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481189
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location New York City
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visits member for 3 years
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I do not participate on this site any longer, except to respond to comments regarding my own text, if that text is unavailable in another form. I do not accept the political moderation atmosphere here, it is not compatible with open science.


1d
comment Path integral vs. measure on infinite dimensional space
@arsmath: This answer misunderstands nothing, you do. The problem you are bringing up is that there are sets whose measure cannot be computed, because it hinges on the answer to some undecided problem in a given axiom system, for example, a set which is the interval if ZFC is consistent and is empty if ZFC is not. Just by saying "all sets are measurable", even including sets with indeterminate measure like this one, you automatically remove any headache in defining measures on infinite volume lattices, you simply define them by Monte-Carlo simulation. This is the major gain.
1d
comment Does a Weak Energy Condition Violation Typically Lead to Causality Violation?
No, I didn't ask for an example of a spacetime that violates weak energy and doesn't have a CTC (reread the question). The negative mass Schwartschild solution is such an example. I asked for a spacetime which violates weak energy where you can't use the violation to produce a different spacetime, which is necessarily present in the theory if the first is, which does contain a CTC.
1d
comment Tensions And Pulleys With Masses
@LarryHarson: Can you read the date, dude? I am not back, I am on physicsoverflow only.
1d
awarded  homework
2d
comment Does a Weak Energy Condition Violation Typically Lead to Causality Violation?
I don't see how to model shrinking black holes classically in any way that doesn't have negative focusing somewhere. Regarding M<0 Vaidya spacetime, there is no CTC in one of these, but if you put together two boosted copies of these moving relative to each other very fast, you get CTCs.
2d
comment Does a Weak Energy Condition Violation Typically Lead to Causality Violation?
The Hawking radiation is not in a consistent classical theory, it's semiclassical (classical gravity and quantum fields) and the back-reaction is inferred, and is not added in a self-consistent way to make a new theory. The answer does not answer the question which is about pure classical GR. If you mocked up Hawking radiation as some sort of classical negative-energy flux into the black hole accompanied by positive energy emissions, it is not clear you would not get causality violations at the same time.
2d
revised Can every particle be regarded as being a combination of Black holes and White holes?
fix
Aug
25
comment Is the EmDrive, or “Relativity Drive” possible?
@Nathan: No they didn't do the test in a vacuum. They did the test in a vacuum chamber at ambient pressure, after putting the device through a vacuum cycle to simulate space. Their excuse for not running it in vacuum was that the microwave cavity devices wouldn't operate, they weren't built to work in vacuum (I suppose because they had parts using air as insulation), but if they had run the machine in vacuum, it would not push. I have no patience for this type of fraud, and I don't participate on this site, I am on physicsoverflow now, but I am responding because you asked me to.
Aug
24
awarded  Yearling
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22
awarded  Good Answer
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22
awarded  Nice Answer
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5
awarded  Nice Answer
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awarded  Nice Answer
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awarded  Curious
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27
awarded  standard-model
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12
awarded  Good Answer
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12
awarded  Nice Answer
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awarded  Nice Question
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30
awarded  Necromancer
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12
awarded  Nice Answer