# All Questions

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### calculating the local energy in neural network quantum state

given a Hamiltonian of Heisenberg 1D model as following: H = $-J\sum_{I}\sigma_{i}^{z}\sigma_{i+1}^{z}$ I am trying to solve it with a neural network function given by Restricted Boltzmann machine ...
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### Images traveling faster than light

Please help me understand my mistake(s) in this reasoning. I will write as if I knew exactly what I'm talking about for the sake of clarity, but I of course don't. Consider observer A and its ...
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### Has anyone read the paper “The scaling of Impact processes in planetary sciences” by Keith Holsapple (Holsapple 1993)?

If anyone has read the paper (and hopefully also understood it), do you think it is possible to extract values for diameter & depth of a crater from a laboratory experiment and then : assuming ...
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### Anti Zeno Effect producing permanent effects

In the Anti Zeno Effect, in which the system required to provide constant measurements of the material for the purpose of speeding up decay is comprised of a high-frequency laser, could exposing a ...
31 views

### So… Just a thought [on hold]

If we spin an electron fast enough to make centrifugal force does it affect the specific gravity of said electron? Does centrifugal force bend spacetime like gravity does? I was thinking if we could ...
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### Meaning of electron displaced to another quantum state in another location

For example, in a p-n junction scenario where the electron is displaced from LOCATION A, due to diffusion to a lower quantum state at LOCATION B in the p-type silicon, as seen in the following diagram ...
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### Why Doesn't Mersenne's Pre-Newtonian Law Violate Conservation of Hamiltonian Energy? [on hold]

Vibrating string frequency is a natural algebraic constant of motion fixed by energy conservation. Mersenne’s pre-Newtonian law for deriving frequency violates energy conservation. String velocity is ...
32 views

### What happens when one side of a convex lens is made fully reflecting?

Will the convex lens behave as a convex mirror when a side of it is mirrored fully?
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### Horsepower, torque, speed and all that [on hold]

can anyone help... I have some vague grasp of the two, and I know that they're related to each other. I can't explain their relationship without lapsing into "uh...uh...uh..." talk. Wikipedia has ...
32 views

### Simple exercise about conservation of momentum

A block of wood of mass $M$ is dropped, with no initial speed, from a height $h$ with respect to the ground. When it is at altitude $\frac{h}{2}$ it is hit by a bullet of mass m that travels ...
30 views

### Physics near null infinity

The concept of null infinity $\mathscr{I}$ is standard in general relativity, and more recently in the analysis of infrared structure of gravity (see e.g. the article by Strominger). I am curious ...
52 views

### Can QM be derived from the Wightman Axioms?

My question is if quantum mechanics can be completely derived from the Wightman Axioms of QFT. According to Wikipedia, the first axiom is the assumption of relativistic quantum mechanics. Does this ...
53 views

### How can a continuous spacetime look discrete on a larger scale?

Referring to Arnold Neumaiers answer here, where he states that: "If time appears discrete (or continuous) at some level, it could still be continuous (or discrete) at higher resolution" This ...
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### At the Fundamental Level, are Radio Waves and Visible Light Produced in the Same Way?

I'm currently writing an essay, that aims to investigate claims that the radiation produced by radio towers (i.e. radio waves) is harmful to human health, using physics Ideas To approach this I've ...
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### How do I calculate the physical effects of jerk (rate of change of acceleration, or $m/s^3$)?

Is F = M x A the same as force = mass x jerk?
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### Why does a sticker slowly peel off, but if it is pulled quickly it tears?

Anyone who has removed a sticker, knows that often they must be pulled off slowly, otherwise they tear. Why is this?
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### Confusion on co-moving distance and the Big Bang

I'm at sea. From the wiki. entry https://en.wikipedia.org/wiki/Comoving_and_proper_distances : “..Most textbooks and research papers define the comoving distance between comoving observers to be a ...
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### Thought experiment and possible contradiction between electromagnetism and special relativity

I have designed a simple and qualitative thought experiment through which I have encountered an inconsistency in the relativistic electromagnetism. A point charge $+q$, with respect to the lab ...
27 views

### Position operator acting on eigenfunctions

Gennaro Auletta in his book makes the following argument to show that multiplicative operator acting on his eigenvectors acts in a multiplicative way on eigenfunctions as well. Here's the argument. ...
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### Correct orientation of the resultant vector

Figure : https://imgur.com/a/v7AYrLb So i was doing my assignment and got confused regarding why my resultant vector's orientation wont look like the answer figure even when i shift it parallel to ...
24 views

### Minimum surface of revolution [migrated]

Let us consider we need to find a curve between $(-x,y)$ to $(x,y)$ such that the surface of revolution of this curve has minimum surface area. I proceeded to find area by considering the infitesimal ...
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### Sum of two observables and corresponding experiments

Scenario: ${\mathcal A}$ and ${\mathcal B}$ are two observables. Mathematically we model them by two Hermitian operators $A\colon H \to H$ and $B\colon H \to H$ on a separable Hilbert space. ...
29 views

### What happen if you approach a magnet to a wire contain a current

When current flow in wire, It generates a magnetic field, But there is no dipole, So how do you know what happen if you approach a magnet to wire contain a current ? In any direction does the magnet ...
32 views

### Using integrals to find an expression for velocity in terms of position [on hold]

A particle moves along a straight line with an acceleration that depends on the velocity such that $a(v)=3-0,08v ^2$ Find the expression of $v^2$ in function of position. Well, I used ...
34 views

### Hermite Functions as Basis for Hilbert Space

It is well-known that the Hermite functions (not Hermite polynomials!) form a orthonormal basis for a Hilbert space. Therefore, cannot all solutions of the Schrodinger equation even the non-Harmonic ...
35 views

### For a body moving in elliptical path why the net angular momentum is zero?

Since angular momentum is $mvr$ . Since neither of the three terms is zero initially and finally so how angular momentum is zero.
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### How would the earth's surface temperature change if the atmosphere was also opaque to light in the visible range?

In Andrew Dressler's 'introduction to modern climate change', a simplified model of the earth and its atmosphere is proposed to investigate the effect of atmospheric layers on the earth's surface ...
24 views

### Angular momentum conservation in decay processes

I am a bit confused about how quantum angular momentum is conserved in decay processes, especially when massless particles are involved. Suppose we have a spin 1/2 particle that decays into a photon ...
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### How does phase transition occur in finite sized ising model?

I was simulating the square lattice Ising model via Metropolis Algorithm and found that at 0 magnetic field, there is spontaneous magnetisation below some temperature. I have used Periodic Boundary ...
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### Is the cosmological horizon of an accelerated observer spherical?

I guess the question says it all. If you move across the universe (I mean: across the cosmic background radiation) with accelerated motion, does your cosmological horizon (I mean: the one you see) ...
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### Finding direction of induced EMF

How should I find out the direction of the EMF induced in a rod of any length $l$ rotating with an angular speed $w$ in a region of magnetic field (perpendicular to the plane of the rotating rod) ...
32 views

### Can quantum disentanglement be triggered by time dilation?

The question is really one question that leads to the final one: Is it possible to realize a qubit that naturally flips between two quantum states on a definite and fixed period without any ongoing ...
31 views

### Clifford algebra formulation of the Nambu-goto action

Using the wedge product one can pair the generators the Clifford algebra $Cl_{1,3}(\mathbb{R})$ to produce 2-vectors (area elements). The Nambu-Goto action is a statement on the evolution of ...
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### Is there a difference between topological defects and topological soliton?

Is there a difference between topological defects and topological soliton? Or are these objects the same thing? I ask this because it very common find some papers whose the authors itself refer, for ...
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### Continuously cooling air at the entry to a vertical tube to get a denser air flow at exit

If you have a well insulated vertically aligned pipe open at the top and bottom to ambient air, and then continuously cool the air at the top entry cross-sectional diameter to create a free-falling ...
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### How to get the energy bands of Haldane model?

I am struggling with how to get the dispersion relationship of Haldane model and plot it.Just like this And then apply it to graphene nanoribbons(armchair) and plot it like this Here's a ...
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### About Energy and the spectral line distance between (pure) rotational states

I'm reading about molecular spectra on Resnick-Eisberg, particularly the Rotational Spectra chapter. I'm wondering how come that the emission (absorption) lines are equally spaced by a constant factor ...
35 views

### Atmospheric water generator

I have a simple project of a water-from-air generator. The vertical cylinder tank is embedded in the ground to a depth of up to 4 meters. The electric van sends ambient air into the cylinder. The ...
25 views

### Counting physical degrees of freedom Higgs field

I have three general complex scalar fields $\phi_1, \phi_2$ and $\phi_3$, combined in a triplet as $$\Phi = \begin{pmatrix} \phi_1 \\ \phi_2 \\ \phi_3 \end{pmatrix}.$$ We have $SU(2) \times U(1)_Y$ ...
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### From Poisson's equation to Laplace's equation

I want to understand how exactly $$\nabla^2 V = - \frac{\rho}{\epsilon_0}$$ turns into $$\nabla^2 V = 0.$$ Of course it is by setting $\rho$ equal to $0$ but what does setting $\rho$ equal to $0$ ...
When the axis of rotation is fixed, the angular momentum is given by: ${\vec{L}=\vec{L}_z+\vec{L}_\bot}$ Where: ${\vec{L}_z}$ is the component parallel to the axis of rotation. ${\vec{L}_\bot}$ is ...