Questions tagged [bosons]
Bosons are integer-spin particles that obey Bose-Einstein statistics. Two bosons can occupy the same quantum state.
472
questions
0
votes
1
answer
2k
views
Understanding concepts of $N$ identical particles
I'm uncomfortable with the concepts of $N$ number of identical fermions and identical bosons and their degeneracies and energies.
For example, lets say we a have a 3-dimensional isotropic harmonic ...
4
votes
1
answer
740
views
Fields: Bosons vs Fermions
Reading Student Friendly Quantum Field Theory by Robert Klauber and he made me realize I've taken as fact for some time that bosons are the "force carriers" in QFT, without really understanding fully ...
1
vote
1
answer
207
views
Extracting the probabilities of single-particle energy measurements from a multi-particle configuration state
I need help understanding how to do a quantum particle-statistics problem, based on the Example 5.4.1 in Griffiths' Introduction to quantum mechanics.
Let's say that I have 3 identical particles in a ...
1
vote
1
answer
571
views
Is a Gravastar more dense than a Neutron Star?
Given:
A Neutron star is the collapsed core of a larger star;
Models for Neutron stars suggest they are composed almost entirely of neutrons;
And if:
Bose-Einstein condensates are extremely dense ...
1
vote
1
answer
3k
views
Integral spin and half integral spin
I am reading a book (Laudau and Lifshitz, Vol. 4, page 94) and it derived why spin-0 should obey Bose quantization and spin-1/2 should obey Fermi Quantization.
Then it says, all integral spin ...
1
vote
2
answers
331
views
Canonical quantization of bosons
During my studies on QFT a fundamental question occurred concerning the canonical quantization. In our course, we mentioned that:
"The canonical quantization of a field with values in the complex ...
3
votes
2
answers
6k
views
Why are He-4 nuclei considered bosons, and He-3 nuclei considered fermions?
Why are helium-4 nuclei considered bosons, while helium-3 nuclei are considered fermions?
From the Wikipedia page on Identical Particles:
Examples of bosons are photons, gluons, phonons, helium-4 ...
6
votes
1
answer
474
views
Can quarks of different generations enter a $Z$ boson vertex?
Reading through my particle physics book (Thomson's "Modern Particle Physics"), it appears that when calculating the possible decays of the $Z$ boson, we do not consider decays such as $Z\rightarrow u ...
0
votes
1
answer
101
views
How to evaluate this weird delta-function like sum
In the process of computing the two-point function for a free boson system, I have been led to the following sum that I'm not sure how to evaluate:
$$\sum_{\vec{k}}e^{i(\vec{k}\cdot\vec{x}-\frac{\vec{...
0
votes
1
answer
747
views
$N$ copies of 1D bosonic harmonic oscillator partition function
I am trying to understand the partition function of $N$ copies of 1D bosonic harmonic oscillator. $$ Z_N{}^B = q^{\frac{N}{2}} \prod_{n=1}^N \frac{1}{1-q^n}\quad\text{ with }\quad q=e^{-\beta \hbar w}....
2
votes
2
answers
2k
views
Partition function for classical indistinguishable particles and Bose particles
We have two particles that can be in either level $E_0 = 0$ or in level $E_1$.
If we treat them as Bose particles, then the partition function will be:
$$ Z = 1 + e^{-\beta E_1} + e^{-2\beta E_1}, $$
...
0
votes
1
answer
177
views
Can all types of particle be created in quantum fluctuation?
In quantum / vacuum fluctuation, a pair of virtual particles is formed. But can all different types of particles be created, both virtual fermions and virtual bosons? For example electrons, quarks, ...
2
votes
1
answer
142
views
Time of flight images of Bose-Hubbard model
on the website of Immanuel Bloch, you can find time of flight images of bosonic particles inside an optical lattice for different values of the depth of the lattice.
(http://www.quantum.physik.uni-...
1
vote
1
answer
713
views
Does the top quark decay into an on-shell W boson?
Considering that the top/truth quark is the only quark with higher mass than the massive bosons, is the W boson in its decay different than the off-shell bosons that mediate the weak decay of other ...
2
votes
0
answers
450
views
Finding the state and wave-function for two identical spin-1 bosons trapped in one-dimensional harmonic oscillator
My question concerns the validity of my approach to a problem and wether the answer is correct. I am tasked with writing the state vector(s) and wave-function(s) for when two identical spin-1 bosons ...
3
votes
2
answers
1k
views
Could new massive bosons ("Massive Photons") explain the dark matter mystery?
I saw a news from an official MIT website about a hypothesis proposed by MIT scientists which "massive photons" could be the sources of dark matter. They've also proposed an experiment for proving ...
0
votes
2
answers
99
views
Is dark energy made by bosons? [closed]
Theoretically speaking, would dark energy be made by bosons or similar particles or by a completely new type of particles?
7
votes
4
answers
742
views
Can we regard a spin-1 particle as combination of two spin-1/2 particles?
As we know, the square of time-reverse operator is -1 acting on fermion and +1 on boson. I can prove it by regarding the time-reverse operator as 2π rotation around $y$-axis multiply the complex ...
1
vote
0
answers
188
views
Why does the weak interaction not conserve the flavour quantum number? [duplicate]
The weak interaction, in contrast to the strong and electromagnetic, is the mediator of the decay of the strange quark, purely because the weak interaction is 'allowed' to break conservation of ...
2
votes
0
answers
157
views
Product of expectation values for multimode operators
If $A_{n}, B_{n'}, C^{\dagger}_{n''}, D^{\dagger}_{n'''}$ are multimode field operators that obey the bosonic commutation relations, under which circumstances the product of expectation values $\...
1
vote
0
answers
57
views
How to relate the number of bosons (fermions) with the number of vertices and external (internal) bosons (fermion) lines?
I am following the QCD book: "QCD: Renormalisation for the Practitioner" by P. Pascual, R. Tarrach. In chapter 3, page 64, equation III.13 they relate the following quantities:
Let us consider a ...
0
votes
1
answer
55
views
Showing phase change for fermions
When discussing identical particles books often use that the states are eigenstates of the permutation operator:
$P_{ij}|\psi\rangle = \lambda |\psi\rangle$
for bosons this is easy to see if I use ...
1
vote
0
answers
79
views
Capturing superfluid condensation with exact diagonalization
Doing exact diagonalization on bosonic systems is tricky, because the possibility of multiple occupancy means that even the single-site Hilbert space is infinite-dimensional. It's my understanding ...
5
votes
0
answers
192
views
Can fermions composing a boson ignore Pauli's principle?
After a discussion with a fellow student, we came above this problem asked as question in the title.
A similar question was answered here.
But it doesn't answer the question for us.
In a BEC, many, ...
-6
votes
2
answers
355
views
Clarification of the concept of Boson Mediator and 'Mediation' in Physics? [closed]
I would like to have a clear concept of Higgs 'mediator' and that 'mediation' speak in physics, what you 'swap' a particle with ...
2
votes
1
answer
2k
views
What does it mean that a Cooper pair behaves as a boson but respects the obligations of fermions?
I refer to the fact that it has integer spin, but antisymmetric wavefunction. How is this possible?
0
votes
0
answers
251
views
What is more fundamental $E=\hbar \omega$ or $E=c\hbar k$?
Let us say I have a massless particle (not necessarily a photon) then in a medium where $\omega \ne c k$ (e.g. a dispersive medium) what is the energy of the particle?
As my title indicates are think ...
3
votes
1
answer
1k
views
Stern-Gerlach experiment with Bosons
I'm new to this forum and I'm studying semiconductor physics at the moment. I just wanted to ask a thing about the concept of spin: when it was studied for the first time, in the Stern-Gerlach ...
5
votes
1
answer
287
views
Super conductivity and energy gap in fermionic/bosonic subspaces
I am trying to understand the phenomena of super-conductivity from a broader level. What I understand for now is that for super-conductivity to be possible in a system, a necessary requirement is that ...
2
votes
1
answer
2k
views
How to determine the direction of arrow on Feynman diagram for $W$ boson line?
I am somewhat confused. Looking through these slides (especially the 11th), which show Feynman diagrams involving $W$-bosons, I can't figure out which way to draw the arrow near the $W$ boson? How do ...
1
vote
2
answers
167
views
Inverting density in favour of fugacity
In these notes on pages 80 and 81 the following step was used
The density in terms of fugacity is
$$
\frac{N}{V} = \frac{z}{\lambda^3}\left ( 1+ \frac{z}{2 \sqrt{2}} + \ldots \right )
$$
and this ...
8
votes
4
answers
680
views
Why don't we call the fermions in the standard model force carriers?
Maybe this is a chicken-and-egg problem, but couldn't we call all the bosons fundamental and treat the fermions as force carriers between them?
EDIT: After all we never see the asymptotic states of ...
7
votes
1
answer
534
views
Why does exchanging coordinates produce a phase of $\pm 1$ in an identical particle wavefunction?
Consider a system of two identical particles described by a wavefunction $\psi(x_1, x_2)$. There are two kinds of exchange operators one can define:
Physical exchange $P$, i.e. swap the positions of ...
0
votes
2
answers
171
views
Exchange principle in terms of states and coordinates?
I have seen the exchange principle written in two ways, one in terms of coordinates and the other in terms of states:
If $\psi_{AB}(1,2)$ represents particle $A$ in state $1$ and particle $B$ in ...
4
votes
0
answers
409
views
Physical interpretation of the chemical potential in Bose and Fermionic gas
I understand that both Fermions and bosons have the chemical potential $\nu <0$ when it is T>0, but still behave classically, the fermions would increase its chemical potential at T=0, whereas the ...
5
votes
1
answer
535
views
Enormous masses of $X$- and $Y$-bosons in GUTs
I was reading an article on Wikipedia about the hypothetical particles called $X$ and $Y$ Bosons.
Looking at their "calculated" masses, I felt quite weirded. Their mass should be
$$
m = 10^{15}\,\...
0
votes
2
answers
179
views
Why $\delta F = B\epsilon$ and not $F=B \epsilon$ in supersymmetry?
We can express supersymmetric transformations as
$$\delta F = B\epsilon, \tag{1} $$
$$\delta B = F\bar{\epsilon},\tag{2}$$
where $B$ and $F$ denote the bosons and fermions, respectively, in the theory ...
2
votes
1
answer
442
views
Unitary Bose gas
A unitary Bose gas (more about it [here]) is defined to occur when the scattering length diverges.
What I don't understand, however, is which quantity/matrix is actually unitary?
I mean, they could ...
0
votes
2
answers
755
views
Can both types of W boson be responsible for a neutron-neutrino interaction?
My textbooks lists the exchange particle for a neutron-neutrino interaction as being the W- boson. Is this the only option, or can it also be a W+ boson? Nothing jumps out at me that would suggest it ...
7
votes
2
answers
4k
views
What is meant by fermionic and bosonic "modes"?
The paper The Dirac quantum automaton: a short review (pdf) starts off by stating:
The starting point for the construction of space–time and the physical laws therein is an unstructured, countably ...
1
vote
1
answer
248
views
Bosonic qubits using BEC versus usual qubit implementations based on energy levels
All condensate atoms in a BEC (say like Rb, etc) effectively occupy the lowest energy-state. If it is that the case, then how are such bosons in a BEC encoded as a qubit? In particular, when Grover ...
1
vote
2
answers
261
views
Two stones (bosons) in one place
A macroscopic object (let's call it "stone") may incidentally be a boson, right?
But identical bosons are "allowed" to have the same quantum state.
From this I conclude that two identical stones may ...
-1
votes
1
answer
288
views
Why do bosons and fermions exist? [duplicate]
if i have two particles in states: |1> and |2> respectavly , and they are not identical then the combined state is |1>|2> ,
but if they are identical then the labels 1 or 2 are arbitrary and could be ...
0
votes
1
answer
98
views
What are the differences among bosons, force-carrier particles and mediators? [closed]
Are all bosons force-carrier particles?
What is the difference between these three concept?
Where can I find a comprehensive & detailed information about these particles?
How it can be related ...
2
votes
1
answer
555
views
Examples for p-form gauge fields [closed]
I don't completely understand the notion "p-form". Can you give me examples of 1-form, 2-form and 3-form gauge fields? What kind of p-form is e.g. the Higgs field, the electromagnetic four-potential, ...
3
votes
3
answers
530
views
Perturbative series for bosons
I have recently read that
... the perturbation series ... is valid only when the perturbed state
is qualitatively similar to (or ‘has the same symmetry as’) the
unperturbed state. This means ...
-1
votes
1
answer
296
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.
...
0
votes
1
answer
257
views
Is there any sense in which mesons could act as force carriers, in the way that gauge bosons do?
Gauge bosons are force carriers. Mesons are composite bosons and have similar characteristics to gauge bosons. Is there any sense in which mesons could act as force carriers?
1
vote
1
answer
268
views
Identical particles: Why only two possibilities?
Given two identical particles, Wikipedia says that the wavefunction of a combined system where the first particle is in state $|n_1\rangle$ and the other one is in $|n_2\rangle$ is $|\psi\rangle=|n_1\...
1
vote
0
answers
449
views
Path integral for boson vs fermion (soft derivation + use )
I have been looking around for a soft derivation with a bit of detail for boson and fermion path integrals that I could understand. I have a passing knowledge generally of what a path integral is in ...