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The discovery potential for detecting new heavy Majorana and Dirac neutrinos at some recently proposed high energy $e^+e^-$ colliders is discussed. These new particles are suggested by grand unified theories and superstring-inspired models.…
The concept of effective particles as degrees of freedom in a relativistic quantum field theory is defined using a non-perturbative renormalization group procedure for Hamiltonians. However, every candidate for a basic physical theory…
Recently proposed idea of unparticles arising due to a scale invariant sector in the theory can give rise to effective operators with different Lorentz structures. We show that by using the different polarization options at the future…
We show that the Flatte formula is not adequate to interpret precision data on a resonance production near an inelastic threshold. A unitary parameterization, satisfying generalized Watson's theorem for the production amplitudes, is…
The beam-plasma instability, i.e. the response of the plasma bulk to the injection of supra thermal charged-particle beams, results to be appropriately characterized by a long-range interaction system. This physical system hosts a number of…
We review the status of theoretical predictions for W-pair production at high energies. We discuss a systematic scenario towards a Monte-Carlo generator for e^+e^- --> 4f(\gamma), which meets the experimental requirements. In particular we…
The concept of effective particles is introduced in the Minkowski space-time Hamiltonians in quantum field theory using a new kind of the relativistic renormalization group procedure that does not integrate out high-energy modes but instead…
A new quantum effect connected with the late time behavior of decaying states is described and its possible observational consequences are analyzed: It is shown that charged unstable particles as well as neutral unstable particles with…
Effective field theory provides a perturbative framework to study the evolution of cosmological large-scale structure. We investigate the underpinnings of this approach, and suggest new ways to compute correlation functions of cosmological…
This thesis gives a comprehensive analysis of hadron production in $e^{+}e^{-}$ collisions at different center of mass energies in the framework of the Statistical Model of the hadron resonance gas. The model used for the analysis is…
The nonlinear interaction, due to quantum electrodynamical (QED) effects, between photons is investigated using a wave-kinetic description. Starting from a coherent wave description, we use the Wigner transform technique to obtain a set of…
Effective Field Theories with higher derivatives often yield equations of motion which define ill-posed problems. We present a method for enhancing control on such theories by coupling them to a field living in one extra dimension. The…
These lectures are centered around a specific problem, the effect of weak repulsive interactions on the transition temperature $T_c$ of a Bose gas. This problem provides indeed a beautiful illustration of many of the techniques which have…
A strongly interacting Fermi gas, such as that of cold atoms operative near a Feshbach resonance, is difficult to study by perturbative many-body theory to go beyond mean field approximation. Here I develop an effective field theory for the…
We show that top-quark pairs are produced in an essentially unique spin configuration in polarized $e^+e^-$ colliders at all energies above the threshold region. Since the directions of the electroweak decay products of polarized top-quarks…
Exploiting the azimuthal angle dependence of the density matrices we construct observables that directly measure the spin of a heavy unstable particle. A novelty of the approach is that the analysis of the azimuthal angle dependence in a…
We establish a mathematically rigorous, general and quantitative framework to describe currents of non- (or weakly) interacting, indistinguishable particles driven far from equilibrium. We derive tight upper and lower bounds for the…
Lecture Notes, Summer School on Effective Theories and Fundamental Interactions, Erice, July 1996. I describe the construction of effective field theories for equilibrium high-temperature plasma of elementary particles.
We question the use of stable asymptotic scattering states in QED of strong magnetic fields. To correctly describe excited Landau states and photons above the pair creation threshold the asymptotic fields are chosen as generalized Licht…
These lectures start with the mean field theory for a symmetric binary fluid mixture, addressing interfacial tension, the stress tensor, and the equations of motion (Model H). We then consider the phase separation kinetics of such a…