I Critical Energy

MathematicalPhysicist

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I believe that once I asked for what is the critical speed that above it it's considered ultra-relativistic speed and below it slow speeds.
I forgot to ask about the critical energy, what is the threshold energy that below it it's considered low energy physics and above it it's considered HEP, is there such an energy? in that case how to compute it?

I would assume one needs to use the equation ##E^2=p^2+m^2##, but which momentum and mass to insert?

Is this distinction between high energies and low energies really have a threshold?
 

sophiecentaur

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Is this distinction between high energies and low energies really have a threshold?
No. The reason is that detecting the effects of SR would depend more on the actual experiment that the velocity involved. Take a high quality Frequency Standard with you on a trip round the Earth in a fast jet and you will detect a relativistic shift. Check the pilot's watch against the watch of his brother, who remains at the airport, and you will see no (measurable) relativistic shift.
Any "threshold" energy would be totally arbitrary. But why would that matter at all?
 

MathematicalPhysicist

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No. The reason is that detecting the effects of SR would depend more on the actual experiment that the velocity involved. Take a high quality Frequency Standard with you on a trip round the Earth in a fast jet and you will detect a relativistic shift. Check the pilot's watch against the watch of his brother, who remains at the airport, and you will see no (measurable) relativistic shift.
Any "threshold" energy would be totally arbitrary. But why would that matter at all?
Then why is there such a distinction between HEP and Condensed Matter Physics?
I mean HEP= High Energy Physics so there's also low energy physics I guess, so where's the critical energy at?
 

sophiecentaur

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Then why is there such a distinction between HEP and Condensed Matter Physics?
Is there "such a distinction"? How slow is the slowest 'fast car' on the road and how low is the lowest mountain that gets climbed?
Research departments have names which give a clue about what is studied but the names are not exclusive. Knowledge about condensed matter is needed in a High Energy Physics lab and you can bet that there will be a high energy specialist working somewhere in a Condensed Matter Physics if measurements involve high energy radiation.
I'd advise not wasting time on categorising. It's the least interesting part of Science, imo.
 

Vanadium 50

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Where do you draw the line between the largest pond and the smallest lake?
 

sophiecentaur

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This is heading in the direction of Zen, I think.:wink:
 

Ibix

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But what is the dividing line between Zen and other forms of Buddhism?

More helpfully for the OP, you can usally approximate relativistic formulae and recover Newtonian ones (e.g. relativistic K.E. is ##(\gamma-1)mc^2=mv^2/2+O(v^4/c^2)##). If the neglected parts are significant to whatever precision you are measuring, you shouldn't neglect them and should consider a full-fledged relativistic treatment.
 

sophiecentaur

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Where do you draw the line between the largest pond and the smallest lake?
If you are an estate agent (realtor?) there can be a large overlap. The seller's lake could be a buyer's pond.
 

MathematicalPhysicist

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Where do you draw the line between the largest pond and the smallest lake?
So there's no difference between high and low energies? it's just a convention.
A condensed matter physicist can work in HEP and vice versa, since there's no difference.
I mean we have particles in both of them... :-)
 
There is the old-fashioned term "elastic scattering" which meant not enough energy to break anything.
 

sophiecentaur

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So there's no difference between high and low energies? it's just a convention.
A condensed matter physicist can work in HEP and vice versa, since there's no difference.
I mean we have particles in both of them... :-)
I'm really not sure what you want out of this thread. You are treating Physics a bit like Top Trumps.
 

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