Viewing profile — hansen

To be a bit pedantic: the identification of tensors with multilinear forms requires finite dimensions (or reflexive topological spaces).

Physicists and philosophers of science give those terms different meanings. E.g. what a philosopher of science would call a theory is called model by physicists. What physicists ca…

Spacetime is extremely stiff or equivalently gravity extremely weak. Only these extreme events result in detectable gravitational waves.

I doubt there are many users out there who care if someones analytics stuff breaks.

The standard (but rather heavy and difficult) is Abraham, Marsden: Foundations of Mechanics More gentle is Vladimir Arnold: Mathematical Methods of Classical Mechanics

I don’t think the typical “change of variables” definition is bad. You take the derivative of L along the fiber of the tangent bundle. If the derivative is non-singular it defines …

Mathematicians messed up here… A manifold with boundary is not a manifold. But a manifold is a manifold with boundary (the empty set).

Gravitational waves are disturbances in a background spacetime, i.e. you linearize the Einstein equations around a given solution. The analogy is less bad as one might initially th…

I always thought it's more about caching

The problems in the classical theory are easily understood. The charge and current densities of point particles are not smooth functions but distributions (think of the Dirac δ-“fu…

> Given the trajectories of charges it will tell you what the electromagnetic field will be, and given the electromagnetic field it will tell you how charges will move. Unfortunate…

And all those Emacs jokes don't work anymore

If you want Cᵏ to be a normed space you do |f| = ∑ᵢ₌₀ᵏ sup|f⁽ⁱ⁾|. On open domains you can also use the topology that forces uniform convergence on all compact subsets. But this wil…

> there is enough experimental evidence that is anomalous to the theories Huh? I have more the impression that Λ-CDM & SM are working just too damn good. I’m not aware of any obser…

> For example, ask a lay person about BB and they will tell you it's an explosion, in the classical sense Give her Weinberg’s book to read and she’ll come to a different conclusion…

All our accepted model of nature assume that in some sense time exists. But in general relativity it doesn’t make much sense to speak of a single event. In the same way it doesn’t …

Yeah, science isn’t about being useful and relevant in day to day life. It’s an important part of human culture and scientist should at least try to communicate their findings to g…

> Sure, but regular quantum mechanics does the same thing. It's > under-constrained and allows for too many possibilities. No it doesn’t. There are a few good guiding principles th…

Because the author is a well respected scientist and quite talented science writer & journalist. https://en.wikipedia.org/wiki/Ethan_Siegel

> their [EU] first ruling is that basically every website is not > allowed to use ads to pay itself. Of course they won’t. This is absurd.

They might be stupid but almost every website is even more stupid. Almost none offers a way out of spying.

> The GDPR requires users to be able to say no Even better, it requires the use to say “yes”.

> If it's anything like the cookie consent, It won’t. It will just replace the common “no one reads but clicks” TOS. And the user can change her mind anytime she wants. > The amoun…

> Seems to come down to having to protect users from their own lack > of understanding. I had the impression that this is rather clearly regulated by the GDPR. A user has to consen…