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On the Pauli Principle

Consider a quantum mechanical system as shown-say a piece of metallic conductor in the shape of a long, thin bar.(Must it be a single crystal to be considered a "system"?). Now focus on two free ...
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29 views

Lepton Universality and Pauli Exclusion [duplicate]

Electrons, Muons and Pauli Exclusion Put in a possibly oversimplified way, lepton universality says that electrons, muons, and taus all behave in the same way except for mass effects. The question ...
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82 views

Mathematical form of the de facto repulsive “force” associated with the Pauli Exclusion Principle [duplicate]

One of the principles of General Relativity is that test objects follow a geodesic unless otherwise acted upon by a force. From this perspective, it is clear that physicists, consciously or ...
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26 views

Pauli-Exclusion Principle, Why not a force? [duplicate]

I understand the mechanics of the Pauli-Exclusion principle and how it is a common sense idea that a fermion can not occupy the same coordinates, quantum state, as another one. Why is the ...
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111 views

Entanglement and the Pauli exclusion priciple

Could you say that two electrons in the ground state of a helium atom experience quantum entanglement? They are both in the same energy level and cannot have the same quantum numbers. If one is spin ...
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1answer
71 views

What is the correct way of writing the antisymmetrized state of two identical fermions?

I am just confused: If I have 2 identical fermions, where one of them is in state A and the other one is in state b, and they are normalised and orthogonal, which statement is right: 1) ...
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1answer
37 views

Antisymmetry requirement for the total wavefunction

My understanding is that if we are dealing with a system of two electrons, the total wavefunction needs to be antisymmetric only when the two electrons have same value of n and l ( i.e. they are ...
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1answer
103 views

Nature of the quantum degeneracy pressure

It is commonly known that it is the electron degeneracy pressure that prevents the collapse of a white dwarf into a neutron star, and it is not the electromagnetic force. However, it is also widely ...
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101 views

Another question on the Pauli Exclusion Principle?

The Pauli exclusion Principle states that two Fermions of the same type cannot exist in the same state at the same time. This means that two electrons cannot both exist in the same spin state and be ...
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1answer
45 views

Derivation of Fermions anticommutation rule

How one might derive fermions anticommutation rule? For bosonic particles, there is no ordering issue, and its commutation relation could be easily derived. However, for fermion, is there any easy way ...
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1answer
272 views

Question on Pauli's Exclusion Principle

Pauli's EP says that electrons in a subshell will have opposing spins. Now, lets say I prepare two electrons with spin up. If I took an alpha particle ($\mathrm{He^{2+}}$) and added one of these ...
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2answers
99 views

Two Particle System

I've read that if the wavefunction of a combined state can be represented as the tensor product of the individual wavefunctions, the two particles involved are non-entangled. Now taking a scenario in ...
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42 views

Which is the mechanism through which dying stars shed their outer atmosphere and leave behind their core? [closed]

I was looking into neutron star creation and I read that when a star dies, it expells its outer atmosphere and leaves behind a really small really dense nucleus (a white dwarf if the first star was a ...
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1answer
80 views

Pauli's exclusion principle and square well potential [closed]

Consider an infinite square potential well with potential $$V(x)=\begin{cases} 0 & \text{if} -a<x<a\\ \infty & \text{otherwise.}\\ \end{cases}$$ The stationary state energies for a ...
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1answer
50 views

Are Neutrons and anti-Neutrons attracted to each other over distance?

Lets create a scenario where you have a total vacuum and you're shooting into this vacuum two streams, one, a Neutron stream and the other an anti-Neutron stream and because you're curious what will ...
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2answers
84 views

Confused about Slater Determinant

Consider a system of 2 identical fermions. $$\psi_{k_1,k_2}(x_1,x_2,m_1, m_2) = \langle x_1\,x_2\,m_1\,m_2\mid \psi \rangle$$ According to what I have read we can construct a state with the right ...
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2answers
54 views

Filling a System of independent Electrons and the Pauli Exclusion Principle

Consider a system of spineless electrons in the independent electron approximation. Thus we consider a one-particle Hamiltonian $H$. Assume for simplicity that $H$ has discrete spectrum labeled by ...
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1answer
91 views

Is this a good argument against time travel? [closed]

Two fermions in two different points of space cannot be made to exist in the same point of space. It follows then that two fermions in two different times cannot be made to exist in the same time. ...
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1answer
168 views

Why must fermions be antisymmetric? [closed]

I have read that fermions cannot exist in the same state simultaneously. I understand why indistinguishable particles with an antisymmetric superposition of states can't exist in the same state ...
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1answer
41 views

Are there different colors of leptons? [closed]

Are there different colors of leptons? The Pauli Exclusion principal made it necessary for quarks to have 3 different colors. However, although leptons don't undergo the strong interaction they still ...
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1answer
206 views

Why does the conjugated $\pi$ bond not violate the Pauli Exclusion Principle?

Let's look at the molecule 1,3 butadiene: $CH_2=CH-CH=CH_2$ and number the carbon atoms 1 to 4 from left to right. The bonds between 1 and 2 and between 3 and 4 are double bonds: each ...
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1answer
127 views

No two identical fermions can have the same quantum state at once?

This is the Pauli Exclusion Principle, but I have a question about it... It states that no two identical fermions can have the same quantum state, but what about different fermions having the same ...
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3answers
192 views

Is every electron in the Universe in a different quantum state?

Is every electron in the Universe in a different quantum state? Is this what the Pauli Exclusion Principle tells us?
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62 views

Is it degeneracy pressure rather than electrostatic repulsion that stops us falling through the floor? [duplicate]

From Wikipedia: Degeneracy Pressure Freeman Dyson showed that the imperviousness of solid matter is due to quantum degeneracy pressure rather than electrostatic repulsion as had been previously ...
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1answer
42 views

What is the range of degeneracy pressure?

In what way is degeneracy pressure related to the separation of fermions? Is there any influence at ranges like a meter and beyond. I expect the influence at those ranges to be immeasurably small. I ...
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1answer
70 views

Are Fermi-Dirac-statistics relevant to view the universal system of neutrinos?

Should the energy distribution of neutrinos be affected by Fermi-Dirac statistics? And if so, what would the consequences be? Could this locally cause weak interaction because of the Pauli Exclusion ...
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209 views

Quantum mechanics and the atom

I was thinking about the nature of the atom, specifically, why electrons do not spiral into the nucleus. My physics book says the principal quantum number $n$ must be an integer number of wave ...
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1answer
75 views

Would Hund's rules still be valid if the electron had spin 3/2?

One of my homework assignments in atomic physics was the following: Given electrons had a Spin of $S = 3/2$, what would be the number of the first 4 noble gasses (complete shells)? The obvious ...
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1answer
95 views

Uncertainty principle within a neutron star or black hole

Take the time-energy uncertainty relation, $\Delta$$E$$\Delta$$T$$\ge$$\hbar/2$. My question is based on my confusion about the effect this relation may have within the interior of a highly ...
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0answers
50 views

What is the equation for the pressure at which neutrons can no longer be supported by neutron degeneracy pressure?

What is the equation for the pressure at which neutrons can no longer be supported by neutron degeneracy pressure? At which point they would collapse into each other. There seems to be one for ...
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2answers
98 views

How does friction product heat?

Suppose there are two similar particle-like objects attempting to "bump" against each other to create friction, they are prevented from colliding against one another due to either electrostatic ...
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2answers
146 views

Can someone explain the quote “there would be no chemistry if electrons acted as bosons”?

I am reading a book and in a quote it says that if electrons acted as bosons, then all the electrons would occupy the lowest energy state, and there would be no chemistry. What does the author mean ...
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2answers
79 views

pauli exclusion principle in electron beam

Do electrons in an electron beam (cathode ray) follow pauli exclusion principle ? or in other words, does pauli exclution principle apply for the beam of electron?
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1answer
89 views

Pauli exclusion principle and relativity

I'm somewhat curious about how the Pauli Exclusion Principle functions when relativistic time becomes a significant factor. Just to clear things up, my (possibly poor) understanding goes like this. ...
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3answers
350 views

Violation of Pauli exclusion principle

From hyperphysics (emphasis mine): Neutron degeneracy is a stellar application of the Pauli Exclusion Principle, as is electron degeneracy. No two neutrons can occupy identical states, even under ...
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2answers
110 views

Why do objects have size? [closed]

What is the reason objects, like coffee mugs, have size?
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2answers
128 views

When does Pauli's exclusion principle kick in?

Imagine that I prepare a fermion in the $\left|\uparrow \right\rangle$ state and a second one far away in the $\left|\downarrow \right\rangle$ state and set them in a path for collision. According to ...
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2answers
49 views

In which part of physics can we utilize the rotational antisymmetry of certain wave functions?

Just a quick question - I fail at Googling this topic since I do not remember clearly, in which case (e.g. for what type of particles) is the wave function antisymmetric in terms of spatial rotation ...
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294 views

Number conservation of bosons and fermions

Why is the number of bosons not conserved while the number of fermions is conserved? Does it have something to do with the Pauli exclusion principle?
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782 views

How is the Pauli Exclusion Principle a consequence of antisymmetric wavefunction?

How is the Pauli Exclusion Principle a consequence of antisymmetric wavefunction?
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1answer
70 views

Spin, statistics and neutron stars

So a thought occurred to a friend of mine the other day: in a neutron star, neutrons are prevented from sitting directly on top of one another due to the Pauli exclusion principle, what with neutrons ...
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1answer
104 views

Pauli exclusion principle for the protons in water

The Pauli exclusion principle applies to all fermions, right? And protons are fermions. So if you consider a water molecule, and swap the protons in the two hydrogens, shouldn't the wavefunction of ...
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1answer
176 views

Why according to Hund's first rule all electron with same spin should occupy orbitals when partially filling?

I get that because of coulomb repulsion initially all the electrons will not occupy the same site but will single occupy the orbitals.But while doing so how do they know to keep their spins aligned ...
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121 views

How are electrons restricted to individual orbitals?

Since orbitals are just regions of electron density, they allow electrons to occupy the same space. I feel like in some sense this contradicts the Pauli exclusion principle limiting two fermions, or ...
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1answer
525 views

Can two electrons have the same momentum and spin directions?

I am trying to understand the Pauli exclusion principle. Here is an except from Feynman Lectures on Physics It just isn’t possible at all for two Fermi particles—such as two electrons—to get into ...
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1answer
121 views

Few particle fermion system wavefuction

Suppose I have 3 fermions($\left|\psi_1\right\rangle$, $\left|\psi_2\right\rangle$, $\left|\psi_3\right\rangle$) and a system with 3 states ( $\left|1\right\rangle$, $\left|2\right\rangle$, ...
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650 views

How does the Pauli exclusion principle create a force in degenerate matter?

My understanding is that when it comes to forming a white dwarf, it is the electron degeneracy pressure, due to the Pauli Exclusion Principle, preventing collapse in of the white dwarf. If the ...
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1answer
238 views

What causes Paulis Exclusion Principle?

Currently I'm taking an astrophysics class and has now come across electron degeneracy. As far as I understand, the reason why white dwarfs and such, does not collapse, is due to this, meaning that ...
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43 views

Pauli's exclusion principle? [duplicate]

What is the idea behind Pauli s exclusion principle? Why should an electron or any particle having non integral spin obey this principle?
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1answer
39 views

Reconciling electron subshell configurations and the Pauli exlcusion principle

I'd like to prefix this with an apology: I have no formal training in QP, and most of what I know has been obtained by reading Wikipedia. As such, it'd be really helpful if any answers took my lack of ...