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Questions tagged [pauli-exclusion-principle]

The Pauli exclusion principle states that two identical fermions, (so with half-integer spin) cannot occupy the same quantum state simultaneously, and thus share all of their quantum numbers. Also use for structure and classification schemes involving antisymmetry.

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Do Helium-4 atoms behave like photons?

I know that the Helium-4 atom is a boson. Does this mean that, like photons, many Helium-4 atoms can be placed at the same point in space? How its possible? It includes fermions (Protons, Neutrons, ...
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Why are orbitals are stable even though they have wierd shapes?

I'm curious to know about why are they stable, let's talk about $p$-orbital , $p$-orbital is dumbbell shaped shouldn't electrons just fall into the nucleus because we need a centrifugal force to ...
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Pauli exclusion principle and van der Waals force

On the Wikipedia article on van der Waals force, one of the contributions to intermolecular forces is A repulsive component resulting from the Pauli exclusion principle that prevents close contact of ...
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Scalar QED atoms - will they pass through each other?

Atoms generally do not pass through each other. This is usually attributed to the Pauli exclusion principal between the electrons (see links below). If the electrons and nucleons were switched with ...
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Why don't electrons occupy infinite degenerate states with the same energy?

I have a question about the degeneracy of energy levels in atoms and the Pauli exclusion principle. I understand that, according to the Pauli exclusion principle, each orbital can host a maximum of ...
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What's the relationship between wavefunction (anti-)symmetrization and entanglement? [duplicate]

Wavefunction symmetrization for bosons, or antisymmetrization for fermions, renders the wavefunction no longer a simple tensor product, i.e. it is no longer separable. This is the same thing that ...
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Is indistinguishability required for the stability of matter?

Classically, it is well-known that a charge-neutral system of electrons and nuclei is thermodynamically unstable. In simplistic terms, nothing in classical mechanics prevents electrons from binding ...
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Why do valence electrons not push each other away?

I asked my physics teacher why two electrons come in pairs and not push each other away as you would expect from negative charges. He said that according to the Pauli exclusion principle, there are a ...
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Is a fermionic boson possible?

We know that bosons need an overall symmetric wavefunction. So is it possible for a boson to have an anti-symmetric spatial wavefunction and an anti-symmetric spin wavefunction? Such that upon ...
Despaxir's user avatar
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2 answers
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A confusion: Why are composite bosons possible?

I am not a physicist, but trying to understand the standard model to some extent. My understanding is that the essential property of Bosons and Fermions is that two distinct Bosons can occupy the same ...
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Multiple excitations of composite bosons?

Fundamental bosons, which are the mediators of the Standard Model interactions, are permitted to have multiple excitations with the same quantum number. Fermions, on the other hand, obey the Pauli ...
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How do I calculate the ground state energy of a number of protons in a 3D potential well?

I came up with a question in a previous physics exam of my professor that I for some reason can't seem to be able to answer, and I'd really appreciate some help in case he gives me the same question ...
Dimitris Konstantinou's user avatar
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Pauli exclusion principle in case of the $H_2$ molecule

Why do electrons in an $H_2$ molecule have opposite spins, while protons do not necessarily exhibit this behavior? Considering that both are fermions, shouldn't they both adhere to the Pauli exclusion ...
QuantumQuasar's user avatar
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Question about the wavefunctions of a system of non-identical fermions

If one interchanges two identical fermions in the wavefunction of a $N$-particle system, the total wavefunction changes by a sign i.e., the total wavefunction should be antisymmetric under the ...
Solidification's user avatar
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Why does the 'exchange interaction' in ferromagnetism favour parallel spins of electrons? Shouldn't the pauli exclusion principle hold?

I am trying to grasp the concept of the "exchange interaction" in ferromagnetism, specifically why it favors the parallel alignment of electron spins. Intuitively, one might expect the Pauli ...
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How can two electrons form the anti-symmetrical state?

Suppose that I have two electrons in a box that were originally spread by a infinite potential wall. The two electrons are in their ground state wave function (sine function). Now I removed the ...
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What determines the energy spacing of individual orbitals within an energy band in a material?

Within a material, electrons exist within energy bands, often referred to as the "conduction" band and the "valence" band (and I imagine there can be other named bands as well). I ...
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Is there a spin-1/2 hadron composed entirely of up quarks? [duplicate]

I am curious to know if there exists a spin-1/2 hadron that is composed of three up quarks. I understand that in quantum chromodynamics, baryons are formed of three quarks, each carrying a distinct ...
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Understanding the Nuclear Spin of Boron-10: Why is it Spin-3?

I am delving into the nuclear spin characteristics of Boron-10, which notably has a nuclear spin of 3. While I have a foundational understanding of some quantum mechanical principles, the specific ...
Darkorse's user avatar
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1 answer
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Mechanistic Explanations for Electron Degeneracy Pressure [closed]

Most explanations of electron (or any fermion) degeneracy pressure cite Pauli's exclusion principle for fermions. I believe such explanations tell us why we should believe such phenomena exist, but ...
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Electrons decaying into heavier particles

Suppose we have a system of electrons a very tightly confined space (like a tiny magnetic trap). Let's say we continually increase the degree of confinement such that the electrons are confined into ...
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Term symbols and the role of antisymmetrization

In the Hartree-Fock method for many-electron atoms, for a given eigenspace $\mathscr{E}$ of the unperturbed Hamiltonian (in a.u.) $$\hat{H}=\sum_{i=1}^Z \Big(-\frac{1}{2}\nabla^2_i-\frac{Z}{|\vec{r}_i|...
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Is Pauli exclusion or not reason for formation of matter in the Universe?

Pauli exclusion principle says multiple fermions having identical quantum state cannot occupy same physical space. When it says "same physical space"... Is it referring to same location in ...
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Help needed to understand whether multiple fermions can occupy same physical space or not

As per my understanding: Multiple fermions cannot have the same quantum state (as per Pauli exclusion principle) Multiple fermions can occupy the same physical space as long as they have different ...
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Antisymmetrization of the electronic wave function

I'm studying systems of many electrons (for Theoretical Quantum Chemistry) from Landau, Quantum Mechanics (non-relativistic theory), chapters 61, 62, and 63. I wanted to ask for good references to ...
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Symmetry of the hydrogen molecule wave function

Due to their overlapping wave functions, electrons in an $H_2$ molecule must posses opposite spins. The nuclei (two protons) on the other hand are far enough apart for the Pauli exclusion principle to ...
QuantumQuasar's user avatar
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Are the protons in dihydrogen in the same quantum state?

The electrons in the hydrogen molecule experience the same potential and are thus in the same state, so the Pauli exclusion forces them to have opposite spins. Since the protons are identical by ...
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Degeneracy of term-symbols and Pauli exclusion principle in the Russell-Saunders scheme

In the Russell-Saunders scheme, let us consider a configuration of $N$ equivalent electrons (i.e., belonging to the same subshell $(n,\ell)$). Let $|L\ S\ M_L\ M_S\rangle$ denote a common eigenstate ...
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State function of two electrons in 1D box

I would like to know how to derive the wave function of two non-intering electrons in one-dimensional space by accounting their spin and Pauli's exclusion principle. $\Psi(x_1, x_2,\sigma_1, \sigma_2)$...
Tommy Wang's user avatar
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Can two electrons (with different quantum numbers) exist at the same place in space?

I was studying about the arrangements of orbitals in an atom and saw a simulation of the arrangement and that some area of a smaller orbital such as a 1s is contained inside a bigger orbital of 2s (a ...
Bhavya Jain's user avatar
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Two electrons in $1\text{s}$ orbit

Suppose that we have two electrons in $1\text{s}$ orbit. According to the Pauli principle, they should have different spins, one up and one down. If I want to calculate the total angular momentum, ...
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Does the Pauli exclusion principle apply to mesons?

According to the Pauli exclusion principle, two identical fermions cannot occupy the same quantum state simultaneously, but two bosons can. Mesons are bosons, but composed of two quarks, and quarks in ...
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Why doesn't the Pauli exclusion principle apply to bosons?

Everything I've read online seems to say/imply that the Pauli exclusions principle only applies to fermions and not bosons. As I understand it the Pauli exclusion principle arises when the spatial ...
kelfic42's user avatar
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Baryon wavefunctions

The textbook I am currently using states that when all quarks have the same flavor, there are no $J=1/2$ baryon wavefunctions for the ground state $l=0$. Is this an experimental result or is there a ...
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Paired electrons and entanglement [duplicate]

Note to duplicate concerns: How is that the same question as asking if different orbitals are entangled? I am talking about paired electrons in the same orbital orientation. Paired electrons in an ...
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Net force on object held vertically due to friction and pauli's exclusion principle

Let us consider a cup that I'm holding vertically in my hand I physically don't go through the cup because of the pauli's exclusion principle where electron with opposite wave function(spin)s dont ...
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Shouldn't there be 3 antibonding orbitals for diatomic hydrogen?

The bonding state of H2 is |Ψ+>|0,0>. This makes sense because there is only 1 spatially symmetric state, in which the electrons experience an attractive exchange force. (|Ψ+> denotes spatial ...
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Help with Shell Model and Pauli Exclusion Principle

As I understand, the occupancy number in the nuclear shell model dictates the number of each type of nucleon that can occupy a specific sub-shell (angular momentum state l). Note: s, p, d, f ...
Thomas's user avatar
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Is the magnetic field related directly to the Pauli exclusion principle? [closed]

The fact that the spin is a quantity related to the magnetic field, is it a consequence of the Pauli exclusion principle or vice versa?
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Can you help me derive an equation regarding Pauli's exclusion principle?

I am writing a book entitled "Atoms" in which I must plow through much of the "old quantum theory" literature. I am reading a paper by Pauli (the first of his two seminal papers ...
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How are the orbitals named?

l = 0 to (n-1). l is azimuthal quantum number. n is principal quantum number. for, l = 0 , it is s. l = 1 , it is p. … l = 99, it is what? What is the name given to it?
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Pauli Exclusion Principle with two electrons in box

Suppose that I measure the spin of two electrons in the z direction, and that they have the same spin. Then we put both electrons in a box. After a long time, we know nothing about the spatial ...
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Are two molecules of matter in BEC phase able to occupy the same space at the same time? [duplicate]

An important property of matter taught in grade school is that it occupies space (has a volume, whether it's relatively fixed like a solid or liquid, or depends on pressure like a gas), and that ...
reductionista's user avatar
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When I push a 24-karat gold bar with my finger, what subatomic physics are at play? [duplicate]

I chose a pure gold bar to eliminate the possibility of any chemical reactions occurring, the same question would apply to any everyday object like a wooden block or a marble. Or it could apply with ...
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Could a $uuuu\bar{u}$ pentaquark exist?

Could a $uuuu\bar{u}$ pentaquark exist or is it forbidden due to Pauli exclusion principle?
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Spin, Pauli, and Heisenberg

Please forgive my possible misunderstandings, but I'm a YouTube physics student, and long since forgot the physics I learned in 1982... I make a few assumptions here... The Pauli Exclusion principle ...
Steve Taylor's user avatar
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2 answers
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What are parahelium and orthohelium?

I have been learning a little about two-electron atoms, and there are some things that I do not fully comprehend. Some context: In the two books I have been reading (Physics of atoms and molecules, by ...
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Physical interpretation of the Pauli Exclusion Principle

As I understand it, the Pauli Exclusion principle states that two electrons in orbitals of a given atom with the same values for quantum numbers $n$, $l$ and $m_j$ must have different (opposite) ...
slithy_tove's user avatar
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1 answer
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Does "non-interacting" (fermions) really mean "no interactions other than Pauli exclusion"?

When one speaks of non-interacting elections (or other ferimons), doesn't one technically mean non-interacting but with the exception of Pauli exclusion? I wonder if it is appropriate to view Pauli ...
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Must fermions be particle sized? Does pauli exclusion principle apply to large bodies?

I am wondering if all fermions must be quantum in nature or if I can build a 'classically sized' fermion. For example, if I ensure that the total spin of all protons, neutrons and electrons in a bulk ...
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