Opened 2 years ago
Last modified 2 years ago
#23427 needs_work defect
intersection of hyperbolic geodesics is wrong
Reported by:  vdelecroix  Owned by:  

Priority:  major  Milestone:  sage8.1 
Component:  geometry  Keywords:  bug 
Cc:  jhonrubia6  Merged in:  
Authors:  Javier Honrubia González  Reviewers:  
Report Upstream:  N/A  Work issues:  
Branch:  u/jhonrubia6/intersection_of_hyperbolic_geodesics_is_wrong (Commits)  Commit:  3f2878194efe7adb432c655c2afcda70c7e33e13 
Dependencies:  Stopgaps: 
Description
The following geodesics do not intersect but Sage thinks they do
sage: UHP = HyperbolicPlane().UHP() sage: g1 = UHP.get_geodesic(2*QQbar.gen(), 5) sage: g2 = UHP.get_geodesic(1/2, Infinity) sage: g1.intersection(g2) [Point in UHP 0.500000000000000? + 1.284523257866513?*I]
Change History (7)
comment:1 Changed 2 years ago by
comment:2 Changed 2 years ago by
 Branch set to u/jhonrubia6/intersection_of_hyperbolic_geodesics_is_wrong
comment:3 Changed 2 years ago by
 Commit set to 3f2878194efe7adb432c655c2afcda70c7e33e13
 Status changed from new to needs_review
New commits:
3f28781  Bug corrected. Some examples on perpendicular_bisector() modified as to pass tests

comment:4 followup: ↓ 5 Changed 2 years ago by
What about vertical geodesics?
comment:5 in reply to: ↑ 4 Changed 2 years ago by
 Status changed from needs_review to needs_work
Replying to vdelecroix:
What about vertical geodesics?
More precisely
sage: UHP = HyperbolicPlane().UHP() sage: g1 = UHP.get_geodesic(I, 2*I) sage: g2 = UHP.get_geodesic(I/2, 4*I) sage: g3 = UHP.get_geodesic(3*I, 4*I) sage: g1.intersection(g2) [Boundary point in UHP +Infinity, Boundary point in UHP 0] sage: g1.intersection(g3) [Boundary point in UHP +Infinity, Boundary point in UHP 0]
comment:6 followup: ↓ 7 Changed 2 years ago by
we also need to correct
sage: UHP = HyperbolicPlane().UHP() sage: g1=UHP.get_geodesic(1,+1) sage: g2=UHP.get_geodesic(1,1+2*I) sage: g1.intersection(g2) []
should return
[Boundary point in UHP 1]
and
UHP = HyperbolicPlane().UHP() g1=UHP.get_geodesic(1,I) g2=UHP.get_geodesic(+1,(+cos(pi/3)+I*sin(pi/3))) [Boundary point in UHP 1, Boundary point in UHP 1]
should return []
What should be the correct answer of the function in the following case?
UHP = HyperbolicPlane().UHP() g1=UHP.get_geodesic(I,3*I) g2=UHP.get_geodesic(2*I,4*I)
Maybe
[2*I,3*I]
or
Geodesic in UHP from 2*I to 3*I
comment:7 in reply to: ↑ 6 Changed 2 years ago by
Replying to jhonrubia6:
<SNIP>
What should be the correct answer of the function in the following case?
UHP = HyperbolicPlane().UHP() g1=UHP.get_geodesic(I,3*I) g2=UHP.get_geodesic(2*I,4*I)Maybe
[2*I,3*I]
definitely not
or
Geodesic in UHP from 2*I to 3*I
Much better
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It seems easy. Checking that the real part of the fixed point of both involutions lies between the real part of endpoints of both geodesics,would be a fast implementation. Are you going to tackle this? I have time these days to code it.