Re: No trace of trace!
- To: mathgroup at smc.vnet.net
- Subject: [mg15140] Re: No trace of trace!
- From: David Annetts <dannetts at laurel.ocs.mq.edu.au>
- Date: Wed, 16 Dec 1998 03:11:15 -0500
- Organization: CRCAMET/Macquarie University
- References: <754ulc$je8@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi Peter,
>
> So I'm doing my QFT homework, and I need to know what the matrices A and
> B would look like if
>
> Tr[A] Tr[B] = Tr[AB]
>
> were true. (For example, it's true if A=B=1 or if A=-B=1). I quickly
> walk over to my computer desk, sit down and power up Mathematica. I
> enter two matrices and type Trace[A] and got wierd output.
>
> So I go to help and find out Trace is not a matrix operation.
>
> After looking for close to 5 minutes, I've concluded that the Trace
> *matrix* operation is either not present or well hidden.
>
> Can someone tell me which one?
From the Online help in version 3.0 ...
"You can get the trace of the matrix by explicitly constructing a sum of
the elements on its leading diagonal. "
eg Sum[ m[[i, i]], {i, 2} ] where m = {{a, b}, {c, d}}
It's in Section 3.7.7: Basic Matrix operations.
--
==================================================================
David Annetts _____________
http://www.ocs.mq.edu.au/~dannetts/ |C R C A M E T|
|-------------|
|_____ |
CRC for Australian Mineral |````` \ |
Exploration Technologies |`````/$\ |
Earth Sciences |````/$$$\____|
Macquarie University, NSW 2109 |```/$$$/.....|
AUSTRALIA |``/$$$/......|
phone: +(1-61-2) 9850 9280, fax (1-61-2) 9850 8366 -------------
==================================================================