Spherical Equilateral Triangle with Neumann Bounds

The region examined here is the Spherical Equilateral Right triangle under Neumann Boundary conditions. Side lengths are pi/2. This triangle was one of our test cases to determine the accuracy of MATLAB's finite element solver in spherical space and whether we could accurately assume that we could treat the remainder of the error as a portion of the geometric series. This is because this triangle is one of the regions for which the eigenvalue spectrum is known: the ith distinct eigenvalue is equal to 2(2i-1)(i-1), and has multiplicity i. It confirmed both that the MATLAB solver was very accurate in Spherical Space, and that our estimate of the remaining error resulted in even more accurate values. Together with our other known cases, this triangle also helped us to determine that the accuracy of the built in solver begins to deteriorate after the first approximately 250 eigenvalues.

Here are the counting graphs for the eigenvalue spectrum, using the true values since the spectrum is known. The first approximately 1250 values were used here.

Here are the difference graphs for the eigenvalue spectrum, using the true values since the spectrum is known. The first approximately 1250 values were used here.

Below is the Eigenvalue spectrum for the Spherical Equilateral Right triangle. These are the calculated and predicted eigenvalues, accompanied by their true values. This also demonstrates that more than three refinements of MATLAB's auto-generated mesh should be done for regions where the true value of the spectrum is not known.

Spherical Equilateral Right Neumann Triangle      
       
Refinements    PredictedTrue Value
0000 -0.0270211320
6.0224739356.0057617026.0014538846.000364586 5.9999818646
6.0514079856.0130129456.0032710286.000819345 5.9999579526
20.2531855520.0648472220.0163570220.00410129 19.9997952820
20.4749809720.1196004320.03001520.00751455 19.9996090720
20.5276285320.1332924520.0334941320.00838938 19.9995688920
43.131621442.2899998842.0732392942.01837384 41.9990970142
43.875792642.4734575942.1189508542.02979249 41.9984669442
44.125397242.5355096942.1345057142.03368731 41.9982650242
44.3801781142.5963026642.149530342.03743369 41.9980488442
75.2989620572.8413980172.2120938372.05317485 71.9973390772
77.0762654773.2844996872.3230605772.0809453 71.9958787272
78.1428835573.5385044872.3857548572.09656718 71.9949618472
78.5467293473.636727372.4100026472.10261061 71.9946092172
79.2474498773.8003267472.4499567372.11252443 71.9939684672
117.6122072111.938759110.4883701110.1224134 109.9938355110
121.1982679112.8246661110.7097894110.1778047 109.9908932110
123.7572266113.4586929110.866706110.2169071 109.988602110
124.7378116113.6908614110.9248748110.2315033 109.987889110
125.063357113.7537964110.9393762110.235044 109.9875787110
126.7967412114.2085195111.0529406110.2634203 109.9860245110
171.1135306159.8340868156.9653951156.2420025 155.9878404156
177.4731258161.4175636157.3601667156.3406479 155.9824426156
181.629507162.4753912157.6243247156.4066538 155.9788282156
184.8327994163.216984157.8083992156.4527059 155.9763865156
185.1158149163.3631838157.8442251156.4615284 155.9757215156
186.9522811163.8063933157.9531464156.4885394 155.9739535156
190.7003731164.6431926158.1497681156.5368743 155.9701882156
237.9921033216.9952988211.7543671210.4392823 209.9772306210
247.8197193219.6017761212.4111204210.6039141 209.9689569210
254.1559756221.2806061212.8282727210.7078883 209.9628966210
259.8683006222.6887228213.1707578210.7929047 209.9574521210
261.3727012223.1607139213.301111210.8264278 209.9569542210
263.5480284223.8695359213.4683447210.8673221 209.9534596210
265.6450881224.5501125213.6254491210.9055662 209.9499424210
268.0263411224.9512275213.7443604210.9370309 209.9506829210
318.3159965283.625032274.9131603272.7292702 271.961966272
332.8021854287.6803215275.9356711272.985558 271.9490433272
341.0452905290.0566677276.5345206273.1355559 271.9413385272
346.9598872292.652752277.1761862273.2941265 271.9301748272
352.342888293.6227812277.4419496273.3640034 271.9312276272
355.4787413294.2476044277.5344185273.3825485 271.9237996272
360.5137388295.8075453277.9349557273.4816536 271.9169974272
364.2046668295.9258686277.961401273.4902485 271.9193206272
365.304924298.4459868278.6067504273.6509143 271.909694272
417.4546348360.7771282346.6789392343.1695511 341.9365367342
434.7783981366.2874707348.0800322343.5213092 341.9196137342
438.4027501370.1472881349.0318599343.7587294 341.9060285342
448.8529086372.6974969349.6881483343.9232409 341.8977556342
452.7876779374.7350528350.2047097344.0522724 341.8906294342
462.2846611376.7052282350.6976902344.1752998 341.8836747342
464.2266032378.6852663351.111677344.2729679 341.870205342
473.5177878379.194184351.2857514344.3218416 341.8750898342
477.8248314380.5401207351.713115344.4320108 341.8738136342
491.306572383.8083331352.4821954344.6214732 341.8596287342
527.9555909447.2686654426.8062077421.7019998 419.9086495420
544.7527604454.7905019428.8063015422.2098506 419.8922045420
556.16824459.7510277430.0256193422.5127261 419.8730904420
565.6607968465.1336374431.3560815422.8430549 419.8520249420
571.9647613468.9432575432.3703342423.1002631 419.8432475420
575.5765583470.3852505432.7508952423.1948267 419.8373267420
578.9785834473.1292163433.37341423.3453069 419.8219588420
588.3124441475.1989406433.8421301423.4622249 419.8152719420
603.5863143478.095471434.3943071423.5884819 419.7918831420
619.0324783482.2507201435.3482487423.8207906 419.7706479420
654.6850222485.5053342436.2113916424.0407706 419.7646543420
657.9245216545.3577806515.8249794508.4566667 505.8678291506
675.1084658560.2760293519.5306892509.3811531 505.8151398506
690.3040127563.1620968520.3421836509.590109 505.8123953506
701.6791494568.5512383521.7982082509.9590219 505.7993543506
706.8464495576.4346726523.747045510.442935 505.7685702506
712.7145366580.3222304524.5201831510.6197337 505.7358466506
718.1572101581.9660267525.0621194510.7659397 505.7430138506
738.9153091585.3452526525.7317981510.9178592 505.7130199506
762.7755784588.6917268526.5090861511.1144349 505.7055639506
772.8486914590.6161457527.0890198511.2571013 505.6945975506
786.2187106594.7247954527.9825322511.4887596 505.6937152506
809.6756322602.8204807530.193181512.0329345 505.6523788506
822.7214113655.5586811613.7884521603.4416981 599.8063927600
839.087962672.814485618.152937604.5369241 599.7529731600
852.6884094681.6366196620.2290584605.0466049 599.712289600
862.0856209690.0072198622.5270006605.6322052 599.6962624600
880.5949464694.4555727623.7350001605.9386329 599.6859252600
894.8034842701.6932216625.4115554606.3370167 599.6352267600
906.5816063707.8939957626.877938606.7069187 599.6198831600
919.9836068711.7723659627.7837739606.9091085 599.5748487600
931.4419853712.4955564628.1227664607.0193139 599.6046703600
945.3014297715.0167014628.7523923607.1748298 599.5936089600
962.0036604718.6445839629.6526928607.3934049 599.5726616600
968.5987905723.6517661631.0033571607.7493676 599.5791384600
981.7565754736.3247094633.8057237608.4206679 599.501694600
993.9730951776.7076088720.6168233706.6508755 701.7439757702
1022.02989795.3604556725.6614239707.9386778 701.7118367702
1035.53577812.2785944729.2022989708.7798367 701.6044573702
1062.464401825.0624992732.5867472709.6263604 701.5592877702
1078.490786830.7928873734.1242196710.0206518 701.5519254702
1098.819412841.2754739736.6684454710.6288897 701.4799589702
1118.809243842.7454391737.1722213710.7916457 701.5228985702
1169.711118850.5704467739.5285926711.3317587 701.4248738702
1185.916501854.356565739.6598777711.3949882 701.4641921702
1192.436173855.5472307740.6544702711.6493925 701.4585332702
1199.560106858.0488865741.3868004711.8472879 701.4686564702
1205.226507865.1910513742.8585939712.164162 701.3797526702
1223.424448872.8907201745.0901305712.7512682 701.3890923702
1252.760949886.0588238748.3527672713.5546723 701.3284514702
1257.499632917.2351432837.8340696818.4294337 811.6116649812
1290.204458939.0340854844.06219820.0382881 811.5975522812
1303.892437959.446227848.1841487820.9940034 811.4408159812
1331.365988970.5906931851.6646644821.9029591 811.4462606812
1338.297089982.8376731853.8487388822.4042907 811.356365812
1347.661194991.7758761857.2305366823.2824549 811.354884812
1355.378862996.3409894858.3332989823.5605611 811.3432493812
1388.4377341009.409013861.3984248824.3155327 811.2865542812
1422.8270571015.412447862.1364774824.406597 811.1503009812
1451.4539471018.857355863.5361963824.8138403 811.2088404812
1482.2638321020.442609864.6308903825.1017541 811.213294812
1508.1401241023.617948865.8157049825.4299734 811.2405508812
1526.0879921027.291174866.4042314825.5572628 811.2057857812
1545.6102011036.84911869.481435826.3975253 811.2601047812
1554.5103071064.273033874.3665404827.4807187 811.0075062812
1590.5811811065.820289963.3727127938.3084831 929.5022307930
1605.1533591096.261605971.4127774940.3456634 929.430313930
1627.645831126.250162977.5004273941.7646995 929.2090437930
1669.8660421132.603485980.9094357942.7213959 929.3041265930
1680.9318131143.193005983.5349376943.3572048 929.240862930
1732.2215461156.758669986.9183407944.221829 929.2205197930
1747.7562891159.638738989.2103894944.8063833 929.2051503930
1822.9724531177.143929992.542855945.6117224 929.1225899930
1867.1892691185.260158994.0531497945.9303939 929.0225877930
1883.7397761191.139278996.1050268946.4762859 929.0393558930
1905.1163641194.998333997.339493946.7738475 929.0077383930
1925.6297371202.96774999.3816401947.2418848 928.9227162930
1944.8687881206.0651941000.797833947.6109298 928.9238487930
1975.0219141211.0608381001.676215947.8512186 928.939945930
2046.2421111221.4720421006.194703949.053404 928.976956930
2134.0005661228.0503551012.019668950.43107 928.7920748930
2162.7396181244.9719871098.5613081066.595149 1055.3639211056
2214.316361265.8748861108.5821231069.161834 1055.3116171056
01301.3169451116.3935841070.983785 1055.0291691056
01310.181521119.7894991071.942154 1055.1311131056
01330.7455421125.0465211073.200927 1054.9851111056
01335.344371127.2084221073.831024 1055.0770131056
01356.4494981133.4268571075.328132 1054.9152951056
01357.9475791134.278941075.581596 1054.9584361056
01372.662991138.1211561076.37123 1054.6755531056
01377.6983351139.1954351076.712476 1054.7592491056
01384.5049381141.7595681077.31713 1054.6754461056
01395.529061142.4701641077.542865 1054.7308251056
01399.5097281145.8537891078.3652 1054.6532591056
01409.1985421148.1496751078.869146 1054.527611056
01413.7385351148.8085621079.093911 1054.5998481056
01419.9530861153.7730071080.46782 1054.7122311056
01420.4421791162.1957391082.484037 1054.4775361056
01449.2962011245.3700051203.731689 1189.1021741190
01454.3355661255.7002371206.425527 1189.1129851190
01502.8528551267.5870861209.184546 1188.6649641190
01509.0069011269.1311111209.796006 1188.948771190
01526.7294131276.7541611211.642809 1188.7661031190
01542.3482931279.3565161212.259963 1188.6857621190
01554.0823831285.8316541214.009978 1188.7756181190
01562.8047311288.2656831214.37258 1188.4104291190
01569.8117641292.9074061215.682048 1188.5491181190
01573.3346721294.5200181216.006039 1188.4203551190
01590.5241991296.9149231216.617016 1188.4045541190
01598.4299691298.0777681216.901715 1188.3807181190
01606.9122461301.3917361217.807641 1188.4405841190
01612.0464831303.9032091218.365384 1188.3118891190
01617.903021308.0727091219.196957 1187.9706911190
01627.1153061308.6227821219.525324 1188.2211621190
01634.8996851314.0025551221.21552 1188.6150341190
01652.6740991323.9732541223.462557 1188.1483831190
01662.6792931401.1567391349.115508 1330.8309551332
01676.2285671414.2415221352.53321 1330.8521541332
01723.142151428.4470591355.852576 1330.3466911332
01726.7759471430.058381356.386102 1330.5015371332
01743.2413941440.2068261358.962978 1330.4181611332
01756.1288391441.1002251359.167511 1330.3806641332
01761.309861448.8501551361.209761 1330.4175351332
01772.9269171454.6359941362.598335 1330.2611411332
01787.0030511457.0948951363.313557 1330.3637261332
01791.173881463.6759581364.709018 1329.9372391332
01804.338651464.569821365.134756 1330.1985021332
01811.2412731467.7149231365.577534 1329.6918261332
01821.3752961469.5659031366.053017 1329.6840321332
01836.6439521472.8284221367.100284 1329.9529761332
01843.2652431476.4163791367.972759 1329.8713731332
01848.9667361479.8431391368.582896 1329.4918971332
01866.4507561480.8787381368.95986 1329.637451332
01868.7093151491.117411372.025294 1330.1825871332
01892.4073761503.2993991374.76406 1329.60351332
01900.8828871568.0305181503.274407 1480.5225151482
01935.7531461582.5357791507.031546 1480.5033291482
01947.6249361599.798511511.251753 1480.1410791482
01957.1864621601.3313661511.571592 1480.0347261482
01979.7091351612.7690141514.553963 1480.0463581482
01984.2154851618.3044361515.976061 1480.0232511482
01991.0423841624.0944171517.538121 1480.0998421482
01998.2650431633.3791941519.697343 1479.7555181482
02005.2395431633.8288921520.029221 1480.0460011482
02019.6643641641.9950841521.83583 1479.6181871482
02026.9916551645.7252981522.523041 1479.2362451482
02038.2375751647.8629031523.314586 1479.5548561482
02058.3814251649.931941523.686698 1479.3307581482
02070.0452351651.9777151524.22466 1479.3389541482
02072.2687311659.4444291526.058038 1479.1930741482
02093.4693981660.693651526.835138 1479.8042951482
02095.0962421664.1128321527.211013 1479.1109121482
02102.8354221667.1373311528.129533 1479.2895011482
02120.7141751679.1664481531.507719 1479.6282061482
02132.9678511694.4829791534.958247 1478.9096431482
02149.4569871744.6354271665.838743 1638.1537311640
02180.9685561758.6958271669.707659 1638.4418951640
02189.7426221780.6194711675.057629 1637.9687481640
02203.7108341784.6040521675.913328 1637.7251231640
02215.4991711797.2260471679.159673 1637.6773561640
02224.80711806.3102021681.403729 1637.5181621640
02234.4605731810.1582741682.465592 1637.6010971640
001821.9015121685.534095 1637.6217541640
001825.0941151686.134773 1637.3117661640
001834.4632391688.325108 1636.9798531640
001837.7471631689.213699 1637.0268491640
001840.5617451690.118382 1637.2604951640
001846.2216291691.347527 1636.932911640
001848.8444771691.629137 1636.3919331640
001849.5758591692.072889 1636.7346261640
001855.7556021694.134904 1637.3498881640
001860.9335541694.927914 1636.6022611640
001864.0248891695.661635 1636.507641640
001868.9395531696.752751 1636.2553621640
001882.2961341701.077413 1637.4066821640
001904.0644251705.671326 1635.9664221640
001934.3906261837.615967 1803.614441806
001952.255891842.374185 1803.7675311806
001976.2473951848.360403 1803.4276391806
001983.1955651849.72132 1802.8254881806
001993.802111852.587807 1802.9725261806
002005.9680811855.829291 1803.0784141806
002006.7388371856.361285 1803.526521806
002022.115711860.092568 1803.1661541806
002030.2670561861.885365 1802.7248921806
002036.7306231863.586096 1802.7522131806
002046.07351865.249828 1801.7178971806
002048.6680981866.258781 1802.1697381806
002049.6783671866.796544 1802.5414881806
002057.2174991867.943539 1801.4426211806
002060.2235111868.996273 1801.8090761806
002062.2190621870.049734 1802.5315371806
002071.8336581872.254463 1802.1328281806
002074.0526061872.853576 1802.1628161806
002078.9094231873.816482 1801.7576071806
002085.8434751875.224738 1801.2243881806
002097.9627231880.534391 1804.1415081806
002124.3552791885.906096 1802.1275911806
002135.5181872018.192524 1976.9704551980
002151.4592142022.711127 1977.4758191980
002183.4811622030.416182 1976.6371951980
002193.3615872032.795513 1976.3810371980
002201.7068832035.269583 1976.7922671980
002216.8343522039.50005 1977.1941011980
002218.9545992039.688643 1976.7040111980
002233.4647862043.497385 1976.7528291980
0002047.053337  1980
0002047.812831  1980
0002050.967382  1980
0002051.780115  1980
0002052.376745  1980
0002053.69863  1980
0002054.833817  1980
0002056.697869  1980
0002057.310221  1980
0002059.85662  1980
0002060.526148  1980
0002061.421791  1980
0002063.296968  1980
0002069.763492  1980
0002075.892584  1980
0002207.334989  2162
0002213.258818  2162
0002221.079148  2162
0002224.770503  2162
0002226.270544  2162
0002232.393472  2162
0002233.403867  2162
0002237.043679  2162

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