xs EriEPSGIWWR
heem er IWWR
fryons s ghirl olitons
y
in the xmu{tonEvsinio wo del
z
F elkoferD rF einhrdt nd rF eigel
snstitute for heoretil hysis
uingen niversity
euf der worgenstelle IR
hEUPHU T uingenD qermny
y
upp orted in prt y the heutshe porshungsgemeinshft @hpqA under ontrt num er e{VSTGPEPF
z
upp orted y rilitnden{sholrship of the heutshe porshungsgemeinshft @hpqAF I
estrt
he desription of ryons s hirl solitons of the xmu{ton{v sinio @xtvA mo del is
reviewedF e motivtion for the soliton desription of ryons is provided from lrge x ghF
g
igorous results on the sp ontneous reking of hirl symmetry in gh re disussedF st
is then rgued tht the xtv mo del provides fir desription of low{energy hdron physisF
he xtv mo del is therefore employed to mimi the low{energy hirl vor dynmis of
ghF he mo del is osonized y funtionl integrl tehniques nd the physil ontent of
the emerging eetive meson theory is disussedF sn prtiulrD its reltion to the kyrme
mo del is estlishedF
he stti soliton solutions of the oson ized xtv mo del re foundD their prop erties disE
ussedD nd the inuene of vrious meson elds studiedF hese onsidertions provide strong
supp ort of itten9s onjeture tht ryons n e understo o d s soliton solutions of eetive
meson theoriesF he hirl soliton of the xtv mo del is then quntized in semilssil fshE
ion nd vrious stti prop erties of the nuleon re studiedF he dominting Iax orretions
g
to the semilssilly quntized soliton re investigtedF ime{dep endent meson ututions
o the hirl soliton re explored nd employed to estimte the quntum orretions to the
soliton mssF pinllyD hyp erons re desri ed s hirl solitons of the xtv mo delF his is done
in othD the olletive rottionl pproh of u nd endo s well s in the ound stte
pproh of glln nd ulenovF P
gontents
I sntro dution S
P igorous results from gh V
PFI vrge x gh X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X V
g
PFP ghirl symmetry nd low{energy theorems X X X X X X X X X X X X X X X X X X X X X IH
PFQ ghirl nomly nd the gh vuum X X X X X X X X X X X X X X X X X X X X X X X IR
Q he xmu{ton{vsinio mo del IU
QFI hesription of the mo del X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X IU
QFP fosoniztion X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X IV
QFQ hynmil reking of hirl symmetry X X X X X X X X X X X X X X X X X X X X X X X PH
QFR ghirl rottion nd hidden lo l symmetry X X X X X X X X X X X X X X X X X X X X X PP
R ietive meson theory PS
RFI qrdient expnsion X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X PS
RFP eltion to the kyrme mo del X X X X X X X X X X X X X X X X X X X X X X X X X X X X PT
RFQ fethe{lp eter equtions X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X PW
RFR ghirl nomly X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X QS
S ghirl olitons QW
SFI op ologil prop erties X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X QW
SFP imergene of the soliton X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X RH
SFQ emilssil quntiztion X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X RP
T tti solitons of the xmu{tonEvsinio mo del RR
TFI he energy funtionl X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X RS
TFP elf{onsistent solutions X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X SI
TFPFI he pseudoslr hedgehog X X X X X X X X X X X X X X X X X X X X X X X X X SP
TFPFP feyond the hirl irle X X X X X X X X X X X X X X X X X X X X X X X X X X X X SS
TFPFQ snlusion of @xilA vetor mesons X X X X X X X X X X X X X X X X X X X X X X SV
TFPFR udrti expnsion for time omp onents of vetor elds X X X X X X X X X TP Q
TFPFS vo l hirl rottion X X X X X X X X X X X X X X X X X X X X X X X X X X X X X TT
U fryons TW
UFI untiztion of the hirl soliton X X X X X X X X X X X X X X X X X X X X X X X X X X TW
UFP tti nuleon prop erties X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X UP
UFPFI iletromgneti prop erties of the nuleon X X X X X X X X X X X X X X X X X UQ
UFPFP exil hrge of the nuleon X X X X X X X X X X X X X X X X X X X X X X X X X UT
UFPFQ emrks on Iax orretions X X X X X X X X X X X X X X X X X X X X X X X X UU
g
UFQ weson ututions o the hirl soliton X X X X X X X X X X X X X X X X X X X X X X X UW
UFR untum orretions to the soliton mss X X X X X X X X X X X X X X X X X X X X X X VP
UFS ryp erons X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X VT
UFSFI golletive rottionl pproh X X X X X X X X X X X X X X X X X X X X X X X X VU
UFSFP found stte pproh X X X X X X X X X X X X X X X X X X X X X X X X X X X X WP
V ummry IHH
epp endix e IHP
epp endix f IHS
epp endix g IHT
epp endix h IHU
epp endix i IIH
eferenes IIP R
I sntro dution
st is generlly epted tht untum ghromo hynmis @ghA is the theory of strong
intertions @for n intro dution see eFgF refsF ID P AF fesides oming in three olors the
fermion elds of ghD the qurksD lso rry vorF he intertions of gh re vor lind
ut sensitive to olorF gh is n symptotilly free theory whih mens tht the fores
etween qurks eome wek for smll qurk seprtionsD or equivlentlyD lrge momentum
trnsfersF his llows one to quntittively lulte oservles of strong intertion physisD
whih re sensitive to the short distne ehvior of ghD y p erturtive tehniquesF es
mtter of ftD the predited sling violtions hve een veried to high ury t existing
elertors IF eording to present knowledge gh is the only renormlizle theory tht
n ount for these sling violtionsF
he sme self{intertions of gluons whih give rise to symptoti freedom led to strong
qurk{qurk intertion for medium nd smll energiesF sing dditionlly the empiril ft
tht neither qurks nor gluons hve een deteted s free4 prtiles hs led to the onneE
ment hyp othesisX ynly singlets of the guge group pp er s physil prtilesF isp eillyD the
qurks elonging to the fundmentl representtion nd the gluons eing in the djoint repreE
senttion n never e oserved diretlyF he p erturtive result tht the oupling onstnt
inreses s the momentum trnsfer eomes smllD or the distne lrgeD is in ordne
with the onnement hyp othesisF nfortuntelyD this ehvior of the oupling onstnt exE
ludes p erturtive lultions for low energiesF hus it is still unproven tht gh is relly
onning theoryF iven worseD until to dy prop erties of hdrons hve not een lulted
from gh without mking use of severe ssumptions or simplitionsF
here is proly one exeption to this sttementX ith the help of wonte{grlo tehE
niques ttempts hve een mde to lulte hdron prop erties diretly from gh using
disrete lttie @for n intro dution to lttie guge theories see eFgF refsF Q or RAF hespite
the ft tht these non{p erturtive lultions should enle the determintion of every
physil quntity the results often devite very strongly from the exp erimentl vluesF here
re severl resons for thisF iven y using high{p erformne4 omputers the p ossile lttie
sizes re still mo destD esp eillyD if one wnts to inlude dynmil fermionsF purthermoreD
lultion using mssless qurks is imp ossileF end there re still op en oneptul questions
onerning the ontinuum limit of lttie theoryF
qiven this stte of irs it is nturl to resort to eetive mo dels of strong intertionsF
hese re intended to mimi the low{energy ehvior of gh s losely s p ossileF por
this purp ose the pproximte hirl symmetry of gh S provides very useful guidelineF
rdron phenomenology hs left no dout tht this symmetry is roken dynmilly y strong
intertionsF equiring the known pttern of expliitD sp ontneous nd nomlous hirl
symmetry reking puts signint onstrints on p ossile mo dels for the strong intertions
of qurksF edditionl guidne n e otined if one generlizes gh to guge theory
with n ritrry num er of olors x F his is euse for lrge x gh redues to n
g g
eetive theory of innitely mny wekly interting mesons nd gluells TF nfortuntelyD
this eetive meson theory nnot e onstruted expliitlyF xeverthelessD itten ws le to
give rguments tht within this eetive theory ryons emerge s soliton solutions UF
elthough itten9s onjeture hs never een proven rigorously the soliton piture of
ryons hs turned out quite suessful in reent yersF he strting p oints hve een pheE
nomenologil eetive meson theoriesD whih p ossess soliton solutionsF he most p opulr
ee eFgF ghpter QFRFP in refFPF S
ones p erhps re the kyrme mo del VD W nd the guged ' Emo del IHD II F snvestigtions
within these mo dels hve stisftorily explined the welth of sp etrosopi ryon dtD see
eFgF refF IP for reent ompiltion of referenes on soliton mo dels for ryonsF st is worthE
while to mention tht mny of the erly diulties enountered for the kyrme mo delD like eFgF
form ftors eing to o soft IQ D IH D the missing intermedite rnge ttrtion in the nuleon{
nuleon fore IR or the linerly rising phse shifts in pion nuleon sttering IID hve found
stisftory solutionsF rtlyD this ws hieved y using eetive meson vgr ngins ISD IT
desriing the meson physis etter thn the originl simple kyrme vgr nginF yn the other
hndD this inresed omplexity lso generted more miguity in the eetive tionF
et tht p oint nturlly the question rises whether more mirosopi piture of the soliton
n provide some guide for ho osing the eetive meson theoryF iven moreD one my im t
justition of the soliton piture of ryons in generlF herefore not only mirosopi
reliztion of the soliton piture in terms of qurk degrees of freedom is wnted ut the
dynmis of the mo del should e leD t lest in priniplD to determine its fvored piture of
the ryonF sn this sense the xmu{tonEv sinio @xtvA mo del IU is uniqueF pirst of llD it
is simple enough tht suh omplited eld ongurtion like solitons n e determined self{
onsistentlyD see ghpter TF eondD it ontins the orret hirl symmetry reking pttern
nd repro dues lot of meson prop erties like mssesD dey onstntsD sttering lengths etFD
using only few input prmetersD see eFgF IVD IW nd referenes thereinF hirdD nd more
imp ortntD it llows for two omplementry pitures of ryonsD nmely either s ordinry
three{vlene{qurk ound stte or s hirl solitonF he ltter will e the su jet of this
reviewF sn the other pproh the ryon wve funtion is otined s solution of pddeev
eqution using diqurks s intermedite uilding lo ks PHD PI F sing funtionl integrl
tehniques one n derive generting funtionl whih llows one to tret oth pitures in
one qurk theory without ny miguities or doule ounting PH F uh theory ontins the
reltivisti qurk mo del nd the kyrmion s symptoti limitsF reliminry results indite
tht suh hyrid mo del n disply unexp eted feturesD eFgF the diqurk mss is drstilly
redued in soliton kground PPF
yviouslyD the simpliity of the xtv mo del whih mkes it suitle for suh omplited
investigtions is lso its most severe drwkF he xtv mo del is non{renormlizle nd
only uniquely dened if the neessry regulriztion presription is sp eiedF his intro dues
n ultrviolet ut{o whih indites the rnge of ppliility of the mo delF he results
for severl oservles dier in vrious regulriztion shemes IV F iven worseD sometimes
the qulittive ehvior hnges when ltering the regulriztion presriptionF portuntelyD
the sitution is not s drmti for most of the oservlesD or n e understo o d from
the deienies of the regulriztion pro edure like eFgF missing guge invrineF he other
serious disdvntge of the xtv mo del is the sene of onnementD or more preiselyD the
pp erne of two{qurk @or qurk{ntiqurkA thresholdsF hese use unphysil imginry
prts in orreltion funtions for lrge @time{likeA momentF herefore the results of the xtv
mo del re restrited to low energies not only y the ultrviolet ut{o intro dued vi the
regulriztion ut lso y the two{qurk thresholdsF
his review is devoted to the soliton desription of ryons within the xtv mo delF st is
not the primry gol of suh investigtions to repro due ll the phenomenologil suesses
of kyrme typ e mo delsF he si motivtion hs rther eenD nd is stillD to inrese our
understnding how the soliton emergesD nd to etter understnd its reltion to the underlying
qurk dynmisF isp eillyD the oneptionl esy nd diret ess to the qurk degrees of
freedom llows one to study questions whih esp e our onsidertions when strting from
purely mesoni mo delF yn the other hndD in order to rrive t physil ryons one hs T
to use tehniques whih re well known from the kyrmionX semilssil quntiztion W
@rnking PQAD lultion of quntum orretions PRD PS D generliztion to three vors y
either olletive quntiztion PTD PU D PV or ound stte pproh PW D QH D nd so onF hese
su jets will e disussed in detil in this reviewD see ghpter UF hey should e onsidered
s sis for mo del lultions where one wnts to desri e ryons s hirl solitons nd
dditionlly wnts to hve ess to the qurk degrees of freedom in one onsistent frmeF
he orgniztion of this review is s followsX sn ghpter P we will present some rigorous
results from gh whih re relevnt for the soliton desription of ryonsF efter short
summry of the lrge x rguments for ryons eing solitons we will outline some low{
g
energy theorems sed on hirl symmetry nd the hirl nomlyF sn ghpter Q we will
desri e the xtv mo del nd its osoniztion QI F sn etion QFQ very imp ortnt prop erty
of the xtv mo delD the dynmil reking of hirl symmetryD is desri edF e will lso use
lo l hirl rottion to disply the hidden guge symmetry IT of the osonized mo del QPF
ghpter R is devoted to the eetive meson theory of the xtv mo delF rereyD the grdient
expnsion do es not only yield pproximte meson msses nd oupling onstnts ut lso
revels the reltion to the kyrme mo delF he determintion of meson msses with the help
of fethe{lp eter equtions is explined in etion RFQF etion RFR ontins some omments
on the hirl nomly in the eetive meson theoryF sn ghpter S the generi sp ets of
hirl solitons re disussedX the top ologil prop ertiesD the emergene of the soliton nd its
semilssil quntiztionF ghpter T is the entrl piee of this reviewF efter giving the
energy funtionl of the stti xtv soliton we disuss the self{onsistent solutions for dierent
meson elds inluded @or negletedAF ghpter U em o dies the desription of ryons s xtv
solitonsF his lso inludes omprehensive explntion of the rnking metho d for two nd
three vors s well s the desription of time{dep endent meson ututions o the stti
solitonF sn ghpter V we give short summryF ome lengthy formuls whih re nevertheless
neessry to mke this review resonly self{ontined re given in ve pp endiesF U
P igorous results from gh
sn this hpter we will present some rigorous gh results whih re relevnt to hdron
physis nd in prtiulr to the soliton desription of ryonsF es disussed in the intro dution
gh nnot e treted p erturtively t low energiesF es onsequene there re very few
suh resultsF hey re either sed on onsidertions ssuming the num er of olors x to
g
e lrge or on the hirl symmetry of mssless gh nd its sp ontneous rekingF es we will
see oth provide sustntil rguments for the hirl soliton piture of ryonsF
PFI vrge x gh
g
sn the low{energy regime there is no ovious expnsion prmeter to tret gh p erturE
tivelyF roweverD in the seventies 9t ro oft T nd itten U demonstrted tht generlizing
gh from the guge group @QA to @x A with x eing lrgeD Iax might e onsidE
g g g
ered s n impliit expnsion prmeterF xturllyD one might wonder whether this provides
sound sis for p erturtive nlysis sine x a Q in the rel worldF xeverthelessD we
g
will see tht this ide is very fruitfulD esp eilly it is the essentil motivtion for identifying
ryons with solitons of meson eldsF
essuming onnement in the lrge x world it n e shown tht gh with x 3 I
g g
P
nd g x xed hs limit whih n e desri ed s keeping only plnr peynmn digrms
g
TF he reson is tht non{plnr digrms or digrms with gluon hndles re suppressed