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56 views

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

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
31 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 ...
2
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1answer
42 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 ...
3
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2answers
178 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
46 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
65 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
42 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
44 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 ...
3
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2answers
108 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 ...
3
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2answers
59 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?
6
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1answer
80 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. ...
2
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3answers
201 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 ...
1
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2answers
105 views

Why do objects have size? [closed]

What is the reason objects, like coffee mugs, have size?
5
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2answers
118 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
45 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 ...
3
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1answer
147 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?
5
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2answers
524 views

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

How is the Pauli Exclusion Principle a consequence of antisymmetric wavefunction?
5
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1answer
64 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 ...
2
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1answer
82 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 ...
3
votes
1answer
134 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 ...
0
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2answers
68 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 ...
0
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0answers
31 views

What's the elementary reason for the formation of a band gap?

Bohr's solution for an isolated hydrogen atom showed that there are only discrete allowed energy levels, $E_n = -{E_0\over n^2}$ and the solution of the Schreodinger equation provided a certain ...
2
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1answer
340 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 ...
0
votes
1answer
81 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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3answers
382 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 ...
8
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1answer
156 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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0answers
41 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?
2
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1answer
37 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 ...
3
votes
1answer
95 views

Is “microbunching” in a free electron laser limited by the Pauli exclusion principle?

As I understand it, a free electron laser can basically be pictured as a synchrotron light source with an undulator which by the particular setup causes the electrons to self-attune so that they ...
5
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3answers
142 views

Question about the exclusion principle

I understand the Pauli exclusion principle like this: For two electrons to occupy the same state their spins must be opposite. If the two electrons are in different states (different spatial ...
5
votes
5answers
1k views

Electron shells in atoms: What causes them to exist as they do?

I have seen similar posts, but I haven't seen what seems to be a clear and direct answer. Why do only a certain number of electrons occupy each shell? Why are the shells arranged in certain distances ...
3
votes
1answer
212 views

Why do the anticommutation relations imply Fermi–Dirac statistics (Pauli Exclusion Principle) for the field quanta?

I was reading the following article Fermion FIelds and discovered the following passage not fully explained to me : It is these anticommutation relations that imply Fermi–Dirac statistics for ...
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0answers
89 views

How to show that two spin one half particles must form a anti-symmetric wavefunction?

I am stuck on how to connect the ideas that two spin half particles must form a anti-symmetric wavefunction. Is there a proof on how to show that two spin one half particles must form a anti-symmetric ...
3
votes
2answers
310 views

Pauli's Exclusion Principle

Can someone tell me how Pauli's Exclusion Principle gives stability to matter? I know two electrons cannot occupy the same energy state so that is why we cannot squeeze bulk matter after a limit and ...
3
votes
2answers
780 views

Why there are no uuu and ddd baryons with spin 1/2?

What is preventing $Δ^{++}$ and $Δ^-$ baryons from going to a lower-energy state with spin 1/2 similar to that of protons and neutrons? I don't think the Pauli exclusion principle can prevent it ...
3
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3answers
478 views

What does the Pauli Exclusion Principle say about a superposition of spin states?

Suppose we have an atom. It is commonly said that because of the PEP, two electrons can't be in the ground state unless they have opposite spins, because no two electrons can have the same ...
2
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2answers
70 views

How do I describe two entangled electrons in the same state except for a different spin

I am trying to formulate the wave function that describes two entangled electons having the same position but opposite spin. According to the Pauli exclusion principle this should be possible. And ...
2
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0answers
67 views

What are the parameters for Pauli's repulsion pseudo-force?

I have found the following formula for the repulsion potential due to the overlap of the electron clouds arising from Pauli's exclusion principle: $$V = A\exp(-r/\phi)$$ where r is the distance ...
2
votes
1answer
143 views

Is there a connection between exclusion principle and the speed of light?

As far as I know exotic stars are composed of degenerate matter created by the balance between gravity and pressure of exclusion principle and as the mass of the star grows it goes into more ...
3
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1answer
91 views

How would Hamiltonian for several fermions with spin look?

All discussions of Pauli exclusion principle I read usually talked about antisymmetric wavefunctions, from which the princinple appears. But I would like to see a Hamiltonian for multiple fermions, ...
3
votes
1answer
111 views

Quantum mechanics and atomic bonding

I'm learning quantum mechanics in high school this year, and I have several doubts. I've done my research on various websites but my understanding is still fuzzy. I understand that when I punch a wall ...
0
votes
1answer
206 views

Aufbau principle in modern quantum theory

What is the rigorous definition of the Aufbau principle and the mathematical model used for its description? From Wikipedia, we have that the principle postulates a hypothetical process in which an ...
3
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0answers
74 views

Can Pauli exclusion be described locally?

Is it possible, in principle, to define the exclusion principle in a "local" sense, as a property of the tangent space at a point, or a single fiber of a spin bundle? Or does it necessitate a global ...
2
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2answers
520 views

What happens when electron degeneracy pressure is being overcome (right before an object turns into a black hole)?

I was wondering about hydrostatic equilibrium (the balance of radially inward and outward forces) in large (i.e. above the Chandrasekhar limit) stars. It is often said that when the gravitational ...
3
votes
2answers
930 views

Electrons, spins, and degeneracy

In an atom, two electrons can have the same set of $n,\ell,m$ quantum numbers as long as they have opposite spins. My introductory physics and chemistry courses have all introduced this as two ...
22
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3answers
1k views

Does black hole formation contradict the Pauli exclusion principle?

A star's collapse can be halted by the degeneracy pressure of electrons or neutrons due to the Pauli exclusion principle. In extreme relativistic conditions, a star will continue to collapse ...
10
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2answers
208 views

How strong is electron degeneracy pressure?

I'm trying to get some specific numbers for electron degeneracy that I can understand, using a concrete example. Take for example this portion of carbon crystal: Exactly how much energy would be ...
1
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2answers
207 views

Is there is a reason for Pauli's Exclusion Principle?

As a starting quantum physicist I am very interested in reasons why does Pauli's Exclusion Principle works. I mean standard explanations are not quite satisfying. Of course we can say that is because ...
8
votes
2answers
302 views

How axiomatic is the symmetrization requirement (i.e. the Pauli principle)? (in QM)

I've so far always been told, that the symmetrization requirement is an axiom on the level of the Schrödinger equation and the statistical interpretation of the wave function (or it's absolute value). ...
5
votes
1answer
125 views

Are composite bosons always bosonic (e.g. the pion-cloud surrounding the nuclei)?

The $\pi$-meson is a boson, but consists of quark-antiquark (fermions). It seems to me that at some energy level (equivalently distance) the inner structure (fermionic nature of the quarks) of the ...