What is the Doppler Shift of Matter?

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Discussion Overview

The discussion centers around the concept of the Doppler shift as it applies to matter, particularly in the context of wave-particle duality and the behavior of electrons emitted from a moving source. Participants explore theoretical implications, mathematical relationships, and interpretations related to the Doppler effect on matter waves.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether matter, given its wave-like nature, experiences a Doppler shift similar to that of waves emitted from a moving source.
  • Another participant asserts that matter can indeed be Doppler shifted, referencing de Broglie's equation and drawing parallels to classical mechanics, such as the analogy of throwing a baseball from a moving car.
  • Further elaboration includes the relationship between momentum and frequency, and how the Doppler effect can be reconciled with relativistic principles.
  • Concerns are raised about the interpretation of matter waves, including the implications of superluminal phase velocities and the source of these waves.
  • Mathematical expressions related to de Broglie and Compton wavelengths are presented, suggesting complex interpretations of energy and momentum in moving reference frames.
  • A participant expresses feeling overwhelmed by the complexities of matter waves and questions the necessity of complex probability amplitudes in quantum mechanics.

Areas of Agreement / Disagreement

Participants express differing views on the implications and interpretations of the Doppler shift in matter waves. While some agree on the applicability of the Doppler effect to matter, others raise questions about the underlying assumptions and interpretations, indicating that the discussion remains unresolved.

Contextual Notes

Participants note various mathematical relationships and assumptions that may not be universally accepted, including the treatment of energy as a complex number and the implications of relativistic effects on wave behavior.

teroenza
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Hello all,
I first must state I have very little formal experience or knowledge of physics or mathematics. This is just a random musing that I could not find an answer for.
My question is that if a source emitting waves is moving, and the waves when observed are affected by the doppler effect. If matter itself has a wave-like nature then would it be effected also? Say, an electron gun emmiting electrons moving at high speed.
Again, sorry if I am overlooking many fundamental things as I am merely an inquisitive layman.
Thank you
-ter
 
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Matter most certainly can be doppler shifted; but its much less exciting than you would think.
According to debroglie's equation, momentum and frequency are directly related (the equation says wavelength; but for our purposes i think frequency is easier to think about). If the electron is shot out, when the gun is moving towards us, it seems to be higher momentum than it is from the stationary gun frame.
This is exactly the same as throwing a baseball from a moving car - the speed of the car will add to the speed of the baseball from a stationary observer.

The doppler effect allows the debroglie relation to hold in front of relativity.
 
Thank you very much. I was afraid I would not be able to understand the answer but that makes sense.
-ter
 
lzkelley said:
Matter most certainly can be doppler shifted; but its much less exciting than you would think.
According to debroglie's equation, momentum and frequency are directly related (the equation says wavelength; but for our purposes i think frequency is easier to think about). If the electron is shot out, when the gun is moving towards us, it seems to be higher momentum than it is from the stationary gun frame.
This is exactly the same as throwing a baseball from a moving car - the speed of the car will add to the speed of the baseball from a stationary observer.

The doppler effect allows the debroglie relation to hold in front of relativity.

There are some issues for Doppler Shift on matter waves.
The wavelength is given by :-
\lambda = \frac{h}{p} where p is the momentum.
The phase velocity of the wave is:-
v_p = \frac{C^2}{v} where v is the velocity of the particle.

The wave is super luminal.
There are more fun to it.
What is exactly the source of this wave?
Assuming the particle to be the source, the wavelength measured should already be Doppler Corrected, as the source is moving with a velocity *v*.

There are loads of other fun, namely :-
\lambda_{compton} = \frac{h}{m_0C}


<br /> \lambda_{DeBroglie} = \frac{h}{mv} = \frac{h}{m_0 v \gamma } = \frac{h}{m_0 \beta C \gamma }<br />

where

<br /> \beta = \frac{v}{C}<br />

Hence,
<br /> \lambda_{DeBroglie} = \frac{ \lambda_{compton}}{\gamma \beta} <br />

Assuming that the Compton effect was done in a moving reference frame, [that is the beauty]
<br /> \lambda_{compton} = \frac{h}{m_0 \gamma C}<br />

And, hence

<br /> \lambda_{DeBroglie} = \frac{ \lambda_{compton}}{ \beta} <br />

Now, why there is a similarity here?

I am working on this for past 20 days, and I am overwhelmed by the amount of things taken to be granted about matter waves.

Some are linked here:-
http://www.springerlink.com/index/G862M2015L774784.pdf
http://linkinghub.elsevier.com/retrieve/pii/0375960184902913

I personally see, there is some issue with interpretation of matter waves.
In fact, that might unravel the idea why we need a complex probability amplitude for quantum systems.

Why I am saying this?
Consider this:-
<br /> E^2 = p^2C^2 + {m_0}^2C^4<br />

Assume this energy is a Complex number.
Check that , the last term is Compton effect. I earlier tend to go with the pC term for De Broglie wavelength, but I was wrong.

You can rewrite
E_{complex} = J pC + m_0C^2
J is the complex number `i' . Why I am assigning J to pC ? Because that is dependent on motion of a particle, which can be frozen out. [May be I am dead wrong].

Any thoughts?
 
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