Fermions Definition and 178 Threads

Homework Statement Prove that the number of electrons whose velocity's x-component is between [x,x+dx] is given by dN = \frac{4\pi V m^2 k_B T}{h^3} ln [exp(\frac{E_F -mv_x^2/2}{k_B T})+1]dv_x Homework Equations The Fermi-Dirac Distribution function: \frac{dn}{dE}=\frac{4\pi V...

Homework Statement I have been given the Hamiltonian H = \sum_{k} (\epsilon_k - \mu) c^{\dag} c_k where c_k and c^{\dag}_k are fermion annihilation and creation operators respectively. I need to calculate the ground state, the energy of the ground state E_0 and the derivative...

how many... till now how many elementary particles are disovered? what are bosons? what happens when fermions interact with bosons?

Hello. I found this forum when i was looking for some help with the following problem: --------------------------------------------------------------- There are 3 neutrons (s=1/2). The hamiltonian of the system is: H = S^2 - Sz^2 - (3/2)hbar^2 I need to found the possible states and...

In the Heisenberg picture, we move the time dependence away from the states and incorporate them in the operators. That is, if we write the time dependent state in the Schrodinger picture as |\Psi(t)\rangle=e^{-iHt}|\Psi\rangle, then an expectation value for an operator Q at time t, which we...

i have read and studyed that 1/ boson are identical particles having zero or integral spin and can not be distinguished because their wave function over lap and they do not obey Pauli Exclusion Principle means a huge number of bosons can exist inte same quantum state like photons.((EB)) 1/...

Hey I have a basic question about the Standard Model. In this forum and on other places the expression left-/righthanded fermions. Can someone explain the difference between these two types of fermions.

Hi all, I have a little problem concerning the coupling of a fermion to CP^N (or better a 2D scalar O(3) model). Its not a mathematical type of problem. I just read on "The coupling of fermions to the three-dimensional noncommutative $CP^{N-1}$ model: minimal and supersymmetric extensions"...

Has it been experimentally verified, that electrons feel gravity?

What distinguishes Fermions form Bosons in Feynman diagrams?

I read that fermions really should be massless when you write down the Lagrangian, as it violates the gauge symmetry. It's the Higgs coupled to them that give them their masses. I was so shocked. I have only learned QED and abit of QCD Lagrangian, and the fermions did have masses in the...

Homework Statement Consider two noninteracting particles p and q each with mass m in a cubical box od size a. Assume the energy of the particles is E = \frac{3 \hbar^2 \pi^2}{2ma^2} + \frac{6\hbar^2 pi^2}{2ma^2} Using the eigenfunctions \psi_{n_{x},n_{y},n_{z}} (x_{p},y_{p},z_{p}) and...

Are spinor wave functions describing e.g. electrons, necessarily describing them as massless? Spinors representing physical entities are often described as corresponding to null vectors in space-time, which suggests that they can only describe massless entities. Nevertheless, the Dirac...

Bosons, Fermions and ?? I have heard in wikipedia (a joke?? ) that appart from Bosons and Fermions (types of particles) there were another kind of 'Probabilistic distribution' ? i don't know how it was called but if we have the number of particles. <n(T)>=\frac{1}{exp(\hbar \omega )-a}...

Two identical spin-1/2 fermions are placed in the one-dimensional harmonic potential V(x)=(1/2) m w^2 x^2, where m is the mass of the fermion and w its angular frequency. (1) Find the energies of the ground and first excited states of this two-fermion system. Express the...

I'm pretty new to particle physics. Actaully, I'm brand new to particle physics (2nd year undergraduate). I've been invited into a course on the Higgs recently and have a few questions I was wondering about. I was wondering what would happen if Higgs did not couple to fermions? Does this mean...

Are they really fundamental? I am under the impression a fundamental particle would be "Stable", i.e first generation fermions. Could second and third generation fermions be composite particles of first generation fermions? Specifically, since the 2nd gen lepton- muon decomposes rapidly into...

Hello... We have 3 fermions (s=1/2) at the ground state of a harmonic oscillator moving over the x-axis with a the classic hamiltonian for a three particle oscillator : H =(1/2m)*(P1)^2 +((1/2)*m(w^2)((x1)^2)) +(1/2m)*(P2)^2 +((1/2)*m(w^2)((x2)^2)) +(1/2m)*(P3)^2 +((1/2)*m(w^2)((x3)^2)) we...

Hi, I am having trouble understanding these concepts. I checked out some websites but it still doesn't help. First of all what's the main postulate? That there exist 2 different kind of particles: bosons and fermions? What are their fundamental definitions which lead to the fact that an integer...

What will happen if two fermions, like electrons, having the same quantum numbers are brought very close to each other?

Consider a system of N (>>1) particles with mass m in a (big) volume V. What is the average energy per particle if the particles are fermions. I did some calculations and I came up with <E> = (2/3)*Fermi-energy. Is this correct? I could post my calculations but my Latech-skills are very...

This paper is interesting in that it posits a repulsive Fermionic effect (DE) to counterbalance the attractive effect (DM). I believe that he's on the right track, but it is the polarized quantum vacuum field that is the source of these forces, and these forces are fundamental properties of the...

Hello all, from Marlon's journal, I read the question "DO YOU KNOW WHY FORCE CARRIERS ARE ALWAYS BOSONS ? WHY DON'T WE HAVE GAUGE FERMIONS ?" Can anyone answer this question? :redface:

Why does 4He act like a boson but 3He doesn't? What accounts for their different behavior at low temperatures? Why does 4He act as a Bose Condensate, but 3He doesn't? I read somewhere that because 4He has an even number of fermions (2 protons, 2 neutrons, 2 electrons), it behaves as a...

I'm having a little difficulty grasping this concept of antisymmetry in a system of particles with half integer spins... well, let me put it this way. I can see what antisymmetry means in that - if we take one of the particles and interchange it with another - because of Pauli's exclusion...

Theres a little confusion in my mind as of late. How can fermions be made to act like bosons allowing it to bypass the Pauli's exclusion principle? Example: The rubidium atom they used to make the first BEC was a bosonic atom. Also, if anyone could lend some insight as to how they recently...

Why is it that when normal ordering the terms in the Hamiltonian for bosons, the commutation rules are ignored, but when normal ordering fermion operators the anti-commutation rules are used to justify a change in sign?

The question, broadly, is how many elementary particles do you expect to be in the final theory. But just to be more concrete, I have narrowed it to "fermions" as Pauli principle is the closest thing we have to ancient "impenetrability", fitting the naive idea of particle.