All Questions

134,106 questions
29 views

Vibrational Question [on hold]

A friend recently asked me this question, which I am not even sure how to comprehend... Three masses are arranged at the vertices of an equilateral triangle and are connected by springs along the ...
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Human perception of temperature

I had the following thought experiment recently: Suppose we have a vibrating plate for which we can tune the amplitude and frequency of vibration, and imagine we hold a finger against the plate. For ...
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Can anybody show me a diagram of a Disevenly accelerated movement?

The problem related to my question is that it should be impossible to integrate such a function or I am just not familiar with doing it for that example. Maybe it helps to understand my question, I ...
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Why is the UV absorption band for molecules not a sudden transition?

From what I have read, when a molecule in solution or gas is excited, it does so from ground state, but may gain the energy for vibrational transitions as well. This would lead me to expect that there ...
92 views

What exactly does the observer's coordinate system mean in special relativity?

This seems like a very basic question but I'm having a hard time understanding it, more precisely hard time visualizing it. Let say there is an observer, and we wish to somewhat formalize his ...
52 views

What equations of general relativity and quantum mechanics are we trying to unify? [duplicate]

In other words, what equations hold the most promise in this endeavour? Are we all looking at the same equations or is this pursuit subjective?
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Why the notion of degree of freedom is correct?

The intuitional definition for number of degrees of freedom is following: it is the minimal amount of numbers which allows us to describe the system's configuration correctly. For example, for dot ...
28 views

How in experimental practice does a momentum measurement reduce a state to a momentum eigenfunction?

It's easy to think of ways to reduce the state of a particle to a position eigenfunction (or at least a narrow spread in position space), whether by trapping the particle in a potential well or by ...
25 views

scientific review [on hold]

what is the scientific review or consensus on the paper titled Non Singular and Cyclic Universe from the modified GUP https://arxiv.org/pdf/1608.00560.pdf
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What does leakage of charge in plate and isolated spherical capacitors mean?

I've read quite a lot of times about leakage of charge in capacitors, but what does it exactly mean? Do we see sparks? Or is it some current flow? Or something else? Say I have a charged sphere, so ...
87 views

Can High Energy Light Escape a Black Hole after Low Energy Light Cannot

Perhaps there is another way to calculate the escape velocity, or perhaps light always has the same kinetic energy regardless of the energy of the light, but shouldn't the event horizon of a black ...
65 views

Mechanism for radiating power when accelerating charged particles

On reading through selection rules constraining transitions from one state to another, it states: Thus, there is no E0 (electric monopoles) or M0 (magnetic monopoles, which do not seem to exist) ...
50 views

What is the QFT state with two distinguishable fermions present?

I want to describe a system with two non-interacting and definitely different fermions, say an electron neutrino, $\nu_e$, and an electron, $e^-$. The state describing a single electron is given ...
27 views

Check that the Poincaré's transformations form a group structure

How can I answer to this question ? I know that this is a Lorentz transformation + a translation but I don't know how to start. What's the difference between group/group structure ?
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When will Hund's rules fail?

I heard someone mentioned that Hund's rules do not always work. Looking at atomic spectrum: (https://qudev.phys.ethz.ch/phys4/PHYS4_lecture10v1_2page.pdf page 10 Hg spectrum) How could singlet (with ...
33 views

How to calculate electrostatic potential at a point w.r.t an ensemble of point charges?

Given an ensemble of charges, how to derive the electrostatic potential at any point due to the ensemble? For example, consider six point charges, each approaching the origin along the three co-...
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Differential equations for the LC circuit

On wikipedia one can find that the DE for an LC circuit is given by $$\ddot I+\frac{1}{LC}I=0$$In one of my papers however I found the equation $$\ddot Q+\frac{1}{LC}Q=0$$ and I've been confused by ...
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A balloon is descending with 10m/s. When it is at 100m from the ground, a stone is thrown. Calculate the velocity of the stone at 20sec [on hold]

Assumed initial velocity of the stone to be 10m/s and found that it would cover 100m in about 3.585 seconds. But, the question is asking its velocity at 20sec.
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Geant 4, simulate Tc-99m decay

I have a setup of Monte Carlo simulations in Geant4, and I'm able to simulate radioactive events from isotopes such as I-131 and F-18, which are defined in the RadioactiveDecayData5.2 files. Tc-99m ...

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