document: our aim in physics is not only to calculate some observable and get a correct number but mainly to understand a physical picture responsible for the given phenomenon . 
   it very often happens that a theory formulated in terms of fundamental degrees of freedom can not answer such a question since it becomes overcomplicated at the related scale . 
   thus a main task in this case is to select those degrees of freedom which are indeed essential . 
   for instance , the fundamental degrees of freedom in crystals are ions in the lattice , electrons and the electromagnetic field . nevertheless , in order to understand electric conductivity , heat capacity , etc . 
   we instead work with `` heavy electrons '' with dynamical mass , phonons and their interaction . in this case 
   a complicated electromagnetic interaction of the electrons with the ions in the lattice is `` hidden '' in the dynamical mass of the electron and the interactions among ions in the lattice are eventually responsible for the collective excitations of the lattice - phonons , which are goldstone bosons of the spontaneously broken translational invariance in the lattice of ions . as a result , 
   the theory becomes rather simple - only the electron and phonon degrees of freedom and their interactions are essential for all the properties of crystals mentioned above . 
   quite a similar situation takes place in qcd . 
   one hopes that sooner or later one can solve the full nonquenched qcd on the lattice and get the correct nucleon and pion mass in terms of underlying degrees of freedom : current quarks and gluon fields . 
   however , qcd at the scale of 1 gev becomes too complicated , and hence it is rather difficult to say in this case what kind of physics , inherent in qcd , is relevant to the nucleon mass and its low - energy properties . in this lecture 
   i will try to answer this question . 
   i will show that it is the spontaneous breaking of chiral symmetry which is the most important qcd phenomenon in this case , and that beyond the scale of spontaneous breaking of chiral symmetry light and strange baryons can be viewed as systems of three constituent quarks which interact by the exchange of goldstone bosons ( pseudoscaler mesons ) , vector and scalar mesons ( which could be considered as a representation of a correlated goldstone boson exchange ) and are subject to confinement . 
   at low temperatures and densities the @xmath6 chiral symmetry of qcd lagrangian is spontaneously broken down to @xmath7 by the qcd vacuum ( in the large @xmath8 limit it would be @xmath9 ) . 
   a direct evidence for the spontaneously broken chiral symmetry is a nonzero value of the quark condensates for the light flavors @xmath10 which represent the order parameter . that this is indeed so , we know from three sources : current algebra , qcd sum rules , and lattice gauge calculations . 
   there are two important generic consequences of the spontaneous breaking of chiral symmetry ( sbcs ) . 
   the first one is an appearance of the octet of pseudoscalar mesons of low mass , @xmath11 , which represent the associated approximate goldstone bosons ( in the large @xmath8 limit the flavor singlet state @xmath12 should be added ) . 
   the second one is that valence ( practically massless ) quarks acquire a dynamical mass , which have been called historically constituent quarks . 
   indeed , the nonzero value of the quark condensate itself implies at the formal level that there should be rather big dynamical mass , which could be in general a moment - dependent quantity . 
   thus the constituent quarks should be considered as quasiparticles whose dynamical mass comes from the nonperturbative gluon and quark - antiquark dressing . 
   the flavor - octet axial current conservation in the chiral limit tells that the constituent quarks and goldstone bosons should be coupled with the strength @xmath13 @xcite , which is a quark analog of the famous goldberger - treiman relation . 
   we can not say at the moment for sure what is the microscopical mechanism for sbcs in qcd . 
   any sufficiently strong scalar interaction between quarks will induce the sbcs ( e.g. the instanton - induced interaction contains the scalar part , or it can be generated by monopole condensation , etc . ) . 
   all these general aspects of sbcs are well illustrated by the nambu and jona - lasinio model @xcite , where the constituent mass is generated by the scalar part of some nonperturbative local gluonic interaction between current quarks while its pseudoscalar part gives rise to a relativistic deeply - bound pseudoscalar @xmath14 systems as goldstone bosons . 
   accordingly one arrives at the following interpretation of light and strange baryons in the low - energy regime . 
   the highly nonperturbative gluodynamics gives rise to correlated quark - antiquark structures in the baryon sea ( virtual mesons ) . at the same time the current valence quarks get dressed by the quark condensates and by the meson loops . 
   the strongly - correlated quark - antiquark pairs in the pseudoscalar channel manifest themselves by virtual pseudoscalar mesons , while the weakly - correlated pairs in other channels - by vector , etc mesons . 
   when one integrates over the meson fields in the baryon wave function one arrives at the simple qqq fock component with confined constituent quarks and with residual interaction between them mediated by the corresponding meson fields @xcite . 
   the complimentary description of the vector - meson fields as well as of the scalar ones as arising from the correlated goldstone bosons is also possible , which does not contradict , however , to their interpretation as weakly bound @xmath14 systems . 
   the coupling of the constituent quarks and the pseudoscalar goldstone bosons will ( in the @xmath15 symmetric approximation ) have the form @xmath16 within the nonlinear realization of chiral symmetry ( it would be @xmath17 within the linear @xmath18-model chiral symmetry representation ) . 
   a coupling of this form , in a nonrelativistic reduction for the constituent quark spinors , will  to lowest order  give rise the @xmath19 structure of the meson - quark vertex , where @xmath20 is meson momentum . 
   thus , the structure of the potential between quarks `` @xmath21 '' and `` @xmath22 '' in momentum representation is    @xmath23    where @xmath24 is dressed green function for chiral field which includes both nonlinear terms of chiral lagrangian and fermion loops , @xmath25 is meson - quark formfactor which takes into account the internal structure of quasiparticles . at big distances ( @xmath26 ) , one has @xmath27 and @xmath28 . 
   it then follows from ( [ 2 ] ) that @xmath29 , which means that the volume integral of the goldstone boson exchange ( gbe ) interaction should vanish ,    @xmath30    this sum rule is not valid in the chiral limit , however , where @xmath31 and , hence , @xmath32 . 
   the sum rule ( [ 1 ] ) is trivial for the tensor component of the pseudoscalar - exchange interaction since the tensor force component automatically vanishes on averaging over the directions of @xmath33 . 
   but for the spin - spin component the sum rule ( [ 1 ] ) indicates that there must be a strong short - range term . 
   indeed , at big interquark separations the spin - spin component of the pseudoscalar - exchange interaction is @xmath34 , it then follows from the sum rule above that at short interquark separations the spin - spin interaction should be opposite in sign as compared to the yukawa tail and very strong :    @xmath35    _ it is this short - range part of the goldstone boson exchange ( gbe ) interaction between the constituent quarks that is of crucial importance for baryons : it has a sign appropriate to reproduce the level splittings and dominates over the yukawa tail towards short distances . 
   _ in a oversimplified consideration with a free klein - gordon green function instead of the dressed one in ( [ 2 ] ) and with @xmath36 , one obtains the following spin - spin component of @xmath37 interaction :    @xmath38    in the chiral limit only the negative short - range part of the gbe interaction survives . 
   as a representation of a multiple correlated goldstone - boson - exchange one can include the exchange by a scalar flavor - singlet `` @xmath18''-meson as well as by vector mesons . 
   the `` @xmath18''-meson exchange does not play a principal role in baryons since it does not contain the spin - spin and tensor - force component . 
   its attractive central potential as well as a weak spin - orbit force can be effectively included into confining interaction in baryons . however , these forces are of significant importance in nn system at medium range . 
   the coupling of constituent quarks with the octet vector meson field @xmath39 in the @xmath40 - symmetric approximation is    @xmath41    where @xmath42 and @xmath43 are the vector- and tensor coupling constants . a coupling of this form - to lowest order - will give rise the spin - spin , tensor , spin - orbit , and central interactions between the constituent quarks . 
   it is very instructive to compare signs of the spin - spin and tensor components of pseudoscalar- and vector - exchange interactions . 
   the spin - spin and tensor components of the pseudoscalar - exchange interaction arise from the @xmath44 structure of the pseudoscalar - meson  constituent quark vertex as :    @xmath45 . \label{3.2}\ ] ]    the coupling of the vector - meson to constituent quark gives @xmath46 structure of the vertex . 
   therefore the spin - spin and tensor components of the vector - meson exchange interaction arise as    @xmath47 . \label{3.3}\ ] ]    comparing ( [ 3.2 ] ) with ( [ 3.3 ] ) one observes that the spin - spin component of the vector - exchange has the same sign as the spin - spin component of the pseudoscalar - exchange interaction and is `` two times stronger '' while their tensor components have opposite signs .    the @xmath46 structure of the vector - meson  constituent quark vertex also suggests that the spin - spin component of the vector - meson - exchange interaction should satisfy the same sum rule ( [ 1 ] ) as the pseudoscalar - exchange interaction . 
   then similar to pseudoscalar - exchange interaction there should be a short - range term in the vector - meson exchange interaction of the form ( [ 1.1 ] ) . 
   again , if one neglects the spatial structure of the meson - quark vertex and uses a free green function for the vector - meson field , this short range term is described by a @xmath48 - function piece similar to equation ( [ 3 ] ) . 
   summarizing , both vector- and pseudoscalar - exchange interactions produce the short - range spin - flavor force ( [ 1.1 ] ) while their tensor forces largely cancel each other in baryons . 
   this observation is crucial for the present model . 
   + the spin - orbit component associated with the vector - meson exchange interaction is big and empirically very important in nn system . 
   so the question is why this spin - orbit force is big in nn system and becomes inessential in baryons , where the spin - orbit splittings are generally very small ( see e.g. at @xmath49 , @xmath50 , ... ls multiplets ) . 
   the reason for this remarkable phenomenon is an explicit flavor dependence of the vector - meson - exchange ls force . 
   consider for simplicity the @xmath51 case , i.e. an exchange by @xmath2- and @xmath3-mesons between u and d quarks . 
   the @xmath2-meson is isovector and the @xmath2-meson exchange potential contains the factor @xmath52 . 
   the @xmath3-meson is isoscalar and the @xmath3-exchange interaction does not contain the isospin - dependent factor . in @xmath53 
   nn partial wave the isospin of the two - nucleon system is @xmath54 and the isospin matrix element for the @xmath2-meson exchange potential is @xmath55 . thus both @xmath3- and @xmath2-meson exchange spin - orbit forces contribute with the same sign in nn system . numerically the contribution from @xmath3-exchange is 2.5 - 3 times bigger than from the @xmath2-meson exchange spin - orbit force . 
   now let us consider @xmath53 state of two light quarks in baryon . 
   in the present case the isospin of the quark pair is @xmath56 , due to the presence of the color part of wave function . 
   then for the @xmath2-meson exchange one obtains @xmath57 . 
   thus the @xmath2-meson exchange spin - orbit force obtains opposite sign and becomes strongly enhanced in baryons . as a result one observes a strong cancellation of the @xmath2- and @xmath3-meson exchange spin - orbit forces in baryons and the net weak spin - orbit interaction does not induce appreciable splittings in baryons . 
   numerical details about both the tensor- and spin - orbit force cancellation in baryons can be found in ref . 
   summarizing previous sections one concludes that the pseudoscalar- and vector - meson exchange interactions produce strong flavor - spin interaction ( [ 1.1 ] ) at short range while the net tensor and spin - orbit forces are rather weak . 
   that the net spin - orbit and tensor interactions between constituent quarks _ in baryons _ should be weak also follows from the typically small splittings in ls - multiplets , which are of the order 10 - 30 mev . 
   these small splittings should be compared with the hyperfine splittings produced by spin - spin force , which are of the order of @xmath58 splitting . 
   thus , indeed , in baryons it is the spin - spin interaction ( [ 1.1 ] ) between constituent quarks is of crucial importance . 
   consider first , for the purposes of illustration , a schematic model which neglects the radial dependence of the potential function @xmath59 in ( [ 1.1 ] ) , and assume a harmonic confinement among quarks as well as @xmath60 . in this model 
   @xmath61    note , that contrary to the color - magnetic interaction from perturbative one - gluon exchange , the chiral interaction is explicitly flavor - dependent . 
   it is this circumstance which allows to solve the long - standing problem of ordering of the lowest positive - negative parity states . 
   if the only interaction between the quarks were the flavor- and spin - independent harmonic confining interaction , the baryon spectrum would be organized in multiplets of the symmetry group @xmath62 . in this case 
   the baryon masses would be determined solely by the orbital structure , and the spectrum would be organized in an _ alternative sequence of positive and negative parity states , _ i.e. in this case the spectrum would be : ground state of positive parity ( @xmath63 shell , @xmath64 is the number of harmonic oscillator excitations in a 3-quark state ) , first excited band of negative parity ( @xmath65 ) , second excited band of positive parity ( @xmath66 ) , etc .    the hamiltonian ( [ 4 ] ) , within a first order perturbation theory , reduces the @xmath62 symmetry down to @xmath67 , which automatically implies a splitting between the octet and decuplet baryons ( e.g. the @xmath68 resonance becomes heavier than nucleon ) . 
   let us now see how the pure confinement spectrum above becomes modified when the gbe hamiltonian ( [ 4 ] ) is switched on . for the octet states 
   @xmath69 , @xmath70 , @xmath71 , @xmath72 ( @xmath63 shell ) as well as for their first radial excitations of positive parity @xmath73 , @xmath74 , @xmath75 , @xmath76 ( @xmath66 shell ) the expectation value of the hamiltonian ( [ 4 ] ) is @xmath77 . 
   for the decuplet states @xmath68 , @xmath78 , @xmath79 , @xmath80 ( @xmath63 shell ) the corresponding matrix element is @xmath81 . in the negative parity excitations ( @xmath65 shell ) in the @xmath69 , @xmath70 and @xmath71 spectra ( @xmath82 - @xmath83 , @xmath84 - @xmath85 and @xmath86 - @xmath87 ) the contribution of the interaction ( [ 4 ] ) is @xmath88 . the first negative parity excitation in the @xmath70 spectrum ( @xmath65 shell ) @xmath89 - @xmath90 is flavor singlet and , in this case , the corresponding matrix element is @xmath91 . 
   the latter state is unique and is absent in other spectra due to its flavor - singlet nature . 
   these matrix elements alone suffice to prove that the ordering of the lowest positive and negative parity states in the baryon spectrum will be correctly predicted by the chiral boson exchange interaction ( [ 4 ] ) . 
   the constant @xmath92 may be determined from the n@xmath93 splitting to be 29.3 mev . 
   the oscillator parameter @xmath94 , which characterizes the effective confining interaction , may be determined as one half of the mass differences between the first excited @xmath95 states and the ground states of the baryons , which have the same flavor - spin , flavor and spin symmetries ( e.g. @xmath73 - @xmath69 , @xmath74 - @xmath70 , @xmath75 - @xmath71 ) , to be @xmath96 mev . 
   thus the two free parameters of this simple model are fixed and we can make now predictions .    in the @xmath69 , @xmath70 and @xmath71 sectors the mass difference between the lowest excited @xmath97 states ( @xmath73 , @xmath74 , and @xmath75 ) and @xmath98 negative parity pairs ( @xmath82 - @xmath83 , @xmath84 - @xmath85 , and @xmath86 - @xmath87 , respectively ) will then be @xmath99 whereas for the lowest states in the @xmath70 system ( @xmath74 , @xmath89 - @xmath90 ) it should be    @xmath100    this simple example shows how the chiral interaction provides different ordering of the lowest positive and negative parity excited states in the spectra of the nucleon and the @xmath70-hyperon . 
   this is a direct consequence of the symmetry properties of the boson - exchange interaction @xcite . 
   namely , completely symmetric fs state in the @xmath73 , @xmath74 and @xmath75 positive parity resonances from the @xmath66 band feels a much stronger attractive interaction than the mixed symmetry state in the @xmath82 - @xmath83 , @xmath84 - @xmath85 and @xmath86 -@xmath87 resonances of negative parity ( @xmath65 shell ) . 
   consequently the masses of the positive parity states @xmath73 , @xmath74 and @xmath75 are shifted down relative to the other ones , which explains the reversal of the otherwise expected `` normal ordering '' . 
   the situation is different for @xmath89 - @xmath90 and @xmath74 , as the flavor state of @xmath89 - @xmath90 is totally antisymmetric . because of 
   this the @xmath89 - @xmath90 gains an attractive energy , which is comparable to that of the @xmath74 , and thus the ordering suggested by the confining oscillator interaction is maintained . 
   note that the problem of the relative position of positive - negative parity states can not be solved with other types of hyperfine interactions between constituent quarks ( the colour - magnetic and instanton - induced ones ) . 
   in the semirelativistic chiral constituent quark model @xcite the dynamical part of the hamiltonian consists of linear pairwise confining interaction with the string tension fixed to the known value 1 gev / fm from regge slopes ( which also follows from the heavy quarkonium spectroscopy and lattice calculations ) , and the chiral interaction , mediated by pseudoscalar , scalar and vector - meson exchanges . both the flavor - octet and flavor - singlet pseudoscalar- and 
   vector - meson exchanges are taken into account . 
   the coupling constants of constituent quarks with mesons are fixed from the empirically known @xmath101 , @xmath102 , and @xmath103 coupling constants . 
   the `` sigma - meson ''  constituent quark coupling constant is taken to be equal the pion 
   constituent quark coupling constant , as constrained by chiral symmetry . for the constituent quark 
   masses one takes typical values @xmath104 mev , @xmath105 mev and do not fit them . 
   the short - range behaviour of the interaction is determined by the cut - off parameters @xmath70 in the constituent quark  meson form - factors , which are taken in monopole form . in order to avoid a proliferation of free parameters , by assuming independent values of @xmath70 for each meson , we adopt the linear scaling prescription @xmath106 , where @xmath107 is meson mass , for pseudoscalar- and vector mesons .    the kinetic - energy operator is taken in relativistic form , @xmath108 . 
   the semirelativistic three - quark hamiltonian was solved along the stochastical variational method @xcite in momentum space . for the whole q - q potential the model involves a total of 4 free parameters whose numerical values 
   are determined from the fit to all 35 confirmed low - lying states .    in fig . 
   1 we present the ground states as well as low - lying excited states in @xmath64 , @xmath68 , @xmath70 , @xmath71 , @xmath72 , and @xmath80 spectra . from the results of fig . 
   1 it becomes evident that within the chiral constituent quark model a unified description of both nonstrange and strange baryon spectra is achieved in good agreement with phenomenology . 
   it is instructive to learn how the spin - spin interaction ( [ 1.1 ] ) affects the energy levels when it is switched on and its strength is gradually increased ( fig . 
   2 ) . starting out from the case with confinement only , one observes that the degeneracy of states is removed and the inversion of ordering of positive and negative parity states is achieved in the @xmath64 spectrum , as well as for some states in the @xmath70 spectrum , while the ordering of the lowest positive - negative parity states is opposite in @xmath64 and @xmath70 spectra . 
   it is clear that the fock components @xmath109 ( including meson continuum ) can not be completely integrated out in favour of the meson - exchange @xmath37 potentials for some states above or near the corresponding meson thresholds . 
   such components in addition to the main one @xmath110 could explain e.g. an exceptionally big splitting of the flavor singlet states @xmath111 , since the @xmath89 lies below the @xmath112 threshold and can be presented as @xmath112 bound system @xcite . 
   note , that in the case of the present approach this old idea is completely natural and does not contradict a flavor - singlet @xmath110 nature of @xmath89 , while it would be in conflict with naive constituent quark model where no room for mesons in baryons . 
   an admixture of such components will be important in order to understand strong decays of some excited states . 
   while technically inclusion of such components in addition to the main one @xmath110 in a coupled - channel approach is rather difficult task , it should be considered as one of the most important future directions . 
   what is an intuitive picture of the nucleon in the low - energy regime ? 
   the goldstone bosons as well as vector meson fields couple to valence quarks . 
   thus the nucleon consists mostly of 3 constituent quarks which are very big objects due to their meson clouds ( see fig . 
   3 ) . these constituent quarks are all the time in strong overlap inside the nucleon . 
   that is why the short - range part of chiral interaction ( which is represented by the contact term in the oversimplified representation ) is so crucially important inside baryons . 
   when constituent quarks are well separated and there is a phase space for meson propagation , the long - range yukawa tails of meson - exchange interactions become very important . 
   it is these parts of meson exchange which produce the necessary long- and intermediate - range attraction in two - nucleon system . 
   if one ascribes a short - range central repulsion in the nn system to the central part of @xmath3 exchange between nucleons , then one should increase the @xmath103 coupling constant by factor 3 as compared to its empirical value , as it is usually done in phenomenological one - boson - exchange nn potentials . 
   evidently the short - range repulsion in the nn system should be connected with the nucleon structure in the low - energy regime and within the quark picture should be related to fermi - nature of constituent quarks and to the specific interactions between them . 
   so far , all studies of the short - range @xmath4 interaction within the constituent quark model were based on the one - gluon exchange interaction between quarks . 
   they explained the short - range repulsion in the @xmath4 system as due to the colour - magnetic part of oge combined with quark interchanges between 3q clusters @xcite . 
   it has been shown , however , that there is practically no room for colour - magnetic interaction in light baryon spectroscopy and any appreciable amount of colour - magnetic interaction , in addition to chiral interaction , destroys the spectrum @xcite . 
   this conclusion is confirmed by recent lattice qcd calculations @xcite . 
   if so , the question arises which interquark interaction is responsible for the short - range @xmath4 repulsion . 
   below i show that the same short - range part of chiral interaction ( [ 1.1 ] ) which causes e.g. @xmath113 splitting and produces good baryon spectra , also induces a short - range repulsion in @xmath4 system when the latter is treated as 6q system @xcite .    at present 
   one can use only a simple nonrelativistic @xmath114 ansatz for the nucleon wave function when one applies the quark model to @xmath4 interaction . 
   thus one needs first an effective nonrelativistic parametrization of chiral interaction interaction which would provide correct nucleon mass , @xmath113 splitting and the nucleon stability with this ansatz . for that one can use the nonrelativistic parametrization @xcite which satisfies approximately the conditions above .        where @xmath116 is a collective ( generator ) 
   coordinate which is the separation distance between the two wells ( it should not be mixed with the relative motion jacobi coordinate ) , @xmath117 is the lowest expectation value of the 6q hamiltonian at fixed @xmath116 , and @xmath118 is a mass of two well - separated nucleons ( @xmath119 ) calculated with the same hamiltonian .    at the moment we are interested in what is the @xmath4 interaction at zero separation between nucleons . 
   it has been proved by harvey that when @xmath120 , then in both @xmath121 and @xmath122 partial waves in the @xmath4 system only two types of orbital 6q configurations survive @xcite : @xmath123_o>$ ] and @xmath124_o>$ ] , where @xmath125_o$ ] is young diagram , describing spatial permutational symmetry in 6q system . 
   there are a few different flavor - spin symmetries , compatible with the spatial symmetries above : @xmath126_o[33]_{fs}$ ] , @xmath127_o[33]_{fs}$ ] , @xmath127_o[51]_{fs}$ ] , @xmath127_o[411]_{fs}$ ] , @xmath127_o[321]_{fs}$ ] , and @xmath127_o[2211]_{fs}$ ] . 
   thus , in order to evaluate the @xmath4 interaction at zero separation between nucleons it is necessary to diagonalize a @xmath5 hamiltonian in the basis above and use the procedure ( [ 6 ] ) .    from the adiabatic born - oppenheimer approximation ( [ 6 ] ) we find that @xmath128 is highly repulsive in both @xmath121 and @xmath122 partial waves , with the core being of order 1 gev . 
   this repulsion implies a strong suppression of the @xmath4 wave function in the nucleon overlap region .    due to the specific flavor - spin symmetry of chiral interaction between 
   quarks the configuration @xmath129_o[51]_{fs}$ ] becomes highly dominant among other possible 6q configurations at zero separation between nucleons ( however , the `` energy '' of this configuration is much higher than the energy of two well - separated nucleons , that is why there is a strong short - range repulsion in @xmath4 system ) . 
   the symmetry structure of this dominant configuration induces `` an additional '' effective repulsion , related to the `` pauli forbidden state '' in this case , and the s - wave @xmath4 relative motion wave function has a node at short range@xcite . 
   the existence of a strong repulsion , related to the energy ballance , discussed above , suggests , however , that the amplitude of the oscillating @xmath4 wave function at short range will be strongly suppressed . 
   thus , within the chiral constituent quark model one has all the necessary ingredients to understand microscopically the @xmath4 interaction . 
   there appears strong short - range repulsion from the same short - range part of chiral interaction which also produces hyperfine splittings in baryon spectroscopy . 
   the long- and intermediate - range attraction in the @xmath4 system is automatically implied by the yukawa part of pion - exchange and correlated two - pion exchanges ( @xmath18-exchange ) between quarks belonging to different nucleons . 
   the necessary tensor and spin - orbit force comes from the pseudoscalar- and vector - exchange yukawa tails . 
   what will be a short - range interaction in other @xmath130 and @xmath131 systems ? in the chiral limit there is no difference between all octet baryons : @xmath132 . 
   thus if one explains a strong short - range repulsion in @xmath4 system as related mostly to the spontaneous breaking of chiral symmetry , as above , then the same short - range repulsion should persist in other @xmath130 and @xmath131 systems @xcite . 
   of course , due to the explicit chiral symmetry breaking the strength of this repulsion should be essentially different as compared to that one in @xmath4 system . 
   one can naively expect that it will be weaker . 
   it is my pleasure to thank d.o.riska , z.papp , w.plessas , k.varga , r. wagenbrunn , fl . 
   stancu , and s. pepin , in collaboration with whom different results discussed in this talk have been obtained . 
   i also thank organizers of the school for the invitation to give this lecture . 
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summary: in the low - energy regime light and strange baryons should be considered as systems of constituent quarks with confining interaction and a chiral interaction that is mediated by goldstone bosons as well as by vector and scalar mesons . 
   the flavor - spin structure and sign of the short - range part of the spin - spin force reduces the @xmath0 symmetry down to @xmath1 , induces hyperfine splittings and provides correct ordering of the lowest states with positive and negative parity . 
   there is a cancellation of the tensor force from pseudoscalar- and vector - exchanges in baryons . 
   the spin - orbit interactions from @xmath2-like and @xmath3-like exchanges also cancel each other in baryons while they produce a big spin - orbit force in nn system . 
   a unified description of light and strange baryon spectra calculated in a semirelativistic framework is presented . 
   it is demonstrated that the same short - range part of spin - spin interaction between the constituent quarks induces a strong short - range repulsion in @xmath4 system when the latter is treated as @xmath5 system . 
   thus one can achieve a simultaneous understanding of a baryon structure and baryon - baryon interaction in the low - energy regime . 
   -1 cm -0.5 cm -1 cm 23 cm    * baryons in a chiral constituent quark model *    l. ya . 
   glozman    _ institute for theoretical physics , university of graz , austria _