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We review arguments that supersymmetric QCD with $N$ colors and $N_f \ge 0$ massive quarks confines. We explain that this remains the case for small soft breakings and small supersymmetric masses for any quarks. These results continue to…
We investigate the nature of the finite-temperature chiral transition in QCD with two light flavors, in the case of an effective suppression of the the U(1)_A symmetry breaking induced by the axial anomaly, which implies the symmetry…
We use a variational procedure to study finite density QCD in an approximation in which the interaction between quarks is modelled by that induced by instantons. We find that uniform states with conventional chiral symmetry breaking have…
Studying heavy flavour physics is driven by multiple motivations: to probe our theoretical control over QCD; enhance our information on gluon and sea quark structure functions; use heavy flavour production as signal for the onset of the…
In order to solve the strong CP problem, we study the possibility that the Peccei--Quinn symmetry is broken {\it below}\/ the QCD scale. We find that a QCD axion can be above GeV, and may be among the observed $\eta$ resonances. It is…
We review recent developments in our understanding of the dynamics of strongly-coupled chiral $SU(N)$ gauge theories in four dimensions, problems which are potentially important in our quest to go beyond the standard $SU(3)_{QCD} \times…
We consider the neutrino physics of models with a sequentially broken U(2) flavor symmetry. Such theories yield the observed pattern of quark and lepton masses, while maintaining sufficient degeneracies between superparticles of the first…
We show that the recently constructed 5-dimensional supersymmetric $S^1/(Z_2\times Z_2')$ orbifold GUT models allow an appealing explanation of the observed hierarchical structure of the quark and lepton masses and mixing angles. Flavor…
We investigate multi-flavour gauge theories confined in $d\es 2n$-dimensional Euclidean bags. The boundary conditions for the 'quarks' break the axial flavour symmetry and depend on a parameter $\theta$. We determine the $\theta$-dependence…
We study vacuum structure of N=2 supersymmetric (SUSY) QCD, based on the gauge group SU(2) with N_f=2 flavors of massive hypermultiplet quarks, in the presence of non-zero baryon chemical potential (\mu). The theory has a classical vacuum…
We present a summary of our results for the light hadron spectrum in quenched lattice QCD and preliminary ones in two-flavor full QCD. For the quenched hadron spectrum we find that the mass formulae predicted by quenched chiral perturbation…
We summarize the results recently reported in Ref.[1] [A. Deuzeman, M.P. Lombardo, T. Nunes da Silva and E. Pallante,"The bulk transition of QCD with twelve flavors and the role of improvement"] for the SU(3) gauge theory with Nf=12…
QCD lattice simulations with 2+1 flavours typically start at rather large up-down and strange quark masses and extrapolate first the strange quark mass to its physical value and then the up-down quark mass. An alternative method of tuning…
If any violation of Lorentz symmetry exists in the hadron sector, its ultimate origins must lie at the quark level. We continue the analysis of how the theories at these two levels are connected, using chiral perturbation theory.…
I report on recent developments in the heavy-quark effective theory and its application to $B$ meson decays. The parameters of the effective theory, the spin-flavor symmetry limit, and the leading symmetry-breaking corrections to it are…
The fundamental constraint on two Higgs doublet models comes from the requirement of sufficiently suppressing flavor-changing neutral currents. There are various standard approaches for dealing with this problem, but they all tend to share…
The couplings and interactions of baryons containing a heavy quark are related by light quark spin-flavor symmetry in the large $N$ limit. The single pion coupling constant which determines all heavy quark baryon-pion couplings is equal to…
We study QCD vacuum structure with the topological $\theta$ angle using a recently proposed semiclassical approach on $\mathbb{R}^2 \times T^2$ with the 't Hooft and baryon magnetic fluxes. Under the assumption of adiabatic continuity in…
I explore the rich phase diagram of two-flavor QCD as a function of the quark masses. The theory involves three parameters, including one that is CP violating. As the masses vary, regions of both first and second order transitions are…
The CP properties of effective operators are closely related to the spacetime and internal symmetries, such as the flavor symmetry, in the standard model effective field theory (SMEFT). In this work, we utilize the flavor symmetry to…