Questions tagged [bosons]
Bosons are integer-spin particles that obey Bose-Einstein statistics.
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1answer
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What happens during a weak interaction?
For e.g. during $\beta^-$ decay a $W^- $ boson is emitted changing an up quark to a down quark. This seems very weird to me as it looks like that up quark is not interacting with some other particle ...
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0answers
31 views
What are gauge symmetries corresponding to forces in particle physics?
I understand that color charge is a gauge symmetry, that leads to connection field and force that is strong nuclear force. This is from professor Sean Carroll from TTC course (higgs boson and beyond)
...
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1answer
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How do I know that gauge fields are bosons?
QED and the Dirac equation have field operators $\psi$ interact with a gauge field $A^{\mu}$.
We identify $\psi$ as a fermionic field and $A^{\mu}$ as a gauge boson - the photon.
Do we or can we ...
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0answers
15 views
Suppressed emission of composite particles
If a composite (pseudo)Goldstone boson $\phi$ emerges in a spontaneous symmetry breaking (similar to the mesons of QCD), is the emission of the $\phi$ particle suppressed in high-energy processes, i.e....
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0answers
63 views
Physics of a Second quantized Hamiltonian?
It is frequently seen that the (Bosonic) Hamiltonian $H=e a^{\dagger}a+f( a^{\dagger}a^{\dagger}+a a)$ is discussed and diagonalized using Bogoliubov transformation. My question is that what is ...
2
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1answer
67 views
Simulating the evolution of many-boson states
My task is to simulate the scheme presented in this paper: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.77.062316.
In this question: Creating an operator for a polarizing beam splitter, I ...
2
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1answer
37 views
Integrals involving Bose-functions (Computational)
In short, I'm looking for some advice/literature how to deal numerically with Bose function.
My physical problem is to calculate a coupled set of Self-energies, thermal loop integrals, self ...
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0answers
35 views
Definition of Ohmic bath and damping force
I have read the Wikipedia article on quantum dissipation where it is talking about the bath spectral function.
The bath spectral function provides a constraint in the choice of the coefficients $...
3
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1answer
50 views
How are computed Branching decay modes (for Higgs boson and from a general point of view)
I would like to know how are computed the branching decay diagram, like for example with Higgs boson represented below (source):
It seems there are 5 ways of decays for Higgs boson.
I suppose there ...
2
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2answers
88 views
Two bosons having the same state — how do you know there are two?
So, suppose that photons have the same quantum state. How do we know that there are 'two' photons having the same state, rather than just one?
Is there a technical way to guarantee that there are ...
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0answers
38 views
Diagonalization of Quadratic Fermionic/Bosonic Hamiltonians
I'm currently reading Quantum Theory of Finite Systems by Blaziot and Ripka, and I have a question regarding the first few pages of chapter 3.
In particular, the chapter takes on the task of ...
0
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1answer
22 views
Frequencies associated with boson/fermion operators
For a Hamiltonian like,
$$\hat{H}=\sum_{k}\hbar\omega_{k}b_{k}^{\dagger}b_{k}$$
What does it mean to say that the frequencies $\omega_{k}$ must be positive if $b_{k}$, $b_{k}^{\dagger}$ are boson ...
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1answer
68 views
Fermoinic and Bosonsic physical Hilbert spaces - are they actually Hilbert spaces?
Consider two identical particles $A$ and $B$. The combined Hilbert space $\mathcal{H}_A\otimes \mathcal{H}_B \newcommand{\ket}[1]{\left|#1\right>} \newcommand{\bra}[1]{\left<#1\right|} $ is a ...
0
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1answer
37 views
Can we have Bose condensation for bosons satisfying a dispersion relation $E=Cp^s$ $\forall$ s?
Suppose a dispersion relation $E=Cp^s$ where $C$ is a constant is known for a collection of massive non-interacting bosons. What is the way to find out whether there will be Bose-Einstein condensation ...
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0answers
22 views
Bose - Einstein Correlation
I want to study about Bose-Einstein correlations and I have been searching online for many days without any luck. Can any of you suggest me some online materials about this topic? I don't have any ...
0
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1answer
31 views
Hard-core bosons and fermions - spinless?
The introduction to this paper about bosonic atoms expanding in an optical lattice says the following:
Are hard-core bosons mapped to spinless fermions?
Because this link shows the mapping ...
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1answer
34 views
What experiments can measure the eigenvalues of the particle exchange operator
In a system with two indistinguishable particles, the eigenvalue to the particle exchange operator $\hat{P_{ij}}$ is $+1$ if the two particles are exchange symmetric, ie. bosons, and $-1$ if they are ...
2
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1answer
83 views
Bogoliubov approximation, coherent states and particle number conservation
I am slightly confused about an aspect of the Bogoloibov approximation for BEC. In it we take:
$$a^\dagger (\vec 0)\approx \sqrt{N_0}$$
$$a(\vec 0)\approx \sqrt{N_0}$$
and find our Hamiltonian in ...
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1answer
80 views
Why is a collection of non-interacting bosons pathological?
In this lecture titled "Disorder and Interactions: From Spin Chains to Cold Atoms" the speaker Thierry Giamarchi claims that a collection of non-interacting bosons is totally pathological. His argues ...
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0answers
80 views
Can matter/antimatter “annihilation” produce “dark matter”?
I was thinking about the following reasoning: If a matter and antimatter reaction produces energy, this energy would have particles itself. I found out (reading...) that one (the main?) product are ...
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1answer
48 views
System of $N$ bosons
What precaution needs to be observed in writing down an expression for the total number of bosons $N$ valid at low temperatures?
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2answers
86 views
Boson or Fermion
How do you deduce that an atom is a fermion or a boson? Do you determine it from the number of neutrons because "electrons and protons cancel out each other in a neutral atom"? What does this have to ...
2
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1answer
64 views
How do you know $W$ and $Z$ bosons are really bosons and not fermions?
It has been always said that $W$ an $Z$ bosons are bosons and not fermions but is there any experimental trial that prove that? Has anyone put two of them in the same quantum state or studies have ...
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1answer
40 views
Goldstone modes $\hat a^\dagger(k) \left|0\right>$ for small $k$ or $\hat a^\dagger(0) \left|0\right>$
Consider the Hamiltonian:
$$H=\sum_{\vec k} \varepsilon (\vec k)a_{\vec k}^\dagger a_{\vec k}$$
with $\varepsilon(\vec k) \rightarrow 0$ as $|\vec k|\rightarrow 0$. I know that this has gapless ...
0
votes
2answers
178 views
Which $W$ boson is involved in electron capture?
I am learning about Electron Capture.
$$p+e\to n+\nu_e$$
My question is whether the $W^+$ boson or the $W^-$ boson is involved in this transfer. I can consider this two ways:
1) Since the electron ...
3
votes
1answer
255 views
Imaginary Frequency in Bosonic Hamiltonian
I'm doing some calculations for my Thesis involving a Bosonic Hamiltonian of the form:
\begin{equation}
H=\sum_{\vec{k}}\alpha\ a^{+}_{\vec{k}}a^{+}_{-\vec{k}} + \beta\ a^{+}_{\vec{k}}a^{-}_{\vec{k}}...
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0answers
34 views
Does the field (force-carrying) of a gluon or boson have a magnetic-like shape? Not spherical
The challenge of force-carrying boson is that many experiments generate results that are not consistent. Hence, quantum statistics.
It is established that things like 'strong nuclear interaction/...
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0answers
39 views
Two particles in a harmonical potential (indistinguishable particles)
In statistical mechanics, we are going to find the difference between the canonical partition function for distinguishable particles and indistinguishable particles.
For understanding this prinicple,...
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1answer
222 views
Spin of a neutral pion
I was going through the book High Energy Physics by DH Perkins.
In the decay $\pi^{0}\rightarrow 2\gamma \ (photon)$, the possible spin components of the system of photons $S_z$ can be $0$ or $2$.
A ...
3
votes
1answer
68 views
Why the $\beta^-$ decay releases $e^-+\nu_e$ and not $\tau$ or $\mu$ generations?
The $\beta^-$ decay is
\begin{equation}
n \rightarrow p + e^- + \bar\nu_e \tag{1}
\end{equation}
It can be broken down into
\begin{align}
d \rightarrow & \ u + W^- \tag{2}\\
W^- \rightarrow &...
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vote
2answers
88 views
Exercise on bosonic vacuum
Consider bosonic canonical transformation, generated by operator $S = e^{\lambda (a^{\dagger})^2}$. Show, that
\begin{equation}
b \equiv SaS^{-1} = a - 2\lambda a^{\dagger}.
\end{equation}
...
0
votes
1answer
74 views
What Makes a $W$-Boson a Gauge Boson?
I understand that in beta decay, a quark changes its flavor and emits a $W$-Boson, and this $W$ (is the W Boson virtual, by the way?) quickly decays into an electron and an electron antineutrino or ...
0
votes
1answer
34 views
Trace with Boson operators
I want to compute the following trace
$$
\operatorname{tr}(\exp(-\sum_k\varepsilon_k a_k^\dagger a_k)a_i a_j)
$$
with bosonic operators $a_i,a_j$. I think the result will be proportional to $\delta_{i,...
1
vote
1answer
59 views
Fock space-Weyl Algebra
I am new to quantum physics, help me out please on this question. I am confuse about how to compute the norm of the states describe below:
Given the operators $a_m, a_m^{\dagger}, m=1,2,\dots, M$, ...
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votes
1answer
33 views
What makes common matter what it is compared to, for example, Electromagnetic Fields?
Last week, I discussed with some friends (we are all Physics Students) what are the differences between photons and electrons that account for the differences between light and matter. One team argued ...
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4answers
644 views
For ideal classical gasses, in terms of the energy levels why do we ignore whether the particles are fermions or bosons?
I am confused as to why when dealing with ideal classical gasses, the dependency of the particles being either fermions or bosons is ignored. How does this relate to the energy levels within the ...
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1answer
129 views
Calculating density of states given energy levels and degeneracy
In my statistical mechanics class, my professors did a problem in which he calculated the density of states, however I am having trouble justifying his approach. I did the problem beforehand in an ...
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1answer
95 views
“Excitatonium” is made of electrons and the holes they leave — so how can they be bosons?
My understanding is that solid matter is made out of fermions (which are subject to the Pauli exclusion principle, which is why they're solid) and bosons (which are not subject to Pauli exclusion and ...
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votes
3answers
190 views
How bosons do not violate conservation of energy?
As far as I understand bosons are energy packets which carry forces: e.g. Higgs bosons carry gravity. What I don't understand is, for example if we have an isolated object which constantly releases ...
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votes
1answer
301 views
Fock space with mixed anti-commutation/commutation relations?
Let's say we have two modes, with the following labeling of occupation number states:
$ \lvert \Psi \rangle = \begin{pmatrix} 0,0 \\ 0,1 \\ 1,0 \\ 1,1 \end{pmatrix} $
An example of (what I assume to ...
6
votes
2answers
141 views
What is special about the indistinguishability of Boson and Fermions?
In the treatment of Bosonic or Fermionic systems that I'm familiar with, you start with a state containing at least two particles:
$$
\left| a_{i}, a_{j} \right\rangle
$$
And define a permutation ...
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vote
0answers
28 views
Mass softening for high-energy interactions?
It is well known (see, e.g., eq. (2) in this paper) that the coupling $g$ of composite, fermion-bilinear bosons (e.g. pomerons) to fermions (e.g. quarks) decreases above the compositeness scale $\mu$ ...
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vote
3answers
214 views
Are bosons matter?
The title explains the question. Are bosons matter? As I have seen, there are three answers to this question:
No, only fermions are matter.
Yes, but only those with mass.
Yes, all bosons are matter.
...
0
votes
1answer
343 views
Eigenvalues of the exchange operator determined by the particle type (boson or fermion) in a two particle system
While dealing with a two particle system in QM (the particles are identical),
the net wave function of the system would be simply the product of the wavefunctions of the individual particles in the ...
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votes
1answer
120 views
Fundamental string theory questions
Can anyone answer some basic string theory questions for me?
The Veneziano Amplitude is celebrated for predicting the scattering amplitude of
mesons and for practically giving birth to string theory....
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0answers
169 views
Interpretation of antiferromagnetic magnons dispersion relation
The dispersion relation of magnons in a ferromagnetic 1d lattice is
\begin{equation}
\omega(k)=\omega_0\big[1-\cos(ka)\big]
\end{equation}
where $\omega_0$ is a constant and $a$ is the spacing ...
0
votes
0answers
28 views
Efimov physics: $N$-body “fundamental forces”?
Can Efimov trimers or generalizations be understood as "fundamental" 3-body interactions (or $N$-body) or are they just special dynamics driven by scale invariance, as suggested by Efimov himself?
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0answers
27 views
Efimov physics: beyond trimers!
Is it possible to get $N$-body $N$-mers in a similar way we get trimers in usual Efimov physics?
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0answers
70 views
Action of Field Operator on Ket
I've very little experience with field operator notation so am trying to get to grips with the fundamentals.
I'm asked, if state $|\Psi \rangle$ has the wavefunction $\Psi(x_1,...,x_N)$, then what ...
0
votes
2answers
64 views
Difference between particle and state
I have recently started studying particle physics, and I was surprised by the description of hadrons. At first I was told that the $\Delta^0$ baryon was composed by one up and two down quarks, and ...
