0
votes
0answers
14 views

Finding the maximum possible uncertainty of an observable [on hold]

Show that the maximum possible uncertainty for any observable X is $\frac{1}{2}$$\|x_1 - x_2|$ where $x_1$ and $x_2$ are the extreme eigenvalues of X. (Maximize ($\sum_{i} p_ix_i^2 ) - (\sum_{i} p_i ...
2
votes
2answers
37 views

Pole and Barn Paradox w/ Spacetime Interval

I'm having trouble with a pole and barn paradox problem. The problem is as follows: A pole vaulter is running with a pole at $ v=\frac{\sqrt3}{2}c $. Her pole has a proper length of $L$. She runs ...
1
vote
0answers
12 views

Equivalent of the word “Attitude” for the other three DoFs [on hold]

When discussing the physical state of a thing (e.g. a satellite), you can refer to its attitude state (which, to me, consists of its attitude and its derivatives/rates) and its.... non-attitude state ...
1
vote
2answers
31 views

Finding the speed of electrons in a magnetic field

So I'm trying to solve this problem in which an electron beam is "drawing a picture" on a TV screen. The electrons are accelerated to a voltage of $3 kV$ by wire coils and are then directed to ...
0
votes
1answer
26 views

How does Modified Newtonian Dynamics (MOND) violate Newton's laws?

I have read some articles on MOND which indicate that a modification of gravity violate Newton's third law, but I don't know how exactly that works. I do know that if Newtonian acceleration is smaller ...
1
vote
1answer
12 views

How is it guaranteed that electrical connections could be made without destroying a diode laser?

A diode laser is a tiny diode and requires a microscope to see it. Since a laser generates a good amount of heat, the diode should be destroyed with the produced heat. But it does not happen. but why ...
0
votes
1answer
29 views

Electron velocity in hydrogen

I was speculating over the feasibility of myon catalysed fusion. Somehow I drifted away from that a little, and I was wondering if one can find a quantum-mechanical expression for the velocity of an ...
0
votes
1answer
59 views

Why is carbon not a semiconductor?

As opposed to silicon and germanium (or tin and lead), carbon is not a semiconductor --even though, they are in the same group. More interestingly, diamond (which is carbon) seems to be a good ...
5
votes
1answer
38 views

Understanding potential energy

I am self-studying the classical mechanics using the book by Taylor, and I have a question about the potential energy. The book (pg 111) says: If all forces on an object are conservative, we can ...
1
vote
1answer
34 views

Quantum teleportation and macroscopic objects

Purely speculative. If not allowed, I'll delete. If quantum teleportation was scalable to macroscopic objects, I assume it would require an amount of matter at the destination, equal to the amount of ...
1
vote
0answers
8 views

What wavelengths of electromagnetic radiation are emitted by the LH2/LOX reaction?

Rocket engines such as the Rocketdyne Rocket System 68 and the Space Shuttle Main Engine use liquid hydrogen and liquid oxygen as propellants. The exhaust from this type of engine is notable in ...
1
vote
2answers
30 views

Annihilation operator in harmonic oscillator

In Wikipedia's QHO page there is a moment when the following is stated: I don't know why "the ground state in the position representation is determined by $a|0\rangle=0$". I would say that the ...
0
votes
0answers
9 views

How to calculate heat emitted and the range

If I have a source of heat and I know it's surface temperature and size (suppose there are no barriers, only vacuum) can I then calculate the length to which the heat will be felt, and create a graph ...
1
vote
0answers
23 views

Conservation of Komar Mass

The definition of Komar Mass in GR is associated with one asymptotically flat end. However, a hypersurface may contain more than one end, such as the spacelike Einstein Rosen bridge in Kruskal ...
0
votes
0answers
24 views

Colliding beams vs static target

In this problem I need to find the threshold energy of a positron-electron collision that creates a Z boson (the reverse of the following picture; Z mass 92 GeV) in two distinct cases: collision ring ...
1
vote
0answers
18 views

Antiunitary operators in the tenfold way

In the classification of free fermion systems in condensed matter, physicists usually divide the systems into ten symmetry classes, first discovered by Altland and Zirnbauer. In their classification, ...
2
votes
3answers
41 views

Does visible light heat things up?

During a sunny day the walls of my house warm up (no surprise). My question: how much of this warming up (if any) comes from visible light? I associate infrared with thermal energy. If my house was ...
-4
votes
0answers
49 views

Where can a particle be found in a wavefunction [on hold]

Let me rephrase my question. Consider the 3d wave packet of a free particle moving along the x-axis. The wave packet will have components in the y and z dimensions as well as the x dimension. What ...
1
vote
1answer
35 views

Surface brightness

I have to compute the surface brightness as a function of the radius from the following set of data: {right ascension ($\alpha$), declination ($\delta$), magnitude (m)}. I also know the center of the ...
-4
votes
0answers
34 views

The Sun's space-time warp [on hold]

Can we infer that the skin of the Sun is (to some depth) blanketed by the space-time warp created by its own mass? Does the Earth's mass create any measure of a space-time warp?
0
votes
0answers
18 views

Charge Magnitude Based on Isoline Spacing

Suppose we have two positive charges of unknown magnitudes. We are given the isoline map (the equipotential lines) for the two-charge system. One has isolines more "squashed together" (more closely ...
1
vote
0answers
21 views

Wire with current in magnetic field $\vec{B}$has force $\vec{F_1}$. When rotated, $\vec{F_2}$. Find $B$ [on hold]

I have the following question: In a wire with $10cm$ there is a current $4A$ going 'upwards' in the $z$ axis. The force over this field, under a constant magnetic field $\vec{B}$ is $F = -0.2\vec{i} ...
-1
votes
0answers
14 views

Question about Bubble chamber reactions [on hold]

The bubble chamber pic of event which was exposed to a K- beam in a liquid hydrogen bubble chamber. So, the target consists of protons.
3
votes
1answer
38 views

Why is the Virial Theorem not a Special Case of the Ergodic Theorem? What is their Relationship?

The virial theorem involves the time-averages of the potential and kinetic energies if the motion of the system is bounded to a finite region of space. An ergodic theorem relates the time and space ...
3
votes
0answers
22 views

Why would oscillation of a gas column inhibit rather than promote mixing?

Many years ago I helped to support an experiment conducted in Japan which investigated the effects of high frequency oscillation ventilation (HFOV) on the mixing and distribution of gas into the ...
3
votes
2answers
143 views

Why are there only 3 Additive Integrals of Motion?

1. I was reading Landau & Lifschitz's book on Mechanics, and came across this sentence on p.19: "There are no other additive integrals of the motion. Thus every closed system has seven such ...
2
votes
0answers
16 views

Equivariance Relation - Superconformal Hypermultiplets

I'm concerned with equation 2.24 of http://arxiv.org/abs/1601.00482 The superconformal hypermultiplets in this paper have a conic hyperkahler target manifold and the authors want to gauge some ...
1
vote
2answers
54 views

Moment of inertia of 4 particle system

Four particles are connected by rigid rods of negligible mass. The origin is at the center of the rectangle. The system rotates in the $xy$ plane about the z axis with an angular speed of $6$ rad/s. ...
0
votes
0answers
32 views

Intuitively, why does pixel density = the diagonal of the screen? [on hold]

Per this website, by the Pythagorean Theorem, $\text{Diagonal Resolution in Pixels} = \sqrt{(\text{Height Resolution in Pixels})^2 + (\text{Width Resolution in Pixels})^2} \tag{1}$ So $PPI = ...
1
vote
0answers
19 views

Reversibility of uniqueness theorem

If we use uniqueness theorem then we know that if the boundary conditions and the charge distribution is same in 2 setups in a certain region then the electric field and potential in that region in ...
0
votes
2answers
63 views

How does electron makes transition from one state to another?

i am not asking why it makes. i am curious about how it makes the transition. Does it go from one state to another via straight line or it makes smaller and smaller orbits till it reaches the next ...
1
vote
1answer
41 views

Magnetic monopoles gauge theories

I'm quoting 't Hooft: "[...] Locally stable field configurations may exist that have some topological twist in them [...].Careful analysis of the existing Lie groups and the way they may be ...
1
vote
0answers
29 views

Can these two systems be equal? [on hold]

Suppose that there are two differents systems, $A$ and $B$, both associated with the same potential $V(x)$ (take, for instance, an infinite well). Then would the eigenstates of $A$ be the same as the ...
0
votes
2answers
51 views

Transformation of $| JM\rangle$ under the group of rotations

I am following the Quantum Mechanics I, Galindo A., Pascual P. and in page 207 explaining the matrix representations of the Rotation Operators in the angular momentum it appears the next (obvious) ...
0
votes
0answers
12 views

Temperature needed during the fabrication of clay products [on hold]

Which type of clay, structural clay or whitewares, requires a relatively higher temperature during fabrication? I believe that whitewares requires a higher temperature, because the whiteware ceramics ...
-4
votes
1answer
48 views

Gravity vs Vacuum: what's the difference? [on hold]

It is taught that there is no gravity in a vacuum. However, there is no where in the observable Universe where there is perfect vacuum. Vacuum is SUCTION POWER...and all energies (powers) need A ...
0
votes
3answers
28 views

Perpendicular Distance for Moments

My question is: Is perpendicular distance in the equation $\tau=Fd$ the distance of the yellow or red line? My belief was that it was the red line, however when I take moments about $O$ I get ...
-3
votes
0answers
25 views

At what point is a particle too small to cause a nuclear reaction?

What size particle is needed, theoretically, to split an atom? Not how we do it do to methods available? Can photons split an atom? I learned uranium atoms can be split using protons, and if an atom ...
0
votes
0answers
35 views

Are quadrilinear weak boson couplings possible?

$ZZ\rightarrow ZZ$, $ZZ\rightarrow W^+ W^-$, etc. Are these interactions possible?
1
vote
1answer
29 views

Is there any electric current in a continuous medium of moving charges?

Suppose that unlike in real life where charge is carried in fixed discrete chunks like electrons that one has a continuous fluid in a bottle that carries charges. Suppose that the fluid is stirred in ...
0
votes
1answer
23 views

Two rising bubbles of differing temperatures

Consider two bubbles rising through some medium (water, for example). Given that the two bubbles have the same initial size, pressure, and temperature but differing velocities, which bubble will be ...
1
vote
0answers
41 views

Density of states from the Retarded Green's function for a rotating black hole

I have been studying the scattering of a scalar field around a rotating black hole in the near-horizon extremal limit. The radial solution provides the retarded Green's function, just by taking the ...
-3
votes
1answer
62 views

Area as a Vector [on hold]

Why can we take area as a vector? And say if we take it as a vector why not on the plane why only perpendicular? What is positive or negative area or what the area has to do with direction?
21
votes
3answers
5k views

If we threw a baseball from the ISS, could we deorbit the ball?

Clearly this is a hypothetical question. Say we bring a star baseball player into NASA, prep them appropriately for a mission in space, and fly them up to the International Space Station. They go on ...
0
votes
2answers
15 views

Refraction of Sound Waves

When sound waves go from air to water what will happen to the wavelength and the angle of refraction? I used the approach that we apply to light waves and concluded the wavelength will decrease and ...
7
votes
4answers
2k views

Am I just some energy traveled at light speed? [on hold]

I don't understand $E=mc^2$ very well, and here is my question: Does this equation mean masses are just condensed energy? And does this mean that the extra energy an object has when traveling at ...
0
votes
0answers
26 views

Feynman Diagram of $\nu_\mu + p \rightarrow \nu_\mu + p + \pi^0$

According to my class notes, the following interaction is possible $$\nu_\mu + p \rightarrow \nu_\mu + p + \pi^0$$ I tried drawing a Feynman diagram and got the below, but don't know what happens ...
0
votes
0answers
16 views

Springs and Cantilevers - how linear and repeatable are they under deformation?

I know you guys only deal with the ideal, but in practice how linear and repeatable is the response of a spring or cantilever when deformed under a test mass?
-1
votes
0answers
34 views

Why do we use a vector space for gluons? [on hold]

If the theory cannot be approximated as an harmonic oscillator I don't see why quantized $e^{ikx}$ mode would make sense as a description of gluons. None of these modes individually solves the Yang ...
0
votes
0answers
21 views

why is it so successful to start of with a pair potential before quantizing [on hold]

As soon as we use the quantum theory all orders of correlation functions start to appear if we move from one scale to another. Eg in a $\phi^4$ theory all $\phi^{2n}$ shoot up as soon as we evolve to ...

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