Glueballs, hybrids and multiquark states are predicted as bound states in models guided by
quantum chromo dynamics (QCD), by QCD sum rules or QCD on a lattice. Estimates for the …

The existence and properties of the sigma meson have been controversial for almost six
decades, despite playing a central role in the spontaneous chiral symmetry of QCD or in the …

We show that it is possible to construct explicit models of electroweak symmetry breaking in
which the number of techniflavors needed to enter the conformal phase of the theory is small …

We study the interesting problem of whether it is possible to distinguish composite from
elementary particles. In particular we generalize a model-independent approach of …

We discuss theoretical predictions for the existence of exotic (non-quark-model) mesons and
review prominent experimental candidates. These are especially the f0 (1500) and f0 (1710) …

We show that two nonets and a glueball provide a consistent description of data on scalar
mesons below 1.7 GeV. Above 1 GeV the states form a conventional q bar q nonet mixed …

Light scalar mesons are found to fit rather well a diquark-antidiquark description. The
resulting nonet obeys mass formulas which respect, to a good extent, the Okubo-Zweig …

We investigate theories in which the technifermions in higher dimensional representations of
the technicolor gauge group dynamically break the electroweak symmetry of the standard …

The description of strong interaction physics of low-lying resonances is out of the valid range
of perturbative QCD. Chiral effective field theories (EFTs) have been developed to tackle the …

We develop a moment QCD sum rule method augmented by fundamental inequalities to
study the existence of exotic doubly hidden-charm/bottom tetraquark states made of four …