Shape-univ January 2003

shape-univ@cosmo.torun.pl

4 participants
2 discussions

all those constraints
by szajtan 15 Jan '03

15 Jan '03

Boud, I got your point about those constraints ;) (Maeybe there arose a little confiusion because I treat everything from the CMB point of view (CMB & rest of the world) as everything else (other methods) were just a kind of supplementary thing, some aid of narrowing our choices in space of parameters.) When we have a theory describing sth. with some free parameters, it doesnt give any constraints on unknown values until we know the values of those parameters. In that moment measurments enter the scene as some kind of calibration. Then we have a model and can derive whatever we want quantitatively. (e.g. LSS constraint - from assumption on model + "calibration" measurments ) But what if we had such a good theory that it doesnt need any additional measurmenst (except some well known physical constants) (nb measurments that introduce additional uncertanities) to predict the thing we're looking for. That would be a constraint of purely theoretical nature. (e.g. BBN constraint - only from physics of high energy particles - which happens to be more less consistent with constraints from observations of Ly_\alpha forest) Do you agree with this approach to the word "constraint" in astronomy ? Bartek ps. mentioned constraints include h uncertanity (which should be constrained externaly (eg. by SNIa constraint :)) (hmm but in this case I treat SNIa constraint supplementary not equivalently which at the beginning wasn't my intent) Maeybe this is just a nomenclature problem. We cannot deal with all methods of estimating parameters simultanously, so we pick one to ESTIMATE (DERIVE) parameters and then as an additional help treat all other estimations (comming from other methods) as CONSTRAINTS. I think thats it ! ***************r-e-k-l-a-m-a************** Chcesz oszczedzic na kosztach obslugi bankowej ? mBIZNES - konto dla firm http://epieniadze.onet.pl/mbiznes

3 5

P(k)
by Bartosz Lew 07 Jan '03

07 Jan '03

what is the true meaning of P(k) ??? bartek

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Shape-univ January 2003