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22 views

What is the most general definition of a bosonic Gaussian state?

I am reading this paper where the definition of the bosonic state is mentioned on page 2 here :- http://arxiv.org/pdf/0806.1625.pdf . From a general definition of any density operator in terms of ...
1
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1answer
42 views

Adding versus multiplying identical photons' wavefunctions?

I am currently confused with understanding many identical photons' wavefunctions. I think that photon wavefunctions are supposed to be multiplied together to describe the total state of all bosons. ...
4
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0answers
61 views

Why are interactions always mediated via bosons (as opposed to fermions)? [duplicate]

Weak, Strong and electromagnetic force are mediated via bosons. I've come across the Walecka-model where the exchange particles are $\sigma$ and $\omega$ mesons; bosons again. why are interactions ...
0
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0answers
38 views

Quick question on degeneracy of harmonic oscillator states

I'm currently learning about symmetry between particles. For a simple case of two non-interacting particles at $x_1$ and $x_2$, we know that the wavefunction can be written as $\psi_{n_1, n_2} = ...
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2answers
2k views

Can He-4 atoms create black holes?

Suppose that in the intergalactic space far from any significant gravitational attractors there is a relatively small concentration of He-4 atoms. Due to gravitational attraction fermions in this case ...
0
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1answer
43 views

Would QM be detectable in a all boson universe

If there was a universe with the same laws as this one, but there were only bosons in it, would QM 'do anything'? Would there be any QM effects - such as an energy level (but that would require ...
0
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0answers
22 views

Is there a finite frequency of physical interactions?

If particles use gauge bosons to convey information about various forces then is there something like a finite "refresh rate" at which they update information about themselves?
0
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1answer
81 views

Amplitudes involving Goldstone bosons

Does anyone know some theorem or statement about amplitudes involving only Goldstone bosons in theories with spontaneous symmetry breaking in the limit of low energies?
4
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2answers
186 views

Spin-statistics theorem proof details

Recently I have read one book where there was some incomprehensible proof of the Pauli's spin-statistics theorem. I want to ask about a few details of the proof. First, the author derives ...
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0answers
43 views

For the two identical particles scattering, How can i identify two particles are bosons or fermions?

If two particles are scattered. How can i know those two particles are bosons or fermions?
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3answers
704 views

Meaning of the chemical potential for a boson gas

My lecturer told me that the mu is the Chemical potential is zero or negative, in the following example, mathematically it acts as a Normalisation constant. But is there any Physical insight about why ...
4
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1answer
106 views

Ground states of Chiral Boson Theory with tunneling

I am reading this paper(pdf) and on page 11, the chiral boson theory on a cylinder is studied when both edges of the cylinder are brought in close proximity so that electron is allowed. Why is it ...
5
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1answer
110 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 ...
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0answers
22 views

Quantum Mechanisms for Isotope Fractionation

Are there any quantum properties that would enable isotope fractionation? For example, atoms with odd versus even numbers of neutrons are fermions and bosons, respectively. Has any work been done ...
3
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1answer
58 views

Boson calculus and Maximum Weight State

I'm just going over a few past exams for tomorrow, and I've come across a question that I'm having quite a bit of difficulty with. Let $\left|0\right\rangle$ denote the Fock vacuum state so that ...
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votes
1answer
182 views

Has the spin and parity of the Higgs boson been experimentally confirmed? [closed]

I read in a newspaper that the Higgs boson might be the new boson but that this was not confirmed, because we don't know its properties, e.g. its spin or parity. Now I see it confirmed that it is the ...
12
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3answers
287 views

Why are all force particles bosons?

All of the force-particles in the standard model are bosons, now my question is pretty short, namely: Why are all force particles bosons? This can't be a coincidence.
1
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1answer
139 views

2N Fermions $\stackrel{?}{=}$ N Bosons

We know that we do have composite particles (for example Atoms) made of fermions or bosons or mixture of them with fermionic or bosonic statistics. So why can't a gas of $2N$ fermions become a gas of ...
2
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1answer
155 views

Almost identical fermions fighting for the same state

In quantum 101, we all learned that identical particles behave strangely, even in the absence of interactions: no two fermions can be in the same state, but bosons love to be in the same state. But ...
3
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1answer
151 views

SUSY as the only way to unify bosons and fermions

Is SUSY really the only known approach to "merge"/unify bosons and fermions in a common framework? BONUS question: If SUSY does exist at high energy, it seems unnatural and "not simple" in the sense ...
2
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1answer
152 views

Vectors of polarizations from vector boson field solution

Let's have the solution for vector boson Lagrangian in form of 4-vector field: $$ A_{\mu } (x) = \int \sum_{n = 1}^{3} e^{n}_{\mu}(\mathbf p) \left( a_{n}(\mathbf {p})e^{-ipx} + b_{n}^{+} (\mathbf p ...
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3answers
197 views

Fermion vs. Bosons and particle vs. wave: is there a link?

I'm puzzled since several years on this basic aspect of quantum mechanics. Quantum theory is supposed to describe particle-wave symmetry of our world. It also describes our universe in term of bosons ...
4
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1answer
255 views

Atoms: boson or fermion? [duplicate]

The spin of fundamental particles determines if they are bosons or fermions. The atoms also have bosonic or fermionic behavior, for example $\require{mhchem}\ce{^4He}$ has bosonic and $\ce{^3He}$ has ...
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2answers
231 views

Fermions in the same state

I need some clarification of what is meant when someone says "fermions cannot occupy the same quantum state". Consider two bosons: $$\psi(\vec{r_1}, s_1, \vec{r_2}, s_2) = \frac{1}{\sqrt{2}} \left( ...
5
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1answer
181 views

Operator norm of creation and annihilation operators

Are the creation and the annihilation operators $a(f)$ and $a^{\dagger}(f)$ for the bosonic Fock space bounded? What is their norm? So far I did not have found any note about this in the linked ...
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2answers
162 views

Indistinguishability in Quantum Mechanics

When describing the defining characteristics of bosons and fermions, I have a problem with the idea of "label switching" - whereby you have the wavefunction for two particles and the particles' labels ...
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0answers
110 views

How to understand the matrix behind a Hamiltonian?

thanks to the answers I received to my previous questions, I could derive correctly an elegant partition function for my problem which resembles a second quantized model taking the particles to be ...
2
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1answer
75 views

Bose gas with $T = 0$ and $\mu < 0$

Is it possible to have a Bose gas with $T = 0$ and $\mu < 0$ ? I think that there is a problem, because all the states $k$ are such as $$\langle n_k \rangle = \dfrac{1}{e^{\beta \{\epsilon_k - ...
3
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2answers
212 views

Composition of squeeze operators?

I'm wondering if it exists a composition law for the squeezing operation ? I guess so for geometric reason, since they are (generalized, and the phase is annoying of course) hyperbolic rotations of ...
4
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3answers
579 views

Chemical potential of a Bose gas

In my course, there is this fact : In a Bose gas, the chemical potential $\mu$ must always be lower than the smaller level of energy $\epsilon_0$. I find this strange, because if we put a Bose ...
1
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1answer
222 views

How to derive the expression for Bose-Einstein distribution variance?

Can anyone point me to a derivation of this expression? $n_s$ is the number of bosons in a state.
4
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3answers
993 views

How do particles become entangled?

A person asked me this and I'm just a lowly physical chemist. I used a classical analogy (how good or bad is this and how to fix?) Basically, light has a net angular momentum of zero, insofar as ...
1
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0answers
42 views

How does a state vector change under an exchange of a boson and a fermion?

How does a state vector change under an exchange of a boson and a fermion ? That's how is $\Psi_{\alpha,\beta}$ related to $\Psi_{\beta,\alpha}$ where $\alpha$ and $\beta$ are a boson and a fermion ...
4
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1answer
153 views

First order coherence function in terms of momentum distribution function

Can someone show me how the first order coherence function $G^1(r,r')\equiv \left \langle \hat{\Psi}(r)\hat{\Psi}(r') \right \rangle $ for a system of bosons is related to the momentum distribution ...
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4answers
692 views

Huge confusion with Fermions and Bosons and how they relate to total spin of atom

I am supremely confused when something has spin or when it does not. For example, atomic Hydrogen has 4 fermions, three quarks to make a proton, and 1 electron. There is an even number of fermions, ...
7
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1answer
603 views

How can a massless boson (Gluon) mediate the short range Strong Force?

I thought massless particles were mediators for long range forces such as electromagnetism and gravitation. How can the massless gluon mediate the short range strong force?
3
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2answers
446 views

Canonical partition of a boson gas

I have a 1D gas made of $N$ particles placed in a harmonic potential well, so the Hamiltonian is: $$ \mathcal H = \sum_{j=1}^N \left ( \frac{p_j^2}{2m} + \frac{1}{2}m\omega^2 x_j^2 \right )$$ The ...
7
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2answers
202 views

Combining two finite number fock spaces into one

Say I have two separate systems of identical Bosons, one with N Bosons the other with M. System one is described by a state $|\psi_1\rangle$ the other with $|\psi_2 \rangle$ which are expressed in a ...
2
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1answer
160 views

number of gravitons launched by a proton

The wikipedia article http://en.wikipedia.org/wiki/Gauge_bosons describes how in QM exchanges of gauge bosons carry force, and describes how the graviton may also be a gauge boson. If the observable ...
7
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3answers
256 views

Why do Photons want to be together?

So I've heard that when a photon flies by a atom excited enough to release a photon there's a good chance it will. Because Photons want to be together and have the same direction etc? Is this true? ...
0
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0answers
68 views

Why is the transition into N proportional to N+1?

I am having trouble understanding the origin of the bosonic stimulated emission. How can I qualitatively understand why bosons Boson's attract each other into similar quantum states. The furtherst I ...
3
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1answer
200 views

Decay of a particle

Would someone please explain the following found on P. 125 of these notes? On the other hand, two $π^0$’s cannot be in an $l = 1$ state. The reason for this is that pions are bosons and so the ...
7
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2answers
274 views

Is there record of a bosonic Stern-Gerlach measurement?

I cannot seem to find any peer-reviewed (or other) reference to an integer-spin Stern-Gerlach experiment. It shouldn't be too hard to do: just find you friendly neighbourhood Deuterium ion and shoot ...
1
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0answers
135 views

Fock picture of bosonification in condensates

I want to understand how bosonification in a condensate must be interpreted in the Fock states picture Say i have uncoupled fermions in a set of states $E_1$, $E_2$ ... over the vacuum $E_0$. They ...
2
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0answers
145 views

photon and Z boson interference?

I'm not certain that this question will make sense, but here goes... In most monte carlo generators, when Z events are produced, there is a lower mass cutoff on the Z pole. I've been told that this ...
5
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1answer
192 views

Probability enhancement for bosons: Probability goes over 1?

It is said that if there is already n bosons in a particular quantum state, the probability of another boson joining them is (n+1) times larger than it would have been otherwise. But if we apply this ...
3
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1answer
245 views

Understanding the Bose-Fermi dichotomy

I'm an amateur on a quest to understand QM. In various places (such as early in chapter III.4 of the Feynman Lectures) I have seen an argument that looks like it's trying to convince me that any class ...
0
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2answers
5k views

Degeneracy of Energy Levels for 2 identical particles in a One Dimensional box [closed]

i am studying for a physics exam and came across an exercise i cannot seem to crack. I have read through Feynmans lecture books & a lot of the internet but i am somewhat stuck. first the question, ...
7
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1answer
198 views

Who added $\frac{3}{2} \partial^2 c$ to the virasoro BRST current (and why)?

I've been looking at the literature on quantizing the bosonic string, and I noticed that there was a change made in the definition of the BRST current around 1992. However, I haven't found any ...
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0answers
196 views

Can the mass of longitudinal and transverse W bosons be measured separately?

Some higgsless unified models of particle physics predict that the mass of longitudinally polarized W bosons and the mass of transversely polarized W bosons are different. In those models, a ...