Problems with UnitStep and DiracDelta
- To: mathgroup at smc.vnet.net
- Subject: [mg22789] Problems with UnitStep and DiracDelta
- From: Scot Hawkins <sah at muriel.physics.uiowa.edu>
- Date: Sat, 25 Mar 2000 03:58:27 -0500 (EST)
- Organization: The University of Iowa
- Sender: owner-wri-mathgroup at wolfram.com
I have a number of Diff Eqs to solve that of the form
r'[t] = DiracDelta[t-t1] UnitStep[t-t2]
By using
DSolve[{r'[t] == DiracDelta[t-t1]
UnitStep[t-t2],r[-Infinity]==0},r[t],t]
I get
r[t] = UnitStep[t-t1] UnitStep[t1-t2] UnitStep[t1]
Instead of my expected
r[t] = UnitStep[t-t1] UnitStep[t1-t2]
Also, I need to redefine UnitStep so that
UnitStep[t] = 0 t<0
UnitStep[t] = 1/2 t=0
UnitStep[t] = 1 t>0
Any suggestions?
Scot