A detail that I left out of my previous post is that Kostelecky and co-workers have developed a framework describing a very general set of extensions to the standard model which violate Lorentz invariance. You can find out more about this set of extensions at his website and in the papers referenced there. His framework (which I don't understand in the detail which I should) includes a set of parameters (whose values must be determined by experiment) which are Lorentz invariant in some underlying high energy theory but lead to CPT and Lorentz violations in the low energy limit (where the low energy limit includes everything from atomic clocks to the highest energy accelerators).
It turns out, however, that a standard atomic clock such as those used in the GPS satellites is not sensitive to these effects. In the measurements Kostelecky is talking about and the measurements we have done on the ground, one looks not at the standard clock frequency (based on the hyperfine transition) but instead at an auxillary frequency (a Zeeman transition) which has a first order magnetic field dependence. This frequency is sensitive (in leading order at low magnetic fields ) to the effects Kostelecky's framework predicts.
Therefore, one needs to operate an atomic clock in a slightly unusual way to search for these effects. In the hydrogen maser measurements we have performed (the Phys. Rev. D paper I mentioned) we measure the standard clock frequency while "tickling" the Zeeman frequency and record the shifts. A similar technique is being proposed in space. I wouldn't think that such a technique would be realistic on the functioning GPS satellites.
The tests that Kostelecky is proposing are somewhat different than the earlier tests. In the previous tests researchers looked for changes in the frequency difference between two clocks when they were moving at different velocities or when they were at different heights in the earth's gravitational field. These tests looked at standard relativity theory (either special or general) and checked that the predictions it made were correct. In the new tests, one looks for changes in the frequency of a clock as it points in different directions (which would be akin to an ether, picking out a prefered direction in space) or a similar effect as the velocity of the clock changes.
These tests have been performed on the ground recently by measuring the frequency of a clock as its direction relative to the stars changes due to the rotation of the earth. (For example, see Phillips, et al., Physical Review D 63, 111101 (2001) or Physical Review Letters 85, 5038 (2000)- showing off is always good.) In space, one could use the faster rotation of the space station as the atomic clocks in space which may substantially outperform ground based clocks.
Ideally, the number of photons in the pulse, after it left the apparatus in which it was trapped would be the same as when it went in. However, while the pulse is stopped, the number of photons is zero. All of the information about the pulse is stored in the atoms and the energy has been carried away by a control light beam.
In the current experiment by Phillips and co-workers which is only a demonstration of the ideas and not a useful device, they can only stop about half the light pulse and it decays away inside the atomic cloud fairly quickly, so only a small fraction of the incident photons actually come out.
In cold fusion research, they are trying to make hydrogen turn into helium. In order for that to happen, they need lots of hydrogen. While it is true that palladium doesn't burn under water very well, you'd better watch out for hydrogen. If memory serves, we've already had one fatality from cold fusion research when an apparatus exploded at SRI. (Actually, I can't remember for sure if some one died or was badly hurt, when the hydrogen exploded.) In news accounts, the researchers are always described as searching for "excess" heat. There is a reason for this! If you tell me that you've got a tank of hydrogen and you want heat, I won't tell you to try to fuse the hydrogen, I'd just burn the stuff. That's how a rocket works.
Slashdot Mirror
A detail that I left out of my previous post is that Kostelecky and co-workers have developed a framework describing a very general set of extensions to the standard model which violate Lorentz invariance. You can find out more about this set of extensions at his website and in the papers referenced there. His framework (which I don't understand in the detail which I should) includes a set of parameters (whose values must be determined by experiment) which are Lorentz invariant in some underlying high energy theory but lead to CPT and Lorentz violations in the low energy limit (where the low energy limit includes everything from atomic clocks to the highest energy accelerators).
It turns out, however, that a standard atomic clock such as those used in the GPS satellites is not sensitive to these effects. In the measurements Kostelecky is talking about and the measurements we have done on the ground, one looks not at the standard clock frequency (based on the hyperfine transition) but instead at an auxillary frequency (a Zeeman transition) which has a first order magnetic field dependence. This frequency is sensitive (in leading order at low magnetic fields ) to the effects Kostelecky's framework predicts.
Therefore, one needs to operate an atomic clock in a slightly unusual way to search for these effects. In the hydrogen maser measurements we have performed (the Phys. Rev. D paper I mentioned) we measure the standard clock frequency while "tickling" the Zeeman frequency and record the shifts. A similar technique is being proposed in space. I wouldn't think that such a technique would be realistic on the functioning GPS satellites.
The tests that Kostelecky is proposing are somewhat different than the earlier tests. In the previous tests researchers looked for changes in the frequency difference between two clocks when they were moving at different velocities or when they were at different heights in the earth's gravitational field. These tests looked at standard relativity theory (either special or general) and checked that the predictions it made were correct. In the new tests, one looks for changes in the frequency of a clock as it points in different directions (which would be akin to an ether, picking out a prefered direction in space) or a similar effect as the velocity of the clock changes.
These tests have been performed on the ground recently by measuring the frequency of a clock as its direction relative to the stars changes due to the rotation of the earth. (For example, see Phillips, et al., Physical Review D 63, 111101 (2001) or Physical Review Letters 85, 5038 (2000)- showing off is always good.) In space, one could use the faster rotation of the space station as the atomic clocks in space which may substantially outperform ground based clocks.
In the current experiment by Phillips and co-workers which is only a demonstration of the ideas and not a useful device, they can only stop about half the light pulse and it decays away inside the atomic cloud fairly quickly, so only a small fraction of the incident photons actually come out.
In cold fusion research, they are trying to make hydrogen turn into helium. In order for that to happen, they need lots of hydrogen. While it is true that palladium doesn't burn under water very well, you'd better watch out for hydrogen. If memory serves, we've already had one fatality from cold fusion research when an apparatus exploded at SRI. (Actually, I can't remember for sure if some one died or was badly hurt, when the hydrogen exploded.)
In news accounts, the researchers are always described as searching for "excess" heat. There is a reason for this! If you tell me that you've got a tank of hydrogen and you want heat, I won't tell you to try to fuse the hydrogen, I'd just burn the stuff. That's how a rocket works.
David