The Slode Package
The Slode package contains functions to find formal power series solutions of linear ordinary differential equations (LODEs), to determine points for some special series solutions (hypergeometric, rational, polynomial, and sparse series).
restart
with⁡Slode:
Create a LODEstruct Structure from a LODE
DEdetermine - Check a LODE and create the LODEstruct structure
ode:=ⅆⅆx⁢y⁡x⁢x−1−y⁡x=0
DEdetermine⁡ode,y⁡x
LODEstruct⁡ⅆⅆx⁢y⁡x⁢x−1−y⁡x=0,y⁡x
Create Formal Power/Taylor Series Solutions
FPseries - Create formal power series solutions
ode:=3⁢x2−6⁢x+3⁢ⅆⅆx⁢ⅆⅆx⁢y⁡x+12⁢x−12⁢ⅆⅆx⁢y⁡x+6⁢y⁡x
ode:=3⁢x2−6⁢x+3⁢ⅆ2ⅆx2⁢y⁡x+12⁢x−12⁢ⅆⅆx⁢y⁡x+6⁢y⁡x
FPseries⁡ode,y⁡x,v⁡n
FPSstruct⁡_C0+_C1⁢x+∑n=2∞v⁡n⁢xn,n2−n⁢v⁡n+−2⁢n2+2⁢n⁢v⁡n−1+n2−n⁢v⁡n−2
FTseries - Create formal Taylor series solutions
FTseries⁡ode,y⁡x,v⁡n,0,_A,2
FPSstruct⁡_A0+_A1⁢x+12⁢−2⁢_A0+4⁢_A1⁢x2+∑n=3∞v⁡n⁢xnn!,v⁡n−2⁢n⁢v⁡n−1+n2−n⁢v⁡n−2
Determine Candidate Points for Some Special Series Solutions
candidate_points - Determine candidate points for hypergeometric, rational and polynomial power series solutions of homogeneous LODEs with polynomial coefficients
candidate_points⁡ode,y⁡x,'polynomial'
0
candidate_points⁡ode,y⁡x,'rational'
1
candidate_points⁡ode,y⁡x,'hypergeom'
1,any_ordinary_point
candidate_mpoints - Determine mpoints for m-sparse power series
ode:=2+x2⁢ⅆ3ⅆx3⁢y⁡x−2⁢ⅆ2ⅆx2⁢y⁡x⁢x+2+x2⁢ⅆⅆx⁢y⁡x−2⁢x⁢y⁡x
candidate_mpoints⁡ode,y⁡x
2,LODEstruct⁡y⁡x+ⅆ2ⅆx2⁢y⁡x,y⁡x,0
candidate_mpoints/irreducible - Use a much faster algorithm that returns all m-points if the equation is irreducible
ode:=ⅆ2ⅆx2⁢y⁡x+x−1⁢y⁡x
candidate_mpoints⁡ode,y⁡x,'irreducible'
3,LODEstruct⁡y⁡x,y⁡x,1
Find Formal Power Series Solutions
polynomial_series_sol - Find formal power series solutions with polynomial coefficients
polynomial_series_sol⁡ode,y⁡x
∑n=0∞_C0+n⁢_C1⁢xn
rational_series_sol - Find formal power series solutions with rational coefficients
ode:=3−x⁢ⅆⅆx⁢ⅆⅆx⁢y⁡x−ⅆⅆx⁢y⁡x
ode:=3−x⁢ⅆ2ⅆx2⁢y⁡x−ⅆⅆx⁢y⁡x
rational_series_sol⁡ode,y⁡x
_C1+_C0⁢∑n=1∞x−2nn
hypergeom_series_sol - Find formal power series solutions with hypergeometric coefficients
ode:=2⁢x⁢x−1⁢ⅆⅆx⁢ⅆⅆx⁢y⁡x+7⁢x−3⁢ⅆⅆx⁢y⁡x+2⁢y⁡x=0
ode:=2⁢x⁢x−1⁢ⅆ2ⅆx2⁢y⁡x+7⁢x−3⁢ⅆⅆx⁢y⁡x+2⁢y⁡x=0
hypergeom_series_sol⁡ode,y⁡x
_C1⁢∑n=0∞n+1⁢xn2⁢n+1,_C1⁢∑n=0∞−1n⁢Γ⁡n+12⁢x−1nΓ⁡n+1,_C1⁢∑n=0∞Γ⁡n+12⁢x+1nn!
msparse_series_sol - Find formal m-sparse power series solutions
ode:=2⁢x3−2⁢x23+1⁢x9⁢ⅆ3ⅆx3⁢y⁡x9+2⁢9⁢x2−4⁢x+13⁢ⅆ2ⅆx2⁢y⁡x9+2⁢18⁢x−4⁢ⅆⅆx⁢y⁡x9+4⁢y⁡x3
ode:=19⁢2⁢x3−43⁢x2+29⁢x⁢ⅆ3ⅆx3⁢y⁡x+19⁢18⁢x2−8⁢x+23⁢ⅆ2ⅆx2⁢y⁡x+19⁢36⁢x−8⁢ⅆⅆx⁢y⁡x+43⁢y⁡x
msparse_series_sol⁡ode,y⁡x,v⁡n
FPSstruct⁡136⁢_C2+_C2⁢x−162+36⁢_C2⁢x−164+∑n=3∞v⁡2⁢n⁢x−162⁢n,−36⁢v⁡2⁢n−2+v⁡2⁢n,FPSstruct⁡_C1⁢x−16+36⁢_C1⁢x−163+1296⁢_C1⁢x−165+∑n=3∞v⁡2⁢n+1⁢x−162⁢n+1,−36⁢v⁡2⁢n−1+v⁡2⁢n+1
mhypergeom_series_sol - Find formal m-sparse m-hypergeometric power series
mhypergeom_series_sol⁡ode,y⁡x
_C1⁢∑n=0∞−19n⁢x−13⁢n+1Γ⁡n+1⁢Γ⁡n+43,_C1⁢∑n=0∞−19n⁢x−13⁢nΓ⁡n+23⁢Γ⁡n+1
hypergeom_formal_sol - Find formal solutions with hypergeometric series
ode:=3⁢x⁢y⁡x+4+4⁢x⁢x⁢ⅆⅆx⁢y⁡x+−3−3⁢x⁢x2⁢ⅆ2ⅆx2⁢y⁡x
hypergeom_formal_sol⁡ode,y⁡x,t,0
x⁡t=t,y⁡t=94⁢Γ⁡23⁢∑n=0∞−1n+1⁢Γ⁡n−76+16⁢85⁢Γ⁡n−76−16⁢85⁢tnΓ⁡n−43⁢Γ⁡n+1Γ⁡−16+16⁢85⁢Γ⁡−16−16⁢85,x⁡t=t,y⁡t=5681⁢t7/3⁢3⁢π⁢∑n=0∞−1n+1⁢Γ⁡n+76+16⁢85⁢Γ⁡n+76−16⁢85⁢tnΓ⁡n+103⁢Γ⁡n+1Γ⁡136+16⁢85⁢Γ⁡136−16⁢85⁢Γ⁡23
References
Abramov, S. "m-Sparse Solutions of Linear Ordinary Differential Equations with Polynomial Coefficients." Discrete Math., Vol. 217, (2000): 3-15.
Abramov, S. "Power Series Solutions with "Eventually Nice" Coefficients of Linear Ordinary Differential Equations." Proc. FPSAC'98. 1998.
Abramov, S. "Solutions of linear differential equations in the class of sparse power series." Proc. FPSAC'97, pp. 1-10. 1997.
Abramov, S.; Bronstein, M.; and Petkovsek, M. "On Polynomial Solutions of Linear Operator Equations." Proceedings of ISSAC '95. 1995.
Abramov, S., and Petkovsek, M. "Special Power Series Solutions Of Linear Differential Equations." Proceedings of FPSAC'96. 1996
Petkovsek, M., and Salvy, B. "Finding all hypergeometric solutions of linear differential equations." Proceedings of ISSAC '93. 1993
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