# 909 Niklas

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Enthusiastic about computer graphics, vintage computing and hardware.

Niklas Rosencrantz (Stockholm, Sweden)

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 Jul9 awarded Famous Question Jul2 awarded Curious Jun22 comment Could the birthday paradox be interpreted also about deaths? The actual situation was that I mentioned the birthday paradox, and a guy said that he went to a funeral and noticed a graveyard where 3/10 deaths where the same date and I think it's perhaps not an instance of the birthday/death probability but rather an instance of locality in time and space, or some other explanation. So I could look at statistics from tombstones for real data about what we spoke about, if we can take the probability from the birthday paradox and expect it to say something about tombstone and graveyard dates in the real world. Jun22 revised Could the birthday paradox be interpreted also about deaths? edited tags Jun22 comment Could the birthday paradox be interpreted also about deaths? Thank you for the info. I studied Markov chains that perhaps could model births and deaths processes, but I couldn't take for granted that they are distributed same way. For example: If an asteroid destroys earth on a particular day and everybody dies the same day, then I suppose that it would make a difference. Jun22 accepted Could the birthday paradox be interpreted also about deaths? Jun22 asked Could the birthday paradox be interpreted also about deaths? Jun19 revised What is the hat number problem? added 3 characters in body Jun9 awarded Popular Question May19 comment Would a set of tensors be an algebraic group closed under some operation? Can we write 2 tensors as 1 tensor of tensors (similar to how we can make a superset of 2 sets)? Could the basics of rotation, translation and scaling make a good example? If the 2 matrices are tensors, can I make a matrix of matrics and still keep it a tensor of 2 or more tensors? In an application we got 3 or more matrices but I have no proof why there must be no less than 3 matrices (rotation matrix, translation matrix and scaling matrix). May19 accepted Would a set of tensors be an algebraic group closed under some operation? May19 comment Would a set of tensors be an algebraic group closed under some operation? According to Norman Biggs book discrete mathematics, a group could be a mathematical object with some operation and I think I remember an interesting example with a triangle with a rotation operation (or numbers with addition). Then I read about the kronecker delta and then I'm not sure whether we can write 2 tensors as 1 tensor of tensors. May19 comment Would a set of tensors be an algebraic group closed under some operation? Thank you for providing details. I thought there was a (conceptual) difference between how to make a statement about "all tensors" and "every tensor" since what's true for every tensor might not be true for "all tensors", which would be a set or some other way to write many tensors at once. I heard that a matrix of matrices could be a tensor, so could there be a tensor of tensors instead and therefore all tensors can be written as one tensor of tensors? May19 awarded Yearling May19 asked Would a set of tensors be an algebraic group closed under some operation? Apr7 revised Does law of excluded middle prove itself? added 189 characters in body Apr4 comment Is there a simple example of how the law of the excluded middle can be inapplicable? Similarly to statistical testing where rejecting a hypothesis is not the same as accepting the alternative hypothesis. Apr4 comment Is there a simple example of how the law of the excluded middle can be inapplicable? @dtldarek That's interesting. A practical problem I had was to model and test for "locked" XOR "unlocked" where the alternatives should be mutually exclusive and therefore we could model that with a boolean variable, but if I test an entity for the value of unlocked and find that it is false that it's unlocked, that doesn't guarantee that the system is consistent and that the entity doesn't get reported as both locked and unlocked since that is testing the system's consistency that entities don't get inconsistent values like a user account that is locked and unlocked at the same time. Apr4 answered Does law of excluded middle prove itself? Apr4 revised Is there a simple example of how the law of the excluded middle can be inapplicable? added 1 characters in body