Euclidean ArrowHead with Dirichlet Boundary Conditions

The region examined here is the Euclidean ArrowHead. We define an arrowhead to be a Euclidean quadrilateral with one concave angle that is formed by joining two triangles with obtuse angles that have a pair of sides of equal length that are adjacent to the obtuse angle so that the concave angle of the resulting quadrilateral has a measure equal to the sum of the measures of the obtuse angles. The angle opposite the concave angle is the sum of the two non-obtuse angles adjacent to the sides that were joined together, and the remaining two angles are the remaining angles in each of the triangles. The sides of the arrowhead are then the sides of the triangles excluding the side they were joined on. Here we specify the two arrowheads we computed by their vertices. 1: [(1,0)(-.5,.5)(0,0)(-1,-1)] and 2: [(1,0)(-1,2)(0,0)(-3,-1)]. This was an important example for us because it allowed us to test our hypothesis on non-convex non-regular geometric regions of R^2.

Here are the counting graphs for the eigenvalue spectrum, using the predicted values. The first approximately 120 eigenvalues values were used here. The equation for the predicted counting function for the first arrowhead is N'(t) = 3/16pi*t - (sqrt(13)/2+3sqrt(2)/2+sqrt(5))/4pi*sqrt(t) + c1 and for the second arrowhead it is N'(t) = 3/8pi*t - (sqrt(5)+sqrt(10)+sqrt(17)+2sqrt(2))/4pi*sqrt(t) + c2. The constants c1 and c2 are equal to the standard constant for Euclidean polygons: Sum(theta/pi-pi/theta) over all internal angles.


Here are the difference graphs for the eigenvalue spectrum, using the predicted values. The first approximately 120 values were used here.


Below is the Eigenvalue spectrum for the Euclidean ArrowHeads under Dirichlet Boundary conditions. The calculated and predicted eigenvalue spectrum is presented here.

ArrowHead 1       
  Refinement      
#Initial12345 Predicted
155.9618084650.8349744949.4315751449.0204355248.892626648.85066001 48.83662491
2106.045261292.4386354589.0820656288.2451084388.0341959887.9807377 87.96285937
3144.0045197122.0506502116.5418327115.0763878114.6643481114.5423192 114.5015084
4165.8944593140.32979133.8364041132.2160236131.8061793131.7015468 131.6665539
5216.3849951178.9826441169.425115167.0346615166.427686166.2716091 166.2194114
6259.0824869208.3691861195.3275532192.0669528191.2352822191.0196294 190.9475075
7281.9951046226.4080015211.5255366207.7824357206.8273316206.5806221 206.4981138
8332.9892709261.2118632241.7034924236.7877168235.5276876235.1996553 235.0899497
9393.0960695294.0697791264.8679137257.8508015256.0897127255.6376981 255.4865285
10419.1344944309.4346582284.2082123278.0222003276.4834407276.0989647 275.9703824
11460.2630093339.8595161308.9543154301.4076033299.514578299.0331019 298.8720793
12523.7329759384.1947675336.367912324.5074397321.5490175320.7982035 320.5471048
13564.6268218394.5099812351.4013224341.4698258339.0086312338.3896866 338.1826898
14595.6801447431.2579333384.5493609373.1128923370.2642112369.548955 369.3097482
15684.9166208473.394784413.8392435399.0164393395.3014861394.3656645 394.0526928
16725.6998172486.0763802422.4654152407.3117271403.5293161402.5559513 402.2304239
17806.7156631509.217478439.3833379422.1017906417.7124548416.564684 416.180829
18917.7266689538.9385833469.2487608452.4772482448.3273948447.2872462 446.939384
190578.6949962497.7354006477.8682028472.9466512471.7172082 471.3060392
200609.8254037516.5410308494.2127766488.7291895487.3641125 486.9075827
210634.809749545.9347396523.9315552518.4836596517.1246975 516.6702128
220671.033028569.4035872543.6274043537.0933434535.4182888 534.8580917
230685.1716047579.7160966552.9156704546.2513413544.5840692 544.0264748
240731.3594252613.1953286584.355826577.2361435575.4571755 574.862226
250752.9878177626.4492549595.0165694587.1737129585.1905756 584.5273447
260782.4201473646.4936766613.05913604.7933604602.7233644 602.0310849
270820.2333282674.8949186637.6881388628.4353948626.1253787 625.3528281
280843.2491717697.7160474662.2610348653.5493228651.379506 650.6538429
290876.7243622718.6171546679.7524361670.2006714667.8234869 667.0284728
300932.3635954755.0357556708.5417467696.7101816693.7196823 692.7195542
310952.2220545777.8354098733.1788306721.6959578718.7607667 717.7791356
320985.8609953789.8804177738.5815769726.6979361723.7955913 722.8249451
3301008.416415805.130026756.8499455745.1828924742.284544 741.3152344
3401038.404628827.9963849777.0019603764.4238753761.2699856 760.2152139
3501076.523456865.5832771811.8082908798.4410196795.086422 793.9645265
3601111.250518891.7536426831.3202218815.8968297812.0056796 810.7043421
3701164.564884919.3704249852.2641908836.4234044832.5228531 831.2183716
3801188.377442929.0897029863.0433316846.5043199842.2773362 840.8636842
3901191.529113951.5964564887.2414063871.2936438867.3041138 865.9698747
4001235.419037975.135884904.8916848887.7250252883.4350572 882.000341
4101262.190693989.8865237921.3136776904.5347473900.3600432 898.9638753
4201303.5485141011.139811938.41953920.4612942915.9783471 914.4790919
4301347.9189551057.021921974.4742264953.5656537948.3570667 946.6151321
4401377.17931079.124391993.549427973.5276137968.5782201 966.9229689
4501413.7399691093.0903141012.353009992.4554775987.494096 985.8348356
4601449.4652581121.0647811027.9643421004.301026998.3286269 996.3312467
4701468.5245151144.3947921052.1118491028.6814381022.775193 1020.799937
4801511.4991981164.4638991063.5272571039.6897091033.832736 1031.873958
4901533.8563211193.7471271096.6748271072.2367141066.102089 1064.050455
5001571.0200811210.6455791107.2493681082.1981441076.010773 1073.941499
5101591.0715521234.7715661131.6889311105.8339791099.201867 1096.983855
5201667.8768991256.610191140.7224151113.1549871106.392714 1104.131173
5301683.026521280.7172551167.9043721139.3799131132.189194 1129.784365
5401718.410991316.018881195.2414141164.9678621157.360531 1154.816372
5501771.1069831351.6141661209.1849031175.6154111167.465534 1164.739928
5601798.3995041360.9920471233.2300091202.2091911194.524826 1191.954904
5701808.9000431379.8563381253.2860221222.0173071214.182773 1211.562629
5801862.6689631410.751091272.458471238.6445611230.266669 1227.464807
5901872.154841434.1526081296.9867931261.8246771253.006701 1250.057659
6001888.0020711459.4039661307.1092611272.3268131263.839038 1261.000428
6101948.7854541489.5461681341.6004891305.520861296.46167 1293.431959
6201976.7278311518.4352411353.2374941313.5169181303.797786 1300.547367
6302013.025271522.0922821368.2276771329.339631319.599337 1316.341841
6402092.0071531548.8642881386.4415821348.2212531338.731979 1335.558432
6502121.2853231584.55391421.1738581380.8929711370.840291 1367.478321
6602150.7681831607.0055591433.9069921390.6695851379.825054 1376.198261
6702192.6331091633.9280811457.2534871413.8734721403.127106 1399.533143
6802211.5515311667.6059131475.0473161429.7853271418.699704 1414.992282
6902258.3400661692.5517071499.7637871451.0040821438.947854 1434.915828
7002304.724891707.0678161515.566761467.2763751454.560511 1450.307879
7102326.7773041727.8482471520.5194451473.2379431462.164664 1458.46137
7202364.6027031754.0650721559.5257541511.9562981500.143132 1496.192393
7302412.7528331780.538521580.3869461531.2156351518.949654 1514.847478
7402459.5134041816.6394841607.5473291556.1292591543.285565 1538.990181
7502471.2677831835.7724091619.2342351565.9081461551.82464 1547.11462
76001860.1020291623.6374611566.5501181553.249832 1548.801748
77001888.3583951656.0770041598.8987731584.739174 1580.003706
78001913.9021981676.354221618.7242921604.308401 1599.48722
79001940.5617361703.473881643.9678261628.855876 1623.801909
80001965.7608651718.5016321657.5908321642.69028 1637.707012
81001985.2550321741.2135851679.7197711664.526646 1659.445531
82002014.8108991753.7697671694.1658841679.627937 1674.765936
83002061.5252791792.7709531724.1487241707.170248 1701.492049
84002073.4504171802.8378731738.5116581722.45054 1717.079137
85002106.0792341829.7897241758.3047941740.649525 1734.744982
86002132.9567921846.9727341781.8745931765.202881 1759.627274
87002140.079031853.107291782.8768571765.934447 1760.268309
88002160.4552921883.2030711813.8721531795.834557 1789.80215
89002213.522961904.1446421826.197651807.329953 1801.019932
90002231.1276461931.8131611855.6991451835.68437 1828.990725
91002259.9149851937.5067431859.932831842.122185 1836.165679
92002280.9886261969.194051888.7615391869.256522 1862.733358
93002300.8244281973.623581897.4235851878.488744 1872.156267
94002329.5973672000.1710391922.8092581903.222516 1896.67202
95002367.3782312017.611341936.3485471916.997167 1910.525386
96002388.5803622046.8959761961.8697561940.844188 1933.812499
97002397.2065082058.9334291977.7422571957.630283 1950.904132
98002456.2537182108.1453192020.2794981997.64293 1990.072466
99002471.4940852116.7853872028.0451912006.152653 1998.831018
100002499.2987622134.449572042.9860252020.719408 2013.272667
1010002157.9409342065.6635782042.327831 2034.523537
1020002166.2148272069.2887082046.406024 2038.75325
1030002191.9587662099.4389132075.448053 2067.424666
1040002199.9076672101.920682078.954336 2071.273583
1050002229.8609562126.2962452100.326803 2091.641708
1060002250.3419562148.5954082123.773851 2115.472649
1070002263.0105282166.9233792143.096746 2135.128282
1080002282.0810212186.005982162.163288 2154.189453
1090002311.6038792200.7836582173.453558 2164.313411
1100002333.3488282229.2426572203.683349 2195.135418
1110002371.1566392253.1150732223.523026 2213.626405
1120002389.5475492274.8022772246.126992 2236.536968
1130002397.4720262283.6950772255.907763 2246.614707
1140002408.6625652297.6155422270.077823 2260.868242
1150002436.9534342327.4192962298.932766 2289.405869
1160002461.6252042339.3346352310.580813 2300.964524
1170002474.060772356.4321392326.800538 2316.890689
1180002506.5485822372.762222340.454362 2329.649478
11900002394.7486672364.224664 2354.016364
12000002425.693372392.51076 2381.413328
12100002444.9808942412.118408 2401.128038
12200002454.7835592424.272394 2414.068387
12300002470.7895852439.592237 2429.158747
12400002481.4640552448.141711 2436.997547


ArrowHead 2       
  Refinement      
#Initial12345 Predicted
136.075609731.2683705230.0325321929.7072646329.6189208229.59399577 29.58559544
261.3347106151.6585640849.1698961148.5443123948.3840726848.34229514 48.32821512
393.2495424675.7528309970.7890436369.5506570869.240902669.16330478 69.13715248
4139.1268945100.607471490.111600187.4065729986.6803306886.47724737 86.40880349
5168.5866582110.795688298.4007666195.4863991794.7521608394.56114264 94.496765
6199.8631931139.5946379122.4037142118.2629904117.2393268116.9840518 116.8980181
7294.3799107156.4970856134.6443998129.4048367128.0930549127.7590918 127.6465383
8914.5119745180.1346201154.8510588148.5833079147.0139211146.6163261 146.4823271
90201.867957171.1134093163.5320119161.6018759161.0947751 160.9238702
100210.6418578177.6042013168.9144076166.6171509165.9858972 165.7731498
110235.092473194.4746944184.636136182.2023303181.5941831 181.3892231
120254.0045742211.7501892201.1838085198.548432197.8868206 197.663842
130274.8575264228.7801854216.9150997213.9184711213.1615159 212.9064041
140287.8437264236.8873621223.9392196220.6932566219.8784244 219.6038066
150310.3251173248.8851874233.1124981229.2427449228.2807895 227.9565878
160327.261254266.0456829249.0723731244.747578243.6572791 243.2898226
170342.2954346276.3171896259.3106496255.0342594253.9358641 253.5656789
180353.6564572284.7723147267.2425036262.904345261.8122187 261.4441464
190372.7116622297.2783056277.1575427272.1640681270.917814 270.4977969
200388.714337313.1372659292.7293558287.5939882286.2864567 285.8457878
210417.7808182327.8294079303.2306045297.1426799295.6263981 295.1153753
220434.9428987338.4552364313.8067248307.7729708306.2691773 305.7623634
230447.5921559354.5617258324.8876137317.6207063315.8135474 315.2044921
240465.0239863356.0655659332.6457441326.9226974325.4954128 325.0143842
250491.7880833385.3015409351.4804989342.9440856340.8062583 340.08576
260501.1653363396.2364754363.5955084355.3567007353.2953398 352.6006125
270515.5753807402.8209184372.3227613364.6972031362.7629665 362.1110831
280534.1272617416.2121209378.7435987369.4809879367.1657862 366.3855085
290543.9490914432.9486581389.939819379.2729201376.6069093 375.7084006
300573.6844036445.3540642409.821706399.0377788396.1240677 395.1420782
310604.2314959462.5439412413.3599984402.6462748400.1635513 399.3268148
320627.7983646472.3424087423.1551717411.6457712408.8029136 407.8448033
330630.8277084486.4015624437.1725626424.6994151421.5641957 420.5075527
340654.9263128489.1828482444.5009904432.5857816429.560752 428.5412455
350692.3966298510.0599768457.9083402446.2712655443.4324879 442.4757528
360702.9603475529.90857474.2977477459.9294861456.3502755 455.1439969
370717.344351540.4515759482.359205466.7788036462.878541 461.5640603
380728.9196405551.1273272493.6218478480.768572477.5397387 476.4515456
390758.4824987562.0803034503.8873695488.6540927484.5443557 483.1592772
400782.4818616580.2125159508.4051836492.4905826488.9073626 487.6997328
410791.5910221590.0492372534.1669716516.4255422511.8651091 510.3281354
420822.7145821610.4987172539.7729596524.7272374520.5989724 519.2076495
430831.364694629.8266073548.6472245529.5217031525.2401478 523.7971625
440849.7154903635.2800721560.7855239541.5172068536.6263711 534.9780439
450864.8712626647.8121067577.4588661554.4574596548.7562248 546.834774
460894.7063933672.0590309583.8287702564.1133381558.2158038 556.2281954
470949.555214680.2993051589.4379702569.3744118565.1447025 563.7191905
480981.017771699.2329403607.5856031583.5735153577.6434169 575.6448336
4901002.498928706.341199620.8995002594.0357511587.3650566 585.1168749
5001028.509414722.6892595625.9054977604.3358967598.7619123 596.8833478
5101100.53191743.419766635.8800023614.7121948609.6390531 607.9292844
5201149.79695750.2626671652.3052528624.0321562617.0296765 614.6696753
5301168.160444766.4491024665.7622812640.4032838633.968995 631.8004877
5400784.5364341678.8027011651.6024115644.5253517 642.1402153
5500802.8836651685.9181241659.7361266653.2070848 651.0066434
5600816.2829948698.7153696669.4130632661.3909523 658.6873113
5700821.6855292703.8292508670.3872244663.2757163 660.8789701
5800841.2949995724.5706646694.5537428685.7480748 682.7803566
5900861.4283361730.027502700.0485068693.3506963 691.0933758
6000867.8343808745.3624946714.4350885706.978759 704.4657998
6100887.5943771753.6713314718.9707504710.3303239 707.418296
6200898.5147822768.694816731.6075254722.3865627 719.2788803
6300926.0355704779.9417883748.0851728737.8490768 734.3992706
6400935.0305168789.7397427749.6438324740.869572 737.912439
6500951.689647793.1300389756.8745671748.8525019 746.1488763
6600959.6887429812.7278821775.4061769765.3596538 761.9737381
6700970.8208557821.4085873778.7893337768.7575815 765.3766439
6800996.1855986834.1478703798.885255787.6705614 783.8909446
69001009.670244846.3817266802.4558671794.0852789 791.2641928
70001031.123472857.4168973813.2978265801.9352982 798.1058577
71001039.345917860.8355877815.9338348805.0114499 801.3303481
72001046.157386878.0601452828.6827507816.784796 812.7749041
73001074.362797880.9789128841.3717167830.8119631 827.2530766
74001077.467667900.4209896857.3349132845.2369694 841.1596765
75001098.508727912.3993356859.9336426848.7775938 845.0177416
76001119.573276930.9675824878.3913864865.0829669 860.597715
77001139.503782935.9648712884.9813259871.2367749 866.6045365
78001148.435864943.0333368894.4080868882.3589616 878.2981216
79001155.535931953.6614051898.278616884.3877163 879.7061549
80001177.633123959.6566789906.7289863893.7583873 889.3869888
81001187.177348972.906572919.4010992907.2666867 903.177103
82001198.081253989.1070141931.9582338917.8716781 913.124176
83001224.643524997.857536947.1014091930.9129857 925.4571044
84001234.3460081013.082241950.1839187937.3395315 933.0106695
850001023.646002963.6283924948.6708406 943.6297923
860001037.146389974.2541818959.7086137 954.8064135
870001041.37192981.4841471966.0867301 960.8974367
880001051.786911988.9491386973.5013242 968.2950457
890001064.0777191003.710517987.3208775 981.7971817
900001070.465421012.448838994.3826602 988.2939315
910001085.9647361013.1217611000.397186 996.1087038
920001100.5460731035.624051017.412961 1011.275394
930001112.6729071043.6932081027.420714 1021.936499
940001126.8958131049.0825971030.627954 1024.408303
950001128.1692591066.6110271047.850152 1041.527293
960001142.3539121069.3470121053.410527 1048.039555
970001147.8122951076.3467291059.222794 1053.451624
980001166.4827611085.1755561065.789416 1059.255828
990001176.0339191103.9175721083.220208 1076.244708
1000001190.6676471113.7792361096.809386 1091.090146
1010001206.9731641128.6706091107.098495 1099.828182
1020001213.3288051135.0101551113.353783 1106.055074
1030001222.7261611136.9680431118.128756 1111.779471
1040001233.9312971144.4588341123.388212 1116.286915
1050001246.3687221164.3418611142.673169 1135.370308
10600001177.7411641156.299688 1149.073404
10700001183.0145731158.307268 1149.980323
10800001185.7544781163.349464 1155.798444
10900001201.3661241178.878065 1171.299057
11000001208.6344421187.136597 1179.891316
11100001226.9383951202.876639 1194.767258
11200001231.1118551204.879724 1196.038875
11300001243.3032671218.594579 1210.267167
11400001245.2839111223.850286 1216.626648

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