N=1 SQCD with SU(N_c) colors and N_F flavors of light quarks is considered within the dynamical scenario which assumes that quarks can be in two different phases only. These are: a) either the HQ (heavy quark) phase where they are confined, b) or the
y are higgsed, at the appropriate values of parameters of the Lagrangian. The mass spectra of this (direct) theory and its Seibergs dual are obtained and compared, for quarks of equal or unequal masses. It is shown that in all cases when there is the additional small parameter at hand (it is 0<(3N_c-N_F)/N_F << 1 for the direct theory, or its analog 0<(2N_F-3N_c)/N_F << 1 for the dual one), the mass spectra of the direct and dual theories are parametrically different. A number of other regimes are also considered.
This is a short review of some hard two-photon processes: $ a) ,,gammagammato {overline P}_1 P_2,,, {overline P}_1 P_2= {pi^+pi^-, K^+ K^-, K_S K_S, pi^opi^o, pi^oeta},, b) ,,gammagammato V_1 V_2,,, V_1 V_2={rho^orho^o, phiphi, omegaphi, omegaomega
}, c) ,,gammagammato {rm baryon-antibaryon}, d) ,,gamma^*gammato P^o,,, P^o={pi^o, eta, eta^prime, eta_c}$. The available experimental data are presented. A number of theoretical approaches to calculation of these processes is described, both those based mainly on QCD and more phenomenological (the handbag model, the diquark model, etc). Some theoretical questions tightly connected with this subject are discussed, in particular: the applications of various types of QCD sum rules, the endpoint behavior of the leading twist meson wave functions, etc.
This paper continues our previous study of similar theories in cite{ch5}. We also consider here the ${cal N}=1$ SQCD-like theories with $SU(N_c)$ colors (and their Seibergs dual with $SU(N_F-N_c)$ dual colors) and $N_F$ flavors of light quarks, and w
ith $N_F^2$ additional colorless flavored fields $Phi^j_i$, but now with $N_F$ in the range $2N_c<N_F<3N_c$. The multiplicities of various vacua and quark and gluino condensates in these vacua are found. The mass spectra of the direct and Seibergs dual theories in various vacua are calculated within the dynamical scenario which assumes that quarks in such ${cal N}=1$ SQCD-like theories can be in two {it standard} phases only. These are either the HQ (heavy quark) phase where they are confined or the Higgs phase. The word {it standard} implies here also that, in such ${cal N}=1$ theories without elementary colored adjoint scalars, no {it additional} parametrically light solitons (e.g. magnetic monopoles or dyons) are formed at those scales where quarks decouple as heavy or are higgsed. Recall that this scenario satisfies all those tests which were used as checks of the Seiberg hypothesis about the equivalence of the direct and dual theories. The mass spectra of these direct and Seibergs dual theories calculated within this framework were found to be different, in general. These parametrical differences of mass spectra of direct and dual theories show, in particular, that all those tests, which were used as checks of the Seiberg hypothesis about the equivalence of the direct and dual theories, although necessary, may well be insufficient. Besides, the mass spectrum of the dual theory with $SU(N_F-N_c)$ colors and $N_c+1<N_F<3N_c/2$ dual quark flavors was calculated. And finally, considered is the direct ${cal N}=2$ SQCD with $SU(N_c)$ colors and $N_c+1<N_F<3N_c/2$ flavors of light quarks...
A short review of leading term QCD predictions vs those of the handbag model for large angle cross sections gammagamma --> P_2 P_1 (P is the pseudoscalar meson pi^{pm,o}, K^{pm,o}, eta), and for gammagamma --> V_2 V_1 (V is the neutral vector meson r
ho^o, omega, phi), in comparison with Belle Collaboration measuments
