All Questions

0
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0answers
3 views

For a real battery, why is two identical bulbs in parrallel slightly more dim than just one in series

Image for reference : r = 0.8 Ohm - Emf = 1.5V - A = B = 6 Ohm The current when the switch is open, the only other resistor is the A bulb, so total resistance is 6.8 Ohms, but when its closed the ...
1
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0answers
2 views

Primitives on Newtonian Mecanic

With simples Newton mecanic laws, (and in a specific context), I learned that the speed $\vec{v}$ of an object is the derivative of the corresponding position vector $\vec{OM}$. So that means that $\...
0
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0answers
6 views

Triviality of Yang Mills in d>4?

It has been proved that the $\phi^4$ theory is trivial in dimensions d>4. By trivial I mean that the field $\phi$ is a generalized free field, or in other words, it's only nonzero connected correlator ...
0
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0answers
5 views

Green's function in a region between a conductor sphere and two charged spheres inside, with point charges inside of each

Please, help me. I have to find the Green's function in the following region, but I don't have any idea how to find it: I have a conducting spherical shell of radius a; in the center there are 2 ...
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0answers
5 views

Which would take more force:a clean cut or a crack

Would it take more force to make a clean cut or a crack. For example would it be harder to crack a rock or to cut it.
0
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1answer
8 views

Is simultaneity of events relative or just our observation of it?

I have already read this post about Relativity of Simultaneity but it doesn't seem to answer my question or it confuses me even more. Please feel free to close this if I am mistaken. I (think I) ...
1
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0answers
8 views

Magnetic field in double slit experiment using electron beams

Say I have an experimental setup like this for a double slit experiment using an electron beam instead of light. There is a magnetic field coming out from the plane of paper. So will we get an ...
0
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1answer
12 views

How was the equation for a gravitational assist derived?

Im currently writing a paper about a hypothetical probe meant to escape our solar system and I want to analyse how gravitational assists would be beneficial for its mission. I found a website with an ...
0
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0answers
10 views

Luttinger model and conform field theory

I'm studying Luttinger model and I'm having a hard time understanding its relation with conformal field theory. I'd like to know something about this. Is Luttinger model conformal only at long ...
1
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0answers
9 views

Radiation Reaction and Acausal Acceleration

The Abraham -Lorentz formula for the radiation reaction force is $${\bf F}_{rad} {= \frac{\mu_0 q^2}{6 \pi c} {\bf \dot a}}$$ and when electric charges are moving Newtons Law for an applied force ${\...
0
votes
1answer
7 views

Is the second diffraction order at different wavelength?

If a monochromatic laser light of wavelength $\lambda$ is incident on a diffraction grating of period $A$, then does the second ($m$=2) diffraction orders have same or different $\lambda$? From the ...
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0answers
3 views

Exciting surface plasmon polaritons - what is the purpose of air gap in Otto configuration?

I am currently reading about exciting surface plasmon polaritons (SPPs). One of the most common methods described in literature for exciting a SPP is using the Otto configuration (image from https://...
2
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1answer
13 views

Inversion applicable to three-dimensional lattices only

I have just started my first course in solid state physics and while studying symmetries, Inversion is defined as "A point operation which is applicable to three-dimensional lattices only. This ...
0
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1answer
21 views

Classification of 2D time dependent diffusion equation

I was trying to classify the following PDE: $\frac{\delta{u}}{\delta{t}}=\frac{\delta^2{u}}{\delta{x^2}}+\frac{\delta^2{u}}{\delta{y^2}}$ where u = u(x,y,t). I was originally using the definition of $...
0
votes
1answer
14 views

Bernouli equation on streamline

I made my first point at the free surface of the water and my datum to be the very bottom. Part b of the question asked to find the velocity of the water in the pipe. I set my second point to be at ...
0
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1answer
33 views

Perturbation to the flat space metric

from the geodesic equation for non-relativistic case where $$v_i\ll c$$ $$\frac{dx^i}{dt}\ll1,{\rm for }\ c =1$$ $$\frac{dx^i}{d\tau}\ll\frac{dt}{d\tau}$$using this the geodesic equation for proper ...
-1
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0answers
11 views

With Bernoulli effect how to calculate pressure drop in adjacent tube to the air flow?

A possibility to draw crank case gases through an oil catch tank under lower pressure (rather than feed back into the carburettor) might be to take a tube to a hole made in the exhaust pipe. Question.....
2
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1answer
16 views

Why wasn't the Stipa-Caproni plane efficient in its flight?

The Stipa-Caproni was an experimental italian plane design. Though it has a very peculiar shape, it seems at first glance like it would have pretty good aerodynamic profile since its reference area ...
2
votes
1answer
34 views

Why does the $\phi$-cubed theory have no ground state?

In the book of Sredinicki's, he claimed that the $\phi^3$ theory has no ground state, hence this is not a physical theory. My question is that I can't see why this system has no ground state. And I ...
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0answers
7 views

Development of quantized Weyl-equation solutions in positive and negative frequency modes

If a massless neutrino or anti-neutrino is considered (in the whole post I consider neutrinos res. anti-neutrinos as mass-less), it is described by the Weyl-equation: $$\overline{\sigma}^{\mu}\...
1
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0answers
18 views

Thickness of a target bombarded with deuterium

I need to calculate de thickness of a sheet of Zinc that is being bombarded by deuterium nuclei. I'm given that the fraction of nuclei dispersed below $\theta=90º$ with $T=8MeV$ is $0.9999$ and the ...
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0answers
14 views

How can one define a covariant rate of change of rest mass for an extended body?

For a point mass I can define a covariant rate of change of its rest mass as $\frac{d}{d\tau}m_0$ where $\tau$ is the proper time. How can I also define a covariant rate of change of rest mass for an ...
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0answers
18 views

Collisions of particles moving under circular motion

A point $O$ is situated a distance $h$ above a smooth horizontal plane, and a particle $A$ of mass $m$ is attached to $O$ by a light in-extensible string of length $h$. A particle $B$ of mass $2m$ is ...
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0answers
23 views

How does one calculate Fourier transform of Feynman propagator?

I am struggling with calculating the following integral on Sredinicki: How did he get the second line of (10.6)? That is, how did he calculate the Fourier transform of Feynman propagator?
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0answers
16 views

Pressure on the outer hull of aeroplane on theoretical emergency landing

I'm trying to figure out the proper way to calculate the pressure on the hull of aeroplane when landing on water. Let's say the horizontal velocity of plane is 1000 km/h and it starts free-falling ...
1
vote
1answer
18 views

Divergent Coulomb integrals in superfluid fluctuations

In Chapter 3 of Kardar's statistical physics of fields, in the context of lower critical dimension, he works out an example about superfluids where starting from the probablity of a particular ...
1
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0answers
22 views

Mathematical Resolution of Overlapping Signals

I would like to take the opinion of physicists (my area is chemistry). During instrumental analysis, the output is a instrument response vs. time. Each peak corresponds to a molecule which is ...
0
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0answers
18 views

Photo-electric effect with light reflected from a blue wall

Suppose we have a metal which has a work function corresponding to yellow. Obviously, if light with frequency greater than yello is made to fall on it, it would show photo-electric effect.Now, ...
0
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0answers
10 views

Re-Radiation from a ferrite rod antenna: Phase relative to the incoming signal

I am working through a problem involving interactions between multiple closely located ferrite bar antennas. I am seeing energy re-radiated from the various antennas coupling into the other ...
-5
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0answers
50 views

Can changing both mass and velocity such that momentum is conserved accelerate a particle? [on hold]

Our book tells us that according to Newton's laws an object will not accelerate if equivalent force is equal to zero. But if the mass and the velocity changes in such a way that the net momentum ...
1
vote
1answer
29 views

Can all canonical transformations be generated using a generating function?

In Classical Mechanics, a gauge transformation is of the form \begin{equation} L \to L' = L + \frac{dF(q,t)}{dt} \, . \end{equation} Any transformation of this kind leaves the Euler-Lagrange equation ...
-4
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0answers
52 views

Are we overthinking our physics equations? [on hold]

This is more of a discussion than a true problem needing solved.... I was reading an article on amplituhedron and how it defines basically the same processes but in a much simpler format. One ...
-4
votes
2answers
50 views

Can a body have a charge of $0.8 × 10^{-19}\:\rm C$? Why or Why not? [on hold]

Can a body have a charge of $0.8 × 10^{-19}\:\rm C$? Why or Why not? Please answer. Justify why and why not.
1
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3answers
28 views

Half-life and muon decay

Imagine that we have a single muon. It has a life span of 2.2 microseconds on average. So normally, after that amount of time, the muon will decay. Now imagine we have two groups of muons. Group A has ...
0
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1answer
36 views

Determining mass and force separately

I have been thinking.. How can we measure the mass of the body separately from the force? Or should we measure the force and acceleration? But by which means can we gauge our equipment e.g. some ...
0
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1answer
14 views

Integer quantum Hall conductance and time-reversal symmetry

If we have a (2+1)-dimensional electronic gapped system with a unique ground state and it has a nonzero integer quantum Hall conductance, then the system (or its ground state) must break the time-...
-1
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0answers
32 views

What mistakes are there in the flying saucer theory?

The work of the wing in the air or water can be described as follows. The wing makes a fast ascending impulse, as a result of which a shock wave is formed above it, and the flying saucer begins to be ...
1
vote
2answers
26 views

Are point transformations necessarily canonical?

A point transformation $ Q(q,t)$ only modifies the location coordinates, while a canonical transformation, in general, also modifies the momentum coordinates $Q(q,p,t)$. In the context of the ...
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0answers
6 views

Does Michelson interferometer help us to calculate the radius of star?

Is Michelson interferometer useful to calculate the radius of a star based on the number of rings or radius of ring?
-3
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0answers
39 views

Mechanism of gravity/general relativity?

Every popular physics book I have read about general relativity uses the balls on the trampoline analogy (or some such analogy of two dimensional space in three dimensional space) for how gravity ...
0
votes
1answer
23 views

Electrostatic field-Field lines relationship

How is the $\frac{1}{r^2}$ dependence of the electric field due to a stationary point charge consistent with the concept of electric field lines?
0
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0answers
10 views

Huge mass changes for flying [on hold]

Can an object with constant, fast and huge mass changes produce gravitational waves and fly?
0
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1answer
25 views

What will happen with the cosmic microwave background radiation if the Big Rip theory is true?

There are three things I can imagine happening: It appears one light year further away every year, which would be a bit weird, because it would be behind the universal event horizon, but still ...
4
votes
1answer
215 views

Is this Article About Possible Mirrored Universe Junk Science?

The article can be found here, entitled "Big Bang May Have Created a Mirror Universe Where Time Runs Backwards". I know any notion of backwards time is probably a dead horse in this site, but given ...
5
votes
3answers
62 views

How is rest mass $m_0$ in $E=m_0c^2$ related to mass $m$ in $F=ma$?

A particle at rest has energy given by $$E=m_0c^2$$ where $m_0$ is defined as its rest mass. So rest mass is essentially a measurement of a particle's intrinsic amount of potential energy. How is ...
0
votes
1answer
68 views

Fusion confusion: what did 12 year old Jackson Oswalt do?

This kid has been showing up in news feeds, but only credulous pop media articles, not hard science reporting. What did he build, and what physics does his device do?
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0answers
14 views

Constraints and time derivative

Consider a system of $N$ particles. There are $C$ holonomic time independent constraints, $$ \begin{aligned} f_1(\mathbf{r}_1,\dots,\mathbf{r}_N) & =0 \\ f_2(\mathbf{r}_1,\dots,\mathbf{r}_N) & ...
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0answers
15 views

What is the definition of coordinates of an observer? [duplicate]

I am confused about coordinates of an observer. Suppose we have an observer $A$ whose world line $\gamma$ is a geodesic and another observer whose world-line $\gamma$ is not. Since coordinates is just ...
0
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0answers
38 views

How does a physicist conduct his work? [on hold]

How does a physicist conduct his work? Compared to say computer programmers, they must be able to utilize equipment. Then how do they get to use that equipment? What do they do at home (maths?)?
0
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1answer
12 views

Does adiabatic quantum computation require the initial and final ground states to be non-orthogonal?

Background At a recent talk, I was told by the speaker that it is not possible to adiabatically transfer from one ground state $|\psi_0 \rangle$ to another $|\psi_1 \rangle$ if these states are ...

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