From mboxrd@z Thu Jan 1 00:00:00 1970 To: 9fans@cse.psu.edu From: "Douglas A. Gwyn" Message-ID: <3C58D3A5.32A15546@null.net> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit References: <3C57AF73.727F8CE9@null.net>, <15447.54321.120322.757656@nanonic.hilbert.space> Subject: Re: [OT] Re: [9fans] Getting started in Plan9 - help Date: Thu, 31 Jan 2002 09:43:03 +0000 Topicbox-Message-UUID: 49bf71da-eaca-11e9-9e20-41e7f4b1d025 paurea@gsyc.escet.urjc.es wrote: > Anyway I think you confusing the c.p. with the wedge product which is > it's dual in an special case. No, read on... > As far as I know the c.p. of two vectors is a vector. No, it is not, and the fact that people treat it as one is the problem. The *geometric object* that is the closest thing to the c.p. is a skew tensor (practically the same as wedge product), which (only) in 3D has Cartesian components that resemble those of a vector, *except* that this pseudo-vector *flips* under reflection (unlike a genuine vector). Unfortunately, physicists have been trained to express Maxwell's laws as a relationship between a genuine vector (field) and a c.p., which means that that expression of those laws *changes* under reflection, something that physicists are *not* taught and which appears to have been overlooked in the analysis of the (nonconservation of) parity experiment. Apologies for being off-topic, but the subject arose in this group..