4
votes
2answers
659 views

Zeta-function regularization in QFT for heat kernels

When one is doing zeta-function regularization of the heat-kernel for QFT then one is doing these following steps, the integral over the imaginary time taking the trace of the heat-kernel or the ...
3
votes
2answers
330 views

Hydrostatics: Log floating in water near a dam

So I am studying for a final and can't seem to solve this. There is a log floating in water and I need to find its weight. The question I have is what parts of the volume of the log count when summing ...
1
vote
1answer
267 views

Numerical algorithms to generate a random wavefunction from a thermal ensemble

I am seeking an algorithm to generate a random wavefunction = $\sum {c_i |\varphi _i\rangle }$ from a thermal ensemble, whose density matrix $\rho \sim e^{-\beta H}$, without the need to diagonalize ...
4
votes
2answers
107 views

Lumped circuit model of Earth and Sun as a thermal system

I want to design a thermal model of the Sun heating up the Earth. The circuit below is my own design (I don't know if there is a better way to model it. If there is, please tell me.). I want to ...
11
votes
1answer
104 views

Higgs Field - Is its discovery truly “around the corner”?

Rather surprised I haven't seen many questions or discussion regarding the rumored confirmation of the Higgs field. As I understand it, the energies where they saw things were actually quite a bit ...
2
votes
8answers
3k views

Real world examples for projectile thrown upwards or downwards

I am preparing a physics course for high school about projectile motions. If a projectile moves with initial velocity $v_0$ in the gravitational field of the earth, the equation $$ s(t) = 1/2 g t^2 ...
35
votes
0answers
1k views

On the Coulomb branch of N=2 supersymmetric gauge theory

The chiral ring of the Coulomb branch of a 4D $\mathcal N=2$ supersymmetric gauge theory is given by the Casimirs of the vector multiplet scalars, and they don't have non-trivial relations; the ...
3
votes
2answers
172 views

Derivatives of delta function and equation of continuity for a single charge…

For a single charge $e$ with position vector $\textbf R$, the charge density $\rho$ and and current density $\textbf{j}$ are fiven by: \begin{equation} \rho(\textbf{r},t)= ...
0
votes
1answer
180 views

Is reflection just a particular case of scattering?

I was talking to a colleague about optical scattering from a metallic nanoparticle, and we had a very simple doubt. If you have a particle that's small compared to the illuminated area, you can use ...
11
votes
5answers
8k views

Why do bass tones travel through walls?

I was in the shower while my roommate was listening to music and got to thinking about the fact that I could only hear the bass and lower drums through the walls. Why is this? The two possibilities I ...
24
votes
5answers
3k views

What symmetry causes the Runge-Lenz vector to be conserved?

Noether's theorem relates symmetries to conserved quantities. For a central potential $V \propto \frac{1}{r}$, the Laplace-Runge-Lenz vector is conserved. What is the symmetry associated with the ...
5
votes
1answer
378 views

Finding coefficient of proportionality

Recently in my AP Physics class I did a lab in which I measured k for a spring by setting up an oscillating system with it, and timing the period, repeating for different masses. Since ...
1
vote
0answers
52 views

catalysts as traces in a monoidal category

I was fooling around with string diagrams in a monoidal category and I was thinking about them in terms of chemical reactions. I wondered about bending a wire around and attaching it to the input of ...
4
votes
1answer
385 views

Some questions about the logics of the principles of independence of motion and composition of motion

In high-school level textbooks* one encounters often the principles of independence of motion and that of composition (or superpositions) of motions. In this context this is used as "independence of ...
4
votes
1answer
178 views

Why can't a stable star have radius 1 < r < 9/8 its Schwarzschild radius?

From http://www.spacetimetravel.org/ssm/ssm.html : A mass of 1.78 [in geometric units] corresponds to a ratio of radius to Schwarzschild radius of 9/8. Theory predicts that a smaller ratio is not ...
5
votes
1answer
407 views

Time-ordering vs normal-ordering and the two-point function/propagator

I don't understand how to calculate this generalized two-point function or propagator, used in some advanced topics in quantum field theory, a normal ordered product (denoted between $::$) is ...
5
votes
5answers
6k views

How can I prevent being zapped by static electricity every time I touch a doorknob or handle in the office?

I don't know what it is about this office, but it seems everything I touch (doorknob, bathroom faucet, edge of kitchen sink in the break room), I get zapped by static electricity. It's getting old. ...
10
votes
2answers
448 views

Virasoro constraints in quantization of the Polyakov action

The generators of the Virasoro algebra (actually two copies thereof) appear as constraints in the classical theory of the Polyakov action (after gauge fixing). However, when quantizing only "half" of ...
4
votes
1answer
193 views

Convergence of quantum effective action to finite loop order

Consider the quantum effective action of a fixed QFT. If we compute it perturbatively to finite loop order $\ell$, we get a sum over an infinite number of Feynman diagrams. For example, the 1-loop ...
3
votes
4answers
409 views

What is escape velocity? In reality, how can something no longer be under the gravitational influence of something else?

Isn't G a continuous function and although you leave the immediate vicinity of the earth with an escape velocity won't it always exert a force, however small it may be. Won't that force eventually ...
2
votes
2answers
139 views

What are some examples of how the discovery of dark energy can impact other, seemingly unrelated, branches of physics?

We know that dark energy is leading to the accelerating expansion of the universe and therefore determines the ultimate fate of our universe, but what other implications might it have on physics and ...
3
votes
3answers
1k views

How do electromagnetic waves carry quantised energy?

If an electron oscillates about a mean position, it will create a time varying electric filed which in turn will create a time varying magnetic field and so on to create an electromagnetic wave. How ...
4
votes
1answer
2k views

Magnetic fields and friction

If I was to pass a metal object through a magnetic field would there be any friction?
5
votes
0answers
26 views

Measurement of Tangential Momentum Accomodation? [duplicate]

Possible Duplicate: Measurement of Tangential Momentum Accomodation? I am using atomic force microscopy (AFM) for characterizing pores of the size of nanometers for application in gas ...
2
votes
1answer
694 views

How does a V formation save fuel for the lead plane?

I'm watching an episode of Mythbusters where they show aircraft saving 3-5% fuel when flying in a tight V formation. Interestingly, this also applies for the lead airplane. How is that possible for ...
2
votes
2answers
194 views

Can the implications of dark energy be used to bridge the gap between Quantum Mechanics and General Relativity?

Can the findings of the Physics Nobel Laureates of 2011, namely the overpowering existence of dark energy (vacuum energy) have any implications in the quest the combine Quantum Mechanics and General ...
5
votes
1answer
63 views

Best observing techniques for a Total Lunar Eclipse?

Is there any good tricks to observing a total lunar eclipse that I should be aware of? Just wanting to know what to do to be prepared for the upcoming one, but please post in general for future ...
4
votes
1answer
206 views

Why is the shadow of earth red?

Reading this article about the forthcoming eclipse on December 10th, I noticed mention that the moon passes through the red shadow of Earth; I'd always held the impression that a shadow is universally ...
1
vote
1answer
170 views

What about the other side of the Black Hole

I was wondering if on the recieving end of a black hole can you see the photons being sucked in
3
votes
3answers
504 views

How scientists estimated that our universe is 4% normal matter, 21% dark matter, and 75% dark energy?

Is there a simple way to understand how scientists estimated/calculated the following percentages?
4
votes
5answers
837 views

Why are $\mu_0$ and $\epsilon_0$, which appear in electrostatics and magnetostatics, related to the speed of light which appears in electrodynamics?

$\epsilon_0$ and $\mu_0$ appear in electrostatics and magnetostatics. When we include time varying fields we have electrodynamics and the appearance of c which turns out to be related to $\epsilon_0$ ...
17
votes
2answers
4k views

How does space affect the human body (no space suit, no space craft)

How does "outer space" affect the human body? Some movies show it as the body exploding, imploding or even freezing solid. I know space is essentially a vacuum with 0 pressure and the dispersion of ...
0
votes
2answers
497 views

How to calculate total distance and time a puck will move?

To simulate a puck's movement, I use the following model (please restrain from discussing the model, it makes the simulation look the way I want it to) and would like to know how to calculate the ...
1
vote
1answer
420 views

Pauli Matrices in orthogonal space

In some literature there is reference to $\tau$ matrices which are the same pauli matrices in an orthogonal space. I have not seen any explicit constructions of this anywhere. Could someone tell me or ...
3
votes
1answer
407 views

How do I calculate the time it would take for a space craft launching from earth to reach another planet?

I am making a matlab program the my final project for my programming class in college. I have chosen this problem, but I am bashing my head against the wall trying to figure out the equations and how ...
1
vote
2answers
50 views

Energy transferring question

If I have a spring being compressed by two bodies, A and B, with different masses, how much energy would be transferred to each one when they are released and the spring expanded?
7
votes
4answers
583 views

Why do 3d spheres and gravity tend to rotating discs on one plane?

Whether is it our solar system or a whole galaxy, there is usually a massive object (star or black hole) at the centre with gas and objects rotating around it. The gravitational effect of the ...
4
votes
3answers
498 views

Calculating stress without strain

I am working on an algorithm for a real-time simulation. I would like to calculate to extremely permissive tolerances approximate values for the stress within a 2D geometry. It will not be difficult ...
0
votes
3answers
956 views

What are brain waves? [closed]

I watched a documentary showing that humans could alter the results of an experiment by thinking about it, and the data these people collected supported their hypothesis. And the reason these people ...
3
votes
1answer
843 views

How to write the Fröhlich Hamiltonian in one dimension?

I am currently working on a (functional) analysis problem refining Pekar's Ansatz (or adiabatic approximation, as it is called in his beautiful 1961 manuscript "Research in Electron Theory of ...
5
votes
1answer
293 views

Is there more mass in stars or interstellar medium?

From what I gather the interstellar medium has about about 1 atom per cubic centimeter. But on the other hand, as they say, "Space is big, really really big" So if it is known (or at least theorized ...
6
votes
2answers
5k views

How might clock synchronization work with RSA SecurID tokens?

My workplace uses these things to generate one-time passwords which only work within a short time period. I have always been curious about how the clock synchronisation between the authentication ...
2
votes
0answers
251 views

The effect of an EMP on circuits

Which of these is the current (also, what about voltage?) induced by an EMP pulse within a circuit most dependent on? The area of the region enclosed by the circuit The orientation of that area with ...
2
votes
1answer
291 views

Calculating the Suns vector and distance from the Earth at one time

I am developing a C++ program where I'd like to be able to see the Suns direction vector and distance from Earth at a given time, since 2000 Jan 0.0 TDT. The reference frame I want to calculate it is ...
0
votes
1answer
371 views

How much energy is contained in a 40 meter wave?

Consider a wave that stands 40 meters high in the sea on very deep water. How much energy would approximately be contained in this wave if it was 100 meters wide and had been produced by wind? Is ...
2
votes
2answers
314 views

Why do balls in a spinning ellipsoid move to the minor axis plane?

There is a question concerning the Physics of a small child's tall that has been bothering me for some time now. I have investigated this to a small degree, but I have not been able to find a ...
5
votes
0answers
100 views

Can the Lamb shift be expressed in more-or-less closed form in terms of the renormalized 2-, 3-,…,n-point VEVs of QED?

I see here that there are three contributions to the Lamb shift, from vacuum polarization (-27 MHz), from electron mass renormalization(+1017 MHz), and from the anomalous magnetic moment (+68 MHz). ...
2
votes
0answers
2k views

Easy to obtain liquid with freezing point a couple of degrees above 0 Celsius [closed]

Please advice me a liquid whose freezing point is 2-5 Celsius. I know that the solution of salt in water can have freezing point of about -3 Celsius. I would like to know if similar liquid but with ...
1
vote
1answer
272 views

Crystal Field Theory

I am literally lost with this question: Suppose that within the set of (2L+1)(2S+1) lowest-lying ionic states the crystal field can be represented in the form a(L_x)^2 + b(L_y)^2 + c(L_z)^2, with ...
15
votes
6answers
728 views

Does Kaluza-Klein theory successfully unify GR and EM? Why can't it be extended to the Standard Model gauge group?

As a quick disclaimer, I thought this might be a better place to ask than Physics.SE. I already searched there with "kaluza" and "klein" keywords to find an answer, but without luck. As background, ...

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