0
votes
0answers
38 views

How to deduce equations 3.6.15 in Polchinski's string theory book? [duplicate]

In polchinski's first course on string, with how to deduce
1
vote
1answer
86 views

Refrigerator cooling power usage

I have a refrigerator, that makes a lot of noise, and we have therefore set a time on it will limit the run time to when we are not at the office. But this is where our discussion begins, should we ...
2
votes
1answer
129 views

Microcanonical Ensemble

I'm having difficulty understanding a statistical mechanics problem. I'm missing some basic understanding of counting the minimum energy states. My thought is that there are three states to choose ...
8
votes
1answer
730 views

Why quantising gravity necessarily give us gravitons?

Gravitons are supposed to be the quanta of gravitational field My question is, if we do not know how to quantize gravity yet, how do we know that quantizing it in principle should give us gravitons, ...
1
vote
2answers
74 views

Quarks are now considered to be fundamentals, but so were atoms some time ago. So the way we see is only limited by our technological advances? [duplicate]

After watching this FuseSchool - Global Education episode, I cannot stop thinking how can something not have a substructure, how it cannot be split? http://www.youtube.com/watch?v=nlv06lSAC7c
0
votes
1answer
109 views

Airfoil theory — Why does air travel faster above? [duplicate]

I do not understand, why the air above the airfoil travels faster than the air below it? The air above has to travel faster than the air below so that both streams meet simultaneously at the ...
2
votes
1answer
326 views

Stress energy tensor and the covariant derivative of the 4-momentum

Another basic question. I have usually seen the stress energy tensor $T^{ij}$ described as the flow of the 4-momentum field $p^i$ along direction $x^j$ in spacetime with $p^0$ as energy and $x^0$ as ...
1
vote
0answers
62 views

Effective Spin Interaction in Helium

My question is: what is the point of forming an effective spin-spin interaction for the exchange term in the variational analysis of Helium? Is there any significance to this term other than on ...
3
votes
1answer
127 views

Is it possible that the universe in its entirety is discrete rather than continuous? [duplicate]

Since electric charge is comprised of discrete units and and mass is formed by discrete units is it possible that space-time itself is discrete as well?
3
votes
1answer
189 views

QM: How to compute position/momentum relation in polar coordinates

So if we are working in one dimensional space, we have the formula: $$\langle x|p\rangle = \frac{1}{\sqrt{2\pi\hbar}} e^{ipx/\hbar}$$ Suppose instead we are confined to a circle of radius $R$ so that ...
2
votes
3answers
86 views

electron levels in a high voltage conductor

what is the electron energy level in a 300,000 volt power line? This voltage is way above the ionisation potential but electrons are not emitted from the wire.
1
vote
2answers
160 views

Understanding fields and their correlation to forces

I seem to be confused between the concept of a "force", and a field. Now let's assume there is a magnetic field of $1$ $\mathrm{Tesla}$, what does that mean in relation to force? Finally, if field is ...
0
votes
0answers
91 views

does an object travelling close to the speed of light in an inertial frame of reference behave Relativistically

The two tenants of Special Relativity are: The laws of physics are the same in all inertial frames of reference. The speed of light in free space has the same value $c$ in all inertial frames of ...
0
votes
1answer
83 views

Regarding derivation of Probability Current

The question for the full derivation of Probability Conservation -> Probability Current was already asked here: Probability current. I apologize for not retyping it out, but it's already beautifully ...
1
vote
2answers
90 views

How does isotropy of free space imply $L(v^2)$ for a free particle? [duplicate]

From Mechanics; Landau and Lifshitz, it's stated on page 5: Since space is isotropic, the Lagrangian must also be indpendent of the direction of $ \mathbf{v}$, and is therfore a function only of ...
0
votes
0answers
31 views

Optimization of a functional defined implicitly

I would like to minimize a functional of the type: $$L[\gamma]=\int_a^b F(T(\gamma(t))dt$$ on the space of paths $\gamma$, where $T=T(\gamma,t)$. Now, usually I would simply apply Euler-Lagrange's ...
4
votes
1answer
149 views

Man on a rope task

Some time ago I came across this simple task. Instead of describing it a lot I will just post a picture and try to explain like that. So the man and the weight on the other side of the rope have ...
1
vote
1answer
51 views

Convert constant of gravitation to days and AUs

I'm working on a problem with celestial bodies and for my purpose days and AUs are more appropriate units than seconds and meters. So I tried to convert the constant of gravitation, $G$, like this: ...
3
votes
1answer
185 views

What is the resolution to Gibb's paradox?

This question is essentially a duplicate of Gibbs Paradox - why should the change in entropy be zero?. The question concerns the following situation: I have some gas of identical particles and they ...
0
votes
0answers
36 views

Is this description of particle's spin strict?

I'm trying to understand a concept spin in QM. I've read some explainations, and it seems that the idea is very easy and straighforward, however I didn't find these exact wordings in my books. My ...
2
votes
2answers
159 views

When do we see particles to be in a superposition of energy states?

I have two doubts: Exactly when does this happen? and If we are in a superposition of states (lets say E1 and E2) and the particle absorbs a photon, what will happen? If E3-E1 = hf, will it go to E3? ...
12
votes
2answers
259 views

Particle/antiparticle annihilation and entanglement

This is a basic question. Suppose that A and B are completely entangled particles and so are C and D. If B and C are antiparticles that annihilate each other will A and D be entangled as a result. It ...
11
votes
1answer
203 views

Why do some sunsets have a green flash?

Some sunsets exhibit a phenomenon called "green flash," where there is a quick flash of green light right as the sun is setting. I have seen this myself several times, and sort of understand it. I am ...
0
votes
0answers
48 views

How hot is it on the slopes of an erupting volcano?

I was watching The Return of the King and just after Frodo and Sam destroy the One Ring, they run out of the mountain and hide on top of a rock as the volcano erupts and lava flows past them. Is this ...
3
votes
1answer
183 views

Electrons skip randomly around their orbits

I read where the electron (as well as a few other particles) skips around in its orbit randomly rather than move around the orbit smoothly. This effect has been repeatedly observed in the laboratory ...
0
votes
0answers
45 views

Would electron degenerate matter be a good x-ray reflector?

I do not know much about x-ray physics or degenerate matter, but I have the intuitive feeling that the high electron density and what must be some crazy band structures in electron degenerate matter ...
1
vote
0answers
37 views

Comprehensive list of $\mathcal{N}=2$ supersymmetric topological quantum field theories in $d=4$

Could anyone provide a comprehensive list of $\mathcal{N}=2$ supersymmetric topological quantum field theories in $d=4$? I know of one - Kapustin-Witten TQFT, but I do not know of any more. Thanks!
4
votes
1answer
244 views

Computing Curvature via Cartan Formalism

Given a metric $g_{\mu \nu}$, one can select an orthonormal basis $\omega^{\hat{a}}$ such that, $$ds^2= \omega^{\hat{t}}\otimes\omega^{\hat{t}} - \omega^{\hat{x}} \otimes \omega^{\hat{x}} - ...$$ By ...
2
votes
0answers
65 views

Statistical Mechanics: Most probable orientation of grain particle in gas chamber?

I'm in an introductory statistical mechanics course, and we've been posed the following situation: Long-shaped dust particle (so imagine something like a grain of rice) is placed in a gas chamber (so ...
-2
votes
1answer
83 views

What is the formula for determining time dilation (as the object in motion)? [duplicate]

The formula for calculating how much time passes for a still observer is T=TO/(1-v^2/c^2)^1/2. How do I calculate what TO is?
1
vote
0answers
40 views

How to calculate the minimum number of extrinsic dimensions of a metric tensor?

The Question How does one calculate the minimum number of dimensions of an extrinsic space that can be used to define the metric tensor \begin{align} g_{mn} = \dfrac{\partial y^k}{\partial x^m} ...
1
vote
0answers
102 views

Confusion With Neutrino Oscillation

Neutrinos produced in the weak interaction are eigenstates of the weak interaction hamiltonian or flavor eigenstates. Right? If this is so, then $\nu_e,\nu_\mu,\nu_\tau$ should be the stationary ...
8
votes
2answers
2k views

What creates the chaotic motion on a double pendulum?

As we know, The double pendulum has a chaotic motion. But, why is this? I mean, the mass of the two pendulums are the same and they have the same length. But, what makes its motion random? I'm just ...
3
votes
1answer
65 views

What decides fission products?

I am learning about nuclear fissions and learned about the fission fragment distribution. It was interesting to see that the fission fragments have unequal masses. I was wondering as to what governs ...
0
votes
4answers
550 views

How to derive Schrödinger equation?

How is the Schrödinger equation $$\frac {\partial }{\partial t}\psi=-\frac {i }{\hbar }H{\psi }$$ being derived?
9
votes
1answer
323 views

Renormalizing IR and UV divergences

In lectures on effective field theory the professor wanted to find the correction to the four point vertex in massless $\phi^4$ theory by calculating the diagram, $\hspace{6cm}$ We consider the zero ...
0
votes
0answers
29 views

where i can find thermodynamics properties of octane

where can I find thermodynamics properties for octane at $T_s$? I need this properties or where can i find all ? $$liquid-density=\rho_l=?$$ $$vapor-density=\rho_v=?$$ ...
4
votes
2answers
259 views

Why do we have a TeV scale?

When model building we don't want to introduce any new scales into our theory. We usually try to have new particles at the Higgs (TeV) scale (to solve the hierarchy problem), at the GUT scale, or at ...
3
votes
0answers
27 views

Experimental results regarding non-extensivity in small systems

From a statistical mechanics point of view, the extensivity of thermodynamics arises from the fact that we can neglect interaction terms in the Hamiltonian. This allows us to infer that when we put ...
2
votes
2answers
338 views

What may be effect of air friction to the velocity of satellite?

What is the effect of air friction to the velocity of satellite? I have heard satellite's speed increases with air friction. But I'm in confusion how is it possible?
4
votes
1answer
177 views

Superconductivity in graphene with spin orbital coupling, is it proper to let the order parameter on two sub-lattice equal?

I am reading this article: Edge superconducting correlation in the attractive-U Kane-Mele-Hubbard model. Considering just the first part of the article, where a negative-U Hubbard model with the ...
0
votes
1answer
408 views

Confusion with LSZ reduction formula

LSZ reduction formula relates the matrix element of the scattering operator to the n-point Green's function $$\langle 0|\phi(x_1)\phi(x_2)...\phi(x_n)|0\rangle$$ My question is: Is the vacuum on the ...
0
votes
0answers
22 views

Building a magnetron powered steamer

I am wanting to build a microwave powered steamer for a reverse engineering project in university. I've read up some on this and know that its not as efficient as a heating element. I'm curious about ...
1
vote
2answers
274 views

What is the third law action pair of buoyancy?

Consider a block floating in a fluid. The force due to gravity balances the buoyant force exerted on the block. But there must be a third-law action pair to the buoyant force. If the block exerts a ...
3
votes
0answers
220 views

Born approximation to Lippmann-Schwinger integral equation

I am having the following problem understanding the Born approximation in the case of the Lippmann-Schwinger equation. This exercise is for something which is entitled "computational physics lab ...
0
votes
2answers
824 views

How can you use magnets to rotate a shaft, which in turn powers a generator? [duplicate]

I recently was given the task to create power using magnets, I would think that if I were to put some same poled magnets together, and they were facing the same poled magnets, they would repel and ...
1
vote
2answers
134 views

Could Gamma ray bursts be caused by matter-antimatter annihilation?

As far as I know a collisions of matter and antimatter leads to the complete annihilation of both, whereby 100% of the rest mass of the particles is converted into gamma rays. Could this mechanism be ...
0
votes
0answers
34 views

Quantum distance ladder

There is a lecture on how facts about the cosmos can be derived form rather simple observation. Is there an analogy for the small scale? Is there a technically simple observation that would imply, ...
2
votes
0answers
92 views

Questions about closed forms and cycles

I read the section closed forms and cycles in Arnold's Mathematical Methods of Classical Mechanics (page 196-200), but the problems in this section is too difficult to solve in the way following the ...
4
votes
2answers
173 views

Tensor product of Hadamard Operators

The Hadamard Operator on one qubit is: \begin{align*} H = \tfrac{1}{\sqrt{2}}\left[\,\left(\color{darkgreen}{|0\rangle + |1\rangle}\right)\color{darkblue}{\langle ...

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