Knowledge (XXG)

Infraparticle

Source šŸ“

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states that for every infinitesimal symmetry transformation that is local (local in the sense that the transformed value of a field at a given point only depends on the field configuration in an arbitrarily small neighborhood of that point), there is a corresponding conserved charge called the
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This assumes that the state in question approaches the vacuum asymptotically at spatial infinity. The first integral is the surface integral at spatial infinity and the second integral is zero by the
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approaches infinity. If we interchange the limits, the directional charges change. This is related to the expanding electromagnetic waves spreading outwards at the speed of light (the soft photons).
233: 978:). The conclusion is that both electrons lie in different superselection sectors no matter how tiny the velocity is. At first sight, this might appear to be in contradiction with 822:
at finite values. This is consistent with the idea that symmetry transformations not affecting the boundaries are gauge symmetries whereas those that do are global symmetries. If
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The directional charges are different for an electron that has always been at rest and an electron that has always been moving at a certain nonzero velocity (because of the
632: 1036: 613: 1062: 119: 99: 845:, conserved scalar charges (the electric charge) are seen as well as conserved vector charges and conserved tensor charges. This is not a violation of the 867: 959:, the conclusion that states with the same electric charge but different values for the directional charges lie in different superselection sectors. 333: 1501: 1336: 1138: 1322: 249: 1555: 55:. However, only a finite number of these photons are detectable, the remainder falling below the measurement threshold. 846: 81:
density of states like an ordinary particle, but instead the density of states rises like an inverse power at the mass
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This conclusion holds both in classical electrodynamics as well as in quantum electrodynamics. If Ī± is taken as the
838:, we get the electric charge. But for other functions, we also get conserved charges (which are not so well known). 178: 979: 1202: 1550: 44: 1468: 1126: 134: 32: 818:). Then, the Noether charge only depends upon the value of Ī± at spatial infinity but not upon the value of 975: 63: 987: 956: 768:{\displaystyle \epsilon _{0}\oint _{S^{2}}\alpha {\vec {E}}\cdot d{\vec {S}}+\int d^{3}x\alpha \left.} 431: 1510: 1441: 1404: 1367: 1264: 1211: 1174: 1076: 999: 963: 623: 153: 149: 78: 1130: 842: 166: 161:, which is the space integral of a Noether density (assuming the integral converges and there is a 28: 1526: 1280: 1254: 1227: 1097: 962:
Even though this result is expressed in terms of a particular spherical coordinates with a given
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and a conserved quantity. Using the result that states with different charges exist in different
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Buchholz, D.; Doplicher, S.; Longo, R (1986). "On Noether's Theorem in Quantum Field Theory".
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Nachrichten von der Kƶniglicher Gesellschaft den Wissenschaft zu Gƶttingen, Math-phys. Klasse
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consist of the particle together with low-energy excitations of the electromagnetic field.
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description, where the Hilbert space includes particle states with different velocities.
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The form of the electric field at infinity, which is determined by the velocity of a
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is really the greatest lower bound of a continuous mass spectrum and eigenstates of
941:{\displaystyle \lim _{r\rightarrow \infty }\epsilon _{0}r^{2}E_{r}(r,\theta ,\phi )} 1313: 328: 59: 1496: 327:
But what if there is a position-dependent (but not time-dependent) infinitesimal
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Because of their infraparticle properties, charged particles do not have a sharp
1006: 24: 415:{\displaystyle \delta \psi ({\vec {x}})=iq\alpha ({\vec {x}})\psi ({\vec {x}})} 1276: 71: 1453: 1430:
Coleman, S.; Mandula, J. (1967). "All Possible Symmetries of the S Matrix".
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Noether, E.; Tavel, M.A. (transl.) (2005). "Invariant Variation Problems".
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is an electrically charged particle together with its surrounding cloud of
952: 850: 1259: 1002:. The electron, and other particles like it is called an infraparticle. 1522: 1223: 324:
is conserved. This is nothing other than the familiar electric charge.
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at the boundary at spatial infinity is zero, which is satisfied if the
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besides QED. The name "infraparticle" still applies in those cases.
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Buchholz, D. (1986). "Gauss' law and the infraparticle problem".
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Schroer, B. (2008). "A note on infraparticles and unparticles".
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More generally, there might exist a similar situation in other
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of the particle. These states which are very close in mass to
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If this is applied to the global U(1) symmetry, the result
303:{\displaystyle \oint _{S^{2}}{\vec {J}}\cdot d{\vec {S}}} 27:ā€”of which there are an infinite number, by virtue of the 1068:
goes to infinity first and only then take the limit as
1005:
The existence of the directional charges is related to
1497:"The Physical State Space of Quantum Electrodynamics" 1293:
Noether, E. (1918). "Invariante Variationsprobleme".
1044: 1015: 870: 635: 592: 434: 336: 252: 181: 107: 87: 1354:"Noether's theorem for Local Gauge Transformations" 1056: 1030: 940: 767: 607: 575: 414: 302: 227: 113: 93: 124: 43:. Whenever electric charges accelerate they emit 872: 1200:Weyl, H. (1929). "Elektron und Gravitation I". 1158: 1156: 1154: 1152: 1150: 228:{\displaystyle Q=\int d^{3}x\rho ({\vec {x}})} 1312:is the integral of the time component of the 853:. In particular, for each direction (a fixed 8: 982:, which implies that the whole one-particle 1121:Quantum Field Theory: A Modern Introduction 125:Noether's theorem for gauge transformations 320:falls off sufficiently fast, the quantity 1258: 1101: 1043: 1014: 911: 901: 891: 875: 869: 746: 745: 733: 706: 685: 684: 667: 666: 655: 650: 640: 634: 594: 593: 591: 554: 553: 527: 526: 512: 511: 505: 484: 483: 463: 462: 442: 433: 398: 397: 377: 376: 347: 346: 335: 289: 288: 271: 270: 262: 257: 251: 211: 210: 195: 180: 106: 86: 1247:Transport Theory and Statistical Physics 1088: 422:where Ī± is some function of position? 239:is the conserved charge where Ļ is the 1502:Communications in Mathematical Physics 1352:Karatas, D.L.; Kowalski, K.L. (1990). 1064:are the same if we take the limit as 7: 148:, there are also position dependent 47:, whereby an infinite number of the 1051: 1025: 882: 739: 544: 243:. As long as the surface integral 14: 970:Implication for particle behavior 576:{\displaystyle \int d^{3}x\left} 1324:The Feynman Lectures on Physics 1327:. Vol. 2 (2nd ed.). 935: 917: 879: 751: 690: 672: 599: 565: 559: 550: 538: 532: 523: 517: 495: 489: 480: 474: 468: 459: 409: 403: 394: 388: 382: 373: 358: 352: 343: 294: 276: 222: 216: 207: 1: 1417:10.1016/0003-4916(86)90086-2 1187:10.1016/0370-2693(86)91110-X 1009:. The directional charge at 1359:American Journal of Physics 70:. This is unlike the usual 1572: 1031:{\displaystyle t=-\infty } 608:{\displaystyle {\vec {E}}} 425:The Noether charge is now 1277:10.1080/00411457108231446 1057:{\displaystyle t=\infty } 1476:philsci-archive.pitt.edu 1454:10.1103/PhysRev.159.1251 990:, but it is not because 814:approaches infinity (in 144:symmetry related to the 45:Bremsstrahlung radiation 16:Type of dressed particle 1127:Oxford University Press 980:Wigner's classification 976:Lorentz transformations 847:Colemanā€“Mandula theorem 135:quantum electrodynamics 33:quantum electrodynamics 1469:"Superselection Rules" 1321:Feynman, R.P. (2005). 1203:Zeitschrift fĆ¼r Physik 1077:quantum field theories 1058: 1032: 957:superselection sectors 942: 769: 609: 577: 416: 304: 229: 115: 95: 64:superselection sectors 1495:Buchholz, D. (1982). 1059: 1033: 988:superselection sector 943: 770: 610: 578: 417: 305: 230: 150:gauge transformations 137:, in addition to the 116: 96: 1556:Quantum field theory 1467:Giulini, D. (2007). 1042: 1013: 1000:rigged Hilbert space 868: 633: 624:integration by parts 590: 432: 334: 329:gauge transformation 250: 179: 105: 85: 51:soft photons become 1515:1982CMaPh..85...49B 1446:1967PhRv..159.1251C 1409:1986AnPhy.170....1B 1372:1990AmJPh..58..123K 1319:by definition. See 1269:1971TTSP....1..186N 1216:1929ZPhy...56..330W 1179:1986PhLB..174..331B 1133:ā€“184, Appendix A6. 843:spherical harmonics 834:) = 1 all over the 782:. Also assume that 235:(over all of space) 167:continuity equation 66:for the particle's 35:. That is, it is a 29:infrared divergence 1523:10.1007/BF02029133 1224:10.1007/BF01339504 1054: 1028: 938: 886: 765: 605: 573: 412: 300: 225: 111: 91: 1396:Annals of Physics 1338:978-0-8053-9065-0 1166:Physics Letters B 1140:978-0-19-507652-3 1117:Kaku, M. (1993). 986:lies in a single 871: 816:polar coordinates 754: 693: 675: 602: 562: 535: 520: 492: 471: 406: 385: 355: 297: 279: 219: 154:Noether's theorem 114:{\displaystyle m} 94:{\displaystyle m} 1563: 1535: 1534: 1492: 1486: 1485: 1483: 1482: 1473: 1464: 1458: 1457: 1440:(5): 1251ā€“1256. 1427: 1421: 1420: 1390: 1384: 1383: 1349: 1343: 1342: 1307: 1301: 1298: 1288: 1262: 1242: 1236: 1235: 1210:(5ā€“6): 330ā€“352. 1197: 1191: 1190: 1160: 1145: 1144: 1124: 1114: 1108: 1107: 1105: 1093: 1063: 1061: 1060: 1055: 1037: 1035: 1034: 1029: 998:only exist in a 947: 945: 944: 939: 916: 915: 906: 905: 896: 895: 885: 861:), the quantity 774: 772: 771: 766: 761: 757: 756: 755: 747: 738: 737: 711: 710: 695: 694: 686: 677: 676: 668: 662: 661: 660: 659: 645: 644: 614: 612: 611: 606: 604: 603: 595: 582: 580: 579: 574: 572: 568: 564: 563: 555: 537: 536: 528: 522: 521: 513: 510: 509: 494: 493: 485: 473: 472: 464: 447: 446: 421: 419: 418: 413: 408: 407: 399: 387: 386: 378: 357: 356: 348: 309: 307: 306: 301: 299: 298: 290: 281: 280: 272: 269: 268: 267: 266: 234: 232: 231: 226: 221: 220: 212: 200: 199: 120: 118: 117: 112: 100: 98: 97: 92: 37:dressed particle 1571: 1570: 1566: 1565: 1564: 1562: 1561: 1560: 1551:Electrodynamics 1541: 1540: 1539: 1538: 1494: 1493: 1489: 1480: 1478: 1471: 1466: 1465: 1461: 1433:Physical Review 1429: 1428: 1424: 1392: 1391: 1387: 1380:10.1119/1.16219 1351: 1350: 1346: 1339: 1320: 1308: 1304: 1292: 1291:Translation of 1260:physics/0503066 1244: 1243: 1239: 1199: 1198: 1194: 1162: 1161: 1148: 1141: 1116: 1115: 1111: 1095: 1094: 1090: 1085: 1040: 1039: 1011: 1010: 972: 907: 897: 887: 866: 865: 849:as there is no 729: 722: 718: 702: 651: 646: 636: 631: 630: 588: 587: 501: 455: 451: 438: 430: 429: 332: 331: 315:current density 258: 253: 248: 247: 191: 177: 176: 165:satisfying the 163:Noether current 146:electric charge 131:electrodynamics 127: 103: 102: 83: 82: 17: 12: 11: 5: 1569: 1567: 1559: 1558: 1553: 1543: 1542: 1537: 1536: 1487: 1459: 1422: 1385: 1366:(2): 123ā€“131. 1344: 1337: 1329:Addison-Wesley 1302: 1300: 1299: 1253:(3): 235ā€“257. 1237: 1192: 1173:(3): 331ā€“334. 1146: 1139: 1109: 1087: 1086: 1084: 1081: 1053: 1050: 1047: 1027: 1024: 1021: 1018: 971: 968: 949: 948: 937: 934: 931: 928: 925: 922: 919: 914: 910: 904: 900: 894: 890: 884: 881: 878: 874: 776: 775: 764: 760: 753: 750: 744: 741: 736: 732: 728: 725: 721: 717: 714: 709: 705: 701: 698: 692: 689: 683: 680: 674: 671: 665: 658: 654: 649: 643: 639: 617:electric field 601: 598: 584: 583: 571: 567: 561: 558: 552: 549: 546: 543: 540: 534: 531: 525: 519: 516: 508: 504: 500: 497: 491: 488: 482: 479: 476: 470: 467: 461: 458: 454: 450: 445: 441: 437: 411: 405: 402: 396: 393: 390: 384: 381: 375: 372: 369: 366: 363: 360: 354: 351: 345: 342: 339: 311: 310: 296: 293: 287: 284: 278: 275: 265: 261: 256: 241:charge density 237: 236: 224: 218: 215: 209: 206: 203: 198: 194: 190: 187: 184: 159:Noether charge 126: 123: 110: 90: 79:delta function 53:real particles 39:rather than a 15: 13: 10: 9: 6: 4: 3: 2: 1568: 1557: 1554: 1552: 1549: 1548: 1546: 1532: 1528: 1524: 1520: 1516: 1512: 1508: 1504: 1503: 1498: 1491: 1488: 1477: 1470: 1463: 1460: 1455: 1451: 1447: 1443: 1439: 1435: 1434: 1426: 1423: 1418: 1414: 1410: 1406: 1402: 1398: 1397: 1389: 1386: 1381: 1377: 1373: 1369: 1365: 1361: 1360: 1355: 1348: 1345: 1340: 1334: 1330: 1326: 1325: 1318: 1315: 1311: 1306: 1303: 1296: 1290: 1289: 1286: 1282: 1278: 1274: 1270: 1266: 1261: 1256: 1252: 1248: 1241: 1238: 1233: 1229: 1225: 1221: 1217: 1213: 1209: 1205: 1204: 1196: 1193: 1188: 1184: 1180: 1176: 1172: 1168: 1167: 1159: 1157: 1155: 1153: 1151: 1147: 1142: 1136: 1132: 1128: 1123: 1122: 1113: 1110: 1104: 1099: 1092: 1089: 1082: 1080: 1078: 1073: 1071: 1067: 1048: 1045: 1022: 1019: 1016: 1008: 1003: 1001: 997: 993: 989: 985: 984:Hilbert space 981: 977: 969: 967: 965: 960: 958: 954: 932: 929: 926: 923: 920: 912: 908: 902: 898: 892: 888: 876: 864: 863: 862: 860: 856: 852: 848: 844: 839: 837: 833: 829: 825: 821: 817: 813: 809: 805: 801: 798:) approaches 797: 793: 789: 785: 781: 762: 758: 748: 742: 734: 730: 726: 723: 719: 715: 712: 707: 703: 699: 696: 687: 681: 678: 669: 663: 656: 652: 647: 641: 637: 629: 628: 627: 625: 620: 618: 596: 569: 556: 547: 541: 529: 514: 506: 502: 498: 486: 477: 465: 456: 452: 448: 443: 439: 435: 428: 427: 426: 423: 400: 391: 379: 370: 367: 364: 361: 349: 340: 337: 330: 325: 323: 319: 316: 291: 285: 282: 273: 263: 259: 254: 246: 245: 244: 242: 213: 204: 201: 196: 192: 188: 185: 182: 175: 174: 173: 170: 168: 164: 160: 155: 151: 147: 143: 140: 136: 132: 122: 108: 88: 80: 75: 73: 69: 68:Hilbert space 65: 61: 56: 54: 50: 46: 42: 41:bare particle 38: 34: 30: 26: 22: 21:infraparticle 1509:(1): 49ā€“71. 1506: 1500: 1490: 1479:. Retrieved 1475: 1462: 1437: 1431: 1425: 1400: 1394: 1388: 1363: 1357: 1347: 1323: 1316: 1314:four-current 1309: 1305: 1294: 1250: 1246: 1240: 1207: 1201: 1195: 1170: 1164: 1120: 1112: 1091: 1074: 1069: 1065: 1007:soft photons 1004: 995: 991: 973: 961: 950: 858: 854: 840: 835: 831: 827: 823: 819: 811: 807: 803: 799: 795: 791: 787: 783: 777: 621: 585: 424: 326: 321: 317: 312: 238: 171: 128: 76: 60:point charge 57: 25:soft photons 20: 18: 1403:(1): 1ā€“17. 1129:. pp.  1545:Categories 1481:2010-02-21 1297:: 235ā€“257. 1083:References 72:Fock space 62:, defines 1531:120467701 1285:119019843 1232:186233130 1103:0804.3563 1052:∞ 1026:∞ 1023:− 933:ϕ 927:θ 889:ϵ 883:∞ 880:→ 780:Gauss law 752:→ 743:⋅ 740:∇ 731:ϵ 727:− 724:ρ 716:α 700:∫ 691:→ 679:⋅ 673:→ 664:α 648:∮ 638:ϵ 600:→ 560:→ 548:α 545:∇ 542:⋅ 533:→ 518:→ 503:ϵ 490:→ 478:ρ 469:→ 457:α 436:∫ 404:→ 392:ψ 383:→ 371:α 353:→ 341:ψ 338:δ 295:→ 283:⋅ 277:→ 255:∮ 217:→ 205:ρ 189:∫ 953:c-number 851:mass gap 1511:Bibcode 1442:Bibcode 1405:Bibcode 1368:Bibcode 1265:Bibcode 1212:Bibcode 1175:Bibcode 615:is the 49:virtual 1529:  1335:  1283:  1230:  1137:  964:origin 622:Using 586:where 139:global 1527:S2CID 1472:(PDF) 1281:S2CID 1255:arXiv 1228:S2CID 1098:arXiv 951:is a 810:) as 1333:ISBN 1135:ISBN 1038:and 857:and 142:U(1) 133:and 1519:doi 1450:doi 1438:159 1413:doi 1401:170 1376:doi 1273:doi 1220:doi 1183:doi 1171:174 1131:177 873:lim 169:). 129:In 31:of 19:An 1547:: 1525:. 1517:. 1507:85 1505:. 1499:. 1474:. 1448:. 1436:. 1411:. 1399:. 1374:. 1364:58 1362:. 1356:. 1331:. 1279:. 1271:. 1263:. 1249:. 1226:. 1218:. 1208:56 1206:. 1181:. 1169:. 1149:^ 1125:. 626:, 619:. 152:. 1533:. 1521:: 1513:: 1484:. 1456:. 1452:: 1444:: 1419:. 1415:: 1407:: 1382:. 1378:: 1370:: 1341:. 1317:J 1310:Q 1287:. 1275:: 1267:: 1257:: 1251:1 1234:. 1222:: 1214:: 1189:. 1185:: 1177:: 1143:. 1106:. 1100:: 1070:t 1066:r 1049:= 1046:t 1020:= 1017:t 996:m 992:m 936:) 930:, 924:, 921:r 918:( 913:r 909:E 903:2 899:r 893:0 877:r 859:Ļ† 855:Īø 836:S 832:Ļ† 830:, 828:Īø 826:( 824:Ī± 820:Ī± 812:r 808:Ļ† 806:, 804:Īø 802:( 800:Ī± 796:Ļ† 794:, 792:Īø 790:, 788:r 786:( 784:Ī± 763:. 759:] 749:E 735:0 720:[ 713:x 708:3 704:d 697:+ 688:S 682:d 670:E 657:2 653:S 642:0 597:E 570:] 566:) 557:x 551:( 539:) 530:x 524:( 515:E 507:0 499:+ 496:) 487:x 481:( 475:) 466:x 460:( 453:[ 449:x 444:3 440:d 410:) 401:x 395:( 389:) 380:x 374:( 368:q 365:i 362:= 359:) 350:x 344:( 322:Q 318:J 292:S 286:d 274:J 264:2 260:S 223:) 214:x 208:( 202:x 197:3 193:d 186:= 183:Q 109:m 89:m

Index

soft photons
infrared divergence
quantum electrodynamics
dressed particle
bare particle
Bremsstrahlung radiation
virtual
real particles
point charge
superselection sectors
Hilbert space
Fock space
delta function
electrodynamics
quantum electrodynamics
global
U(1)
electric charge
gauge transformations
Noether's theorem
Noether charge
Noether current
continuity equation
charge density
current density
gauge transformation
electric field
integration by parts
Gauss law
polar coordinates

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