- #1
PeteSampras
- 44
- 2
Hello,I am reading the link http://math.mit.edu/~jspeck/18.152_Fall2011/Lecture%20notes/18152%20lecture%20notes%20-%204.pdfSays :
[tex]w_t-D w_{xx}=f [/tex] with f<0w at [tex]\bar{Q}_T[/tex] has its maximum in [tex]\partial_p {Q}_T[/tex]. If w is strictly negative at [tex]\partial_p {Q}_T[/tex] then also is strictly negative in [tex]\bar{Q}_T[/tex](it is OK)Says [tex]u=w-\epsilon t [/tex] , [tex]u \leq w [/tex], [tex]w \leq u + \epsilon T [/tex], T is cota,
then [tex]u_{t}-Du_{xx}=f-\epsilon <0 [/tex] (1)(it is OK)Says: Claim that the maximum of u in [tex]\bar{Q}_{T-\epsilon}[/tex] is on [tex]\partial_p {Q}_{T-\epsilon}[/tex]. To verify the claim we use [tex](t_0,x_0) \in \bar{Q}_{T-\epsilon}[/tex].Says: [tex]t_0 \in (0,T-\epsilon][/tex] since if [tex]t=0[/tex] the claim is true I don't understand this .Says [tex]u_t=0[/tex] if [tex]t_0 \in (0,T-\epsilon)[/tex] (it is OK), but says [tex]u_t \geq 0[/tex] if [tex]t_0 =T-\epsilon[/tex] I don't understand this .Then using Taylor and claims:[tex]u_{t}-Du_{xx}>0 [/tex] (2) and says "which contradicts (1)" I don't understand thisBest regard.
[tex]w_t-D w_{xx}=f [/tex] with f<0w at [tex]\bar{Q}_T[/tex] has its maximum in [tex]\partial_p {Q}_T[/tex]. If w is strictly negative at [tex]\partial_p {Q}_T[/tex] then also is strictly negative in [tex]\bar{Q}_T[/tex](it is OK)Says [tex]u=w-\epsilon t [/tex] , [tex]u \leq w [/tex], [tex]w \leq u + \epsilon T [/tex], T is cota,
then [tex]u_{t}-Du_{xx}=f-\epsilon <0 [/tex] (1)(it is OK)Says: Claim that the maximum of u in [tex]\bar{Q}_{T-\epsilon}[/tex] is on [tex]\partial_p {Q}_{T-\epsilon}[/tex]. To verify the claim we use [tex](t_0,x_0) \in \bar{Q}_{T-\epsilon}[/tex].Says: [tex]t_0 \in (0,T-\epsilon][/tex] since if [tex]t=0[/tex] the claim is true I don't understand this .Says [tex]u_t=0[/tex] if [tex]t_0 \in (0,T-\epsilon)[/tex] (it is OK), but says [tex]u_t \geq 0[/tex] if [tex]t_0 =T-\epsilon[/tex] I don't understand this .Then using Taylor and claims:[tex]u_{t}-Du_{xx}>0 [/tex] (2) and says "which contradicts (1)" I don't understand thisBest regard.