ab}+Bg_{ab}+CRg_{ab}$$ ...
3
votes
4answers
2k views

Polarization of sound

Sound can't be polarized because the vibration of such type can't be polarized i.e, it can't be limited or controlled by any barriers and so polarization is not possible in them. This is what my ...

15 30 50 per page