SMeznaric

491 reputation

bio	website	physics.ox.ac.uk/qubit/…
	location	Oxford, United Kingdom
	age
visits	member for	9 months
	seen	5 hours ago
stats	profile views	40

	491 reputation	bio	website	physics.ox.ac.uk/qubit/…	visits	member for	9 months
12 badges		location	Oxford, United Kingdom		seen	5 hours ago

summary answers questions tags badges favorites bounties reputation activity

124 Actions

suggestions reviews revisions comments badges posts accepts all

Sep 14	comment	Is “Causality” the equivalent of a claim that the future is predictable based on the present and the past? You asked and I am quoting "Is the predictability of the future to whatever extent is possible (based on the present and the past) equivalent to the principle of causality?" And my answer is no. I suspect you just don't like the answer, because you want it to be yes since you thought the idea up. Sorry for disappointing you.
Sep 14	comment	Is “Causality” the equivalent of a claim that the future is predictable based on the present and the past? Whether the universe really acts this way or not is unfortunately outside the scope of science.
Sep 14	comment	Is “Causality” the equivalent of a claim that the future is predictable based on the present and the past? First, remember that the way science works is by constructing a theory that makes predictions, which are tested by experiments. If the experiments fail to square with predictions, the theory is thrown away. Now suppose you have two theories with equivalent predictions, but one says everything is caused by some point in the future and the other says it is caused by the past. It is impossible to distinguish the two theories by experiment because they make the same predictions. Therefore, the only thing I can tell you is if the concepts of causality and predictability are necessarily related.
Sep 14	answered	Is “Causality” the equivalent of a claim that the future is predictable based on the present and the past?
Sep 13	comment	Information relationship to Special Relativity Thank you for your comment. I have updated the answer to reflect what you say.
Sep 13	revised	Information relationship to Special Relativity added 82 characters in body
Sep 13	comment	Information relationship to Special Relativity OK. So basically you are saying correlations can't just arise out of the blue by themselves only through local actions. That's fine then. I missed your qualifying sentence.
Sep 13	comment	Information relationship to Special Relativity This is what you say: "Results of experiments carried out at a space-like distance are not correlated."
Sep 13	comment	Information relationship to Special Relativity I just checked it out now. There you also say that causality (Einstein locality) means that spacelike separated experiments are not correlated. Several of the other things you mention are very closely related, but seem good to me.
Sep 13	comment	Information relationship to Special Relativity This statement "This equation summarizes the fact that information cannot travel faster than light because it says that the results of two experiments separated by a space-like interval cannot be correlated." is actually not true even classically. For example $\rho = \sum_k p_k \|k><k\| \otimes \|k><k\|$. Spacelike separated measurements on this system will give correlated results. What is not possible is to send information one has control over, such as the choice of measurement operators.
Sep 13	answered	Entanglement: Is it possible to prepare and reset probabilities to send information?
Sep 13	revised	Information relationship to Special Relativity added 297 characters in body
Sep 12	revised	Tracking down the locality assumption in a CHSH inequality derivation added 720 characters in body
Sep 12	revised	Tracking down the locality assumption in a CHSH inequality derivation added 31 characters in body
Sep 11	comment	Understanding tension Think of tension as just another force. You are pulling on a rope and the rope is pulling the object. The force of the rope acting on the object is tension. This is the definition of tension, see Tension (physics).
Sep 11	revised	Tracking down the locality assumption in a CHSH inequality derivation added 469 characters in body
Sep 11	revised	Information relationship to Special Relativity added 221 characters in body
Sep 11	comment	Tracking down the locality assumption in a CHSH inequality derivation Just to clarify, I think if I used it it would probably have to be at the point where you say. But you need to convince me that I did actually use it there. This is what I cannot see - how I used it.
Sep 11	answered	Information relationship to Special Relativity
Sep 11	comment	Tracking down the locality assumption in a CHSH inequality derivation Yes, we are agreed about that. Namely, we agree that expectation of the sum is not the sum of the expectation in the quantum case. But my above argument to show that sum of expectation is expectation of sums in the local realist models used, as far as I can see, only realism. What I want to know is where did I use locality.