# All Questions

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### Yang-Mills CP violation

Why does a term proportional to $\left(F,\,\tilde{F}\right)\propto Tr\left[ F_{\mu\nu}\tilde{F}^{\mu\nu}\right]$ in the Lagrangian of the pure Yang-Mills theory violate CP?
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### Estimating quantum efficiency of gated avalanche photodiode

I have a photon counting system that uses a gated avalanche diode to detect single photons. The repetition frequency of the gates is $f_1$ and the temporal gate width is $\tau_1$ (so the duty cycle is ...
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### No monopoles in the Weinberg-Salam model

I'm reading Chapter 10.4 on the 't Hooft-Polyakov monopoles in Ryder's Quantum Field Theory. On page 412 he explains why magnetic monopoles cannot appear in the Weinberg-Salam model. I'm I right by ...
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### Gravity fed containers

Curiosity got the better of me, and was wondering if you have two containers full of sand each at different heights but both fed in a tube from a with the containers being in Y configuration, is there ...
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### Basic Field Calculations

I'm trying to derive the relation: $\phi(x)\phi(y)=:\phi(x)\phi(y):+\langle 0|\phi(x)\phi(y)|0 \rangle$ but struggling to see the first few steps I need to make. I've made the substitutions ...
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### How do we know quantum entanglement exists/happens? [closed]

We know that this strange behavior is there but I am not to able grasp, how do we know it exists? Have we ever tried any experiments confirming this? Do we make use of this?
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### Charge Distribution On Hollow Sphere

Say we have a hollow conducting sphere (with some finite thickness). If this object has an excess charge amounting to +Q coulomb, and there is no extra electric field in the surroundings (due to ...
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### What can you use voice sound for? [closed]

Moreover, how can you make your voice productive? for example, using it to light an LED, charge a battery, purificating water, growing plants in a more efficient way. I want to do a project that ...
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### The properity of $\mathbb{R}^4$ that has infinitely many differential structures is related to Yang-Mills field?

I heard a saying that $\mathbb{R}^4$ having infinitely many differential structures which are not diffeomorphic to each other has a relationship with Yang-Mills field. Does anyone can explain it, and ...
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### Static wave's equation

In my book equation for two advanced wave which created this static wave are $$y_1=asin{\frac{2\pi}{\lambda}(vt+x)}$$ $$y_2=asin{\frac{2\pi}{\lambda}(vt-x)}$$ and equation for static wave is ...
111 views

### Spin FET Transistor

Spin FET Transistor. When a gate voltage is applied to a current of spin polarized electrons, a spin precession will occur. If this spin precession is enough to make the bulk electron spin ...
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### Magdeburg Hemispheres

The Magdeburg Hemisphere experiment was the experiment that showed the effect of pressure differences on a vacuumed sphere. We know that the Force caused by pressure is $\Delta p A$ and so you can ...
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### Compute and plot satellite position on 2D Earth map

I would like to create a simple satellite tracking software, that will compute the position of a satellite at any time, and show its location on a 2D map of Earth. Let's assume it is possible to ...
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### Is there a simple layman way to explain the incompatibilities between quantum mechanics and (general) relativity to high school students?

Is there a simple layman way that I can use to explain the incompatibilities between quantum mechanics and (general) relativity to high school students (people with not much knowledge of the intricate ...
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### Determining if a decay is due to strong or weak interaction

How do we determine if a decay is due to weak or strong interaction. Is it true that as long as any one of the 6 flavour numbers are not conserved, then it must be due to weak interaction? Is there a ...
865 views

### “Periodic Table” of Particles of the Standard Model?

What is a good, single, "periodic table" of all the particles of the Standard Model? I thought Particle Data Group would have a single-page PDF of this, but I couldn't find a single table listing all ...
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### A question on IR cancellation caculation in peskin schroeder

In Peskin and Schroeder Introduction to Quantum Field Theory book, above equation 6.64 on pg. 200, it was said that "to gain better understanding, of the divergence, let us evaluate the coefficient of ...
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### Physical Interpretation of EM Field Lagrangian

Using differential forms and their picture interpretations, I wonder if it's possible to give a nice geometric & physical motivation for the form of the Electromagnetic Lagrangian density? The ...
131 views

### Definition of Information in Information Theory

I am not sure in which SE site I have to put this question. But since I have learnt Shannon Entropy in the context of Statistical Physics, I am putting this question here. In the case of Shannon ...
444 views

### Entropy $dQ=TdS$ and Work $dW = -pdV$ conditions?

What are the conditions in order for the equations: Entropy $dQ = TdS$ and Work $dW = -p dV$ to work? I think for $dQ = T dS$, it must be a reversible process? But for $dW = -p dV$, shouldn't it ...
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### Primordial flunctuation gave rise to cosmic structures?

I'm not a physicist, not even a physics student. I'm just reading Lawrence Krauss's book A Universe From Nothing and I got stuck understanding a concept. In his book, Lawrence says: Quantum ...
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### Does the application of a magnetic field on degenerate spin states (zeeman effect) cause photon emission?

In zeeman effect, before applying any magnetic field, we have two spin states, up and down each of energy $E_0$. Apply a magnetic field, and get $E_+\neq E_- \neq E_0$. Now the question is the ...
1k views

### Time dilation all messed up!

Okay! There is a problem with my logic and i cannot seem to point out where. There's a rocket ship travelling at close-to-c speed v without any acceleration (hypothetically), and there is an observer ...
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### Is light and sound waves interconvertible? [duplicate]

Light is produced when an air bubble underwater is collapsed with sound wave. Why does it happen so?
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### Supernovae and black holes?

I think i am correct in saying that a supernova ($Type$ $II$) is caused by the collapse of the core of a giant star. This contraction of the core is stopped by the Pauli exclusion principle and the ...
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### Question Regarding Lorentz Transformation

I have question regarding the following velocity transform formula: $$v_b = \frac{v_a - u}{1-uv_a/c^2}$$ $u$ here refers to the speed that one frame is moving relative to another. How do I decide ...