All Questions

1
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0answers
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 ...
3
votes
1answer
71 views

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 ...
0
votes
1answer
39 views

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 ...
0
votes
1answer
32 views

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 ...
3
votes
3answers
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 ...
0
votes
0answers
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?
0
votes
1answer
37 views

Derivation of the dynamical matrix

I am following a derivation of the dynamical matrix given at http://physik.uni-graz.at/~pep/Lehre/PP/DynMat.pdf. Here T and W are kinetic and potential energies. $T=\sum_{n\alpha i}\frac{M_{\alpha}}{...
0
votes
1answer
35 views

Would any continuous model of the universe have/be based on hypercomputational laws?

I've read that when Turing-Church thesis is applied to the universe and physics, one of the three interpretations that we can use and is defended by some important physicists is that: "The universe ...
1
vote
0answers
39 views

Why intuitively, do we define symmetries as transformations that map solutions of the equations of motion into other solutions?

Of course, strictly speaking, a symmetry is always a transformation that leaves a given object unchanged. But I'm curious why observable symmetries of physical systems are exactly those ...
1
vote
1answer
63 views

Why is the electrostatic energy of a nucleus proportional to $Z(Z-1)$?

The complete binding energy is (more details in Krane's book, page 68): $$B = a_v A - a_s A^{2/3} - a_c Z(Z-1)A^{-1/3} - a_{sym} \frac{(A-2Z)^2}{A} + \delta$$ I want to explain the $Z(Z-1)$ term. ...
1
vote
0answers
24 views

How to calculate drag caused by string?

An example - I throw a tennis ball with a short string hanging off one side. As the ball flies the string is dragged to the side opposite the direction of the ball's velocity vector, anchoring the ...
3
votes
1answer
61 views

How to interpret $\left[f(A), B\right] = \left[A, B \right]\frac{\partial f}{\partial A}$ - how to differentiate with respect to an operator?

From here and here I know the commutation relation for two operators are: $$\left[f(A), B\right] = \left[A, B \right]\frac{\partial f}{\partial A}$$ if $\left[A, \left[A, B \right]\right] =0$ and $f$ ...
2
votes
0answers
26 views

What particle is created when a B- or E-field operator acts on the vacuum

I have some conceptual trouble understanding what the different field operators in QED do. According to Wikipedia, the field operators are given by $\mathbf A(\mathbf{r} )=\sum _{\mathbf {k} ,\mu }{\...
1
vote
2answers
46 views

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 ...
3
votes
1answer
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 ...
-5
votes
0answers
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
0
votes
3answers
39 views

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 ...
3
votes
3answers
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 ...
1
vote
2answers
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) ...
0
votes
0answers
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 ...
0
votes
0answers
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 ?
1
vote
0answers
50 views

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 ...
0
votes
1answer
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-...
0
votes
2answers
50 views

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 ...
1
vote
1answer
59 views

An intuitive explanation of the basis-independency of EPR pair

As usual, we write the EPR pair as $$ \frac{1}{\sqrt2}(\left|00\right> + \left|11\right>). $$ A property of the EPR pair is that this definition is basis-independent, which means $$ \frac{1}{\...
1
vote
0answers
23 views

Derive the virial theorem from hydrostatic equikibrium

Consider the equation of hydrostatic equilibirium as follows as applied to a stellar object: $$ \frac{dP}{dr } = \frac{-GM\rho}{r^2} $$ I know it is intimately related to the virial theorem but I ...
2
votes
0answers
70 views

What orbit does a planet have to have to be a planet? [on hold]

Other questions have dealt with where you could find a planet-like object, and what a planet has to consist of to count as a planet. But this question is directed as what orbit or path an object would ...
0
votes
1answer
34 views

Fringe pattern in Michelson interferometer

It's given that CA - CB is d, the angle CAE is $\theta$. (E is not on the normal of mirror M1). I want to find the condition for maxima at E (as a function of $\theta$). I tried finding the path ...
0
votes
0answers
34 views

Can someone help me get the S&M package for my thesis on spinor helicity amplitude formalism? [on hold]

So my thesis director told me to download a package for Mathematica called S&M (Spin and Mathematica) and i couldn't find it when i googled it.
1
vote
1answer
50 views

$sp^3$ Hybridization wavefunctions and probability density

I have plotted a hydrogen-like sp3-hybrid orbital probability density and it looks like this: I can plot 4 overlapping probability densities in a tetrahedral shape: So far it looks OK. But when I'm ...
-2
votes
1answer
32 views

Time difference between all particles and waves

Since all particles and waves were created simultaneously in the big-bang would there be any time difference between any interacting particles and/or waves?
-4
votes
0answers
35 views

Has anyone measured more than just one polarisation on each side in a quantum entanglement experiment?

I've been looking at the literature about quantum entanglement. More specifically, I am referring to experiments such as this https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.49.1804 that ...
-1
votes
0answers
40 views

Confused with formula used for graph [on hold]

Can anyone explain to me how you get both the distance and velocity to zero using the following formula? I keep getting a different answer than that of the graph below. By the way, the object is ...
0
votes
0answers
12 views

spinless and time reversal symmetry breaking of p-wave pairing in topological superconductors

In the context of Majorana zero modes, I often hear that the p-wave pairing is effectively 'spinless' and time reversal symmetry broken. I understand that s-wave and p-wave refer to the spin portion ...
0
votes
0answers
32 views

Wilson loop and Polyakov loop

As I understand, the Wilson line is the operator $W(x) = P\exp(i\int_{xi}^{xf} A.dx)$, where $P$ is path ordering. The Polyakov loop $P(x)$ on the other hand is the trace of the Wilson loop $W(x)$ ...
-4
votes
0answers
23 views

Vertical oscillation [on hold]

In the figure, A mass of m=1kg is held with two springs of force constant k=50N/m.When the mass is suspended, it makes an angle,θ=30degree. What's the angular frequency of vertical oscillation?
-2
votes
0answers
30 views

Work done against electric field [on hold]

If a charged body has $10^{-4}$ C charge and radius of $1 m$ then find the amount of work done against the elctric field in contracting the body for $0.5$ m radius. I am fed up with the question.I am ...
0
votes
0answers
26 views

Gravitational lensing, indices of refraction and the size of the universe

Been pondering the following question for over 15 years now. Is it possible that the size of the universe has been over estimated due to the effects of gravitational lensing and boundary indices of ...
1
vote
0answers
32 views

How is Inönü-wigner contraction done?

I have read that little group for the massive particles is $SO(3)$ and for the massless particles is $E(2)$ in 4 dimensions. How does one take zero mass limits for the representations and show that it ...
0
votes
0answers
19 views

Hölder exponent and its relation to multifractality

Suppose that for a function $f(x)$, I have discrete set of numbers for $x$ with size $N$ (and the corresponding values for $f(x)$). They show multi-fractality properties: $P_q = \sum_{x=1}^N f(x)^{2q}...
1
vote
0answers
21 views

Book recommendations : Classical Mechanics [duplicate]

I know this question has been asked so many times on this website but neither do the questions nor the answers satisfy my requirements accordingly. I'm yet to go to a university with a keen interest ...
-6
votes
0answers
75 views

How to understand kinetic energy intuitively in moving object in sense of mass and velocity squared [on hold]

Momentum = P(vector) = m x V I can understand momentum as quantity of motion , inertial mass in motion, strength of non-accelerated moving object. $K.E = 1/2 mv^2 = 1/2 m V.V = 1/2(mV).(V) = 1/2 P....
0
votes
1answer
57 views

What's the difference between a generating function and a generator?

Usually in physics we use the notion generator to describe the infinitesimal elements associated with any finite Lie group transformation. But in the context of the Hamiltonian formalism, all authors ...
0
votes
1answer
54 views

Are symmetries necessarily canonical transformations?

A canonical transformation is defined as a transformation such that afterwards Hamilton's equations still hold. It can then be shown that this requirement implies that canonical transformations are ...
-3
votes
1answer
32 views

Which direction the currect will flow? [on hold]

I know if there is no R3 and R4, the R2 will be short circuited (Current most likely flow through the circuit that has smaller resistance). My confusion is, if the R3 and R4 are there, should we short ...
-2
votes
0answers
16 views

any information about Magnetoresistance please? [on hold]

i need any imformation or explaination or some resources too magnetoresistance please i didn't find nothing in google . any help please thank you
0
votes
1answer
44 views

Vacuum polarization contribution to magnetic moment

Where I can find the calculation of muonic (or electronic, it does not matter) vacuum polarization contribution to the anomalous electron magnetic moment? I mean the diagram (c):
2
votes
3answers
96 views

How can we derive from $\{G,H\}=0$ that $G$ generates a transformations which leaves the form of Hamilton's equations unchanged?

In the Hamiltonian formalism, a symmetry is defined as transformation generated by a function $G$ is a symmetry if $$\{G,H\}=0 ,$$ where $H$ denotes the Hamiltonian. On the other hand, a symmetry is ...
-4
votes
0answers
18 views

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.
1
vote
0answers
21 views

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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