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Quantum Physics

- Mathematical description of the motion and interaction of subatomic particles. Quantum Mechanics & Field Theory
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Before posting anything, please review the Physics Forums Global Guidelines. If you are seeking help with a...
Feb23-13 08:38 AM
ZapperZ
1 30,328
I have a question in Srednicki's book regarding path integrals, but first I'll set it up so that no familiarity of the...
Aug19-09 01:49 AM
RedX
2 824
For the free photon-field: Z=exp(\frac{i}{2} \int d^4x \int d^4y J^\mu(x)\Delta_{\mu \nu}} (x-y) J^\nu(y)) ...
Aug28-09 01:29 AM
Ben Niehoff
3 693
A Dirac field can be written as two Weyl fields stacked on top of each other: \Psi= \left( \begin{array}{cc} \psi \\...
Oct22-09 11:04 PM
RedX
0 738
Both (i d/dx) and (-i d/dx ) are Hermitian. For some reason (-i d/dx ) is chosen to be the momentum operator, and the...
Oct24-09 12:08 AM
Ben Niehoff
1 632
In the expression ln(-s^2-i\epsilon) , s^2 and \epsilon are positive (this expression can result from for example a...
Nov10-09 10:35 AM
RedX
2 612
How does one begin to prove the renormalizability of a theory? Power-counting can give you a big clue about...
Nov10-09 10:28 AM
RedX
0 572
I read somewhere that the irreducible representations of Lie groups were countable. But what about translations? Isn't...
Dec12-09 09:28 PM
RedX
11 1,313
When solving Schrodinger's eqn. one comes across the expression: \frac{d^2 \psi}{dx^2}=(V-E)\psi where the mass...
Dec17-09 04:18 PM
RedX
0 811
I was posting on another thread and it got me wondering: how come a photon is absorbed in the photoelectric effect but...
Aug14-09 02:02 AM
vin300
6 1,284
I've never really understood how electron taking the form of a standing wave in the orbit of a nucleus can have...
Aug19-09 01:50 PM
Naty1
27 2,353
I'm really confused on this concept. Why is gravity considered a fictitious force and is it true that this concept is...
Jul23-10 06:11 PM
Glen Bartusch
3 1,304
I began my physics study about one year ago and learned all of classical mechanics in that year; but I am now studying...
Jul31-08 03:23 PM
humanino
4 1,768
I've been shopping economically for textbooks, and I was wondering how much difference there is between the 1994 and...
Aug25-08 05:54 PM
Reedeegi
0 1,620
After finding and reading Geroch's notes on Quantum Mechanics formulated within Differential Geometry, I was wondering...
Feb15-10 08:24 PM
humanino
3 916
I'm having trouble relating the classical (Maxwell) model for electromagnetic radiation to the quantum mechanical...
Nov30-08 01:39 PM
clem
1 1,323
A few of the formulas that I have seen for calculating Planck's constant involve, amoung other things, dividing by the...
Jan4-09 10:53 AM
jtbell
5 3,079
In QM, the energy of a particle with a non-zero rest mass is Planck's constant times the frequency. How does the...
Jan10-09 12:00 AM
daschaich
3 1,721
Does a charged particle at rest (m0>0) have more total energy than an uncharged particle with the same rest mass at...
Feb16-09 01:06 PM
Bob_for_short
7 1,470
The Uncertainty Principle is largely mathematical. For any two probability densities, if one is the Fourier...
Feb22-09 11:03 AM
nicksauce
2 2,660
In the Energy-Momentum 4-Vector of SR, energy is associated with the time coordinate and momentum is associated with...
Mar1-09 04:13 PM
atyy
7 1,190
Suppose that I have a source of monochromatic light of which I can lower that intensity so that it emits one photon,...
Aug29-09 10:00 PM
alexepascual
9 2,933
It seems like if you accelerated a massive particle to a high enough velocity (momentum), you could get it's...
Apr19-10 01:22 AM
IttyBittyBit
15 5,731
Suppose I setup a double-slit experiment and run it for, say, 15 minutes. Nothing in the experimental setup changes...
Nov25-09 10:30 PM
referframe
0 514
Suppose we are given an arbitrary multi-particle quantum system whose state function / probability density does not...
Dec8-09 03:31 AM
dmtr
1 1,551
It seems to me that, by definition, QM particles are localized in time. A “particle” in QM and the act of measuring...
Jan14-10 01:41 PM
elibj123
1 1,122
Consider a free particle traveling in one dimension represented by a wave packet with a Gaussian amplitude function. ...
Jan30-10 03:32 PM
referframe
0 830
When a photon encounters a beam splitter, say a half-silvered mirror, there is a 50-50 chance it will be reflected or...
Feb1-10 01:37 PM
Peter Morgan
3 809
Will a double-slit experiment work (exhibit an interference pattern) with a source of photons that is just...
Feb14-10 11:54 AM
the_house
3 1,015
Energy (frequency) and Time are related via the Fourier Transform of the Wave Function. A quantum state has to hang...
Feb23-10 11:41 AM
referframe
2 927
In a paper in Physical Review A, the author discusses a wave function for one particle, Ψ(r,t), where r is the...
Apr16-10 01:46 PM
SpectraCat
1 1,522
Wave functions are, of course, almost always complex-valued. In all of the examples that I have seen (infinite square...
Apr17-10 02:35 PM
referframe
0 3,570
In non-relativistic wave mechanics, the momentum-position uncertainty relationship and the energy-time relationship...
May4-10 03:29 AM
Demystifier
5 2,676
An alpha-particle produced by radioactive decay leaves a visible continuous track in a Wilson Cloud Chamber. As it...
May10-10 03:25 PM
humanino
1 904
Most of the literature that I have read on non-relativistic wave mechanics discusses experiments that measure a...
Sep18-10 09:46 AM
sweet springs
18 3,865
Massive particles have a rest energy, m0c2, and therefore a matching rest or intrinsic frequency. So, does that...
May28-10 05:36 PM
sweet springs
17 1,732
A Gaussian function is often chosen as the amplitude function for the wave packet of a single particle. It is handy...
Jun17-10 10:15 AM
alxm
2 790
What does the Ground State of a quantum simple harmonic oscillator represent physically? Thanks in advance.
Jul11-10 09:46 PM
jtbell
9 2,161
The Hermite Polynomials are solutions to the Schrödinger equation for the Quantum Simple Harmonic Oscillator. But the...
Aug15-10 08:25 PM
jtbell
1 1,310
Consider the double-slit experiment using a low-intensity source of monochromatic photons: If the intensity is low...
Aug15-10 07:57 PM
referframe
2 957
Consider 2 entangled fermions. If the spin direction of one particle is measured, then the spin direction of the...
Jun13-11 08:41 AM
Demystifier
6 902

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