0
votes
1answer
39 views

Difference between 1 unit of a physical quantity and the unit of that physical quanity and how is the unit of derived quanities obtained? [on hold]

Is there any difference between the unit and 1 units of a physical quantity and how do we define the unit of a derived quantity. For example,the SI unit of length is m and 1 unit of length is 1m.Are ...
0
votes
0answers
28 views

How can we orient light in vacuum?

Let's consider the mirror clock used to show time dilation in special relativity: In the rest frame of the clock, the light pulse from the laser pen propagates in vertical direction down then up: ...
0
votes
1answer
37 views

Infinitesimal gauge invariance of Yang--Mills Lagrangian

Under an infinitesimal gauge transformation $g(x) = 1 - i\alpha{}_i(x)T{}^i$, where $[T{}^a, T{}^b] = if{}^{ab}{}_c T{}^c$, I want to know what happens to the Lagrangian $\mathcal{L} = ...
2
votes
2answers
35 views

Momentum conserving delta-function in the transfer matrix of quantum-field-theoretic scattering theory

The $S$-matrix vanishes unless the initial and final states have the same total $4$-momentum, so it is helpful to factor an overall momentum-conserving $\delta$-function: ...
-5
votes
1answer
66 views

What is exact difference between gravitational force and magnetic force? [on hold]

I've read that gravitational force is due to mass only and magnetic field is due to moving charged particles. But my question is: what are other difference between them? Can we set up a small ...
0
votes
1answer
61 views

Does gravity exist between quarks in a neutron?

Does gravity exist between quarks in a neutron? I mean, I've learned that gravity exists between objects that have mass/energy. But does this apply between quarks in a neutron?
2
votes
1answer
56 views

Work done in bringing down a body [on hold]

A block of mass $30$ kg is being brought down by a chain. If the block acquires a speed of 40.0 cm/s in dropping down $2.00$ m, find the work done by the chain during the process. I have calculated ...
1
vote
0answers
13 views

Database for work functions for exotic crystallographic faces

Is there a database, which holds work functions (found either from experiment or calculations) for some more exotic crystallographic faces, such as (221) or (311) for copper? I dug around and found ...
0
votes
0answers
6 views

How to describe the process of fluorescence physically,and further more, to add interaction to quench it

We investigated the quenching of fluorescence of R6G molecules on different substrates, e.g. graphene, h-BN. I am curious about how to describe the process of fluorescence physically,and further more, ...
1
vote
2answers
50 views

Which wave carries more energy?

Which wave carries more energy? This is a school question (in a course a friend is taking) but I am interested in the answer:
1
vote
4answers
87 views

Electron losing its charge

If the electron is said to be a charge carrier, then could it lose its charge ? It wouldn't remain an electron ofcourse , because charge is one of its important properties . But am talking about the ...
1
vote
0answers
29 views

Show that partial derivative with respect to time is anti-hermitian [on hold]

I have a definition that $$<s_1,s_2> = \int_{-\infty}^{+\infty}s_1^*(t)s_2(t) dt$$ I need to show that $\partial_t$ operator which is just the partial derivative with respect to time is ...
0
votes
1answer
32 views

Issues of normalization & differential final state momenta in analysis of normalized differential quantum-field-theoretic probability of scattering

The normalized differential quantum-field-theoretic probability $dP$ of scattering is given by $$dP=\frac{|\langle f |S|i\rangle|^{2}}{\langle f|f\rangle\langle i|i\rangle}d\Pi,$$ where $|i\rangle$ ...
1
vote
0answers
28 views

Symmetry properties of gamma matrices

While reading a paper on supersymmetry i faced the following problem. Its about the symmetry property of charge conjugation matrix in different space time dimension. The charge conjugation matrix is ...
1
vote
3answers
53 views

how could Kinetic energy increase if no energy was there in the system?

i was reading Physics-Halliday, Resnick, Krane(fifth edition) there on page 638 it is written: if the external agent does positive work in assembling the charge ...
-1
votes
1answer
24 views

Power current Electicity [on hold]

When A 500 W electric bulb and 500 W heater operates at their rated voltages,the filament of the bulb reaches a higher temperature than the filament of the heater.The most important reason for this is ...
0
votes
0answers
25 views

Rotating droplet of liquid

I'm interested in the fluid dynamics of a spherical droplet of liquid whose surface is forced to rotate at a constant velocity. I'm interested in either steady-state solutions (the internal flow ...
0
votes
0answers
23 views

Keplerian orbits and radial velocities: problem with true anomalies

I am writing a pure Python code to calculate radial velocities of stars with massive objects orbiting them. I am following the formalism from Murray & Correia (2011) (hereafter MC11). In a given ...
1
vote
0answers
41 views

Centripetal acceleration [on hold]

I know if a particle is accelerating around the earth it has $$a= \omega*v$$ My question is how do I express this in terms of the unit vector. Would it go something like this. $$|a| = |\omega*v| $$ ...
5
votes
1answer
51 views

The calculation of the entropy of a single atom

I used to think that the entropy of a single atom could not be calculated, for in my mind only the entropy of a system containing many atoms could be calculated. But my professor told me the entropy ...
0
votes
0answers
20 views

Huyegns Principle and data transmission

Huygens's principle (The Gist) states that for every object on which light is incident every point on that object acts a light source till light is being incident on it. So is it possible than WiFi ...
0
votes
1answer
20 views

How does gas friction emerge?

The fluid parcel model states that a gas can be modelled as the sum of infinitesimal small parcels. According to this model, the friction of a gas with a solid surface (e.g. the wall of a pipe) ...
0
votes
1answer
17 views

Why does increasing heat conductivity decrease Nusselt number?

Normally we expect that when heat conductivity(k) increases heat transfer is also increases. But for fluids increasing k decreases Nusselt number. My senses tell that using high conductive fluid cause ...
0
votes
0answers
28 views

Electromagnetic Field caused by accelerating and oscillating charge particles?

Will accelerating and oscillating charges will cause EM waves of different shapes ? As EM waves are always shown as sinusoidal Electric and Magnetic Fields perpendicular to each other. Does it mean ...
1
vote
0answers
33 views

Newton's third law confusion [duplicate]

If A exerts a force of 200N on B, then by newton's third law, 200N would be exerted on it. Similarly, if B exerts 100N on A, by newton's third law, 100N would be exerted on it. Therefore the net ...
-2
votes
1answer
60 views

What does $P = Fv$ mean? [on hold]

The engine of a car is developing a power of 90kW when it is moving on a horizontal road at a constant speed of 100 km h−1. Estimate the total horizontal force opposing the motion of the car. I ...
0
votes
1answer
30 views

Can condensation occur in a unsaturated vapor?

Consider that a gas mixture of vapor$+$inert gas is unsaturated with concentration (or molar fraction) $x_\infty$ far from a clear, cooled substrate of temperature $T_\text{w}$, i.e. ...
0
votes
0answers
30 views

Is the visible light from “red-hot glass” at least close to Blackbody Radiation?

In this really nice answer @RobJeffries explains the difference between the ideas of Thermal Radiation and Blackbody Radiation in the context of a source which may be in thermal equilibrium, but who's ...
0
votes
1answer
22 views

How can excite a semiconductor to make a photon just by heat in room temperature?

I want to know if a semiconductor in room temperature can excite by heat, producing photon, without any other source of energy?
-1
votes
2answers
61 views

What factors will make Earth re-rotate again if it stopped? [on hold]

"What will happen if Earth stopped rotating?" have been answered multiple times with a lot of informative and interesting answers. Continuing this hypothetical question, I have another one in mind. ...
0
votes
0answers
18 views

What is the Relationship Between Poisson Brackets and Additive Integrals of Motion?

Question in the title: what is the relationship, if any, between Poisson brackets and additive integrals of motion? Context: Is there anything we can say about additive integrals of motion in ...
0
votes
0answers
11 views

Slowly Varying Functions for Adiabatic Invariants - The Same as Karamata's?

In section 49 (and 50) of Landau and Lifschitz's "Classical Mechanics", adiabatic invariants are discussed, which are related to functions which vary adiabatically or "slowly" with time. Admittedly ...
0
votes
1answer
36 views

How does pressure change over time in an open box?

Imagine that you have a 1 cubic meter metal box with two 20 mm diameter holes. One of them is connected to an air-compressor that constantly pressurizes the inside of cube. Let's say 5 atm. The other ...
4
votes
2answers
60 views

Do gases have phonons?

A phonon is a quantized unit of sound; they are encountered when quantizing lattice vibrations in solids. Now, even an ideal gas supports sound waves, but in such a case, interactions between atoms ...
17
votes
3answers
2k views

Same photon or different photon?

Consider a typical optical focusing system: A small light source, then a collimating lens, then a focussing lens, and then a detector (e.g. CCD). Assume that source intensity is so low that only one ...
1
vote
0answers
37 views

What is a good mathematical introduction to QFT [duplicate]

I've noticed that, any time I try to pick up Peskin and Schroeder, the main stumbling block it the leap in mathematical constructs from QM. Is there a good textbook that could teach me some of the ...
2
votes
0answers
42 views

Gimbal Lock: why is it a problem?

I was watching this video http://www.youtube.com/watch?v=rrUCBOlJdt4 about the gimbal lock problem. I understood that during rotations it could happen that one DOF disappear. Looking at the middle ...
0
votes
1answer
46 views

Why is standing still easier than walking? [on hold]

Both the works basically push force into the ground.So why does walking require more work?
-1
votes
3answers
30 views

Frequency of other light in white light [on hold]

I have this question in mind because I read that the frequency of light depends only on the source of light. If we consider a source of white light then it emits light of different colours also. Then ...
0
votes
0answers
20 views

Relativistic Mass and Potential Energy

In the chapter 16–4 of the Feynman Lectures, Feynman employs a thought experiment to explain why "if two particles come together and produce potential or any other form of energy; if the pieces are ...
0
votes
1answer
16 views

Counting states

Assume we have 6 particles, 3 with spin $\frac{1}{2}$ and another 3 with spin 1. The particles are distinguishable. The energy of a spin s is $\epsilon=-s \mu H$. How many energy states the system ...
0
votes
1answer
36 views

Do all solid objects emit visible light?

Are there solid objects that do not emit visible light? To my limited and humble knowledge, creating such an object would require us to "only" shift the spectrum of emitted radiation. Is it possible? ...
0
votes
0answers
15 views

Where is the zero electric potential energy point?

Does the point of the electric potential energy of zero is defined by human or dominated by the indefinite integral of the electric force?
0
votes
0answers
35 views

Double-slit intensity distribution for particles

For waves, the intensity pattern for the double-slit experiment is given by the following equation (as of David Morin's notes on waves) $$ I(x) = I(0) \frac{D}{\sqrt{x^{2} + D^{2}}}cos^{2} \left ( ...
0
votes
1answer
46 views

Can tearing a piece of paper be chaotic?

When one thinks of chaos, then automatically the thought pops up that a very little difference in the initial conditions enlarges over time and you end up with a totally different end situation. When ...
0
votes
1answer
30 views

Which of the following bulbs will glow? [on hold]

When the switch is closed which of the following resistors are parallel. Here is my thought process. Consider the current flow from the voltage source. When the charges reach the junction where ...
1
vote
0answers
24 views

Applying AdS-CFT to traversable wormholes? [on hold]

ER=EPR recently brought up the connection between non-traversable wormholes and entanglements. What about traversable wormholes? Can we apply AdS/CFT to traversable wormholes?
0
votes
1answer
25 views

acceleration of water when it travels through garden hose

How to derive average acceleration of water as it travels through nozzle of garden hose. Suggest some assumptions for better understanding
7
votes
1answer
56 views

How can dimensional regularization “analytically continue” from a discrete set?

The procedure of dimensional regularization for UV-divergent integrals is generally described as first evaluating the integral in dimensions low enough for it to converge, then "analytically ...
2
votes
1answer
113 views

The mass of the proton times its charge radius is very close to 4ħ/c. Is this a coincidence?

The claim is $r_p m_p = 4 L_0 M_0 = 4\hbar/c$, where $r_p$ and $m_p$ are the proton's charge radius and mass, and $L_0$ and $M_0$ are the Planck length and mass. Using the muon measurement ...

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