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| PritishKamat |
 Posted: Thu Apr 24, 2008 8:26 am Post subject: Particle physics |
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I am reading a book which contains some, elementary info on particle physics. There are some things which i didn't get, like what's Planck's mass and what is its value?
Secondly,what is a 'scale' of energy (eg. unification scale, weak interaction scalt, etc.)?
Lastly, can we observe a force, which is a compound of two distinct fundamental forces (eg. electroweak force) if we conduct experiments at a certain energy called their "unification energy"?
I just couldn't digest the last one. Please help.
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| PritishKamat |
| Posted: Tue Apr 29, 2008 10:21 pm Post subject: |
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Why doesnt anyone answer this?
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| mitchellmckain |
| Posted: Wed Apr 30, 2008 5:16 am Post subject: Re: Particle physics |
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| PritishKamat wrote: |
I am reading a book which contains some, elementary info on particle physics. There are some things which i didn't get, like what's Planck's mass and what is its value?
Secondly,what is a 'scale' of energy (eg. unification scale, weak interaction scalt, etc.)?
Lastly, can we observe a force, which is a compound of two distinct fundamental forces (eg. electroweak force) if we conduct experiments at a certain energy called their "unification energy"?
I just couldn't digest the last one. Please help. |
Planck's mass 2.176 × 10-8 kg is the maximum mass for a quantum black hole. The idea is that a black hole this small would be affected by the principles of quantum physics and thus this would be a phenomenon of interest in the effort to develop an quantum theory of gravity - it is a test case where the effect of both general relativity and quantum mechanics would be important. This is because at this mass the Schwarzschild radius would be about the same as it quantum (Compton) wavelength (h/mc), for according to quantum physics all particles and objects can be treated as waves with a wavelength that is calculated by this formula h/mc (Planck's constant divided by the mass and by the speed of light).
The Schwarzschild radius Rs=2.96M/Ms km, since Ms = 1.98892 × 10^30 kg, for this Planck's mass this is Rs = 3.2 x 10^-35 m, which is twice the Planck's length of 1.6 x 10^-35 m. But what immediately comes to mind when I consider this is to question how long such a black hole could possibly exist since we know that black holes decay via Hawking radiation and the smaller they are the faster they decay.
Well the idea of a scale of energy is that when we look backwards in time during the big bang the temperature is higher and that represents the average energy of particle interactions at that time in the history of the universe. This is important because these represent times when symmetries between particles would exist that we do not see now because they have been spontaneously broken as the temperature of the universe decreased.
The electroweak interaction (with unification energy of 100 GeV) was verified on the Super Proton Synchrotron which reaches energies of 300 Gev. This machine discovered the W and Z gauge bosons which were predicted by the theory of Abdus Salam, Sheldon Glashow and Steven Weinberg to be the exchange particles for the weak force, by their theory which showed how the weak and electromagnetic forces could be described by the same mathematical theory.
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Last edited by mitchellmckain on Thu May 01, 2008 7:42 am; edited 1 time in total |
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| PritishKamat |
| Posted: Wed Apr 30, 2008 10:16 am Post subject: |
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What I still don't get, is that, how can you regulate the energy level or scale at which you conduct an experiment? and how do we actually "see" that two forces have been unified?
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| mitchellmckain |
| Posted: Wed Apr 30, 2008 3:40 pm Post subject: |
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| PritishKamat wrote: |
What I still don't get, is that, how can you regulate the energy level or scale at which you conduct an experiment?
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You probe these energy scales with the big colliders, like the Super Proton Synchrotron which smashes protons at high velocity create an energy interaction up to 300 GeV. When you do this then interaction which require energies of 100 GeV start to occur among all the other particle interactions which can occur.
| PritishKamat wrote: |
and how do we actually "see" that two forces have been unified?
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You don't. At least I don't think that is something you can "see". The point is that forces are described by theories and when you have a single theory that describes both forces that makes predictions and those predictions turn out correct then you say that the two forces are "united", which means they are described by the same theory. In addition such theories usually see these different forces as being the product of some kind of symmetry and that the force are not the same despite this symmetry because of spontaneous symmetry breaking. I suppose you could say that this is another prediction of the theory which you come to trust because the other predictions are correct.
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| PritishKamat |
| Posted: Thu May 01, 2008 9:42 am Post subject: |
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thanks a lot.
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