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 ------------- ==================================================================