2
votes
3answers
149 views

Please explain this statement about Lorentz transformations

I'm reading Sternberg's Group Theory and Physics. I have a question about chapter 1.2 Homeomorphisms. Background: A Lorentz Metric is defined as $||{\bf x}||^2=x_0^2-x_1^2-x_2^2-x_3^2$ And a ...
6
votes
7answers
4k views

Entropy and Crystal Growth

I was reading about growing single crystals and I'm a little confused about this - In most crystal growing processes, a "seed crystal" is used, and the rest of the material crystallizes on the seed ...
1
vote
2answers
146 views

Can the speed of an electromagnetic wave be measured in the absence of neutrinos?

Let me explain better: from what I understand neutrinos are so pervasive they are literally everywhere. And since they have such a tiny electric charge they barely interact with anything and cannot be ...
2
votes
1answer
58 views

Is it possible to calculate chromacity coordinates using absorbance values?

I have absorbance values for blood plasma. Absorbance was measured in range of 380 – 600 nm every 5 nm ending up with absorbance values for 45 wave lengths. I was browsing through literature, and I ...
4
votes
1answer
155 views

Link between Earth and Mars

I am trying to the calculate the link budget for link between a ground station on Earth (with a particular latitude and longitude) and a rover at a particular location on the surface of Mars, either ...
3
votes
4answers
533 views

Why is linear independence of harmonic oscillator solutions important?

The equation of motion for the harmonic oscillator (mass on spring model) $$\frac{d^2x}{dt^2} + \omega_0^2 x = 0$$ with $\omega_0^2 = D/m$, $D$ and $m$ being the force constant of the spring and the ...
0
votes
0answers
47 views

Suggestions for a physics oriented book on Variational Calculus [duplicate]

I would like to buy a good book on Variational Calculus. Most of the books that I find seem to be rather formal in a mathematical sense, which is not necessarily bad, but makes the studying a bit ...
-1
votes
2answers
251 views

Stone thrown in empty space

This is a supplementary question to What happens if object is thrown in empty space? Via the following logic: $$E = \frac{(mv)v}{2}\\ E = \frac{pv}{2}\\ \Delta E = \Delta p\times \Delta \frac{v}{2}\\...
1
vote
1answer
431 views

parallel=time, perpendicular=space? on multiple time dimensions

There are some discussions on more than one time dimensions, e.g., Intuition for multiple temporal dimensions and More than one time dimension. If we define that the parallel direction is time, of ...
1
vote
0answers
358 views

Online magnetic field solver

Is there a site that allows you to give the approximate specs of a set of magnets and then it produces the graph of the magnetic field for you? Here is a situation I try to understand: I have a set ...
0
votes
1answer
369 views

Does the measurement on a subatomic particle give its mass value?

No doubt I am wondering about the Young's double slit phenomena. If we observe or measure the properties of a subatomic particle, we are able to know its mass, velocity and it comes to existence. So ...
-6
votes
1answer
471 views

Where the fine structure constant $\alpha$ is speed parameter of electron $\beta_e$, How can it be a constant?

The fine structure constant $\alpha$ actually is speed parameter of electron $\beta_e$, moving around proton in hydrogen atom. $v_n=\frac {\alpha_c}{n}=c\frac {\alpha}{n}=c\frac {\beta_e}{n}$ How ...
-4
votes
1answer
178 views

How do I publish a physical constant [closed]

I think what i've found is a physical constant that is a physical quantity, universal in nature and constant in time. but It contrasted with a mathematical constant, which is a fixed mathematical ...
0
votes
0answers
529 views

Starting string theory studies in grad school

How is it possible for a grad student to do research in any modern area of string theory like AdS/CFT or ABJM if they need to start grad school by having to learn QFT from scratch? Is there a time-...
4
votes
1answer
417 views

Is momentum still conserved in non-phase-matched nonlinear optical processes?

To be efficient, a phase-matching condition has to be fulfilled in many nonlinear optical processes. For instance, the phase-matching requirement for second-harmonic generation is $k_{2\omega}=2k_{\...
3
votes
2answers
2k views

How does Earth carry Moon with it, if it can not force Moon to touch it by gravitational force?

Earth's gravitational force is acting on its Moon in such a way that it forces the Moon to rotate round its orbit by centripetal force and carries it while rotating round the Sun by gravitational ...
2
votes
1answer
593 views

Physical Significance of Operator Norm/Spectral Norm of a Quantum Operator

Is there any physical significance of operator norm/spectral norm of a hermitian operator?
1
vote
2answers
129 views

What are some ways of inducing spin polarization?

I saw a talk today and they mentioned how nitrogen-vacancy diamond centers can be used to optically induce spin polarization and now I wonder what other ways there are to induce a spin polarization. ...
2
votes
2answers
1k views

How much better is salt water at letting through microwaves than pure water?

Radio Wave Attenuation There are two general types of matter (substances) in the universe that affect electromagnetic waves, conductors and insulators which are called dielectrics by ...
0
votes
0answers
125 views

Electric field singularity

What's a general proof for the log-singularity of electric field near the edge of a uniformly charged surface?
1
vote
1answer
161 views

Learning more about String theory [duplicate]

I know the concept behind String Theory. But I was wondering if anyone knows of a good place to start learning more about the theoretical physics behind it? Maybe a book someone can recommend to me! I ...
12
votes
3answers
1k views

Can we make images of single atoms?

I was wondering how far in imaging physics had gotten. Do we hold the technology to actually take a picture of, say, an alpha particle, or even a single atom? I realise we aren't talking about camera ...
1
vote
2answers
3k views

Is it possible to calculate atmospheric pressure if given temperature (F) and elevation?

I am working on a report at work and need to determine the atmospheric pressure for small intervals over a 24 hour period. Searching Google, I've found charts which give a base pressure of 14.65 psia ...
8
votes
1answer
463 views

Is that true that real quantum chaos doesn't exist?

I read several books and papers on quantum chaos, to my understanding they all emphases that the quantum chaos does not really exist because the linearity of the Schrodinger equation. Some works were ...
4
votes
3answers
1k views

Does zero strain always imply zero stress?

In solid mechanics, can I always assume that if an object undergoes no strain, then no stress is applied to it? I think it's true only because I can't seem to find a counter-example.
1
vote
0answers
81 views

Is sonoluminescence relevant to the behaviour of Navier-Stokes (or converse)?

More precisely, could Sonoluminescence be a singularity of Navier-Stokes(NS)? Is there some other connection that might be interesting, or is it completely irrelevant? Wiki page mentions NS, but says ...
3
votes
2answers
2k views

Higgs-Boson/Graviton [duplicate]

The Higgs boson gives particles mass. And the graviton is the theoretical force-carrier of gravity. Gravity depends on mass. So if the Higgs Boson gives things mass, it therefore gives them gravity. ...
1
vote
1answer
399 views

Interpreting Vector fields as Derivations on Physics

I have a subtle doubt about the physical interpretation of the mathematical definition of vector field as a derivation. In basic physics we understand a vector quantity as a quantity that needs more ...
3
votes
1answer
509 views

What conservation law corresponds to this local $U(1)$ symmetry of the CCR?

It is known that canonical commutation relations do not fix the form of momentum operator. That means that if canonical commutation relations (CCR) are given by $$[\hat{x}^i,\hat{p}_j]~=~i\hbar~\...
12
votes
2answers
331 views

Combining two finite number fock spaces into one

Say I have two separate systems of identical Bosons, one with N Bosons the other with M. System one is described by a state $|\psi_1\rangle$ the other with $|\psi_2 \rangle$ which are expressed in a ...
2
votes
1answer
74 views

Isotope exchange between heavy water and plastic container

It is known that pure heavy water will quickly get contaminated by light hydrogen atoms if exposed to air due to isotope exchange. Does the same thing happens when heavy water is stored in plastic ...
1
vote
1answer
255 views

Two-photon scattering: colours

Is there a particular conservation principle that necessitates that the outcoming photon pair has the same frequencies as the incoming photon pair? I'm thinking in particular of these Feynman-like ...
0
votes
1answer
2k views

What happens if object is thrown in empty space?

If I throw a object in empty space, I apply a force to throw that. Then it gains some acceleration and it's speed increases. So will it's speed keep on increasing, or it will get stable? If yes, ...
2
votes
1answer
86 views

Please provide the simplest example you can think of, of generators of time evolution and generalized coordinates

I was reading the Wikipedia article about Noether's theorem and this thing popped out: Then the resultant perturbation can be written as a linear sum of the individual types of perturbations ...
1
vote
2answers
141 views

Was the fractional model of quarks electric charge found before discovery of the $\Delta^{++}$?

From Wikipedia: Existence of the $\Delta^{++}$ , with its unusual +2 electric charge, was a crucial clue in the development of the quark model. the fractional model of Quarks electric charge was ...
21
votes
11answers
5k views

Are there still 'everyday' phenomena unexplained by Physics? [closed]

There are two very famous quotes from German Nobel Laureate Albert Abraham Michelson that are remembered mainly for being extremely wrong (especially since he said them just before two major ...
-3
votes
1answer
709 views

Does this experiment on wave-particle duality and complementarity disprove quantum mechanics and prove the EPR viewpoint on it?

I recently read Photons act like they go through two paths, even when we know which they took, at Ars Technica, which reports on the paper Wave-particle dualism and complementarity unraveled ...
6
votes
6answers
6k views

Difference between torque and moment

What is the difference between torque and moment? I would like to see mathematical definitions for both quantities. I also do not prefer definitions like "It is the tendancy..../It is a measure of ......
1
vote
0answers
120 views

Photons interact with themselves

We know that photons are the antiparticles of themselves and if they interact with each other through higher order process do they annihilate and again produce photons? Here is the Phys.SE question ...
2
votes
2answers
545 views

In Dirac notation, what do the subscripts represent? (Solution for particle in a box in mind)

So the set of solutions for the particle in a box is given by $$\psi_n(x) = \sqrt{\frac{2}{L}}\sin(\frac{n\pi x}{L}).$$ In Dirac notation $<\psi_i|\psi_j>=\delta_{ij}$ assuming $|\psi_i>$ ...
7
votes
1answer
1k views

Why is the majorana particle a fermion?

My knowledge of quantum mechanics is rather limited, but what I always understood was that Bosons have integer spins and Fermions have half-integer spins. My question is very simple: the Majorana ...
3
votes
1answer
2k views

three-particle quantum entanglement

So I know that two particles can be entangled in a quantum way, but is it possible that more than two particles be entangled in a quantum way? Most descriptions provide with two-particles cases, so I ...
3
votes
2answers
338 views

Sound Wave Propagation: Why HF are more specular while LF are more omni

The propagation of high frequencies sound waves is more directional (specular), and they don't diffract as much as low frequencies. Low-frequencies diffract and thus propagate in a more omni-spherical ...
2
votes
1answer
149 views

Phonon wavevector $q\le 2k_{F}$ for Electron-Phonon Scattering

I am reading "Supercollision cooling in undoped graphene." There the authors write: ``Above $T_{BG}$ (the Bloch-Gruneisen temperature), only a fraction of acoustic phonons with wave vector $q\le 2k_{F}...
6
votes
2answers
502 views

How does locality decouple the UV and IR behaviour of a QFT?

I came a comment in this paper: Scattering Amplitudes and the positive grassmannian in the last paragraph of page 104 which says: "One of the most fundamental consequences of space-time locality is ...
3
votes
1answer
352 views

Influence of air resistance in space

Consider the following situation: You are locked inside a cylindric container allowing you to move around freely without being in contact with any of the items or surfaces aboard. The container is ...
3
votes
2answers
162 views

What symmetries does a lattice calculation need to preserve?

I've heard that it is impossible to have a properly Lorentz-invariant lattice QFT simulation, as the Lorentz invariance is spoiled by the nonzero lattice distance $a$. I've also heard that there are ...
7
votes
1answer
506 views

Does the Standard Model have a Landau pole?

I have seen the statement that the Standard Model has a Landau pole, or at least it its believed that it does at $\sim 10^{34}$ GeV. Has this actually been proven (at least in perturbation theory, as ...
1
vote
1answer
1k views

Finding the Electric Field (and other information, besides)

The problem I am working on is: Two parallel plates having charges of equal magnitude but opposite sign are separated by 29.0 cm. Each plate has a surface charge density of 33.0 nC/m2. A proton is ...
6
votes
1answer
2k views

Historic derivation of Wien's law

Every book I've read, including a lot of websites, Wikipedia, etc, say that Wien derived this: $$\rho_\nu(T)=\rho(\nu,T)=\nu^3f\left(\frac{\nu}{T}\right)$$ Being $\rho_v(T)$ the spectral enegy ...

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